Anti Phaser ProjectMusic effects

Electronics FromThe StartBeginner's guide

Distortion MeterProject

Computer ReviewCommodore 16

5 74 3 8

June 1985

ting Enthusiasts

$3.25kiM70924

onelist of

PU. For(one ROM

PIO) no buf-e buffers would

the CPU than the

how to connect a buffers using a 74LS245 bidirec-

r. The WR signal is connectedon the 74LS245, controlling the

n of data flowing from the buffer.19 is connected to the BUSAK signal

EXCELTRONIX

'"BEST MK I

The BEST Mark 11As described above using 41256 RAM chips.Two 360K DS, DO disk drives, RS232 andparallel port, Real Time Clock, 7 slots,Phoenix BIOS, Colour Video and Disk Con-troller Cards, Keyboard and much, muchmore

With 256K$1695

With 512K$1795

SuperI PC and XT

Compatibility

Look what you get as standard! Uses 8088 microprocessor. New Feature, 256K RAM as standard. New Feature. Comes with the latest 41256 RAM chips. Expandable up to 512K and more on main board using 41256

RAM chips. New Feature. 7 expansion slots, each being Identical for the

user to upgrade as required. New Feature. Fitted with 150W power supply so system can

be upgraded to a hard disk without changing power supply. New Feature. Flip -Top case. DMA controller. Three of the DMA channels are available to

the user. New Feature. Even most basic versions come with Parallel

and Serial Ports and Real Time Clock. Half watt speaker. Pre -socketed for optional coprocessors such as the 8087

math processor. Keyboard Interface compatible with IBM compatible

keyboards through a 5 -pin DIN connector. Three ROM sockets are available to the user, one generally

holding the Phoenix BIOS. New Feature. Reset switch. Timer/Counter used by the system for Real Time Clock, time

base and for tone generation. Complete with the Phoenix BIOS, identical to that used by

many of the large US companies manufacturing IBM compati.ble computers.

Comes with two ShmlIne DS, DD 51/2" 360K Disk Drives. Colour Video (RGB and composite) and Disk Controller cards

included. 230V models available. 300 Day warranty.

Tape Drive option backup suitable for allsystems ScanIBM is registered trademark of IBM Canada Ltd.

The BEST10 Meg Hard Drive

As the BEST Mark II but with 10 Meg Harddrive (supplied with one Floppy Drive. Forsecond drive add $200).

With 256K With 512K$2695 $2795

The BEST20 Meg Hard Drive

As the BEST Mark II but with 20 Meg Harddrive (supplied with one Floppy Drive. Forsecond drive add $200).

With 256K With 512K$2995 $3095

Also the Basic BEST $1595.00As the BEST Mark II described above but without Parallel Port or Real Time Clock

The Best 256K PENTARAM BEST SELLER

$359.00 with 256K RAM, Real Time Clock Parallel,serial and Game Port (512K now available)FLOPPY CONTROLLER BOARD AND OPTIONS

5129.00 With Real Time Clock and Serial Port only 5189.00

EPROM Programmer 599.00(with ZIF Socket Adapter 5159.00)Parallel/Game Port $79.00 (cables Extra)

BEST 512K RAM BOARD

SPECIAL: $365.00! with 512K. With 64K $179.00

Colour Graphics Video Board

,1111111111111' 11111111111111

$179.00 (Composite and RGB Output)

Quantity, Students and Teacher discount's available.

Exceltronix Computer Division Computers at unbeatableprices! (416) 921-8941, 319 College St., Toronto, Ontario

No returns or exchanges after 7 days. 15'o restocking charge. MST 152Prices may change without notification 1-800-268-3798 -217 Bank Street, Ottawa (613) 230-9000 Order line only

2 Circle No. 3 on Reader Service Card Electronics Today June 1985

EXCELTRONIX-Long Distance Order line only:1-800-268-3798

MonitorsZenithDataSystems

B EST SELLER ZVM 122A 12" diagonalscreen non -glare amber display composile input 25lines x 40/80 characters $139.00B EST SELLER ZVM 123A 12" diagonalscreen non -glare green display composite input 25lines x 40/80 characters 9129.00ZVM 133 13" diagonal screen RGB input 25lines x 80 characters 640 x 240 pixels green screenonly switch 16 colours including PC brown

$799.00

319 College Street, Toronto, Ont, MST 152 (416) 921-8941217 Bank Street, Ottawa, (613) 230-9000We guarantee you the combination of BEST Prices & Service in Canada!Star Micronics Gemini 10X1 year warranty 120 c.p.s., 816 characters print buf-fer, option 4K or 8K standard paralleloptional RS232C tractor & frictionfeed. super Special 5299.00

....afteio. (Time limited offer)

Gemini 15XSame as Gemini 10X. 1

5599.005.5" carriage

New from Star MicronicSSG -10 PrinterIdeal for Text & Graphics(Similar appearance to Gemini 10X115X)

Dual Mode - NLQ/draft standard (NLQ = near letterquality) 120 CPS and 20% faster throughput Bidirectional logic/seeking 2K buffer (expandableto 6K with optional buffer interface) 100% IBM PC orStar standard control codes -switch selected Fric-tion and tractor standard full 1 year warranty 10"wide carriage Standard parallel interface (serial op-tional) $399.00

SG -15 same as SG -10Except with 15" carriage and standard16K buffer $599.00

Radix - $995.00 SR -15 5995.00POWER TYPE LETTER QUALITY 5639.00 18 CPS bidirectional logic seeking. 96 Petal Wheel

APPLE COMPATIBLEDISK DRIVE "Now also available for Apple IlcFamousMultiflexDiskDrive

5199.00 1 year full warranty

Features: Apple compatible Attractively packaged Profes-sionally built and tested Canadian Made. We believethat Multiflex put out more drives in the last year thanall other Canadian manufacturers combined.

300 BAUD MODEM foryour APr V $79.00Auto Answer, Dial, Direct, Con. Plugsright into your Apple, comes with soft-ware.

mamma

Multiflex 300Baur' Ale -

For your Apple (Super com-patibility) $159.00

IBM COMPATIBLE KEYBOARDSCherry... Super Special 99.00Maxiswitch $135.00

Super SpecialKeytronics ProgrammableKeyboard (no case) $69.00

IBM Compatible isk DriveSA455 s (with warranty)

5179

CASES FOR YOURIBM Compatibles Hinged top cases allowing easy access

by opening top half of the case. Can be sup-plied with plain back or for 5 or 8 slots. Pleasespecify when ordering. $74.95

Above case with power supply and fanFor Apple compatible 75 Watt ....$169.00For IBM compatible 150 Watt $219.00Hinged Case with 90W (max.)Power Supply with fan $178.00As above with 175W (max.)Power Supply and fan $228.00

Spectacular Pricing onApple Products - Callfor best price

Peripherals for your AppleZ80 $ 45.0080 x 24 Video Card withSoft Switch S 69.0016K RAM Card 5 49.00128K RAM Card 5129.00Parallel Card with Cable

$ 65.00Serial Card $ 69.00Apple Programmer $ 65.00

Hard Disk DrivesSeagate (industry favoured)10 MEG. slimline $8119.0010 MEG Seagate, slimline drive and hard disk con-troller. This controller can handle up to two 10 MEGhard drives. LOWEST PRICE OF 51099.00

Quantity Discounts AvailableSeagate 20 MEG. slimline 51099.00Seg 20 MEG. with controller 51395.00Controller alone (for 10 or 20 MEG) 5349.00Cables (for 10 or 20 MEG) 538.00

MEMORY Untouchable Prices!Guaranteed Prime Stock

Dynamic RAMs4116 1x16k (15Ons)4164 1x64k (15Ons)4164's (15Ons). Set of 941256 1x256k (150ns)41256 (15Ons) Set of 9

5 0.992.99

$26.70$12.99$99.95

Static RAM2114L 4x1k 200ns S 2.256514 4x1k CMOS 45Ons S 4.996116 8x2k 150ns S 6.952016 8x2k 15Ons S 6.006164 8x8k 150ns $35.00

EPROMS2716 450ns 8x2k S 6.192716 300ns 8x2k S 7.452732 450ns 8x4k S 5.952732 250ns 8x4k S 5.952764 300ns 8x8k S 6.9527128 350ns 8x16k $13.95

BEST IBM CompatibleModem Plugs into motherboard Excellent Hayes compatibility Auto Dial, Auto Answer, Direct -

connect

300 Baud 5179 300/1200 Baud $379

Special Parts for yourIBM & Apple CompatiblesIntel Parts8087 5219.008088 514.958237A-5 514.958250 511.508253A-5 7.458255A-5 $ 6.908259A 5 6.958284A 7.758288 514.95NEC765/8272 Equiv. 514.9574LS322 6.9562 Pin Card Edge Connectors 5 2.195 Pin Din Connector $ 1.20100ns Delay Line 6.006502 CPU 5.45Z80A CPU $ 4.9968A45 CRT cont. $ 9.75TMS99532 FSK Modem $18.95Set of 8088, 8255A-5, 8237A-5,8288,8284, 8253A-5, 8259A $64.00

Electronics Today June 1985 Circle No. 26 on Reader Service Card 3

SURPLUSTRONICSwe will not be undersold

8088 computeritteisciff.edi

rits"w99Includes: 8088 motherboard

with 256K and allparts (except 8087)

Phoenix Bios One 360K DS,

DD disk driveand controller

Power Supply withfan

Flip -top case

11111111111111111

LAll you need extra is a keyboard, video board and monitor.8088 Motherboard only with 64K, fully assembled andtested, no Bios (one blank 2764). Expandable to 1 Megon -board memory. Flow soldered. Provisionfor 8087 5299.00

6502SystemsThe Famous6502 Board

Assembled andfully tested (flow soldered)

64K, 80 x 24 video with soft -switch, floppy controller. System comes with blank EPROM'S on board, does not

come with any proprietary software or Basic . 5289.00Complete System 6502 board (as bove) as Illustrated with case, keyboard

and power supply 5499.00Complete System Using 6502 board above in IBM style flip -top case, using

powerful 75 watt power supply with fan, programmableserial keyboard adaptor, IBM style keyboard ... 5599.00As above with one built in disk drive $789.00As above with two drives $969.00Switching Power Supplies. +5V 5A, +12V 2.8A, +12V 2.0Amps -12V 0.5A (open frame) 544.95Panasonic Printers (open frame) $39.95

PERIPHERAL CARDS FORYOUR IBM AND

COMPATIBLE COMPUTERColour Video Board $159.00Composite video or RGB VideoFloppy Controller $119.00Floppy Controller with RS232 . $149.00Floppy Controller w. clock/RS232 5159.00Parallel and Game Port Card . . . $59.00Cable and connector extra.Peripheral Interface Card 5139.00Includes two serial ports, parallel port, game portand provision for (but not including) real time clock.Clock/Calendar Option 529.00With battery backup.256K Multifunction BoardIncludes: Serial port, parallel port, game port, provi-sion for optional real time clock/calendar andsocketed for up to 256K RAM.With 64K RAM $175.00512K BOCIIII.Socketed for 512K including:64K RAM $169.00IBM Compatible Disk Drives . . $185.00Brand New, fresh from factory. Shugart SA455 40 track,double sided, double density Slimline. We have ordered10,000 from Shugart - that is why we can pass the savingson to you.IBM Compatible KeyboardsKeytronics programmable (no case)

5516429..00WMaxiswitchCherry $129.00Case - High QualityHinged for easy access, can be supplied with plain backoor7fo4r.595or 8 slots. Please specifyAbove case with power supply and fan.For Apple compatible (75W) 5169.00For IBM compatible (150W) 5219.00PERIPHERAL CARDS FOR YOURAPPLE & COMPATIBLEAssembled, flow-soldered/cleaned and 100% tested16K RAM Card 549.9580x24 video card 569.95Z80A Card $47.00Parallel Printer Card (cables extra) $49.95128K RAM Card with 64K $99.00128K RAM Card with 128K 5139.00EPROM Programmer with Software 563.00(programs 2716, 2732, 2732A, 2764)8" Floppy Controller $79.00Modem Autoanswer/autodial, touch tone or pulse dial. Plugs rightinto the system $69.00.Apple Compatible Disk Drives (SA390) $189.00Case with numeric keyboard $129.00Power Supply (Hydro Approved) $69.00IBM is a registered Trade Mark of IBM Canada Limited Apple is a registeredTrade Mark of Apple Canada Limited

Mail Orders add $5.00 minimum for shipping & handling. Ontarioresidents add 7% P.S.T. Visa, Mastercard and American Express cardsaccepted: send card number, expiry date, name of bank and signature.Send certified cheque or money order, do not send cash. All prices onthis page are final sale. No warranty, No returns, No refunds but HUGEsavings. Warranties available at extra cost.

More lines to serve you betterSurplustronics, 310 College Street, Toronto, Ontario, M5T 1S3 (416) 960.1350

4 Clrels No. 11 on Roeder Electronics Today June 1985

(416)

raMts

, Our CoverP

Satellite -to -home TVreception has started a

growing industry; a guideappears on page 32.Equipment courtesy of/1 Vexus Telecommun ca-

.

i/ tions, Mississauga;jallailli i photo ...by Bill Markwick.

e) Audit Bureau of CirculationsElectronics Today is Published by:Moorshead Publications Ltd.(12 times a year)Suite 601, 25 Overlea Blvd.Toronto, Ont. M4H 1BI

423-3262

Editor: William MarkwickEditorial Assistant: Edward ZapletalDirector of Production: Erik BlomkwistCreative Manager: Ann RodriguesProduction: Douglas Goddard

Naznin SunderjiSandra Hemburrow

Circulation Manager: Lisa SalvatoriAdvertising Director: Kenneth MarskellAdvertising (Que.) John McCown & Associates

(514) 735-5191Advertising (B.C.) (604) 688-5914

Publisher: H.W. Moorshead; Executive Vice -President: V.K. Marskell; General Manager:S. Harrison; Controller: B. Shankman; Accounts:P. Dunphy; Reader Services: R. Cree, H. Brooks,M. Greenan; Advertising Services: A. LeBrocq.

Newsstand Distribution:Master Media, Oakville, Ontariosubscriptions:$19.95 (one year), $34.95 (two years). For US add$3.00 per year, other countries add $5.00 per year.Please specify if subscription is new or a renewal.

Postal Information:Second Class Mail Registration No. 3955. Mailingaddress for subscription orders, undeliverablecopies and change of address notice is:Electronics Today, Suite 601, 25 Overlea Blvd.,Toronto, Ontario, M4H 1131

Printed by Heritage Press Ltd., MississaugaISSN 07038984.

Moorshead Publications also publishes Computing Now!,Computers in Education, and Software Now!.

Advertisers' IndexActive Components Sales Corp 37A-1 Electronics 60BCS Electronics Ltd. 28, 58Computer Parts Galore 62, 63Dacor Ltd 59Daetron 57Duncan Instruments Ltd. 35Electronic Control Systems 57Exceltronix 2, 3Information Unlimited 31

K.B. Electronics 27Kaientai Electronics Merchants Ltd .8Varah's Direct 7

McGraw Hill 25Software Link 64Soltech Industries Inc 40Sunix Inc. 8

Surplustronics 4

Electronics Today June 1985

ElectronicsTodaJune 1985

Vol. 9 No.6

Canada's Magazine for Electronics Et Computing Enthusiasts

MTHS-80 Interface, p. 26 Supercomputers, p. 29

FeaturesSupercomputers 29

Satellite Reception 32

ReviewsMTHS-80 Interface 26

Commodore 16 Computer 36

ProjectsDistortion Meter 13

Timed Nicad Charger 22Anti Phaser 55

SeriesElectronics From The Start 9

Configurations: Optoelectronics 16

Computing Today: Z80 Design 39

Designer's Notebook: Power Amps 42

Columns, News, and InformationFor Your Information 6 Order Form 51Next Month 18 Subscriptions 52Computing Now! This Month 19 Product Mart 54Software Now! This Month 19 Circuit Ideas 59Bookshelf 20

5

For Your InformationCopyrightAll material is subject to worldwide copyrightprotection. All PCB patterns are copyrightand no company can sell boards to our designwithout our permission.

liabilityWhile every effort has been made to ensurethat all constructional projects referred to inthis magazine will operate as indicated effi-ciently and properly and that all necessarycomponents are available, no responsibilitywhatsoever is accepted in respect of the failurefor any reason at all of the project to operateefficiently or at all whether due to any fault inthe design or otherwise and no responsibility isaccepted for the failure to obtain componentparts in respect of any such project. Further noresponsibility is accepted in respect of any in-jury or damage caused by any fault in designof any such project as aforesaid.

Editorial QueriesWritten queries can only be answered when ac-companied by a self-addressed, stampedenvelope. These must relate to recent articlesand not involve the staff in any research. Marksuch letter Electronics TodayQuery. We can-not answer telephone queries.

BindersBinders made especially for Electronics Today(ETI) are available for 59,25 including postageand handling. Ontario residents please addprovincial sales tax.

Back Issues and PhotocopiesPrevious issues of Electronics Today Canadaare available direct from our office for $4.00each; please specify by month, not by featureyou require. See order card for issue available.

We can supply photocopies of any articlepublished in Electronics Today Canada; thecharge is $2.00 per article, regardless of length.Please specify both issue and article.

Component Notation and UnitsWe normally specify components using an in-ternational standard. Many readers will be un-familiar with this but it's simple, less likely tolead to error and will be widely usedeverywhere sooner or later. Electronics Todayhas opted for sooner!Firstly decimal points are dropped andsubstituted with the multiplier: thus 4.7uF iswritten 4u7. Capacitors also use the multipliernano (one nanofarad is 1000pF). Thus 0.1 uFis 100nF, 5600pF is 5n6. Other examples are5.6pF = 5p6 and 0.5pF = OpS.Resistors are treated similarly: I.8Mohms is1M8, 56kohms is the same, 4.7kohms is 4k7,100ohms is 100R and 5.60hms is 5R6.

PCB SuppliersElectronics Today magazine does NOT supplyPCBs or kits but we do issue manufacturingpermits for companies to manufacture boardsand kits to our designs, Contact the followingcompanies when ordering boards.

Please note we do not keep track of whatis available from who so please don't contactus for information on PCBs and kits. Similarydo not ask PCB suppliers for help with pro-jects.

K.S.K. Associates, P.O. Box 266, Milton,Ont. L9T 4N9.Wentworth Electronics, R.R. No. 1 Water -down, Ont. LOR 2H0.Danocinths Inc., P.O. Box 261, Westland MI48185, USA.Arkon Electronics Ltd., 409 Queen Street W.,Toronto, Ont., M5V 2A5.Beyer & Martin Electronic Ltd., 2 Jodi Ave.,Unit C, Downsview, Ontario M3N 11-11.Spectrum Electronics, 14 Knightswood Cres-cent, Brantford, Ontario N3R 7E6.

Intelligent ProgrammableLEDsSiemens Electric of MississaugaOntario recently revealed a new in-telligent programmable LEDdisplay capable of such functionsas underlining and adjustabledisplay intensity.

Now the intensity of the redemission can be reduced by 50 to75% so as to downgrade thesignificance of the informationdisplayed or adapt the brightnessto the ambient conditions. Whenthe display flashes, the memorycontents remain intact. In contrastto conventional displays with anexternal flasher, the characters on-ly need to be input once and not inthe rhythm at which the LEDs lightup.

The PD 2816 is comprised of acharacter generator (ROM),multiplexer, timer logic and driverlogic, and also the CMOS circuitfor the supplementary program-mable functions. The LEDs areconfigured in eight 18 -segmentunits only 4.1mm high. Anynumber of eight -element displayscan be cascaded to form long linesof text.

For more information con-tact: Siemens Electric Ltd., 1180Courtney Park Dr., MississauugaOnt., L5T 1P2.

Cellular Service AreasAnnouncedCantel, the company selected bythe D.O.T. to provide cellularphone service to 23 Canadianmarkets, recently announced twoareas of initial service.

Commencing July 1st, con-tinuous coverage will begin in andbetween Toronto, Hamilton, Dun-das, Burlington, Oakville,Mississauga, Georgetown, Bramp-ton, Etobicoke, Bramalea, Bolton,Scarborough, Richmond Hill,Markham, Newmarket, Aurora,Pickering, Whitby, Ajax, andOshawa.

Also commencing on July 1st,the Montreal area service will in-clude: Montreal, L'Assomption,Vercheres, St. Hyacinthe,Chambly, La Prairie, St. Jean,Beauharnois, Laval, Hudson, Ste.Therese, Terrebonne, St. Jeromeand Ste. Adele.

If you would like more detail-ed information on cellular phoneservice contact: Cantel Inc., 20Queen St. W., Suite 1204, P.O.Box 70, Toronto Ont., M5H 3R3.

The popular ELP power amplifiermodules are now available in stan-dard 19 inch racks for professionaluse. They're available in bipolar orMOSFET versions, and featurefast slew rate, low noise and lowdistortion. Various power levelsare available up to 180 watts perchannel. They're from EDG Elec-tronic Distributors, 3950Chesswood Dr., Downsview, Ont.M3J 2W6 (416) 636-9404.

NewmarketAurora Whitby

PickeringMarkham Ajax

RichmondHill

Bolton

Bramalea

EtobicokeBrampton

Georgetown

Dundas

Scarborough

TORONTO

Mississauga

Oakville

Burlington

HAMILTON

OSHAWA

6 Electronics Today June 1985

Flat Bed RecorderNo, this won't check for saggy spr-ings in your mattress, but it willplot XY or y/t charts quite nicely.

The new PL 4 from J.J. Lloydis portable and is driven by a fullyintegrated quartz -controlled chartdrive. Both inputs are fullyfloating and have a constant inputimpedance of greater than1Mohm, as well each amplifier isfitted with an 18 -range attenuatorprovideng a maximum sensitivityof 25uV/mm.

The electonically controlleddrive unit has 9 speeds from2mm/min to 20mm/min with anaccuracy of greater than 0.01%.Linearity and repeatability areboth better than 0.107o and thecalibration accuracy is greater than0.2%.

For more information on thePL 4 chart recorder please write to:Omnitronix Ltd., 2410 DunwinDr., # 4, Mississauga Ont.,L5L 1J9.

New 100 MHz ScopeThe LEADER LBO 516 provides a5mV/div to 100MHz and a500uV/div sensitivity to 5 MHz.The newly developed 6 inch rec-tangular CRT having an accelera-tion potential of 20kV provides acrisp display and an internalgraticule is also incorporated toprovide parallex freemeasurements. Alternate sweep onmain and delayed time base, a2nS/div sweep speed and triggerview make this an ideal scope forservice/maintainence, researchand development and teaching. Achannel 1 out feature is also pro-vided for fast and accurate fre-quency measurements. The frontpanel is ergonomically designedand the unit is light and compact.For more information please write:OMNITRONIX LTD., 2410 Dun -win Dr., #4, Mississauga, OntarioL5L 1J9 (416) 828-6221.

Electronics Today June 1985

't.444,444446 41,4tvw044,4*#*4-"to416-842-8833 416-842-8833 416-842-8833

FINALLYA complete range of electronic components DIRECT fromVarah's and leading manufacturers. Absolutely no surplus,no rejects, no old date codes, and all at DIRECT fromthe distributor prices!

7400 LSStk 4 Oty Price Stk # Oty Price14000 7400 4 1.95 14200 74L500 4 1.7514004 7404 4 2.25 14202 74LS02 4 1.7514006 7406 4 3.00 14204 74LSO4 4 1.8514007 7407 4 3.00 14206 74LS08 4 1.8514010 7410 4 2.20 14208 74LS10 4 1.8514012 7414 4 3.00 14220 74LS32 4 1.8514014 7416 4 3.00 14235 74LS74 4 1.9514015 7417 4 3.00 14241 74LS86 4 2.2514022 7427 4 2.20 14260 74LS138 4 3.0014026 7438 4 3.00 14261 74LS139 4 3.0014035 7450 4 2.20 14264 74LS174 4 3.5014042 7474 4 3.00 14285 74LS175 4 3.5014062 74123 4 3.00 14300 74LS240 2 2.9514082 74161 2 2.25 14304 74LS244 2 2.9514110 74365 4 4.15 14305 74LS245 1 2.3014112 74367 4 4.15 14340 74LS373 1 1.80HCMOS LINEARStk k Oty Price Stk k Oty Price15000 74HC00 4 2.25 16010 555 5 2.5015002 74HCO2 4 2.40 16297 XRL555 5 2.5015004 74HC04 4 2.40 16015 556 2 1.7515014 74HC27 4 2.40 16160 339 2 1.3515018 74HC32 4 2.40 16130 324 2 1.3515025 74HC74 4 3.40 16115 741CP 5 2.5015028 74HC86 4 3.20 16210 4558 4 2.7515042 74HC138 2 2.80 16234 T L082 2 1.9515055 74HC161 2 3.05 16090 1488 2 1.5015066 74HC193 1 2.55 16092 1489 2 1 5015072 74HC240 1 4.25 16300 7805CT 2 1.9515074 74HC244 1 2.40 16310 7905CT 2 2.1515075 74HC245 1 3.60 16306 7812CT 2 1.9515098 74HC373 2 4.40 16314 7912CT 2 2.1515099 74HC374 2 4.40 16308 7815CT 2 1.9515104 74HC393 2 3.25 16318 7915CT 2 2.15

All of our semiconductors are protected with Varah's Directexclusive static -tree" package and guaranteed perfect.

TAKE

A

PAGE

FROM

I OUR BOOK

opto resistors ferritess scopes instrumentation-iard crystals data books

o nnectors I/O modulesh eatsinks transformersbridges zeners SCR's-ignals sockets cores

rack & panel BNC.eters tools testersire & cable knobsible ties chemicals

s bulbs batteries' iqs and jacks

'ocessorsrworks

,trotsmicters

Electrolytic capacitors31410 100uF 16V radial31420 1000uF 16V radial31480 10uF 35V radial31540 4.7uF 63V radial31545 10uF 63V radial31580 tuF 100V radial31610 10uF 16V axial31625 470uF 16V axial31675 10uF 35V axial31720 luF 63V axialMini -toggle switches44047 SPDT on -off -on44049 DPDT on -off -on44046 SPDT on -none -on44048 DPDT on -none -onPC mount slide switch44115 DPDT44120 DPDT rt. angle

20/2205/2.20

20/1.9520/22020/2.4020/22020/3.505/2.1020/3.7020/3.50

3/4.5/6/7.5/9/12VDCselectable power supply

63200 $7.95

PC board holder

67105 $9.95

crimping tool

43440 $7.95

Cable assemblies72500 6' M -M IBM compatible 42.9072510 8%.1-M RS232 serial 1-1 41.8072520 8' M -F RS232 serial 1-1 41.80

6/1.95 72540 81N -M modem 1-8x20,22 35.205/1.95 72560 8' M -M null modem 35.20

1.952.951.952.95

page 96 BO&

The DIRECT CatalogOur detailed catalog with full specs on over 2000electronic components will be available soon.Reserve your free copy by circling the readerservice number below, or by dialing (416) 842-8833 between 8:30 - 5.00 Monday -Friday.

The DIRECT GuaranteeWe back our products 100%. If you are notcompletely satisfied with an item, return itfor a full and prompt refund.

Member. CanadianDirect MarketingASSOc.tton

Order nowt All parts shipped from stock within 24 hours of receipt of payment and fullyguaranteed. Orders under $100 please add $3.00 shipping and handling 1. $1 00 insurance ifdesired). Ont. residents add 7% PST. Mastercard, Visa (incl. card no., cardholders name &expiry date), cheque, money order welcome.

Mall Orders & Oakville Store:Varah's Direct Mail Order

504 Iroquois Shore Rd.Oakville, Ont., L6H 3K4, 842-8833

Store Only Plus locations In:Ottawa(Nepean) Vancouver35 Stafford Rd. Edmonton(613) 726-8884 Calgary Winnipeg

Circle No. 28 on Reader Service Card 7

For Your Information

Signal GeneratorTritron S.A. of Norway has ap-pointed KB Electronics of Oakvilleexclusive importers for their line ofgenerators, counters, and modula-tion meters. The SD -1003 RFgenerator shown covers the rangeof 8 to 512MHz; AM is 0-90 per-cent and FM is in 10-30-100KHzsteps. The output attenuator is in10dB steps with a vernier fine con-trol. It is available from KB for 30to 40 percent below "industrystandard" prices. Contact KBElectronics, 355 Iroquois Road,Oakville, Ontario L6H 1M3 (416)842-6888.

46,* TRiTRotyfrequ.ncv FM ________

StEIVERATO

Hce.

e

Portable TerminalThe iXO handheld terminal allowsthe user to communicate withdatabases such as Compuserve orremote with office via regulartelephone lines. It featuresautomatic dialing, a 16 characterdisplay, a full typewriter stylekeyboard, and a versatile editingfunction with a 1300 charactermemory that allows composingand correcting a message beforetransmitting. A built-in modemlets the user connect to modularphonejacks.. For further informa-tion, contact TAS, 10 KodiakCrescent, Suite 100, Downsview,Ontario M3J 3G5 (416) 6330-1175.

According to a recent press release,IBM scientists in New York havemade the world's densest in-tegrated circuits. We said that lastmonth, too, but this is new stuff.This month's breakthrough useshalf -micron line widths, aboutone-fourth the width of produc-tion chips. Two type of experimen-tal chips were made: one was alogic circuit with 1700 transistorsin one -tenth of a squaremillimeter, and the other was amemory array using the world'ssmallest one -transistor memorycell, 8.5 square microns. Unfor-tunately, a scientist sneezed andthe chips haven't been seen since.

Apple Logic AnalyzerThe AP512 is a dedicated self-con-tained logic analyzer for the AppleII, Ile or compatible. The unitmonitors the machine level opera-tions of the Apple during programexecution and stores a trace of 512cycles around a trigger pointspecified in the setup menu. Theinformation can be analyzed ineither Hex or disassembled for-mats. Programmers can debugRAM or ROM based assemblylanguage programs. Contact Ap-tron Design Ltd., PO Box 13193,Kanata, Ont. (613) 831-0163.

continued on page 11

11COMPUTER ANDE AI ELECTRONICS

K EM CUSTOMHOW TO DROW YOUR ARTWORK

.11 Using black ink, tapes, letterings, drawyour artwork on white paper or cleardrawing film, taking care to letter clearly.Put the dimensions on the artwork inat least two places as shown in Fig.1.

21 Your artwork can be drawn eitheractual size or double size.

31 Write down the diameter of holes ona second copy of the artwork.

41 We can make a film from your magazine,send your original issue.

ESTIMATE

PHOTO FINISHING

510.00/1 shot ( max. 4.5" a 6.5" )$13.00/1shot (max. 7.5" a 9.5"/

PCB MAKE

PC BOARD

Fig.1 Sample artwork(Solder side)

Single sided 65C/sq. inch a PCB size(max 20 sq. inch) or min charge $6.0050C/sq. inch a PCB sizelfor over 20 eq. inch)

Double sided 95C/sq. inch (for ma: 20 sq. inch ) or min charge 510.00(no plated througlE 75C/sq. inch( for over 20 sq. inch I

DRILLING ---.------. 3C/each hole (No charge if not ordered)DIP -TIN PLATING -- 52.00/each board No charge if not ordered)

I Available for Nikel plating or Solder coating. /

SAMPLE ESTIMATE FOR FIG. I11 Photo 510.002I PCB 11.70 ( 65C a 18sq. inch)3)Drilling - - 8.49 1 283 holes)41Tin plating 2.00

Plus $3.00 for shipping charge.Plus provincial sales tea.Please send CHEQUE or MONEYORDER.COD mail order can NOT be acceptedfor photo finishing & PCB order.

KAIENTAI ELECTRONICS MERCHANTS LTDMAIL TO: P.O. BOX 69126 STATION 'IC

VANCOUVER, B.C., CANADA V5K4W4PHONE: 16041 435 -9697

ATTENTION! Hobbyist, Technician,Compare Quality, Spec. & Price

Before Buying Your Logic Probe!

Enginner:

-----. CI ICailetalleal

The MF504/MF505 Logic Probe is designed for quick servicingand checking of integrated logic systems. With its unique multi -lamp readouts, the logic probe visually displays the presence ofcorrect logic levels by illumination of colored readouts. Incorrectlogic levels are shown by the absence of colored readouts.

LOGIC PROBE MF504 MF505

Input Impedance: Minimum Detectable Pulse Width: Max. Input Frequency Displayed:

3 Megohms2Ons

30MHz

1 Megohms5ns

100MHz

PRICE $32.50 $37.50

LOGIC PULSER MF512 $38.50

Pulse Repetition Rate: 0.5pps/400 pps. Pulser: Normally high impedance ( 1 Meg ohms) output. Pulse Width in Pulser Mode: lOus typical Signal Delay from EXT SYNC to Output: 1.5us typical. Power Supply (Vcc): DC 5V 15V, 15mA 60mA

MAIL ORDER: Cheque, Money Order, VISA, Master Card plus$2.00 min. For Shipping & Handling. Ontario Residents add 7%P.S.T.

Dealer and Institution Discount Price Available

578 Marlee

5UkiiX iklE.Ave., To(onto, Ont. Canada

M6B 3J5, Tel: (416) 781-3263In U.S.A.: (214) 985-1842

06-217736 SUNIX TOR.TELEX:

8 Circle No. 29 on Reader Service Card Circle No. 30 on Reader Service Card

Electronics From The StartA new series for thecomplete beginner. Thismonth we look at thebasic theories and toolsof the trade.

By Keith BrindleyINTRODUCING THE START of ourbrand new series on electronics; mon-th -by -month we take you through all themajor principles and concepts you need toknow, in a fascinating and practical way.You'll find out about electronic com-ponents: what they are; what they do;how they're made and why this affectstheir operation. You'll see the laws andprinciples which govern electronic cir-cuits, right before your own eyes - not ina boring old text -book manner, but in anovel and interesting way, helping you toremember the things you need to know.You'll be able to build some of the circuitswe show you, too. We'll give you instruc-tions and details of how to do-it-yourself,so you'll have a permanent reminder ofwhat you learn.

Tools of the TradeThe first tool you need is a pair of cutters.There are many types but the most usefulsorts are side cutters. Generally speaking,buy a small pair - the larger ones are OKfor cutting thick wires but not for muchelse. In electronics most wires you want to

TANK OF WATER

SPECKS OF DUST AREEVENLY DISTRIBUTEDTHROUGHOUT WATER -10 SPECKS OF DUST

IN EVERY ad

WATER FLOWS THROUGHPIPE AND INTO BUCKET

BUCKET

Fig. 1. Water flowing in a pipe is like electricityin a wire.

Electronics Today June 1985

cut are thin, so the smaller the cutters, thebetter.

You can expect to pay from $5 to $25for a good quality pair, so look aroundand decide how much you want to spend.If you buy a small pair (as we recommend)don't use them for cutting thick wires, oryou'll find they don't last very long, andyou'll have wasted your money.

You can use side cutters for strippingthe insulation from wires, too, if you'recareful. But if you feel rich, a proper wirestripping tool makes the job much easier.There are many different types of wire

HEADER TANKOF WATER

ATO

WATER FLOW IS GREATERTHAN F4.1, AS WATERRESSURE IS GREATER

Fig. 2. A header tank's potential energy forcesthe water with a higher pressure.

strippers ranging in price from $3 to $40.Of course, if you don't mind paying largedentist's bills you can always use yourteeth - but don't say we said so.

A small pair of pliers is useful forlightly gripping components etc. Flat -nos-ed or, better still snipe nosed varieties arepreferable, costing between $5 to $25.Like side cutters, however, these are notmeant for heavy-duty engineering work.

The last essential tool we're going tolook at now, is a soldering iron. Solderingis the process used to connect electroniccomponents together, in a good perma-nent joint. We'll look at how to solder in afuture article, so don't worry about itnow. Soldering irons range in price from$5 to $30, but the price doesn't necessarilyreflect how useful they are in electronics.This is because irons used in electronics

generally should be of a low power rating.Power rating will be specified on the ironor its packaging and a useful iron will bearound 25 watts.

It is possible to get soldering ironsrated up to and over 100 watts, but theseare of no use to you - stick with an ironwith a power rating of no more than 25watts.

Ideas About ElectricityElectricity is a funny thing. Even thoughwe know how to use it, how to make itwork for us, to amplify, to switch, to con-trol, to create light or heat (you'll find outabout all of these aspects of electricityover the coming months of this series) wecan still only guess at what it is. It is ac-tually impossible to see electricity: we onlysee what it does!

The truth of the matter is that wemay only hypothesize about electricity.Fortunately, the hypothesis can be seen to

EVEN THOUGH BATTERY IS NOTCONNECTED TO THE BULB. ITSTILL HAS THE POTENTIAL ToLIGHT THE BULB

BULB IS NOT LIT UAS NO ELECTRONS FLOW

THIS LEAD IS NOT 'XINNECTEDTO BULP SO NO ELECTRONS CAN FLOW

Fig. 3a. A battery forces electrons around a cirsuit.

BATTERY GENERATES ELECTRONSAT ONE TERMINAL AND TAKES INELECTRONS AT THE OTHER TERMINAL

BULB LIGHTS UP AS ELECTRONSFLOW AROUND THE CIRCUIT

ELECTRONS FLOW AROUNDTHE CIRCUIT DUE TO POTENTIALDIFFERENCE OF BATTERY

Fig. 3b. Even when the battery is disconnectedand electrons don't flow, the battery still has apotential difference.

9

Themost

importantperipheral

you'lleveruse:

$19.95

SoftwareNow!

MagazineEach month Software Now! is cramm-ed with reviews, surveys and newsabout business, home and hacker pro-grams. If you buy only one softwarepackage a year, it is still valid becauseit can make sure that you buy the rightpackage. And because we are Cana-dian, we give Canadian sources andprices - we don't leave you with that"Yankee Magazine Frustration" feel-ing.

Available across Canada onnewsstands and in many computerstores for 52.95 a month, a lot less ifyou subscribe.

$19.95 a year (12 issues).$34.95 for two years (24 issues)Remember, you can get a refund on the unex-pired portion of a subscription at any time,for any reason or no reason.

Software Now!Subscriptions,

25 Overlea Blvd.,Suite 601,

Toronto, Ontario,M4H 1B1

Please see subscription card in this Issue.

Electronics from the Startstand in all of the aspects of electricity andelectronics we are likely to look at, so toall intents and purposes the hypothesis wehave is absolute. This means we can buildup ideas about electricity and be fairlysure they are correct.

With that out of the way, let's moveon to the first idea: that electricity is aflow of electrons. To put it another way,any flow of electrons is electricity. If wecan measure the electricity, we musttherefore be able to say how many elec-trons were in the flow. Think of ananalogy, say, the flow of water through apipe (Fig. 1). The water has an evenlydistributed number of foreign bodies in it.Let's say there are ten foreign bodies inevery cm' of water.

Now, if 1 litre of water pours out ofthe end of the pipe into the bucket shownin Fig. 1, we can calculate the number offoreign bodies which have flowed throughthe pipe. There are 1000 cm' of water in alitre, so:

10 x 1000 = 10000

foreign bodies must have flowed throughthe pipe.

Alternatively, by knowing thenumber of foreign bodies which haveflowed through the pipe, we may calculatethe volume of water. If, for example,25000 foreign bodies have flowed, then2.5 litres of water will be in the bucket.

ChargeIt's the same with electricity, except thatwe measure an amount of electricity notas a volume in litres, but as a charge incoulombs. The foreign bodies which makeup the charge are, of course, electrons.

There is a definite relationship bet-ween electrons and charge: in fact, thereare 6,250,000,000,000,000,000 electronsin one coulomb. But don't worry, it's nota number you have to remember - youdon't even have to think about electronsand coulombs because the concept of elec-tricity, as far as we're concerned, is notabout electron flow, or volumes of elec-trons, but about flow rate and flowpressure. And as you'll now see, electrici-ty flow rate and pressure are given theirown names which don't even refer to elec-trons or coulombs.

Going back to the water and pipeanalogy, flow rate would be measured as avolume of water which flowed throughthe pipe during a defined period of time,say 10 litres in one minute, 1000 litres inone hour or one litre in one second.

With electricity, flow rate ismeasured in a similar way, as a volumewhich flows past a point, during a definedperiod of time, except that volume is, ofcourse, in coulombs. So, we could saythat a flow rate of electricity is 10coulombs in one minute, 1000 coulombs

in one hour or one coulomb in one se-cond.

We could say that, but we don't! In-stead, in electricity, flow rate is called cur-rent (and given the symbol I, when drawnin a diagram). Electric current is measuredin amperes (shortened to amps, or evenfurther shortened to the unit A), whereone amp is defined as a quantity of onecoulomb passing a point in one second.Instead of saying 10 coulombs in oneminute we would therefore say:

10/60 coulombs per second = 0.166A

Similarly, instead of a flow rate of 1000coulombs in one hour, we say:

1000/3600 coulombs per second = 0.3A

The other important thing we need toknow about electricity is flow pressure.Back to our analogy with the water andthe pipe, Fig. 2 shows a header tank ofwater at a height, h, in metres, is the head.The effect of gravity pushes down thewater in the header tank, forming a flowpressure, forcing the water out of thepipe. It is the energy contained in thewater in the header tank due to its higherposition - its potential energy - whichdefines the water pressure.

With electricity the flow pressure isdefined by the difference in numbers ofelectrons between two points. We say thatthis is a potential difference, partlybecause the difference depends on thepositions of the points and how manyelectrons potentially exist. Another reasonfor the name potential difference comesfrom the early days in the pioneering ofelectricity, when the scientists of the daywere making the first batteries. Fig. 3ashows the basic operating principle of abattery, which simply generates electronsat one terminal and takes in electrons atthe other terminal. Fig. 3a also shows howthe electrons from the battery flowaround the circuit, lighting the bulb.

Under the conditions of Fig. 3b,however, nothing happens. This isbecause the two terminals aren't joinedand so electrons can't flow. (If you thinkabout it, they are joined by air, but air isan example of a material which doesn'tallow electrons to flow through it undernormal conditions. Air is an insulator oran non-conductor.) Nevertheless the bat-tery has the potential to light the bulb andso the difference in numbers of electronsbetween two points (terminals in the caseof the battery) is known as the potentialdifference.

A more usual name for the potentialdifference, though, is voltage. Cells arerated in volts (symbol: V) and so a cellhaving a voltage of 3V has a greaterpotential difference than a cell having avoltage of 2V. The higher the voltage, the

10 Electronics Today June 1985

harder the cell can force electrons arounda circuit. Voltage is simply a way of ex-pressing electric pushing power.

RelationshipsYou'd be right in thinking that there mustbe some form of relationship between thispushing power in volts and the rate ofelectron flow in amps. After all, thehigher the voltage, the more pushingpower the electrons have behind them andso the faster they should flow. The rela-tionship was first discovered by a scientistcalled Ohm, and so is commonly knownas Ohm's Law. It may be summarized bythe expression :

V/I = a constant

where the constant depends on thesubstance through which the current flowsand the voltage is applied across. Fig. 4gives an example of a substance which isconnected to a cell. The cell has a voltageof 2V, so the voltage applied across thesubstance is also 2V. The current throughthe substance is, in this case, 0.4A. Thismeans, from Ohm's law, that the constantfor the substance is:

2/0.4 = 5

The constant is commonly called thesubstance's resistance (because it is ameasure of the amount the substanceresists the flow of current through it) andis given the unit:Si(pronounced ohm). In

Ohm's LawA simple method to help youremember Ohm's law: remember atriangle, divided into three parts.Voltage (V) is at the top. Current (I)and resistance (R) are at the bottom. Itdoesn't matter which way around theR and I are - the important thing toremember is the V on top.

If you have any two of the con-stants, cover up the missing one withyour finger and the formula forcalculating the missing one will appear.

Say you know the voltage across aresistor and the current through it, butyou need to know the resistance itself.Simply cover the letter R with yourfinger:

and the formula to calculate the resis-tance is V/I.

Electronics Today June 1985

our example of Fig. 4, the resistance is5 S2. Different substances may have dif-ferent resistances and may thereforechange the current flowing.

This is a vitally important concept,probably the most important one in thewhole world of electronics, and yet isoften misunderstood. Even if it is notmisunderstood, it is often misinterpreted.Lets recap it and see what it all means:If a voltage (V in volts) is applied across aresistance (R in ohms), a current (I inamps) will flow. The voltage, current andresistance are related by expression (1) asV/I = R.

The importance of this is that the currentwhich flows depends entirely on the valuesof the resistance and the voltage. Thevalue of the current may be determinedsimply by rearranging expression 1, sothat it gives (2):

V/R = I

So, a voltage of say 10V, applied across aresistance of 20 ohms produces a currentof:

10/20 = 0.5A

Similarly, if we have a resistance, and acurrent is made to flow through it, then avoltage is produced across it. The value ofthe voltage may be determined by againrearranging expression (1), so that it nowgives (3):

V = IR

Thus, a current of IA flowing through aresistance of 5 ohms produces a voltage of1 x 5 = 5V across the resistance.

These three expressions are the mostcommon ones you'll meet in electronics,so look at 'em, read 'em, use 'em, andlearn 'em, inwardly digest 'em - justdon't forget 'em. Right? Right.

And another thing. See the way we'vesaid throughout, that a voltage is appliedor produced across a resistance. Similarlya current flows through a resistance. Justremember that a voltage is across: avoltage does not flow through. Likewise,a current flows through: it is not across.There is no such thing as a flow of voltagethrough a resistance, or a current across aresistance.

Electronic ComponentsThe fact that different resistances producedifferent currents if a voltage is appliedacross them, or produce different voltagesif a current is applied through them, is oneof the most useful facts in electronics.

In electronics, an amp of current is avery large quantity - usually we only usemuch smaller currents, say, a thousandth

or so of an amp. Sometimes we even usecurrents smaller than this, as little as amillionth of amp! Similarly, wesometimes need only small voltages, too.

Resistances are extremely useful inthese cases, because they can be used toreduce the current flow or the voltage pro-duce across them, due to the effects ofOhm's law. We'll look at ways and meansof doing this later on in the series. All weneed to know for now is that resistancesare used in electronics to control currentand voltage.

Table 1 shows how amps are relatedto the smaller values of current. Athousandth of an amp, for example, isknown as a milliamp (unit: mA). Amillionth of an amp is a microamp (unit:

CELLVOLTAGE

2V

CURRENT FLOWS AROUNDCIRCUIT AND THROUGHSUBSTANCE 10.4A)

SUBSTANCE. WHICH HASRESISTANCE GIVENBY OHM'S LAW.

024

Fig. 4. The cell's voltage is 2V, and a current of0.4A flows; the cubes resistance can becalculated by Ohm's law.

uA). Even smaller values of current arepossible: a thousand millionth is ananoamp (unit: nA); a million millionth isa picoamp (unit: pA). Chances are, youwill never use or even specify a currentvalue smaller than these, and you willrarely even use picoamps. Milliamps andmicroamps are quite commonly used.

It is easy to move from one currentvalue range to another, simply by movingthe decimal point one way or the other bythe correct multiple of three decimalplaces. In this way, a current of 0.01mA isthe same as a current of 10uA which is thesame as a current of 10000nA and so on.

Table 2 shows how volts are relatedto smaller values of voltage. Sometimes,however, large voltages exist (not so muchin electronics, but in power electricity)and so these have been included in thetable. The smaller values correspond tothose of current, that is, a thousandth of avolt is a millivolt (unit: mV), a millionthof a volt is a microvolt (unit: uV) and soon - although anything smaller than amillivolt is only rarely used.

Larger values of voltage are thekilovolt (unit: kV), that is, one thousandvolts, and the megavolt (unit: MV) whichis one million volts.

ResistorsThe components which are used asresistances are called, naturally, resistors.So that we can control current and voltagein specified ways, resistors are available in

11

Electronics from the Start

a number of values. Obviously, it wouldbe impractical to have resistors of everypossible value (152, 2Q, 3Q, etc.) becauseliterally hundreds of thousands - if notmillions would exist.

Instead, agreed ranges of values exist:and manufacturers make their resistors tohave those values, within a certaintolerance. Table 3 shows a typical range ofresistor values. This range is the mostcommon. You can see from it that largevalues of resistors are available, measuredin kilohms (thousands of ohms) and evenin megohms (millions of ohms).

Current elem.

TableMeaning

one Inousandth of an amprni,roamp one millionth of an ampnenoamp one thousand millanth of an ampPicoamp one millice millionth of ad amp

-,G one thousand million millionth of an amp

Valve100A10-1A10 -so

10-'A10-ItA10-tto

Symbol

uAnA

PAIA

Voltage name

r/I.Crovalnnovol,

Table 2Meaning

one moron voltsone thousand volts

one thousandth of a voltone millionth of a volt

one thousand millionth of a volt

Value104V

10e/10.1V10-4V10-e/

SymbolMV

kVV

mVtrV

nV

Table 31 0 100 1000 1k 10k 1000 1M 101A1 20 120 120 0 102 1200 1M2 -1 50 150 1500 105 150 150k180 len ,son 108 18k 1800220 220 2200 2k2 220 220k270 27n 2700 207 276 270k 20,330 330 330 0 303 330 330k 3M3390 390 3900 3k9 39k 3900 3M9470 470 470 0 4k7 470 470k 4M7560 560 5600 506 56k 560k 5M6680 680 6800 608 68k 6800 6M8820 920 820 0 602 82k 820k 8M2

Resistor tolerance is specified as aplus or minus percentage. A 10 ohm 10%resistor may have an actual resistancewithin the range between 9 and 11 ohms.

As well as being rated in value andtolerance, resistors are also rated by thepower they can safely dissipate as heat,without being damaged. As you'll wellremember from our earlier discussion onsoldering irons, power rating is expressedin watts, and this is true of resistor powerratings, too.

As the currents and voltages we use inelectronics are normally pretty small, theresistors we use also have small powerratings. Typical everyday resistors haveratings of 1/4W, 1/3W, 1/2W, 1W etc.On the other end of the scale, for use inpower electrical work, resistors areavailable with power ratings up to andover 100W or so. To be continued.

continued from page 7 For Your Information

MicroterminalThe Burr -Brown TM2000Microterminal can replace fragileCRTs in harsh industrial en-vironments. It features an 8 -bitmicroprocessor with RAM and

ROM, EPROM capability, a40 -character fluorescent displayand a 27 -key keypad. ContactAllan Crawford Associates,System Products Division, 5835Coopers Ave., Mississauga, Ont.L4Z 1Y2 (416) 890-2010.

The Technical Service Council,One St. Clair Ave. E., Toronto,says that job vacancies forengineers and other professionalsdecreased 8 percent in the last threemonths but changed little in thelast year. Of 99 specialists soughtby employers, only systemsanalysts, computer programmersand mechanical sales engineers

recorded more than 40 vacancies ina 1700 -firm survey. Electricaltechnologists rated only ten vacan-cies. Sigh. On the other hand, theCanadian Appliance Manufac-turers Association reports a stablebut moderate growth formicrowave ovens and air condi-tioners. All is not lost.

DigitizerThe HS-241-IE digitizer workswith personal computers over a 24by 36 inch area. It has 0.001 inchresolution, RS232 output,metric/imperial conversion, and

fixed or floating origin. It can runin five different modes and variousoptions are available. ContactGentian Electronics, PO Box 1240,Stittsville, Ont. KOA 3G0 (613)836-3987.

Mitsubishi Electric Corporation,jointly with Korakuen StadiumCo., recently started marketing the"Flying Cabin" amusementmachine that moves in syn-chronization with the image on ascreen inside the cabin.

A six axis hydraulic systemused for a flight simulator isemployed in the Flying Cabin forcomputer -controlled synchroniza-tion of the moves of the 44 -mancabin with the screen's crisp im-

ages and six channel sound.The Flying Cabin simulates

space travel: the cabin sways,careens and dives in line withchanging magnificent scenes ofground surfaces and deep spaceprojected on the huge 1.5m -by -4mscreen. The two companies hope tosell 20 of the $60,000 systemsmachine in Japan and 40 systemsabroad in the coming five years,chiefly to amusement parks, shop-ping centers and science museums.

12Electronics Today June 1985

Project

0 '

OP AMP .1

Ral

Fig. I The configuration of the Wien bridge used by the author; it has advantagesover the more common differential version.

Distortion MeterThe distortion meter isa useful piece of testequipment that canquickly give a circuit aclean bill of health (ornot). Here is the first oftwo parts on buildingyour own.

By John Linsley Hood

THE IDEAL power amplifier, along withother pieces of audio signal handling gearnot intended to modify the frequencyresponse of a system, is best described bythe old adage "a piece of wire with gain".This implies that the equipment does notmodify or impair the signal being handledexcept to amplify or add muscle power.

However, if this is the specification,how do we check to see how well or howbadly this requirement is being met? Thisis, alas something on which there is verylittle agreement between audio engineersor circuit designers. So, before we con-sider the hardware, we need to examinethe job we want it to do.

In simple terms, what we want is thatthe output from an amplifier should beidentical to the input, except that it mightbe bigger or smaller or perhaps one part ofthe frequency spectrum has been enlargedor diminished. This is an awkward bit, solet's leave that to one side for the momentand just look a the simple flat -frequencyresponse area.

When people first considered thisElectronics Today June 1985

problem, their thoughts turned to the ex-amination of a continuous, fixed -fre-quency sine wave somewhere in the mid-dle of the audible band, say at 1000Hz.The logic of this was that any distortion ofthis waveform would lead to the genera-tion of harmonics of the input signal, andthese could be isolated and measured.

The problem with this approach is..hat it is highly artificial. We simply donot listen for enjoyment to steady singletones. Nevertheless, the technique is auseful one, especially if the output fromthe distortion meter can be examined onan oscilloscope. Quite a lot of informa-tion about its defects can then be gained,allowing the affects of changes to beassessed.

The most common of this kind ofmeter is the simple notch filter which willremove the incoming sine wave and leaveonly the waveform impurities which havebeen added by the hardware which we aretesting.

The sort of result we would get at theoutput of the distortion meter is a smallwaveform which when added back to thedistorted output would give us the puresignal with which we started. Thewaveform of the distortion products maybe symmetrical about the zero axis, in-dicating distortion on both halves of thecycles, or it may be negative or positivespikes, indicating trouble on only one halfof the cycle (such as an amplifier clippingon only the negative cycle).

The most conspicuous audible effectof the presence of large amounts oflow -order distortion (mostly 2nd and 3rd)is that harmonic tones are added to thesignal, making the system sound rathershrill. Those of us with long memories willrecall the sound of output pentode powertubes, which caused generous quantitiesof 3rd order distortion. Triodes were

much preferred since they generated most-ly 2nd harmonic distortion, and this waslower down in the spectrum and soundedless "squawky".

Also, as one might guess, theselow -order harmonics do in fact har-monize with the input signal; once onegets beyond the 3rd in the odd -orders orthe 6th in the evens, the tones become in-creasingly dissonant and objectionable tothe listener.

This was one of the reasons why thefirst transistor amplifiers were so muchworse than the tubes they replaced, evenat 0.1 percent distortion; the distortionproducts were 7th, 9th, 11th and otherdissonant odd harmonics.

A way of measuring distortiondistinct from the notch method is to put ina high -purity sine wave and then displaythe output of the amplifier as a sweep ofthe frequency response on a spectrumanalyzer. The various harmonic productswill be displayed on a vertical log scale,either on a paper printout or a videoscreen. While the display is very effective,it's a bit hard to read if the distortion isdown around 0.01 percent, not to mentionthe cost of the equipment required.

NotchingThe Total Harmonic Distortion meter inthis project is the Wien bridge notch type;it produces a sharp notch in the frequencyresponse which removes the fundamentalof the test tone being used. Anything leftover should consist of distortion productsplus hum and noise. The noise can be sub-tracted by disconnecting the signal source;we'll come back to applications in the se-cond part of the article.

The basic layout of the meter isshown in Fig. 1 and the circuit diagram inFig. 2. The total circuit consists of themeter, a millivoltmeter, a built-in

13

Distortion Meter

SitTHO METER

INPUT

C1470n

VE

11;101

IC la

16V

-VE

RI12k

RV2a10L

cs47n

RS4708

RV310OR

C4470n 204001,

301........1)142 s VW*

40kIls

407

319

1470nOV

C20T470..

IbV

RIOMe

RIke

OV

C2ba0

R3 R4 RV4eke 1011 252

VE 1C3

ReSeOR

C7470n

3040014.

100%

10%

W, 45,F 3.31___L.L.h.

AVID3k 40101:

3% v 9/121. Co1% %- 4n7

02%

147R

OV

CIO47u

RV2b105

VE

3

1C2.

2

172V

RS2208

NOTE1C12.3 TL072

SPI3

C1347n

R13

S

Cl.3n3

CIS R14Urn 257OV

VE

ICU

VE

9/14

R1S252

CIS .1.33n T

OV

R le252

CIS1n0

R17310 VE

C17.11.4700

7

R IS252

"VW

-VE

R1021113

R20elM

R21233/I

RIIMO

R2310111

0.2%

1%

um r"

100%

9R2b

SCOPE,9) OUTPUT

SK2

UTFSD

° MOE rEVR

Fig. 2 The final circuit diagram of THD meter.

oscillator, and a regulated power supply.There is also a converter for running theunit from a single battery.

The Meter BridgeIn Fig. 2, RV1 acts as a gain control in theinput circuit of ICla, a buffer stage thatensures that the Wien network is alwaysdriven from a low impedance. From theoutput of this the signal is divided intothree paths, the upper RC parallel net-work, the inverter stage, and a feed to themode switch SW2, which allows the net-work to be bypassed for setting the fullscale meter reading.

In the other positions of SW2, thetwo halves of the network are connectedto produce the notch characteristic re-quired. For a perfect balance to be obtain-ed, the input from the inverter to thelower section needs to be exactly twice aslarge as the input to the upper. To arrangethis, a 2K2 10 -turn pot, RV4, is connectedin series with the op -amp feedbackresistor so that its gain can be adjusted.This is the Trim control on the frontpanel.

Ideally, the tuning of this instrumentwould be done by dual gang pots, Ra andRb. However, I wanted to keep circuit im-14

pedances as low as possible for minimumhum pickup and circuit noise, and 1K dualpots are hard to come by. I havetherefore, with regret, because it makesthe instrument a little more difficult touse, opted for a single fine-tune pot, the100 ohm RV3. This means that notchingout requires the interaction of RV3 andRV4. If a decent quality low resistancedual pot is available, the other half shouldbe inserted in series with R6, whose valuecan then be reduced to 470 ohms.

It is necessary to sharpen up thenotch a bit to prevent unwanted attenua-tion of the lower harmonics, and this isdone by negative feedback to ICI fromIC2 through R9, R2, and R8.

There are two signal infiltrationstages. IC3a is a highpass hum filter with aturnover frequency of 250Hz and a slopeof 18dB/octave; a similar lowpass builtaround IC3b has a similar slope and a tur-nover frequency of 4700Hz. These twooptions are selected by SW3 and SW4.The lowpass HF-noise filter allows an in-strumental identification of the harmonicsassociated with crossover distortion,which with a 1KHz signal would be at 7, 9,11, and 13KHz.

So, if the minimum signal is noted on

a test at 1KHz and the lowpass filter isthen switched in and the new minimumnoted, the amount of high -order har-monics present can be determined by anRMS subtraction of the two values. Todistinguish between high -order harmonicsand general noise, the extent to which thedifference between the filtered and un-filtered signal levels changes when thesignal input is removed can be noted.

The final stage of the distortionmeter part of the circuit is the bufferamplifier, which precedes the meter at-tenuator, and from which an oscilloscopemonitor signal can be obtained if needed.

An option included is the 50KHz,12dB/oct, unity -gain rolloff buffer IC2b,which serves as a useful bandwidth limit.If this is not required, the output of SW4can be sent to the non -inverting input ofIC2b and C17, C18, R16, and R17deleted.

The MillivoltmeterSince any distortion meter requires an ACmillivoltmeter to display its result, and themillivoltmeter is a useful bench instru-ment, I have decided to make the input tothe measuring circuit available separatelyby way of a switched attenuator, Fig. 3.

Electronics Today June 1985

The circuit is straightforward, with a100uA meter in a diode bridge in the feed-back network of an op -amp. I have used adual FET amp (TL072 or LF353) in whichthe first half acts as a gain stage. Thisallows both high input impedance and a20Hz-100KHz -3dB bandwidth.

The input attenuator has a resistanceof 100K ohms; this can be scaled up to 1Mif the constructor takes care to shield it toprevent pickup from other parts of the cir-cuit. Calculating the actual resistors iseasily done by using the current flowdown the chain. For instance, 100V across100k gives a current of 1 mA. This willdevelop l0mV across 10 ohms, and hencethe value of R32, and so on. Odd resistorvalues can be made up by paralleling stan-dard values, depending on the accuracyrequired. For instance, a 6k66 resistor canbe made up by putting a 330k and a 6k8 inparallel.

The proper operation of this type ofcircuit depends on a low impedance fromthe non -inverting input to ground, so thetantalum beads are bypassed with smallnon-polarzied types (C22 and C24). Thesupply lines are also bypassed to groundwith 0.47uF capacitors.

The OscillatorIt's a great convenience to have anoscillator actually on the instrument, andfrom my experience I find that one doesnot need a continuous spread of frequen-cies, but rather a few spot points. Thereason for this is that if you know how asystem behaves at, say, 1KHz or 3Khz, itsbehaviour at 1500Hz or 3500Hz is unlikelyto be anything but intermediate betweenthe known points.

The basic circuit used is the Wienbridge system. The inverting input is fedwith two feedback signals through the sec-tions of the Wien network. A positivefeedback signal is obtained from the twoinverting amplifiers connected in seriesthrough the RC element, and the negativefeedback signal is fed to the same pointfrom the output of the invertingamplifier.

The gain of the second amplifier iscontrolled by a thermistor in the feedbackpath. When the thermistor is cold, itsresistance is high and ICb has a high gain.This makes the positive feedback largerthan the negative and the systemoscillates. The output signal warms thethermistor, lowers its resistance, and in-creases the negative feedback to lower thegain to just enough to keep the circuitoscillating at a constant amplitude.

Because op amps have a lower distor-tion in the non -inverting mode (surprisingbut true), and because the circuit has nocommon -mode signal which the op -ampmust cancel, the distortion produced bythis circuit is extremely low. Table 1 showsthe distortion performance of theoscillator. The high distortion a low fre-quencies is mostly third harmonic, causedby the thermistor resistance actually vary-ing with the waveform amplitude. This isinherent in amplitude -stabilized systems.

The output from ICb is about600-700mV with an RA53, and the signallevel at the output of ICa is about halfthis. I mention this because ICa is an in-tegrator with a response which decreaseswith frequency, reducing the third har-monic distortion to about one-third atICa, making a very low distortion

SK3,..-, MILLIVOLTMETER FROMI) INPUT 0 THD

METER_l_ C21

470,,

R2466k6

1OrnV

R2523k3

30mV

100mV

R26

V

3V

R272k33

1V

R28666R

R29233R

101/

R3066R6

30V

R3123R

10011

R32lOR

OV

S1N6

I

WE

IC4a

-VE

R332k7

C22 I- It C23100n

17"

R3468k

6

NOTE:IC4 TL072

sVE

RV52k7

C24 + C25470n

T 47"

Fig. 3 The circuit diagram of the milli voltmeter.Electronics Today June 1985

oscillator indeed. However, for a THDmeter with a minimum reading of .005percent, the circuit shown is adequate.

The final circuit is shown in Fig. 5.The value of C is constant and R is chang-ed to alter the frequency; this allows theuse of easily -obtained resistors and onlytwo close -tolerance polystyrenecapacitors.

A three -stage output attenuator is us-ed in combination with the output poten-tiometer to give output signal levels of0-6mV, 0-60mV and 0-600mV. The out-put can be increased to about one volt byputting a resistor of 500 ohms and 1k5ohms in series with RA53. This will lowerthe distortion slightly, but will increase thesettling time. On the prototype this is 2000cycles, about 20 seconds at 100 Hz, butthis will vary from one thermistor toanother.

Fig. 4 The basic arrangement used in the spotfrequency oscillator.

Power SupplyThe total current consumption of the in-strument is 18mA at plus and minus 15volts, which is obtained from a smallstabilized supply.

It is possible to make the instrumentoperate from batteries. Two options exist.The first is use a pair of 6V or 9V bat-teries, such as the popular 9V radio bat-tery, and switch both supply rails. The se-cond is to use a single 9V battery and usethe adapter shown to give plus and minus4V5. In both cases it is worthwhilesubstituting TL062s for ICI, IC2, IC3,and IC5, and a TL061 for IC4. Thisreduces current consumption to 1.5 to2mA with little performance penalty.

FREQUENCY (Hz) THD (%)100 0.02300 0.0051k3k10k20k

less than 0.003less than 0.003less than 0.003less than 0.003

Table I Measured performance of the spotfrequency oscillator.

continued on page 48 15

S

ConfigurationsThis month, a look at -opto-electronics.

By Ian Sinclair

OPTO-ELECTRONICS is a word thathadn't been thought of a few years ago,but which is now used to describe a set ofdevices that are important enough tomerit a part of this series all to themselves.An opto-electronics device is one whichmakes use of light as part of its electronicfunction, so this label includes all varietiesof devices that convert light signals intoelectrical signals or the other way around.

The simplest opto-electronic devicesof the electricity -to -light type are thefamiliar LEDs. Familiar they may be, buteven experienced engineers are not alwaysaware of their eccentricities. Like anyother diode the LED has an anode and acathode, and passes current in the for-ward bias direction; this is when the lightis emitted. What is not nearly so wellknown is that the peak reverse voltage ofthese diodes is very low; if you get an LEDthe wrong way round in a circuit, it'susually curtains for the LED when thevoltage is switched on. A typical value ofpeak reverse voltage is 3V, so practicallyany circuit that will operate the LED whenit is connected the right way round (Fig. 1)will blow it up if it happens to be thewrong way round.

In addition, the forward voltageacross the LED is very much higher thanthe OV6 that we merrily assume for asilicon diode. For gallium arsenide, thematerial used for many types of LEDs,the forward voltage is more like 2V1 to2V4, so that LEDs are of little use in verylow -voltage circuit - they won't, for ex-ample, work from a 1V5 cell.

Current AffairsOne of the major snags about LEDs

is that they consume a surprising amountof current. Manufacturers quote 'ade-quate' light output for red LEDs with 5 to16

+5.15V

22010-150

1E01

Fig. I The basic LED operating circuit. Acurrent -limiting resistor must always be usedunless the output resistance of the driving cir-cuit is high.

25mA, and for the green/yellow varietieswith 10 to 40 mA. This wouldn't be miss-ed in a circuit operating at 5 V, 2.5 amps,but it can be quite a drain on batteryequipment, often considerably more thanall the CMOS ICs in a circuit intended forbattery operation.

LEDs can be used with AC suppliesproviding there is a diode connected inreverse across each LED (to prevent ex-cessive reverse voltage) as well as the usual

Fig. 2 LED operation. (a) For use with AC, asilicon diode must be connected across theLED terminals as shown. (b) The two-colourLED uses two LED junctions connected in op-posite direction. (c) The tri-colour LED usesseparate LEDs with a common cathode con-nection.

current limiting resistor (Fig. 2a). Bi-colour LEDs consist of a package of twoLEDs in one casing, connected in inverseparallel so that current in one directionwill give a light of one colour, while theother colour is achieved by reversing thecurrent (Fig. 2b). In this circuit, one LEDprotects the other against reverse voltage.Tri-colour indicators (Fig. 2c) use twodiodes with a common cathode connec-tion and separate anode leads, so thatthree colours can be indicated, one in eachlead, plus yellow when both LED sectionsare activated. Personally, for indicatingwhen power is on, I much prefer the old-fashioned neon.

On DisplayWhen it comes to digit displays, LEDtypes have quite a lot of competition. Thetraditional seven -segment display (Fig. 3)comes as a common anode or a common -cathode type (Fig. 4), and each type needsa separate limiting resistor in each driverlead. The normal method of use is to con -

No SEGMENTS LIT

0 abcdef1

2 ab de- g3 abcd g

4 bc. ef g5 a, ccl.. 1.0.

6 a cdef g7 abc8 abcdef g9 abc- -

d

Fig. 3 Layout of the seven -segment display,with segment guide. An eighth segment, thedecimal point, is often added.

nect the display to a decoder chip such asthe 7448 or 7447, which in turn takes thedigital information in as BCD signals -four bits per digit. The snag again is thecurrent consumption, 10-20 mA per seg-ment, which means that displaying afigure '8' uses 7 x 20 mA - 140 mA justto display one digit! While mains -poweredequipment isn't too upset by this size ofcurrent, the LED seven -segment displaydid not last very long in battery -powereddevices, even when multiplexing was used.

Electronics Today June 1985

Multiplexing means that only one digit ata time is activated, the digits being switch-ed on in sequence fast enough to presentthe appearance of all the digits being il-luminated at once.

Oddly enough, the forward voltagefor the segments of an LED seven -segment display tends to be lower than fordiodes, around 1V3 to 1V7. At tempera-tures above about 25 °C, the maximumcurrent has to be reduced by 0.3 mA perdegree to avoid over -dissipation of thejunction in each segment.

One competitive display that seems tobe much less well-known is the filamentseven -segment display. This can use as lit-tle as 5 mA per segment, and looks sur-prisingly bright - it can be driven by a

ANODES

a b c de

r i1 1

i1

1 1

1 1

L J

CATHODE

ANON.

-

L

CATHODESCATHODES

Fig. 4 Internal connections for common anodeand common cathode displays. Whichever typeis used, there must be a separate limitingresistor for each segment.

decoder directly with no limiting resistors,and for many purposes is superior to LEDdisplays. The usual reason for preferringsolid-state displays is long life, but thequoted life of more than 100,000 hoursfor the filament type of display is prettycompetitive and some LED displays arenotorious for short life.

Oldies But GoodiesThe two older types of displays which arealso worth considering are the electron -beam type and the gas -discharge type. Theelectron beam display uses a miniaturecathode wire to emit electrons, which willthen be attracted to any positive anode.The anodes are coated with phosphors(similar to the phosphors used in cathoderay tubes), and any anode which ispositive to the cathode by a sufficientElectronics Today June 1985

DISPLAY FRED. OUT

BCDINPUTS

DISPLAY FRED. IN

DRIVEPULSES

IN

BCDVOLTAGES

IN

b

1.5V

oV

-5VEGMENT ON

V

7 -SEGMENTOUTPUTS

+-5VIVDDI

COMMONDRIVEPULSE

SEGMENTS

-5v(vEE)

SEGMENT OFF SEGMENT ON

Fig. 5 Driving LCD displays. The common leadbe returned to the driver IC. The waveform (b)

voltage will glow. A 24-40 V supply isneeded, which usually means the use of aninverter when low -voltage batteries are us-ed, as in calculators. The display easy toread, and uses less current than the LEDtype - I still prefer a calculator using thistype of display to one using the more -common LCD display.

The gas -discharge display is an oldertype which uses the principle of the neonlight - ionisation of a low-pressure gas inan electric field. Like all gas -discharge,this needs a high operating voltage,around 150-250 V, but the operating cur-rent is very low: only 0.7 mA per segmentin a typical application. The display isvery bright, and is worth considering for120 operated equipment whose displayhas to be viewed under difficult illumina-tion conditions, such as alternatebrightness and darkness. A driver IC isavailable nowadays - in times past (darewe say the Dark Ages?), the major handi-

of the LCD display must not be earthed; it has toapplied is AC with no trace of DC.

cap of using this type of display was thelack of suitable driver transistors.

Liquid LightLast among the displays, of course, thereis the LCD. A good LCD can give a denseblack indication against a light greybackground, is clearly visible in brightlight, and reasonably visible even in low il-lumination conditions. There's a lot ofvariation between displays, however, evenfrom the same manufacturer and some arepoor, with low contrast and very slowresponse to changing digits. Prices alsovary considerably - one catalogue liststhe price of a calculator -size display as be-ing twice as much as I would have to payfor a complete calculator using a similardisplay!

Operating conditions for thesedisplays are very different from those ofther types of displays, because they haveto be operated from high -frequency AC

17

Configurations

supplies. For this reason, display eithercome with all the necessary circuitry forgenerating their driver pulses built in, orthey can be used with a standard chip in-tended for this purpose. It's particularlyimportant not to apply DC to thesegments of an LCD display, because thiscan kill the display very rapidly.

On The Receiving EndMoving to the other end of the opto-electronics business, we find the photo-cells. Vacuum photocells and photomulti-pliers are rather specialised, and we'll onlytouch briefly on these types. They rely onphotocathodes, surfaces which emit elec-trons into a vacuum when they are stuckby light. The anode which collects theelectrons (Fig. 6) must be at a fairly highvoltage (100-500 V), and the currents aresmall: microamps rather than milliamps.P,hotomultipliers obtain greater sensitivity

111 DY NOD: I. 100V

3rd DYNODE 1.30001 -Ow

YO'r DYNODE I .500V1

6111 DYNODE -10.RE I L ECT0.11400V1

PINS FOR CONNECTION

GI ASS riINDOW

PHOTOCATRODEI,M1

2nd DYNODE 1.200,

4)5 DYNODE 140001

- ANODE 1100V1

Fig. 6 The vacuum photocell, and a typical cir- Fig. 7 Cross-section of a photomultiplier, usedcuit arrangement. for detection of very low light levels.

and increased output by using secondarymultiplication, meaning that the elctronsfrom the cathode (Fig. 7) are acceleratedto surfaces, called dynodes, which willrelease elctrons each time an electronstrikes the surface. If each of thesemultipliers releases two to five electronsfor each striking electron, spectacular gaincan be achieved which, unlike amplifica-tion of signals by conventional methods,is practically noise -free.

The more familiar solid-state light -to -electrical -signal devices that we use are thesolid-state photodetectors, of which themost commonly used is the cadmium sul-phide cell. The ORP 12 is the standarddevice of this type, often called an LDR(light dependent resistor). The cell con-sists of a strip of cadmium sulphide whoseresitance decreases as light falls on it. Theresistance in the dark is high, up to 10M,and the resistance can fall as low as 100Rin bright sunlight. A less well-knownaspect of these cells is that they can with-stand a fairly high voltage, around 100 V;subject to their dissipation limit of 200mW, meaning that you might need alimiting resistor connected in series. Thecadmium sulphide cell is a slow -actingdevice, needing about 350 mS for theresistance to fall on exposure to light, andaround 75 mS for the resistance to rise

NEXTMONTHIN

ElectronicsToday

Dual Tracking PowerSupply ProjectA professional lab -quality powersupply for upgrading your testbench.

RS232 Project For The 64Commodore 64 and VIC-20 owners caneasily add an RS232 serial port for com-municating with peripherals.

NAPLPS For MicrosTelecommunications graphics for per-sonal computers is explained.

For Advertising Information call (416) 423-3262For Subscription Information call (416) 423-3263

18 Electronics Today June 1985

Fig. 8 The photoresistive cell or light -dependent resistor (LDR)

again when the light is shut off. Theresponse to different colours is generallysimilar to that of the human eye, but thecadmium sulphide is much more sensitiveto red and infrared, which is why its use incameras is now less common than it wassome 10 years ago.

Fun With PhotodiodesOther light detectors need some degree ofamplification. Photodiodes are diodes offairly conventional construction, with atransparent window over the junction,which is used reverse -biased. For such adiode, the reverse leakage current in-creases as the intensity of light on thejunction is increased. This current is

small, ranging from around 1 nA in

darkness to almost 1 mA in very brightlight, so that amplification is usuallynecessary, as in the circuit of Fig. 9. Theresponse time is about 250 nS, so that theop -amps shown in Fig. 9 would have to bereplaced by a transistor circuit, usinghigh-speed switching tansistors, if youwanted to use the photodiode for high-speed signals. Combined photodiode/op-amp packages can be bought for medium -speed applications.

Th old-style phototransistor, whichwas a transistor formed with a windowabove the base -collector junction, is athing of the past; what is now called aphototransistor is a combination of siliconphotodiode and transistor in one package.This combines a sensitivity that is muchgreater than that of a photodiode alonewith a good fast response time, givingtypically a 2 MHz bandwidth. This is par-ticularly useful for receiver use in light -beam transmission systems.

Finally the opto-isolators, which con-sist of a combination of LED andphototransistor is a single package. Thesecomponents are embedded in clear plastic,which allows light transmission but whichis a good electrical insulator. It's easy toachieve isolation to at least 4 kV, withreasonable signal transmission. For an or-dinary isolator the output signal will be

Fig. 9 Using a photodiode in conjunction withFET op -amp. The FET type is needed becauseof the very high impedance of the photodiodecircuit.

about 20 per cent of the amplitude of theinput, but when a Darlington phototran-sistor is used, the output can be threetimes or more the amplitude of the input.It's just the device I was looking for 25years ago when I wanted to modulate thegrid of a cathode-ray tube which wasworking at -4 kV!

This Month inS

Now!oftware

Sloth For The Z80Build a small Z80 -based computer.

Walking Fingers For the PCA directory sort similar to CPM's D.COM.

PROM Night For The AppleA Z80 assembler program to run an EPROM burner.

Tandy 200 ReviewA look at Tandy's upgrade of the popular Model

Apple Assembly AnimationHi -Res shape handling for the Apple.

PlusMore reviews, articles and listings.

100.

Microcomputer Training SeminarsTalking with some seminar organizers and sitting in onclasses to give you an idea of what to expect from your money.

ExecuvisionA review of Prentice -Hall's cut and paste graphics package.

GEM Desktop and GEM DrawA preview of the first GEM (Graphics Environment Manager)applications from Digital Research.

Mind ProberA spooky piece of software that lets you analyze otherpeople's personalities. Skeptical? I knew it!

PlusMore reviews, news and features for Canadian micro users.

For Subscription Information call (416) 423-3262.

Electronics Today June 1985 19

BABANI BOOKSImported from England and exclusivelyavailable in Canada from MoorsheadPublications.B PS3: PRACTICAL ELECTRONICS CALCULATIONS ANDFORMULAE $11.75A book that bridges the gap between complicated technicaltheory and the 'cut and try. method. A good reference book

B P136: 25 SIMPLE INDOOR AND WINDOWAERIALS $6.65People living in apartments who would like to improve short-wave listening can benefit from these instructions on op-timising the indoor aerial.

B P147: AN INTRODUCTION TO 6502 MACHINECODE $7.75The popular 6502 microprocessor is used in many home cornputers; this is a guide to beginning assembly language.

B P150: AN INTRO. TO PROGRAMMING THESINCLAIR QL $7.75Helps the reader make the best use of the Sinclair QC,almost unlimited range of features. Complements themanufacturer's handbook.

B P225: A PRACTICAL INTRODUCTION TODIGITAL ICs $6.65This book deals mainly with TTL type chips such as the 7400series. Simple projects and a complete practical constructionof a Logic Test Circuit Set are included as well as details for amore complicated Digital Counter Timer project.

B P130: MICRO INTERFACING CIRUITS -B OOK 1 $8.55Aimed at those who have some previous knowledge of elec-tronics, but not necessarily an extensive one, the basis of thebook is to help the individual understand the principles of in-terfacing circuits to microprocessor equipment.

B P131: MICRO INTERFACING CIRCUITS -BOOK 2 $8.55Intended to carry on from Book 1, this book deals with prac-tical applications beyond the parallel and serial interface"Real world" interfacing such as sound and speechgenerators, temperature and optical sensors, and motor con-trols are discussed using practical circuit descriptions.

BP111: AUDIO $13.25This one is ideal for readers who want to really get intosound. A wide range of material is covered from analysis ofthe sound wave, mechanisms of hearing, room acoustics,microphones and loudspeakers, amplifiers, and magneticdisc recording.

B P82: ELECTRONIC PROJECTS USING SOLAR CELLS $7.75A collection of simple circuits which have applications inand around the home using the energy of the sun to powerthem. The book deals with practical solar power supplies in-cluding voltage doubler and triplet circuits, as well as anumber of projects.

BP156: AN INTRODUCTION TO QL MACHINE CODE$7.75

The powerful Sinclair QL microcomputer has some outstand-ing capabilities in terms of its internal structure. With a 32 -bitarchitecture, the QL has a large address range, advanced in-structions which include multiplication and division. Thesefeatures give the budding machine code programmer a goodstart at advanced programming methods. This book assumesno previous knowledge of either the 68008 or machine codeprogramming.

BP47: MOBILE DISCOTHEQUE HANDBOOK $5.25Divided into six parts, this book covers such areas of mobile"disco" as, Basic Electricity, Audio, Ancillary Equipment,Cables and Plugs, Loudspeakers, and Lighting. All the infor-mation has been considerably sub -divided for quick and easyreference.

BP59: SECOND BOOK OF CMOS IC PROJECTS $7.75This book carries on from its predecessor and provides a fur-ther selection of useful circuits, mainly of a simple nature.the book will be well within the capabilities of the beginnerand more advanced constructor.

B P32: HOW TO BUILD YOUR OWN METAL &TREASURE LOCATORS $7.75Several fascinating applications with complete electronicand practical details on the simple, and inexpensive con-struction of Heterodyne Metal Locators.

andiocootrciArsgeginnefr

ELECTRONIC THEORYELEMENTS OF ELECTRONICS - AN ON -GOING SERIESF.A. WILSON, C.G.I.A., C.Eng.,B P62: BOOK 1. The Simple Electronic Circuit

and Components $11.70B P63: BOOK 2. Alternating CurrentTheory $ 8.55

B P64: BOOK 3. SemiconductorTechnology $18.55

1P77: BOOK 4. Microprocessing Systems $11.70And CircuitsB PB9: BOOK 5. Communication $11.70The aim of this series of books can be stated quite simply -it is to provide an inexpensive introduction to modern elec-tronics so that the reader will start on the right road bythoroughly understanding the fundamental principles involv-ed

Although written especially for readers with no morethan ordinary arithmetical skills, the use of mathematics isnot avoided. and all the mathematics required is taught asthe reader progresses

Each book is a complete treatise of a particular branchof the subject and, therefore, can be used on its own with oneproviso. that the later books do not duplicate material fromtheir predecessors, thus a working knowledge of the subjectscovered by the earlier books is assumed.

BOOK 1 This book contains all the fundamental theorynecessary to lead to a full understanding of the simple elec-tronic circuit and its main components.

BOOK 2 This book continues with alternating currenttheory without which there can be no comprehension ofspeech, music, radio. television or even the electricityutilities

BOOK 3 Follows on semiconductor technology.leading up to transistors and integrated circuits.

BOOK 4. A complete description of the internal work-ings of microprocessor

BOOK 5 A book covering the whole communicationscene

PROJECTS

B P48 ELECTRONIC PROJECTS FOR BEGINNERS $ 7,75F.G. RAVER, T.Eng.(CEI), AseocIEREAnother book written by the very experienced author - Mr.F G Rayer - and in it the newcomer to electronics, will finda wide range of easily made protects. Also, there are a con-siderable number of actual component and wiring layouts, toaid the beginner

Furthermore, a number of protects have been arrangedso that they can be constructed without any need for solder-ing and. thus, avoid the need for a soldering iron.

Also, many of the later projects can be built along thelines as those in the 'No Soldering' section so this may con-siderably increase the scope of projects which the newcomercan build and use.

11P37: SO PROJECTS USING RELAYS,SCR's& TRIACS $7.75F.G.RAYER, T.Ing.(CE1),Assoc.IERERelays, silicon controlled rectifiers (SCR's) and bi-directionaltriodes (TRIACs) have a wide range of applications in elec-tronics today This book gives tried and practical working cir-cuits which should present the minimum of difficulty for theenthusiast to construct In most of the circuits there is a widelatitude in component values and types, allowing easymodification of circuits or ready adaptation of them to in-dividual needs

PracticalElectronicsCalculations andFormulae

u)1S,

IL>4tNeS

' w

4.1vo`

...- 1

\

RPM: 28 TESTED TRANSISTOR PROJECTSR.TORRENS $5.00Mr Richard Torrens is a well experienced electronicsdevelopment engineer and has designed, developed, builtand tested the many useful and interesting circuits includedin this book The protects themselves can be split down intosimpler building blocks, which are shown separated by boxesin the circuits for ease of description, and also to enable anyreader who wishes to combine boxes from different projectsto realise ideas of his own

B P71: ELECTRONIC HOUSEHOLD PROJECTSR. A. PENFOLDSome of the most useful and popular electronic constructionprojects are those that can be used in or around the homeThe circuits range from such things as '2 Tone Door Buzzer'.Intercom, through Smoke or Gas Detectors to Baby andFreezer Alarms

$7.20

11P73. REMOTE CONTROL PROJECTS $8.10OWEN BISHOPThis book is aimed primarily at the rte.( Ironic, enthusiastwho wishes to experiment with remote control Full explanaIons have been given so that the reader can fully understandhow the cite utts work and t an more easily see how to modifythem for other purposes, depending on personal re['sidemen's Not only are radio control systems consideredbut also infra -red, visible light and ultrasonic systems as arethe use of Logic ICs and Pulse position modulation etc

B P90: AUDIO PROJECTS $7.60F.G. RAVERCovers in detail the «mstrut lion of a wide range of audioprole( ts The text has been divided into preamplifiers andmixers, power amplifiers, tone controls Ind matching andmiscellaneous protects

BP74: ELECTRONIC MUSIC PROJECTS $7.20R.A. PENFOLDAlthough one of the more recent branches of amateur ONtronics. electronic music has now become extremely popularand there are many protects which fall into this category Thepurpose of this book is to provide the constructor with anumber of practical circuits for the less complex items 01electronic music equipment. Including such things as a FuzzBox. Waa-Waa Pedal. Sustain Unit. Reverberation andPhaser-Units, Tremelo Generator etc

BP44: IC SSS PROJECTS $ 7.75E.A. PARR, B.Sc.,C.Ing., M.I.E.E.Every so of ten a device appears that is so useful that onewonders how life went on before without it. The 555 timer ussuch a device Included in this book are Basic and GeneralCircuits. Motor Car and Model Railway Circuits, Alarms andNoise Makers as well as a section on the 556, 558 and 559timers

B P82: ELECTRONIC PROJECTS USING SOLAR CELLS$7.75

A book of simple circuits which have applications in andaround the home and that are designed to be powered by theenergy of the sun. Although, if the reader wishes, they couldbe powered by ordinary button cells or batteries.

20 SOO order form in this issue. Electronics Today June 1985

BABANI BOOKSBP49: POPULAR ELECTRONIC PROJECTS $ 7.75R.A. PENFOLDIncludes a collection of the most pop Aar types of circuitsand projects which, we feel sure, will provide a number ofdesigns to interest most electronics constructors. The pro-jects selected cover a very wide range and are divided intofour basic types: Radio Projects. Audio Projects, HouseholdProjects and Test Equipment.

BP94: ELECTRONIC PROJECTS FOR CARS AND BOATSR.A. PENFOLD $7.60Projects, fifteen in all, which use a 12V supply are the basisof this book. Included are projects on Windscreen WiperControl, Courtesy Light Delay, Battery Monitor, CassettePower Supply, Lights Timer, Vehicle Immobiliser, Gas andSmoke Alarm, Depth Warning and Shaver Inverter.

B P95: MODEL RAILWAY PROJECTS $7.60Electronic projects for model railways are fairly recent andhave made possible an amazing degree of realism. The pro-jects covered include controllers, signals and sound effects:striboard layouts are provided for each project.

8P93: ELECTRONIC TIMER PROJECTS $7.60E.G. RAYERWindscreen wiper delay, darkroom timer and metronomeprojects are included. Some of the more complex circuits aremade up from simpler sub -circuits which are dealt with in-dividually.

BP113: 30 Solderless Breadboard ProjectsBook 2R.A. Penfold $8.85A companion to BP107. Describes a variety of projects thatcan be built on plug-in breadboards using CMOS logic IC's.Each project contains a schematic, parts list and operationalnotes.

B P104: Electronic Science ProjectsOwen Bishop $8.85Contains 12 electronic projects with a strong scientificflavour. Includes Simple Colour Temperature Meter, Infra -Red Laser, Electronic clock regulated by a resonating spring,a 'Scope with a solid state display, pH meter and electro-cardiograph.

B P110: HOW TO GET YOUR ELECTRONIC PROJECTSWORKING $7.60R.A. PENFOLDWe have all built circuits from magazines and books only tofind that they did not work correctly, or at all, when first swit-ched on. The aim of this book is to help the reader overcomejust these problems by indicating how and where to startlooking for many of the common faults that can occur whenbuilding up projects.

B P84: DIGITAL IC PROJECTS $7.60E.G. RAVER, T.Ing.(CE1),Assoc.IEREThis book contains both simple and more advanced projectsand it is hoped that these will be found of help to the readerdeveloping a knowledge of the workings of digital circuits.To help the newcomer to the hobby the author has includeda number of board layouts and wiring diagrams. Also themore ambitious projects can be built and tested section bysection and this should help avoid or correct faults thatcould otherwise be troublesome. An ideal book for bothbeginner and more advanced enthusiast alike.

B P67: COUNTER DRIVER AND NUMERAL DISPLAYPROJECTS $7.05E.G. RAYER, T.Eng.(CEI), Assoc. IERENumeral indicating devices have come very much to theforefront in recent years and will, undoubtedly, find increas-ing applications in all sorts of equipment. With present dayintegrated circuits, it is easy to count, divide and displaynumerically the electrical pulses obtained from a great rangeof driver circuits.

In this book many applications and projects usingvarious types of numeral displays, popular counter anddriver IC's etc. are considered.

B P99: MINI -MATRIX BOARD PROJECTS $7.60PENFOLD

Twenty useful projects which can all be built on a 24 x 10hole matrix board with copper strips. Includes Doorbuzzer,Low -voltage Alarm, AM Radio, Signal Generator, ProjectorTimer. Guitar Headphone Amp, Transistor Checker andmore.

B P103: MULTI -CIRCUIT BOARD PROJECTS $7.60R.A. PENFOLDThis book allows the reader to build 21 fairly simple elec-tronic projects, all of which may be constructed on the sameprinted circuit board. Wherever possible, the same com-ponents have been used in each design so that with arelatively small number of components and hence low cost,it is possible to make any one of the projects or by re -usingthe components and P C B. all of the projects.

B P107: 30 SOLDERLESS BREADBOARD PROJECTS -BOOK 1 $8.85R.A. PENFOLDA "Solderless Breadboard" is simply a special board onwhich electronic circuits can be built and tested. The com-ponents used are just plugged in and unplugged as desired.The 30 projects featured in this book have been speciallydesigned to be built on a "Verobloc" breadboard. Whereverpossible the components used are common to several pro-jects, hence with only a modest number of reasonably inex-pensive components it is possible to build, in turn, every pro-ject shown.

BP106: MODERN OP -AMP PROJECTS $7.60LA. PENFOLDFeatures a wide range of constructional projects which makeuse of op -amps including low -noise, low distortion. ultra -highinput impedance, high slew -rate and high output currenttypes.

CIRCUITS

How to Design Electronic ProjectsB P127 $8.95Although information on standard circuit blocks is available,there is less information on combing these circuit partstogether. This title does just that. Practical examples are usedand each is analysed to show what each does and how to ap-ply this to other designs.

Audio Amplifier Construction8P122 $8.95A wide circuits is given, from low noise microphone and tapehead preamps to a 100W MOSFET type. There is also the cir-cuit for 12V bridge amp giving 18W. Circuit board or strip -board layout are included. Most of the circuits are wellwithin the capabilities for even those with limited ex-perience.

BP80: POPULAR ELECTRONIC CIRCUITS -B OOK 1 $7.75R.A. PENFOLDAnother book by the very popular author, Mr. R.A. Penfold,who has designed and developed a large number of variouscircuits. These are grouped under the following generalheadings; Audio Circuits, Radio Circuits, Test Gear Circuits,Music Project Circuits, Household Project Circuits andMiscellaneous Circuits.

8P98: POPULAR ELECTRONIC CIRCUITS, BOOK 2 $ 8.8 $R.A. PENFOLD70 plus circuits based on modern components aimed at thosewith some experience.

BP39: SO (FET) FIELD EFFECT TRANSISTORPROJECTS $6.751F.G. RAVER, T.Eng.(CEI),Assoc.IEREField effect transistors (FETs), find application in a widevariety of circuits. The projects described here include radiofrequency amplifiers and converters, test equipment andreceiver aids, tuners, receivers, mixers and tone controls, aswell as various miscellaneous devices which are useful in thehome.

This book contains something of particular interest forevery class of enthusiast - short wave listener, radioamateur, experimenter or audio devotee.

BP87: SIMPLE L.E.D. CIRCUITS $5.40R.N. SOARSince it first appeared in 1977, Mr. R.N. Soar's book has prov-ed very popular. The author has developed a further range ofcircuits and these are included in Book 2. Projects include aTransistor Tester, Various Voltage Regulators, Testers and soon.

BP24: 50 PROJECTS USING IC 741 $6.75A unique book containing 52 different projects that can besimply constructed wing the 741 op amp and a few com-ponents. Originally published in Germany, this book will bean valuable asset to any hobbyist.

BNB: HOW TO USE OP AMPS $8.85E.A. PARRA designer's guide covering several op amps. serving as asource book of circuits and a reference book for designcalculations. The approach has been made as non -mathematical as possible.

BP65: SINGLE IC PROJECTS $6.05R.A.PENFOLDThere is now a vast range of ICs available to the amateurmarket, the majority of which are not necessarily designedfor use in a single application and can offer unlimitedpossibilities. All the projects contained in this book are sim-ple to construct and are based on a single IC. A few projectsemploy one or two transistors in addition to an IC but in mostcases the IC is the only active device used.

223: 50 PROJECTS USING IC CA3130 $5.00R.A.PENFOLDIn this book, the author has designed and developed anumber of interesting and useful projects which are dividedinto five general categories. I - Audio Projects II - R.F.Projects Ill - Test Equipment IV - Household Projects V- Miscellaneous Projects.

BP117: PRACTICAL ELECTRONIC BUILDING BLOCKSBOOK 1 $7.60Virtually any electronic circuit will be found to consist of anumber of distinct stages when analysed. Some circuits in-evitably have unusual stages using specialised circuitry, butin most cases circuits ..re built up from building blocks ofstandard types.

This book is designed to aid electronics enthusiasts wholike to experiment with circuits and produce their own pro-jects rather than simply follow published project designs

The circuits for a number of useful building blocks areincluded in this book. Where relevant, details of how tochange the parameters of each circuit are given so that theycan easily be modified to suit individual requirements.

BP102: THE 6809 COMPANION $7.60Written for machine language programmers who want to ex-pand their knowledge of microprocessors. Outlines history,architecture, addressing modes, and the instruction set of the6809 microprocessor. The book also covers such topics asconverting programs from the 6800, program style, andspecifics of 6809 hardware and software availability.

BP118: PRACTICAL ELECTRONIC BUILDING BLOCKS -Book 2R.A. PENFOLD $7.60This sequel to BP117 is written to help the reader create andexperiment with his own circuits by combining standard typecircuit building blocks. Circuits concerned with generatingsignals were covered in Book 1, this one deals with process-ing signals. Amplifiers and filters account for most of thebook but comparators, Schmitt triggers and other circuits arecovered.

B P24: 50 PROJECTS USING IC741 $6.75RUDI a UWE REDMERThis book, originally published in Germany by TOPP, hasachieved phenomenal sales on the Continent and Babanidecided. in view of the fact that the integrated circuit used inthis book is inexpensive to buy, to make this unique bookavailable to the English speaking reader. Translated from theoriginal German with copious notes, data and circuitry, a"must" for everyone whatever their interest in electronics.

B P83: VMOS PROJECTS $ 7.70R.A. PENFOLDAlthough modern bipolar power transistors give excellentresults in a wide range of applications, they are not withouttheir drawbacks or limitations. This book will primarily beconcerned with VMOS power FETs although powerMOSFETs will be dealt with in the chapter on audio circuits.A number of varied and interesting projects are coveredunder the main headings of. Audio Circuits, SoundGenerator Circuits, DC Control Circuits and Signal ControlCircuits.

RADIO ANDCOMMUNICATIONS

BP96: CB PROJECTS $7.60LA. PENFOLDProjects include speech processor, aerial booster, cordlessmike, aerial and harmonic filters. field strength meter, powersupply, CB receiver and more.

222: SOLID STATE SHORT WAVE RECEIVERS FORB EGINNERS $ 7.60R.A. PENFOLDIn this book, R.A. Penfold has designed and developedseveral modern solid state short wave receiver circuits thatwill give a fairly high level of performance, despite the factthat they use only relatively few and inexpensive com-ponents

BP91: AN INTRODUCTION TO RADIO DXing $7.60This book is divided into two main sections one to amateurband reception, the other to broadcast bands. Advice is givento suitable equipment and techniques. A number of relatedconstructional projects are described

B P105: AERIAL PROJECTS $7.60R.A. PENFOLDThe subject of aerials is vast but in this book the author hasconsidered practical designs including active, loop and fer-rite aerials, which give good performances and arereasonably simple and inexpensive to build. The complextheory and math of aerial design are avoided.

Electronics Today June 1985 See order form in this issue. 21

Project

Timed NICAD ChargerExtend the capacity andlife of your nicad bat-teries by optimizing thecharge.

By Robert CardNICAD batteries are an increasinglypopular replacement for dry cell batteries.Their one disadvantage is that you have tohave a special charging unit, and althoughrelatively cheap units are available, theyhave the drawback that they don't haveany facility for timing. Timing the lengthof charge is important; overcharging canactually reduce the capacity of the bat-tery.

The unit described here avoids thisproblem by providing a timed charging in-terval after which it switches off the cur-rent and flashes a ready light.

The way the circuit works is shown inthe block diagram. It is quite difficult togenerate a low frequency accurately, sothe first section generates a relatively highfrequency, 5KHz or higher, and then usesa binary counter to divide this down by16384 to give a frequency of about 0.3Hz.This section is the clock generator, and itsfrequency is set by the value of Rx.

The next section, divide and stop, isanother binary counter but one whichturns itself off when it reaches its max-imum count. The output from this stagegoes to the control logic, which turns offthe constant current generator and flashesthe indicator light.

The final section is the constant cur-rent generator; this provides a constantcurrent to the battery regardless of thevoltage across the battery's terminals.This is the usual way of charging nicads,and has the advantage that several bat-teries can be put in series and charged atthe same time. The magnitude of thecharging current is set by selecting one ofthe resistors using the switch shown. Thisis necessary because different battery sizesrequire different charging currents.

Other sections are: the power supply,which converts the 115VAC to 15VDC,the GO switch, which, when off, resets thedivide and stop function and holds off thecharging current and indicator light, andthe indicator lights with drivers Q1 andQ2.

22

CLOCKGENERATOR

(IC1,2)

GO SWITCH

AC MAINS 0

t

INDICATORLEDs

(012,LED1,2)

IN DIVIDEAND STOP

OUT -1.-11C3a,41

STOP

POWERSUPPLY

(T1,D1,2,IC5)

CONTROLLOGIC

(IC3b,e,d)

*VE SUPPLY

BATTERYUNDER =,

CHARGE -

TO ALL SECTIONS OF

CIRCUIT

CONSTANTCURRENT

GENERATOR(2D1,03,4I

SETCHARGE

CHARGINGCURRENT

Fig. 1 The block diagram. Several batteries can

Choosing and SettingNicads have capacities usually measuredin milliamp-hours (mAH) or amp -hours(AH). In theory, a battery with a capacityof 1 AH could deliver a current of oneamp for one hour, but in practice itdoesn't work this way; the battery'svoltage tails off as it runs down. There isalso some energy dissipated in thebattery's internal resistance. Nonetheless,the capacity is a guide to how much charg-ing is necessary.

Generally, nicads prefer reasonablylong charging periods, say ten hours, andfor this Rx should be 33K. Other periodsare possible: Rx is equal to 3456T - 1350where T is the required charge time inhours. Table 1 shows some charge times ifyou don't trust your math.

Actually, choosing ten hours makesthe choice of charging current mucheasier, so we recommend sticking to this.Note that some batteries can be charged ata very high rate, requiring a much shorterperiod.

The next step is to work out thecharging current: this is the battery'scapacity divided by the charging time. AlAH battery for ten hours would be a 100mA charge.

The value of Ry sets the charging cur-rent, and unless you only use one type ofbattery you'll find it useful to use aswitch, SW3, to select different values ofRy according to Table 2. If none of thesevalues suit you, you can work out thevalue of Ry from the equation Ry =2.5/I, where I is the required current inamps, and Ry is in ohms.

be charged in series. There are limitations.

To prevent overcharging, be sure thatthe batteries are discharged before charg-ing them. A fully charged nicad has alower voltage than standard cells, about1.2V compared to about 1.5V. This maymake them unsuitable for certain applica-tions.

One final point on this section is thata switch, Si, can be used to select the fulldivide chain, or miss off the final dividerstage by taking the output from pin 2rather than pin 3. This latter option halvesthe timing period.

The output from this section is pass-ed to IC3d, and this gates the output fromthe divide and stop section and gates itwith the GO switch. As long as both thesesignals are low, the output of IC3d is high,which keeps the constant current

NUT

CRINKLE WASHER

.,,INSULATING BUSHPOWER

4- rgrsTORMICA WASHER

CHASSIS

AI- METAL WASHER

SCREW

E B CBC107 BC104C

(FROM BOTTOMI (FROM BOTTOMI03.04 01

C

TIP41C(FROM TOPI

02

Fig. 2 The heatsinking arrangement for thepower transistor, plus connection detailsfor the other transistor types.

Electronics Today June 1985

You can't go outside any more without being inundated with adver-tisements for computers. In fact, even staying inside won't help verymuch, unless you unplug the TV and the radio and threaten thepostman with violence so he'll stay away. Computers are becomingas much a part of our culture as are TV, cars and central heating. Infive years, computer illiteracy may be as much of a handicap asprint illiteracy was five years ago.

Despite the colourful advertisements that have turned up in themedia for computer hardware, micros are still understandably for-bidding for many people. In fact, though, most new computerowners are amazed at just how small the leap from unpacking thething, to getting it to do what they want it to do really is.

A computer is an everything tool. It can do anything you canconceive of having it do, limited only by your own ingenuity in tell-ing it how. This is the art of programming, an experience not unlikethat of an artist with every colour of paint imaginable and a blankcanvas the size of Australia. However, the canvas of a computernever gets full ... the more you learn how to do, the more you'llrealize it is possible to tackle.

Computing Now! magazine can be the most useful accessoryyou can buy for your system. Every issue is stuffed full of newsabout products which will enhance your system, programs to run onit, ideas and applications to give you new things to do with yourmachine, articles about programming techniques, and tricks tomake your computer a better tool for realizing your ideas, and pilesof other features to help you get the most out of your system.

Whether you are looking at a computer as a hobby or to runyour business, Computing Now! can provide you with informationand applications to make your system the most useful thing you'veever bought next to the can opener. The articles in CN! are writtenby people who are using computers daily, and are among the mostexperienced small computer users in the country.

Computing Now! is published and wholly owned in Canada. Assuch, the articles and advertisements in it relate specifically to pro-ducts you can get North of the border. There is nothing morefrustrating that finding something interesting in an Americanmagazine, only to discover that it will take four months to drag itthrough customs.

We know microcomputers and we practise what we preach -in fact, we are probably one of the most computerized companies inCanada. Here are just some of the systems we currently own: AppleII and compatibles (15 systems); Apple Macintosh; IBM PC and com-patibles (BEST; Corona, Columbia, )LS); Nelma Persona (2); TRS-80Model II (2); Commodore 64; Vic -20; Commodore PET; ZX81; if800;Acorn Atom; Multiflex. These are just some of the systems we ownand use ourselves; our contributing editor's systems are additionalto this list.

With powerful computers becoming widely available, you can'tafford not to be aware of the expanding universe of micros Com-puting Now! can provide you with an understandable, incisive andvaried insight into this powerful new technology. It is written to be

both understandable by the beginner and intormative for the moreexperienced user with a depth and variety unequalled by any othercontemporary computer publication.

Recent articles: Local Area Networks Hexes and How toThrow Them Interrupts on the IBM Review of Three IBMClones Bandit (a game) What is MS-DOS? Rescuing LostData on the 64 Backing Up Protected Disks Stockboy (an in-ventory control program) Computer Aided Drawing Survey ofPortables Infomart Digging up CP/M Drum Card Review forthe Apple Review of the HP 150 Hacking Modem7 How toUse the Smartmodem CP/M MAC Macro Assembler PopularBusiness Software Directory Explaining the IBM Serial Interface Directory of Microcomputer Paraphernalia Xerox ServiceCentres CN!'s Most Asked Questions dBASE II ReportGenerator Dimension 68000 Review Review of Radio Shack's2000 IBM Telecommunications Business On Line A Potfulof BASIC Routines

SAVE UP TO 51%To: Computing Now! Subscriptions, Moorshead Publications,

25 Overlea Blvd., Suite 601,Toronto, Ontario, M4H 1B1 (416) 423-3262

YES, I want to subscribe to Computing Now! I understand that Imay cancel my subscription at any time and receive a refund onthe unexpired portion.

Please send me a full year of Computing Now! (12 issues) atthe special rate of $22.95, a 41% saving off the newsstand rate.

I would prefer two years (24 issues) at 834.95, a saving of 51%from the newsstand rate.

Cheque/Money Order enclosed. Visa MasterCard Am. Exp.

Card No Expiry Date

Name

Address

City

LProvincePost Code FL 01/85

Electronics Today June 1985 23

continued on page 18 Timed NICAD Charger

Table 1 ChargingTimes And Resistor

ValuesTime(hours)

1

25

101420

Rx

2k1 (or 2k2)5k616k (or 15k)33k47k68k

generator on. If either the counter outputor the output from the circuit aroundSW2a goes high, the output from IC3dgoes high. SW2a also controls the input tothe rest of the divide and stop section, pin11 of IC4; opening SW2a takes this inputhigh and resets all the stages of the dividerIC.

The CCGThe output of IC3d goes to the constantcurrent generator (CCG). This uses thefact that transistors have a relatively cons-tant voltage between base and emitter. Ifwe hold the base voltage constant bymeans of a Zener regulator diode, theemitter will also be held at this voltage(less the B -E drop). Now any resistorfrom the emitter to ground will have aconstant current through it (because ofthe constant voltage), and this currentflows through the collector circuit. If weplace the load (in this case, the battery)from the collector to the power supply, ithas a constant current through it. Thiscurrent can be changed by varying theemitter resistor.

In this circuit, Q3 and Q4 form aDarlington amplifier; Q3 is used to reducethe control current into the base of Q4and prevent loading of IC3d, a CMOSgate.

A limitation of the circuit is that sincethere has to be a volt or two between Q3'scollector and its base, plus 3V9 for theZener diode, the maximum output voltageis limited to about 10 volts. This meansthat a maximum of about six cells can becharged in series, less for some types ofcells.

The indicator drivers are formedfrom IC3. IC3c keeps IC3b off while theinput to IC3c from the divide and stop islow. This means that the output for IC3cwill be high, holding IC3b off, until thedivide and stop output goes high. Fromthen on, when the other input to to IC3bfrom the clock generator goes low, IC3bcan turn on and illuminate LED 2 via Q1.When the clock generator goes high, IC3bis turned off, switching off the LED. Asthe line oscillates between high and low,LED 2 will flash.

The overall effect of this circuit is asfollows: while charging is taking place,

24

Table 2 Battery Capacities AndCharging Currents

Battery Charging Current Ry Rycapacity for 10hr charge value power(mAH) (mA) (ohms) (watts)

110 11 230 (or 220) 1/4

200 20 125 (or 120) 1/4

500 50 50 (or 47) 1/4

1 AH 200 25 (or 24) 1/2

4AH 400 6.25 (or 4.7 + 1.8) 2

311

MA

MUST OE CONNECTED INS..

Fig. 3 The Circuit.

Fig. 4 The PCB overlay. Assembly isstraightforward, but observe the usual safe-ty precautions in fitting and grounding thepower connections and transformer.

OVEXTERNAL SUPPLY

mi

LED 3 will be on, driven by Q2 from theoutput of IC3c. When the charging periodis finished, this turns off and LED 2 willflash. Moving the GO switch to OFF turnsoff LED 2 via SW2b. LED I is on all thetime as a pilot light.

More WorkingsIC1, a 555 timer, is configured as a con-tinuous oscillator with the frequency set

111

a"BEE TEX

N

E

by C4 and Rx. The output at pin 3 is sentto IC2, a 14 -stage binary counter whichdivides by 16384. This divided output atpin 3 comprises the output of the clockgenerator section. The output from IC2pin 14 is taken from part way along thedivider chain; it's the 555 signal divided by1024, and this is used to pulse the "chargefinished" LED.

The divide and stop section is basedcontinued on page 28

Train for the Fastest Growing Job Skill in North America

Only NRI teaches you to service andrepair all computers as you buildyour own 16 -bit IBM-compatiblemicro 7:7

As computers move intooffices and homes by the millions,the demand for trained computerservice technicians surges forward.The Department of Labor estimatesthat computer service jobs will actuallydouble in the next ten years-a fastergrowth than any other occupation.

Anal System TrainingAs an NRI student, you'll get total

hands-on training as you actually build yourown Sanyo MBC-550-2 computer from thekeyboard up. Only a person who knows allthe underlying fundamentals can cope withall the significant brands of computers. Andas an NRI graduate, you'll possess the up-to-the-minute combination of theory andpractical experience that will lead you tosuccess on the job.

You learn at your own convenience, inyour own home, at your own comfortablepace. Without classroom pressures, withoutrigid night -school schedules,without wasted time. Your ownpersonal NRI instructor and NRI'scomplete technical staff willanswer your questions, give youguidance and special helpwhenever you may need it.

The Exciting SanyoMBC-550.2-Yours712Keep

Critics hail the new Sanyo asthe "most intriguing" of all theIBM-PC compatible computers. It uses thesame 8088 microprocessor as the IBM-PCand the MS/DOS operating system. So, you'llbe able to choose thousands of off -the -shelfsoftware programs to run on your completedSanyo.

As you build the Sanyo from thekeyboard up, you'll perform demonstiationsand experiments that will give you a totalmastery of computer operations andservicing techniques. You'll do programmingin BASIC language. Yel,'11 prepare interfacesfor peripherals such as printers and joysticks.Using utility programs, you'll check out 8088functioning. NRI's easy step-by-stepdirections will guide you all the way rightinto one of today's fastest growing fields as acomputer service technician. And the entire

system, including allthe bundled softwareand extensive datamanuals, is yours tokeep as part of yourtraining.

100 -Page FreeCatalog TellsMore

NRI is the only homestudy school thattrains you as youassemble a top -brand micro-computer. Afterbuilding your ownlogic probe, you'llassemble the"intelligent"keyboard

then installthe computerpower supply,checking all thecircuits andconnections withNRI's DigitalMultimeter. Fromthere you'll moveon to install thedisk drive andmonitor.

Send the postage -paid reply card todayfor NRI's big 100 -page color catalog, whichgives you all the facts about NRI training inMicrocomputers, Robotics, Data Com-munications, TV/Video/Audio Servicing,and other growing high-tech career fields.If the card is missing write to NRI at theaddress below.

Your NRI Course Includesa Sanyo MBC-550-2 Computerwith 128K RAM, Monitor, Disk Drive,and "Intelligent" Keyboard; The NRIDiscovery Lab', Teaching Circuit Design andOperations; a Digital Multimeter, BundledSpread Sheet and Word Processing SoftwareWorth $1500 at Retail-and More.

ArAP7CHOOLSMcGraw-Hill Continuing Education Center330 Progress AvenueScarborough, Ontario MI P 2Z5or telephone 416-293-8787

We'll give you tomorrow.IBM is a Registered Trademark of InternationalBusiness Machine Corporation.

11101

Review

MTHS-80

A Z80 controller that makes an intelligent inter-face; use it as a stand-alone or as part of a system.

By E. Penn

LISTEN, I bought a printer at a surplusstore for $29.95 and the guy said "Sureit'll print with your computer, man, nosweat, we sell a million of 'em, here's yourchange." Good deal.

Of course it didn't work and it justsat like a bump on a log, didn't it, exceptfor the letter "A" which made it spool thepaper out onto the floor. Hosed again.I'm told that the code used by the printerdoesn't correspond with the computer'sASCII and a translator is needed.

Now I've been handed this PCB anda chip and a manual and all, I'm told, isnot lost. The package comes fromNicologix, of Streetsville, Ontario, and aninteresting package it is, too. What youget, actually, is a printed circuit about 8by 4 inches with lots of room on it for aCPU and support chips, plus an area ofuncommitted pads where you can stick thecircuit of your dreams. This circuit can bewire -wrapped or soldered, what withspace being provided for your choice ofconnectors.26

The entire point of this, the veryessence, is that you now have a Z80ACPU that's crystal -controlled at 3.57MHzand has a buffered data bus, two I/Oports via a Z80-PIO, and software inROM. There's also 2k of static RAMwhich can be expanded to 8k. This givesthe hardware hacker the ability to noodleout all sorts of designs without opening upthe old Apple clone and disturbing its can-tankerous, precarious innards.

This little gadget is known as theHS -80 system, and will solve problems foryou such as building a translator for acheap printer that doesn't speak yourcomputer's language. All you need is apower supply that can let it have five voltsand at least 300mA. Plus, of course, themanual, which, although not a designer'scoursebook, covers the layout, as well asthe operation, of the HS -80, superbly.Love them commas.

The bare PCB sets you back $20, nota bad bite for quality double -sided stuff,and the nifty manual another $5.00. The

In

erf

t

eThe HS -80 circuit board with the MTHS-80ROM. The 5V supply is at right, and a keypad(foreground) has been wired in for enteringcodes.

parts you'll need are the garden varietystuff like a CPU and gates; the only weirdpart is the Z80-PIO port chip, and Z80CPU dealers should carry it.

If you're really into this by now, anddesperate to make that printer work, foranother $40 you can get the MTHSmulti -tasking software on a ROM chipplus another manual. This manual is eventhicker and better than the first, and ex-plains in detail the simple assembler -stylelanguage for turning the board into an in-telligent interface. You'll note in thephoto that the board has a small keyboardand 7 -segment readout attached; a fewsimple codes and we had the board beep-ing a beeper while leaving the CPU freefor other tasks. Some of those other taskswould be making a printer buffer or smartEPROM programmer or smart keyboardencoder or a terminal controller or aparallel -serial converter or even, bless'em, a printer driver.

The uses for this little intelligentbreadboard are - dare I say it? - limited

Electronics Today June 1985

RESET

Z80 -CPU

MTh6116(6264)

EPROM(2716)27322764

SYSTEM OVERVIEW - Figure 1.0

NMI

74LS139

.16

74LS74

r

74LS04

ZOO -P 10

PORT A PORT

74L 5245

IDATA BUS

74LS138 7415138

STROBES ENABLES CLOCK

Fig. I The block diagram of the HS -80 hardware; the MTHS multi -tasking system is added via theROM chip.

only by your imagination. After you'vedecided to get some use out of your homecomputer by making it run the householdappliances and the robot, this little boardcan do it all for you and prevent tying upyour home computer and now you'reback where you started trying to find a usefor the old Atari. Maybe you could pro-gram it to write song lyrics - they'll pro-bably be better than most of the stuffaround now. Developing one-time cir-cuits no longer means a custom PCB or atangly breadboard. Software for theboard can be developed on an Apple orIBM.

Least I lead anyone astray with rav-ing on here, this board is not an instantsolution to your interface problems;Nicologix assumes that you have a work-ing knowledge of the CPU and its supportchips, and that you understand the wantsand needs of the circuits you're trying tointerface.

But assuming you're good at logiccircuits, this little card should save you noend of time and trouble when you're in-venting your concoctions. I should havethat printer interfaced to my wristwatch inno time. It's available at Exceltronix, 319College St., Toronto, (416) 921-8941, orcontact:

Nicologix,PO Box 976,Streetsville, OntarioL5M 2C5Electronics Today June 1985

LDLDHS8 0

JR

ERROR: EQU

A,PAGEHL,PROCESSFEAREPLC,ERROR

Fig. 2 An example from the manual showing thesimple code used in the MTHS system.

We Service What We SellBEST QUALITY INSTRUMENTS AT LOWEST COST!

Why Pay More? ... Just a Few Examples:

DMM 60131/2 dig. 0.25% acc.0.1 mV- 1000 VDC0.1 uA - 2 A AC/DC0.1 mV - 750 VAC0.1 ohm - 20 M ohmsSafety test leads incl.

$63.90

Dmm 6010 (same as 601) except: max.10 A AC/DC $69.50

OSCILLOSCOPE 33330 - 2 Chan.20mHz bandwidthBuilt-in componentstester5 mV vert. sensitivitySpecial Price $495.00in areas not servedby distributers.Probes extra.

Precision Analog Multimeter Model 5050E Input resistance, 10M /DC Introductory 43 measuring AC/DC current Price $67.50

ranges max. 12A

Authorized Distributors: A-1 Electronics, 5062 Dundas St. W. Toronto, 231-4331.Waterloo Electronics Supply Co. In. 219 Hartwood Ave., Waterloo, Ont. 745-9421.Mail Orders Accepted: Certified Cheque, Money Order, C.O.D.'s F.O.B. Oakville. Ontario residents add 7% P.S.T.

Adi oft,"

OSCILLOSCOPE 505 - 1 Chan.4.5mHZ bandwith20 mV vert.

sensitivityInternal sinewave

calibrator(probe extra)IntroductoryPrice $300.00

Model 605RF Generator100KHz - 70 mHzOn fundamentals

or.Introductoryprice $179.00

KB ELECTRONICS355 Iroquois Shore Rd., Oakville, Ont. L6H 1M3

(416) 842.6888 Telex 06-982396 (KBEL OKVL)Circle No. 27 on Reader Service Card 27

continued from page 24 Timed NICAD Charger

on IC4, another 14 -stage counter. Toreach the counter, the clock pulses have topass through a NOR gate, IC3a. While theother input to this gate, from the outputof the binary counter, is low, pulses fromthe clock generator can pass, althoughthey are inverted by the gate. Once theother input to the gate goes high, the out-put of the gate will go low whatever theclock generator output is doing, so no fur-ther pulses pass to IC4. Otherwise, IC4would carry on counting and eventuallyturn on the CCG via the control logic.

ConstructionThe prototype was built in a metal boxwith the PCB mounted on plastic pillars.The power transistor, Q4, becomes quitehot when fully loaded. This has todissipate up to 20 watts, so it will require aheatsink. This can be achieved by boltingQ4 to the bottom of the box, using asuitable insulator and heatsink compoundon both sides of the insulator.

TestingThe voltage across Cl should be 18 to 25volts and the red LED should be il-luminated. The voltage across ZDI shouldbe zero when SW2 is OFF, and about3.9V in the ON position. The yellow LEDshould illuminate in the ON position.

Resistors(All carbon film 1/4W 5% unless noted)R1 2k7, 2070R2 22kR3 lkR4 5 6kR5, 6, 7 12k

CapacitorsCl 2200u, 25V

electroC2, 3, 6 1u, 35V

tantalumC4 5n6, 2%

polyestyreneC5 22n

polyesterC7 47u, 6V3

tantalumC8 10u, 25V

tantalum

SemiconductorsQ I , 2 BC107Q3 BC184C

Q4 TIP41CICI 555 timerIC2, 3 4020IC4 4001IC5 7815DI -4 IN4001ZDI 3 9V, 400mW

Zener diodeLED 1-4 0 2in

red, green and yellow

MiscellaneousT1 18-0-18V, IA

mains transformerFl 800mA

quick blow fuseSWI SPDTSW2 DPDTSW3 single pole, six way rotary

(See text)

Metal case to fit; 4mm wander plugs andsockets; heat sink for Q4; PCB pillars, nutsand bolts; cable gland for mains cable;PCB, wire, solder etc.

Check that the calculated values of cur-rent are flowing through the battery ter-minals by placing an ammeter acrossthem.

To ensure that the timing circuit isworking without having to wait for thefull charge time, calculate a value for Rxso that the time is one hour, for example

ES FOR SALESOURCE FOR OSCILLOSCOPE PROBES

AND DMMNOM TEST LEAD SETS.

Your PrSpecialists

Colin Canadian Sales Et Stocking

44%11h1104446

Low cost High Quality Excelent Performance Slender, Flexible Cable

Wide Range of Choice Switchable XI and X10

Attenuation Factor 100 MHz Bandwith

416 MODEL SP100

ilk $5010

Store liars: Monday to Friday 8f10 am to 5110 pm,Setwday 10110 an to ISO pm.

980 Alness St. Unit 7,Dawnsview, Ontario,

M3J 2S2(4161 661.5585

TELEX 085-28169

(try 47K and 2K2 in parallel). The switchSI to the half charge position and start thecharge using SW2. The yellow LEDshould light and charging current flow forthirty minutes and then stop; the yellowLED goes off and the green one flashes toindicate a charge. Now replace Rx withthe proper value.

0 00000

LLD

81

28 Circle No. 31 on Reader Service Card Electronics Today June 1985

Supercomputers

The Cray X -MP series of supercomputers is among the most powerful available today. Photo courtesy of Cray Canada Inc.

WHEN the Japanese National SuperspeedComputer Project got under way inJanuary, 1982, few would have believedthat just three years later it would beamong the highest priority items on theUS -Japan diplomatic agenda discussed byPresident Ronald Reagan and PrimeMinister Yasuhiro Nakasone at theirCalifornia summit.

At the time of their meeting inJanuary, 1985, there were still scarcelymore than 130 supercomputers in opera-tion worldwide. Less than ten of these hadbeen built by Japanese computer makers,and virtually all the rest were products oftwo American firms, Cray Research, Inc.,and Control Data Corporation (CDC), aduopoly which had dominated worldmarkets since the first ultra -highspeednumber crunchers were built at the begin-ning of the 1970s. About 70° of the super-computers then in operation were sup-plied by Cray Research.

Electronics Today June 1985

Ultra -highspeed computerscan run at 400 million opera-tions per second, and thesmall market is turning into a

US/Japan sweepstakes.

By Gene Gregory

The immediate problem which hadbeen raised at earlier technical meetingsbetween representatives of the two coun-tries was access to Japanese markets, par-ticularly universities. But in thebackground loomed a larger issue: theJapanese supercomputer project, not to

be confused with the Fifth GenerationComputer Project intended to develop ar-tificial intelligence, had set for its specificobjectives the design of machines with asustained execution rate of about 10billion floating-point operations per se-cond (gigaflops), or 100 times faster thanAmerican computers and ten times fasterthan the projected peak speed of the nextgeneration of American machines.

GigaflopsThe measure of computing speed, theFlop, refers to the binary version ofrepresenting scientific notation, in whicha number is represented by a mantissa bet-ween 0.1 and 1 raised to an exact power often. A single Flop is arithmetic betweentwo floating point operands to get afloating point result.

Speed in the 10-gigaflop range wouldbe attained by using entirely new semicon-ductor devices, distributed parallel -

29

Supercomputers

processing architecture, one billion bytes(a gigabyte) of memory and a memorybandwidth of 1.5 gigabytes per second.To meet these specifications, the ScientificComputer Research Association wasestablished, combining six leading in-tegrated circuit manufacturers under thecoordination of the national Elec-trotechnical Laboratories in TsukubaScience City.

After years of being virtually aone -company industry (dominated byCray), the market was teeming with newplayers, projects and funding.

The Japanese ApproachJapanese policymakers had unequivocallyacted on the premise that the wealth of na-tions will be largely determined in thefuture by information technology, andthat, in the absence of other than humanresources, Japan is more dependent onthat technology for its economic futurethan are most other advanced industrialcountries. New generations of computerswill therefore serve as the prime movers inan increasing range of industries, helpingto improve efficiency where productivityhas in the past been little influenced byautomation.

But computers are also much morethan critical tools; they will also benecessary for the management of theecosystem and dealing with a myriad ofproblems of an ageing society, processingmassive amounts of data to aid in themathematical simulations of multi-dimensional physical phenomena. Here isthe rub. What in a techno-economic con-text is vital to the security of Japan is seenin the United States as a threat to nationalsupremacy in critical military technology.It is these conflicting interests, then, thathave resulted in the current US -Japanconfrontation. Japanese leaders havemade clear their intentions to push for-ward the state of the art in supercom-puting as well as Fifth Generationtechnology. The intention is not only toassure the competitive strength ofJapanese industry and the wealth of thenation, but to contribute to the forwardmarch of human progress.

However, the Japanese do not seetheir action as replacing US dominance insupercomputers, or as a threat to USsecurity; given the high technological levelof the Japanese electronics industry, thedevelopment of supercomputer produc-tion capability is seen rather as a naturalcourse of open worldwide competition.

Japanese computer makers takeseriously the expressed confidence of Crayexecutives that they will be able to matchJapanese advances in supercomputers; theexisting park of Cray supercomputersconstitutes a formidable advantage in thecompetitive marketplace. There are alsofew illusions among Japanese leaders that30

they will be able to penetrate the USgovernment market, which has accountedfor the bulk of supercomputer sales in thepast.

StrategiesJapanese strategies differ significantlyfrom those of the US pioneers. Supercom-puters were not built by IBM, but by"dwarf" companies looking for niches inthe market where they could survive un-molested by the Big Blue. When SeymourCray left Control Data, which he hadhelped create but later found to be unableor unwilling to sustain a commitment to

Supercomputer PrimerSupercomputer: A computer which canprocess data at 20 megaflops or higher,but the fastest run at a sustained 400megaflops and a peak of I gigaflop orhigher. In future, supercomputers mayuse multidimensional arrays with manyparallel operations being performed in apipelined way. Over the last 30 years,computer speed has tended to double eachyear.

Flops: Floating point operations, a

measure of computer speed. An operationis arithmetic performed on two floatingpoint operands to get a floating pointresult. A megaflop is one million opera-tions per second, and a gigaflop is onebillion.

Scalar Processing: Operating on in-dividual data elements with instructionsthat yield one result for each instruction.To operate on all elements of an array, forinstance, the computer loops through thetable of numbers, repeating the same in-structions on each.

Vector Processing: Uses only one instruc-tion to perform calculations on an arrayof data all in one operation. In supercom-puters, the more data vectorized, thefaster the operation. Vector processing isusually not available on mainframes.

Array Processing: Does not include scalarprocessing. Processors are usuallyperipheral devices, allowing mainframeusers to run vectorized portions of pro-grams.

Parallel Processing: Two or more pro-cessors performing simultaneous opera-tions in a single task. Supercomputersmay use vector processors in tandem withscalar processors, dividing each task foroptimal use of the processors under cen-tral control; they may or not be pipelined.

Pipelining: Speeding computer operationsby breaking down instructions intodiscrete steps for processing in anassembly -line system, with different stepsin the execution of an instruction per-formed simultaneously. Vector registers,or high-speed memories, store instruc-tions and feed them to the pipeline at aspeed greater than calling instructionsfrom the main memory.

supercomputers, he originally intended tobuild only one of his projected giantnumber crunchers a year for scientificpurposes. He saw no great market for themachines, and even after favourableresponse from the Los Alamos NationalLaboratory which took the first Cray in1976, the new company that began in anabandoned Wisconsin shoe factory onlyincreased production to four machines ayear in 1978 and 13 in 1984.

In 1982, when Japanese computermakers announced their imminent entryinto the field, there were only 50 super-computers in operation worldwide. 35 ofthese had been built by Cray Research, 14by Control Data, and one by Denelcor, asmall Colorado builder. Fully 38 of thosesuperspeed computers were operating inthe United States for Los Alamos andgovernment agencies. It was a restrictedmarket, for which the builders haddeveloped special machines that were pro-grammed in a completely different man-ner from standard general-purpose main-frames.

The new Japanese entrants, Fujitsu,Hitachi and NEC, are major highly -integrated companies producing a full lineof computers from micros to mainframes,and are at the same time among theworld's top ten computer manufacturers.Not only did these makers build their newsuperspeed machines to operate on thesame software used by their standardmainframe models, but this meant thatboth Fujitsu and Hitachi would supplymachines compatible with mainframemodels built by IBM, which had not so fargiven any sign that it would add super-computers to its product line. By produc-ing IBM-compatible machines, Fujitsuand Hitachi offer the widest number ofcomputer users at home and abroad theoption of moving to more powerfulmachines without heavy expenditures fortime and money for adapting special soft-ware.

The NeedThe global strategies of Japanese makersare based on other elements that have notweighed as heavily in plans and operationsof Americans.

Firms in a widening range of high-technology industries are beginning to feelthe need of ultrafast computer processingcapabilities. Advanced graphics, com-puter -aided design, and distributionsystems all require massive volumes ofdata, necessitating a processing improve-ment of two to three orders of magnitudeduring the current decade.

Supercomputer development is itselflinked with the design of Very Large ScaleIntegrated circuits. They require deviceswith increasingly faster switching speeds,speeds which can be obtained only bydeveloping entirely new technology.

Electronics Today June 1985

By effectively responding toworldwide demand, Japanese makers seethe possibility of cutting prices sharply;industrial users are likely to be more sen-sitive to lower prices.

The Near FutureSupercomputers still occupy the niche thatfirst generation computers held in the1950s. Those earlier machines cost evenmore, allowing for inflation, and were sopowerful that only a very special group ofusers could find applications for them.Yet in the US there were 13 computermanufacturers, with Remington Rand inthe lead.

By comparison, the worldwide super-computer park at the beginning of 1985had reached 130, with only nine installa-tions in Japan. By 1990, it is estimatedthat at least 100 will be operating inJapan, about the same number installedworldwide in 1984. World marketestimates for 1990 vary widely from400-500 machines to as many as 1000. Notsurprisingly, the higher estimates of de-mand come from the Japanese, who areaiming at a broader range of users.

The MachinesFujitsu has concluded arrangements withthe Amdahl Corporation, in which itholds a 49 percent equity, to market itssupercomputers in North America andEurope. Initial benchmark tests in the USindicate that sustained throughput, con-sisting of both CPU and input/outputspeed, of the Amdahl 1100 and 1200(identical to the Fujitsu VP -100 andVP -200) compares favourably with thecompetition. The 1100 sustains speeds of175 megaflops and the 1200 300 mega -flops. The 1100, in sustained throughput,is 1-2 times faster than the Cray X -MPuniprocessor and twice as fast as thetwo -pipeline Control Data Cyber 205,while the 1200 is about as fast as the Craytop -of -the -line X -MP two-way pro-cessor.

While some computer scientists dis-count the advantage of IBM compatibili-ty, pointing out that if a customer isprepared to vectorize the scalar softwarecode, the same results can be obtained ona Cray with an IBM up front, others assertthat programs developed from the startfor vector processing on supercomputerswill run 20 to 30 times better than scalerconverted to vector.

Hitachi has followed the Fujitsustrategy, supplying National Semiconduc-tor's subsidiary, National AdvancedSystems (NAS), on an OEM basis. In1982, Hitachi introduced the two -modelS-810 series, one with speeds up to 630megaflops, and the other rated at 315megaflops. In Europe, Hitachi -madesupercomputers are being offered byNAS, Olivetti and BASF as vector pro -Electronics Today June 1985

cessing extensions of Hitachi -built main-frames.

NEC is following a different strategy.While its new SX series is compatible withNEC mainframes, neither are IBM-com-patible. "IBM architecture is 20 yearsold," NEC manager Akihiro Iwayopoints out. "To assure IBM -compatibili-ty some performance compromises arenecessary, which NEC chooses to avoid."As a result, NEC surpasses both Hitachiand Fujitsu, unveiling machines withoperating speeds up to 1.3 gigaflops, orten times the speed of the Cray 1S andtwice as fast as the X -MP two-way pro-cessor, which has a peak 630 megaflopthroughput.

ArchitectureBoth NEC machines, the SX-1 and SX-2,feature logic LSI with a density of 1000gates per chip and delay times of only 250picoseconds. The SX system utilizes uni-que, high -density packaging with 36 LSIchips mounted on a substrate 10 cmsquare, achieving higher speeds due toshorter pathlength. Cooling, which is acritical factor in supercomputer design, isa direct liquid system within the LSIpackages, but the cooling unit itself is aircooled and needs no special equipment.High speed main memory elements with amaximum data supply rate of 11 gigabytesper second is supplemented by an extend-ed memory, offering significantly higherperformance than obtainable withmagnetic disks.

The architecture of the world's firstgiga-level machine is based on multipleparallel processing using four sets of fourvector pipelines, enabling a maximum of16 parallel vector operations to be per-formed simultaneously. Although theSX-2 is ten times faster than the Cray IS,the price is substantially the same.

Both Fujitsu and NEC use an ad-vanced type of Fortran 77, a compiler thatcan vectorize standard Fortran programs.Since 20 to 80 percent of Fortran pro-grams can be vectorized, this approach inthe main software issues will likely proveadvantageous, since no special operatortraining would be required.

The FutureThe six Japanese semiconductor manufac-turers have joined in the NationalSuperspeed Computer Project. The goal isto produce a computer capable of sustain-ed processing speeds of at least 10gigaflops by 1989, one year before thecompletion of the separate Fifth Genera-tion project.

The super -cooled Josephson junc-tion, developed in 1983, is unlikely to beselected for supercomputers; despite its 7picosecond delay, it requires specialpackaging and maintainence, and mustbe operated at a temperature near ab-

solute zero. Much more likely are galliumarsenide (GaAs) devices. Jointlydeveloped by the project, it features highspeed, low power consumption, and alarge number of gates.

From 1985 to 1989 the focus will beon development of the actual supercom-puter, stepping up work on distributedparallel processing architecture andrelated software. What will happen after1990 is anyone's guess. Chances are goodthat by 1990 the three Japanese supercom-puter makers will have as high as 50 per-cent of the world market, likely to be at $2billion a year and climbing. The US willnot be standing still; Cray will remain amajor power in the marketplace for theforeseeable future, and IBM may enterthe market as it reaches volumes ap-proaching $2 billion. National projects inthe UK, France and Germany will pro-bably bring new actors onto the scene. Itremains to be seen whether any future in-ventions will emerge to bring about asignificant departure from the revolution.

Dr. Gene Gregory is a professor ofbusiness at Sophia University in Tokyo.

AMAZINGSCIENTIFIC and ELECTRONIC

DEVICESLASER DEVICES LC5 BURNING CUTTING CO2 LASER $15.00 RUB3 RUBY LASER RAY PISTOL 15.00 LRG3 IR LASER RIFLE/PISTOL 10.00 LGU3 VISIBLE RED LASER RIFLE 10.00 LHP/LLD LASER LIGHT XMTR/RCVR SYS 10.00 LHC2 BEGINNER simulated VISIBLE LASER .5.00

SCIENTIFIC & ELECT TCL3 SOLID STATE TESLA COIL 35KV 600 BTC3 250 THOUSAND VOLT TESLA COIL ..9.00 BTC5 1.5 MILLION VOLT TESLA COIL 15.00 HVM3 125 THOUSAND VOLT DC SUPPLY ....8.00 10G3 ION RAY FORCE FIELD GUN 8.00 HEG1 MILLION WATT 500 JOULE SOURCE ..10.00

ULTRASONIC ACCOUSTICAL PPF1 PHASOR PAIN FIELD GENERATOR .15.00 PSP3 PHASOR SHOCK WAVE PISTOL 700 IPG5 POCKET PAIN FIELD GENERATOR 700 RAT2 RAT AND PEST ELIMINATOR 600 HT9 HIGH FREQ. LISTENING DEVICE 800

SECURITY & PROTECTION

DEVI DEVASTATING DEVICES 10.00 PPG1 PHASOR PROPERTY GUARD 15.00 MFT1 MINI VOICE XMTR 2-3 MILE 700 INF1 INFINITY TRANSMITTER 15.00 PSW3 PHASOR BURNING STUN WAND 700 ITMI INTIMIDATOR PLASMA GUN 10.00

WE STOCK ALL PARTS NECESSARY FORCONSTRUCTION OF THE ABOVE PROJECTS

CATALOG CONTAINING HUNDREDS MORE OFALL NEW AMAZING and FASCINATING PLANS.EASY TO BUILD KITS AND ASSEMBLED ITEMS$1.00. CATALOG INCLUDED FREE WITH ANY OFTHE ABOVE PROJECT PLANS. SEND CASH,CHECK, MO, VISA, MC IN US FUNDS.

INFORMATION UNLIMITEDP.O. Box 716, DEPT. ET, AMHERST, NH 03031

Circle No. 32 on Reader Service Card 31

Direct reception ofsatellite relays meansan enormous choice ofvideo and audio pro-grams; buy a completesystem or build yourown.

By Bill Mark widcIF you'd like a wider choice of programs,or if you live in an area where cable is notavailable, you can receive the broadcastsfrom satellites that are used to relay net-work programming across the continent.You might expect the received signal to befeeble, and it is; you might also expectthat some sophisticated hardware is re-quired, and that's true as well. It's a bitmore complicated and expensive than theaverage rooftop antenna, but thepopularity of the systems is bringingprices down. You can also build yourown; various companies supply kits andassistance.

The Basic IdeaNetworks use satellites as relay links; ifyou have sensitive enough equipment, youcan receive and decode the satellite signal.This obviously lets you in on a wealth ofcommercial -free programming.

The catch is that the signal is under-standably small; the satellite may covermost of Canada using a transmitter withabout ten watts of power. In addition, thesignal is in the microwave region; satellitesreceive the ground signal at about 6gigaliertz and rebroadcast it at about4GHz (for audio fans who feel that theuniverse ends at 20kHz, a gig is 1000megaHertz). There are some regionalbroadcasts from Canada's Anik that usethe 14/12 gig band.

A whole lot of signal has to be col-lected with a parabolic reflector eight orten feet in diameter. The signal is concen-trated into a feedhorn which guides it intothe low noise microwave amplifier, orLNA, which has about 40-50dB of gain.As you can imagine, a 4 gig signal isn't tooeasy to handle, particularly with longcable runs, so it's immediately sent to thedownconverter to be changed to a band offrequencies surrounding 70MHz. This issent by coaxial cable to the receiver unitindoors. The receiver extracts the par-ticular station you want and sends the RFsignal to your TV.

Nothing to it, except maybe cost anda big dish sitting in your backyard.

The OptionsJust like buying a car. The jazzier32

Satellite Rec

receivers have microprocessors in them toeliminate knob -twiddling and simplifychanging channels. There are remote con-trol units to run the receivers; these aresimilar to the familiar cable -TV handheldremotes. Some receivers have stereodecoding for audio signals.

Because the satellite signal is so small,it's necessary to aim the dish accuratelywhen changing to another satellite, andyou may not fancy going out in the coldand wet to do this manually. There are

Fig. I A feedhorn assembly which guides thesignal into the Low Noise Amplifier shownwith it; equipment courtesy of Vexus Telecom-munications.

lots of actuators available. It's a ser-vomotor that rotates the dish on its mountunder control of a microprocessor thatsits near the receiver. Some just move thedish until your picture looks good, andthe more expensive ones can be prepro-grammed with satellite locations.

The number of bells and whistlesnaturally send the price up rapidly, so itall depends on how much you want doneby gadgetry and how much you're willingto do by hand. One place where you pro-bably shouldn't scrimp is in the dish andmount; a large dish is subject to immensewind loading, and even if it doesn't blowover, it may be easily knocked off op-timum positioning.

There are lots of dealers around nowwho can advise you on complete systemsthat can be made to work right away. Butfor those of you with a sense of adven-ture, how about building your own? Youdo have a sense of adventure, don't you?

An AdventureOne of the most costly items in a satellitereception system is the dish. If you'rereasonably good at basic carpentry and

Electronics Today June 1985

eption

can either do welding or get it donesomewhere, Sothis Satellite Systems ofNew Brunswick will send you an instruc-tion manual and blueprints for a dish thatyou can make yourself. It's rectangularrather than round ("spheribolic"), and isconstructed largely from plywood ribscovered with mesh; the mount is madefrom angle iron. Its final size is 8 feet; itsgain is said to be 36dB and its efficiency 68percent. Studio -quality reception is claim-ed. In addition, the see-through mesh hasa better look than a solid dish, and it'salso more tolerant of wind loading.

We obtained a copy of the instruc-tions and blueprints and found them to bewell -written. There's a large blueprint forthe wooden frame and another for themount; both include comprehensive partslists. Mind you, there's one spec I bet itcan't live up to: it's claimed that theantenna can be assembled in four hours.Obviously the Sothis company has neverseen me at work; I decided to renovate myhouse two years ago, and today it's still apatchwork of holes, plaster, drywall bits,and pink insulation. Now that I have theplans, maybe I'll have a go at building myElectronics Today June 1985

own dish; I'll let you know how it turnedout by early 1996.

If you're itching to get at the powersaw, the manual and drawings can be hadby sending a money order or bank draftfor $24.95 to:

Sothis Satellite Systems,Box 6637, Station A,Saint John, New BrunswickE2L 4S1

ElectronicsHaving assembled your dish, you maywant to mop your brow and just headdown to the satellite store for all the restof the stuff. On the other hand, that thrillof accomplishment may make you want togo whole hog and take a stab at buildingthe electronics, which will mean a LowNoise Amplifier and a receiver unit.

If this appeals to you, Electronics To-day published a do-it-yourself project forthe LNA, the downconverter and thereceiver, written by Ron D.C. Coles andappearing in July and August, 1983 (backissues are available; see the Order Form inthis issue).

This project is not for the faint ofheart. The signal presented to the LNA byeven a large dish is typically only 6dBabove the thermal noise that exists in allcircuits courtesy of Mother Nature. It'sreadily apparent that any amplificationhas to be done by gain stages which addan absolute minimum amount of theirown noise. The usual choice is cascadedGaAsFETs mounted on a special micro-wave -grade PCB; the project featuresplans for this type of amplifier, which hasa noise figure of 1.5dB. Noise perfor-mance for LNAs is usually given indegrees Kelvin; 1.5dB corresponds to 120degrees. Better performance than this ispossible, but the exotic techniques re-quired will mean an exotic price tag.

If you're a bit nervous about buildingcircuits that whiz along at 4GHz, andafter all, the known universe does end at20KHz, Ron received enough feedbackfrom the article that he has now started acompany to assist the constructor as wellas supply complete systems. He can solvesupply problems for you; some of the

high -frequency components aren'tavailable at your local Radio Shack, to saythe least. So, if you're game, contact:Colesat Systems,RR 2,Tantallon,Nova Scotia BOJ 3J0(902) 826-2875

Other FeaturesRadio stations use satellite services aswell; there are stereo stations available onsubcarriers from most satellite transmis-sions. Some specialize in particular typesof music. Needless to say, you need areceiver with the necessary decoding op-tion to hear the audio subcarrier.

A question that comes to mind: whyshould broadcasters let you have all thiscommercial -free TV? There has beensome talk of scrambling the transmis-sions, but nothing firm has emerged sofar. Some of the channels have at least afew commercials on them, so it isn't intheir interest to scramble, and for theothers, the number of people with satellitedishes may be too few to make it wor-thwhile. What they worry about is so-meone using a dish to obtain movies andso forth for commercial purposes, but thisis illegal anyway, since the CanadianRadio -television and CommunicationsCommission rules say that you can have adish for your own use, but you can'tdistribute the signal to others without alicence, and they probably won't give youa licence.

The smaller dishes are also generatingsome interest; nobody wants a ten -footmonster if a three -footer will work.There's the vague idea around that dishesand electronics have improved to thepoint where the three- and four -footersare adequate replacements for the largerdishes, but this isn't 100 percent true. Asmaller dish receives a smaller signal,period. There's a limit to how good youcan make the electronics, sincesignal-to-noise is largely controlled by thelaws of physics rather than engineering.However, if you live in an area thatreceives a strong signal, or you're tuningin to the newer more powerful satellites,or you don't mind doing without some of

Fig. 2 An actuator and control panel for remote adjustment of the dish position.

33

Satellite Reception

=ME11111111110101INIMIMON

"

Fig. 3 The original receiver developed byR.D.C. Coles and described in one of our pro-jects (see text).

Fig. 4 A do-it-yourself dish antenna fromSothis Satellite plans.

Fig. 5 The angle iron mount from SothisSatellite plans.

the weaker broadcasts, then the smallerdish is adequate. And, of course, awell -designed small dish beats a poorlymanufactured large dish any time.

There are a number of publicationsaround dealing with satellite reception. Ifyou'd like a Canadian magazine, there'sSIGNAL, from Fennwood Publishing

Ltd., Box 238, Station D, Scarborough,Ontario. It's published six times yearlyand available on newsstands, and dealswith general aspects of satellite reception.If you'd like a more technical guide, abook stuffed full of goodies is the SatelliteExperimenter's Guide, published in 1984by the American Radio Relay League anddealing with TV -broadcast, amateurradio, and weather satellites. If you can'tfind it in speciality stores, you can contactthem at the ARRL, 225 Main St., New-ington, CT 06111. It costs $11 US.

SourcesHere are some of the manufacturers anddistributors who can supply you withsystems, components, and advice. Ourapologies to anyone who didn't get listedthrough oversight.

Delta Satellite Systems,40 Rivermede Rd. N., Unit 1,Concord, Ont. L4K 2H3(416) 736-0930

Sigmacom Consumer Products,111 Industrial Drive, Unit 6Whitby, Ontario,(416) 666-16614

Pulsar Communications,801A - 57 St. East,Saskatoon, Saskatchewan(306) 931-3090

Millman's Communications,11427 - 160 St.,Edmonton, Alberta(403) 451-3127

Geocom Inc.,13120 Bathgate Place,Richmond, BC(604) 273-1079

Paco Electronics Ltd.,45 Stinson St.,Ville St. Laurent,Quebec H4N 2E1(also Markham, Ont. and Winnipeg,Man.)

Gensat Communications Corp.,951 Alness St.,Downsview, Ont. M3J 2J1,(416) 736-4555

MSE Systems Ltd.,2015 West 12th Avenue,Vancouver, BC V6J 2G3(604) 736-1141

CSE Satellite Equipment,200 Hamford St.,Lachute, Que. J8H 3N8,(514) 562-3741

Cale Communications,693 Henderson Dr.,Regina, Sask. S4N 6A8,(306) 949-9181

Evolution Technology,1155 Appleby Line,Burlington, Ont. L7L 5H9(416) 335-4422

Commander Satellite Systems,309 Steeles Ave., E,Milton, Ont. L9T 1 Y2,(416) 876-4707

Columbia Satellite SIstems,2080 - 21 St. NE,Calgary, Alberta T2E 6S5(403) 250-5271

Vexus Telecommunications,2240 Argentia Rd.,Mississauga, Ont. L5N 2X6,(416) 821-8900

Haussen Tech Inc.,PO Box 2126,Moncton, NB EIC 8H7(506) 534-2530

MISAT Corp. (Fanon),20701 Langley Bypass, No. 4,Langley, BC,(604) 534-4104

Petphil Electronics Inc.,254 St -Anne St.,Senneville, Que. H9X 1N8(514) 457-1N8

Communications Gigahertz Ltd.,4649 Des Grandes Prairies,St -Leonard, Que. HIR 1A5,(514) 323-0030

34 Electronics Today June 1985

DUNCAN INSTRUMENTS LTD.ELECTRONIC INSTRUMENT SPECIALISTS

Providing the finest,state-of-the-art electronic instruments available.

Backed by superior post sales service and acomprehensive 12 month warranty. Many of our

products are unavailable anywhere else. Examine justa few of the many products we currently stock.

Recognizable value.

MODEL 6022

DUAL TRACEOSCILLOSCOPE

20 MHz bandwidth dual trace 6" CRT component tester 5 mV sensitivity complete with two dual probes

$63500 MODEL 2310B

SINGLE TRACEOSCILLOSCOPE

10 MHz bandwidth 3" CRT 5 mV to 5V/Div. in 4 ranges test lead supplied

FR MO lin, 1 MN,

121 MILVAN DRIVETORONTO, ONTARIOM9L 1Z8(416) 742-4448TELEX: 065-27271

$39500 $59500

HIGH TECH. LOW COST.INNOVATION. QUALITY. VALUE.

All prices include Federal Sales Tax.In Ontario add 70/0 Provincial Sales Tax.Call or write for additional information.Telephone and mail orders invited.

MODEL 8055F

DIGITAL FREQUENCYCOUNTER

Frequency range:1 Hz - 550 MHz/3 ranges

Sensitivity: A: 1Hz-100MHzL:-20mVB: 50 MHz - 550

MHz __ 150 mV 8 digit LED displayModel 8010F: 1 Hz - 120 MHzin 2 ranges - $395.

MODEL 5030 $22000DIGITALMULTIMETER

31/2 digit, 0.5" LCD display Diode test Continuity buzzer full AC/DC current/voltage/

ohms. Ranges

1999

*

MODEL 3000

DIGITALMULTIMETER

low cost handheld DMM forelectronic, electrical andserious experimenter use

31/2 digit, LCD 0.5" display single knob switching 10A AC/DC ranges accuracy generally 0.50/0 carry case, battery, leads

included

$9500

Electronics Today June 1985

MODEL 3100

DIGITALMULTIMETER

large 5 mm LCD display continuity buzzer auto zero, auto polarity AC/DC volts and ohms

$8500 MODEL 8016D

DIGITAL DISPLAYFUNCTION GENERATOR

0.2 Hz to 2 MHz frequencyrange

Wave forms: Sine, triangle,square, pulse and ramp

Output level:20V p -p open circuit

V.C.F: 0 to 10V (1000:1) Frequency counter:

6 -digit displayAvailable without digital display(Model 8015F) - $260.

Circle No. 33 on Reader Service Card

$43500REGULATED DC POWER SUPPLIESPower supplies designed forproduction line or laboratoryuse. They feature constantcurrent and voltage outputs,with excellent regulation.SINGLE OUTPUT MODELSGPS-6010: .010/0 regulation,0-60 Volts,0-1 Amps. $32900GPS-3020: .010/0 regulation,0-30 Volts,0-2 Amps. $32900

DUAL OUTPUT MODELSGPD-6010: .020/0 regulation,0-60 x 2 Volts,0-1 x 2 Amps. $57500GPD-3020: .02% regulation,0-30 x 2 Volts,0-2 x 2 Amps. $57500

35

Review

Commodore 16

211,1t;

Commodore offers asmaller version of thepopular C64 for twohundred dollars,. featur-ing 16K and a powerfulBASIC.

By Bill Mark wick

THE CRAZE for home computers haslevelled off these days, and if you haven'tbought one yet, you might be wonderingabout the various plastic boxes that youcan just see through the settling dustcloud. The emerging standard seems to beIBM, or at least compatible MS-DOSmachines, and Apple appears to be secondfavourite. Both of these machines and36

their attendant clones are still a bit pricey,and the next one down the list would bethe Commodore 64. These aren't par-ticularly expensive, but if you're stillafraid that you might not be able to findto get your money's worth out of a homecomputer, CBM now has the model 16.It's powerful enough to do a fair amountof programming, plus cheap enough thatit can gather dust in the closet withoutcausing twinges of regret. However, it's alot more fun to use it:

Using ItIf you're familiar with the C64, you'llnotice right away that the 16 is in the samecase, though its power supply is a tinyplugpack instead of the large box that sitsin the middle of the 64's power cord. Theconnector is not the 64 DIN -type, either,but the sleeve type that you find on por-table radios. The rear connectors aresimilar to the 64, except that there are noedge connectors for the cassette port anduser port; the cassette port is now a tiny

circular 7 -pin jack. The plastic connectorremains, now labelled "memory expan-sion".

The right end looks about the sameexcept for the smaller power connectorand the addition of a Reset button; thetwo joystick ports are still there, nowmarked "Joy 1" and "Joy 2", whichshould puzzle archaeologists in the futurewho may wonder about the machine's in-tended function.

You can use either a TV set (RCAjack output, channels 3 or 4) or a monitor(DIN socket). That's about all the hard-ware you can get at from the outside.

On booting it up, you'll notice thatthe screen is 40 characters by 25 lines andthat the characters are a bit different thanthe 64's; somewhat blockier, but very easyto read. The 64 is noticeably fuzzy whenplugged into a monochrome monitor andrequires eliminating the colour withPOKE 53281, CRTL-2. You don't haveto do this with the 16; the display is crispand clear.

Electronics Today June 1985

You'll also notice the message thatonly 12,227 bytes are available; somememory is lost to the 16's operatingsystem. The 12k should be more thanenough for most BASIC programmingand for running small games; a memoryexpansion module plugs into the back ifyou'd prefer something of a safetymargin.

BASICThe 16 boots with the announcement thatit contains Version 3.5 of Commodore'sBASIC. Just in case you're using it with aTV set that snips off a bit of the image,you can use ESC R to reduce the displayto 38 columns. Arg - get a monitor.

The included manual gives only thebarest of introductions to BASIC; it rat-tles off a few things like PRINT andSOUND and COLOUR in a half -dozenpages. However, CBM has more advanc-ed manuals available; presumably the ideais that most users will run ROM packs andso forth, and the minority who want tocreate programs will have to buy themanual.

The first BASIC function in themanual, after the usual introduction, isSOUND. SOUND 1,266,60 is the syntax,and in order, selects one of three voices(the third is white noise), the next is thepitch, and finally the duration. The note

A (number 770) works out to 440.4Hz,which ought to be close enough to concertpitch to please anybody. The VOL com-mand, from 0 to 8, sets the volume of theoutput. The output is, of course, a squarewave, giving that familiar robotic drone.It's suitable for jazzing up your game pro-grams.

The next tiny section deals withgraphics, and these functions are certainlycomprehensive. You can have the familiarblock graphics marked on the front ofCBM computer keys, or you can inventyour own via DRAW, CIRCLE, BOX,etc.There are 16 colours available and you canset the border, characters, andbackground. Again,. you'll need the moreadvanced programming guide to take fulladvantage of these.

A memory expansion may well benecessary if you want to use the snappygraphics; they take about 10k of memoryfor themselves, leaving you with diddlyfor programming.

The BASIC ROM contains someupgrading compared to previous CBMversions. You'll find PRINT USING forformatting the display, AUTO for linenumbering, and RENUMBER for gettingrid of those odd numbering sequences thattestify that you didn't program it right the

PRODUCT MARTWhere Buyers Seek Sellers!

An advertising feature where companies can reachthousands of Electronics Today, Computing Now! and Soft-ware Now! readers on a nation-wide basis to sell productsand services - where individuals can buy, sell, or swap hard-ware, software, or just information.

Look for it in this month's issues of Electronics Today,Computing Now! or Software Now! It's a classified advertis-ing forum for readers and advertisers alike.

For advertising information call (416) 423-3262, or write:

MoorsheadPublications

Suite 601, 25 Overlea Blvd.,Toronto, Ontario M4H 1B1

Publishers of Electronics Today, Computing Now!, Software Now!and Computers in Education.

first time. There's also a DO loop; thisgives you about the same function as thefamiliar FOR -NEXT, except that it loopsuntil a specified value occurs somewhereinstead of a fixed number of iterations.

There's also a monitor, a real livemachine code monitor. Type MONITORand you can assemble and disassemblecode, load and save machine languageprograms, edit memory, move and com-pare memory, and check out what's hap-pening in the various registers. The CPUis an 8501 which is similar to a 6502 whichis similar to the 6510 in the C64.

PeripheralsThe first peripheral you'll want is pro-bably some kind of storage system. Com-modore offers the 1531 Datasette, the1541 disk drive, and the 1551 disk drive.The cassette is a low-cost alternative todisks, but it's as slow as an arthritic turtle.The 1541 disk drive is only a little bitfaster; you can expect one or two minutesto go by when you load a program. Themanual lists a few other related CBM pro-ducts: their line of printers, the 1700 seriescolour monitors, etc. They also mentionthe Commodore 16 Intermediate User'SManual and the Series 264 Programmer'sReference Guide, manuals well worthhaving.

Return thisad for yourcomplimentarycatalog

11110

"INCREASEYOUR MEMORY

WITH 64K DRAMMEMORY CHIPS"

SEREtkivt"Computerchips

4116 16K 150 NS S 1.494164 64K 150 NS S 3.39

41256 256K 150 NS $22.95

CALL FOR QUANTITY PRICING

Books Breadboard & Accessories Capaci ors Chemicals Connectors Crystals Plugs a Jacks Enclosures Fans Filters Fuses Heal Shr nk Tubing Heal Sinks Kits Knobs Peripherals Probes Opto PC8 Products Pmentameters Power Supples Relays Resistors Cable Assemblms Sockets

db

ActiveYOUR ELECTRONIC

COMPONENT CENTER

MAIL ORDERPROCESSED WITHIN 24 HRS

SELF SERVE STORESUS WESTBOROUGH BELLEVUE

MASS. WASH.(617) 366-9684 (206) 881-8191

CANADA MONTREAL DOWNSVIEW(514) 731-7441 (416) 630-0400

ComirendoneP 0 9103

wesemough. Mass015111 USA

5651 Fem., Stwarty. CV=MP Olt CAN.

1-800-361-5884U.S. 1-800-343-0874

OTTAWA EDMONTON(613) 728-7900 (403) 438-5888TORONTO VANCOUVER(416) 977-7692 (604) 438-3321

CALGARY(403) 235-5300

6E1

37

s 411 The interior of the Model 16 with the RF shield removed.

Other FeaturesThere's a HELP key nested in with thefunction keys. When you encounter a syn-tax error, this key will write the offendingline to the screen in flashing type. Not toouseful, since the computer has alreadytold you which line is wrong.

The other function keys arepreprogrammed to hold GRAPHICS,DLOAD, DIRECTORY, CLEAR,DSAVE, RUN and LIST. They can bereprogrammed from BASIC to whateverelse you prefer. GRAPHICS helps selectthe desired mode by printing the word"graphics" in a BASIC statement; youfollow it with the appropriate number.DLOAD, DSAVE and DIRECTORY arefor the disk operating system; they surebeat the previous Commodore system oftyping in a string of symbols to list thedirectory or load a file.

Most of the other keyboard featuresof the 64 are on the model 16. Besides thelarge selection of graphics characters,there are the screen colour control keys,flashing and inverse video, plus Com-modore's excellent cursoring andfell -screen editing.

SoftwareThere are three possibilities here. The first

is to purchase and plug in a ROM pack;on powering up, it takes over the com-puter and runs whatever's contained in it.Simple enough. The second is the 1531Datasette which plugs into the rear of thecomputer and doesn't require any externalpower. This is the lowest -cost, simplestway for the beginner to load and save pro-grams, but it's frustratingly slow,especially if you have to try and find a filesomewhere in the middle of the tape.There's no directory in one place; if youcan't remember the filename exactly,you'll have to wait for the cassettemachine to trundle through the taperhyming off filenames as it comes tothem. If there's any advantage to the 1531compared to audio recorders, it's that themotor is controlled by the computer andabout all you have to do is press Play orRewind as instructed.

The 1541 disk drive is the next stepup; it's much faster than a cassette tape,though it's still molasses compared to anApple or IBM drive. It also costs morethan the computer, and you can't graft onanother manufacturer's drive because theCommodore operating system is unique.CompatibilityAs mentioned, there's no problem with

The rear of the 16 is similar to the 64, but lacks one user port.

38

Commodore 16

CBM peripherals such as the disk drive,and the CBM works with either a TV or amonitor, monochrome or colour. Soft-ware is another thing. The tiny memorymeans a different layout from itspredecessors, as well as the more obviousproblem that large programs simply won'tfit; the owner of a 16 will have to checkcarefully when offered software that isn'tspecifically designed for it. Incidentally,the general trend in memory devices ismore for less, so it's a good question whyCBM sees fit to put only 16k in the com-puter. Maybe they want to move more ex-pansion packs.

GenerallyAt two hundred dollars, or even less if dis-counted, the 16 is a good deal, with itscomprehensive BASIC and compatibilitywith CBM hardware. Keep in mind thatyou'll need a proper manual and probablya memory expansion cartridge. It isn't amachine for the serious computer addict,but it looks ideal for the beginner.

Quick Reference

Commodore 16CPU: 8501RAM: 16kUser RAM: 12kStorage: optional disk, cassetteVideo: 40 by 25Audio: 3 voice music tonesPrice: $199.95

50 Top Projects156 Pages $4.95

Fifty all-time best projects from ETImagazine packed into one giant 156 pagesspecial. There are projects for the beginnerto the more advanced builder, including:Semiconductor Tester, Universal Counter,LED Level Meter, AM radio, and much,much more.

ORDER TODAY FROMMoorshead Publications, 25 Overlea Boulevard,

Toronto, Ont. M4H 1B1 (416) 423-3262Postage and Handling included.Credit Card payment accepted

Electronics Today June 1985

By Hagen Kornberger

Computing TodayDesigning Z80Projects, Part 1Create practical projectswith the ever -popular,low-cost Z80 CPU

THIS SERIES takes a look at a practicalapproach to designing Z80 projects. Con-necting ROM, RAM, and I/O ports willbe discussed as well as reliable circuits tointerface the Z80 CPU to the externalworld. First let's take a look at the Z80CPU itself.

Z80 InputsThe power inputs, GND and VCC, shouldbe connected to a regulated 5V power sup-ply such as the one shown in Fig. 2, utiliz-ing the popular 7805 regulator. Thispower supply can be used to power TTLas well as other microprocessor chips. It isimportant that a 0.1uF bypass capacitorbe connected across the power inputs ofeach VLSI chip and one for every 5 TTLchips, eliminating any sporadic failurescaused by power spikes induced from thehigh-speed switching elements of theCPU. Also, if the power supply ismounted off the CPU board, a 10 uF elec-trolytic capacitor should be connectedacross the power inputs to the CPUboard.

The master clock frequency, whichcan range from 1MHz to 4MHz, is con-nected to pin 6, the clock input. The com-mon clock frequencies are: 2MHz for theZ80 and 4MHz for the Z80A CPUs. Thisclock frequency is used by the CPU as atiming reference when performing variousoperations. Fig. 3 shows a reliable clockcircuit that will operate in the desiredrange without modification.

When the power is first applied, theCPU needs a special pulse to trigger it inElectronics Today June 1985

All - -A101 40

Al2 - 2 39 -A9A13- 3 38 -ABA14 - 4 37 -A7A15 - 5 36 -A6CLK- 6 35 -A5D4 - 7 34 -A4D3 - 8 33 -A3D5 - 9 32 -A2D6 - 10 31 -AlVCC- 11 30 -AO

D2 - 12 29 -GND

D7 - 13 28 -RrSHDI - 14 27 -MI

DO - 15 26 -RESETINT - 16 25 -BUSRQ

NMI - 17 24 -WAIT

HALT- 18 23 -BUSAKMREQ- 19 22 -WR

IORQ - 20 21 -RD

Fig. 1 Z80 CPU pinout.

Fig. 2 5V regulated power supply.

the right direction. This input is called thereset input. A suitable power -on reset cir-cuit is shown in Fig. 4 with a manual resetbutton included. This reset circuit can beused to drive other LSI chips requiring areset input.

The interrupt feature allows the CPUto finish the instruction that it's doing,and then accept an instruction fromanother peripheral while the first onewaits. The NMI and INT inputs providethe CPU with two types of interrupts. Thefirst is a non-maskable interrupt, whichmeans that it cannot be internally disabledby the CPU itself, whereas the secondcan. In addition, the INT can operate inthree different modes, allowing up to 128devices to be connected to this input. In-terrupts will be further discussed later onin the series, so for now these may be tiedto the 5V line via a 1K pull-up resistor.

The WAIT input allows slow I/O andmemory devices to be connected to theCPU. When this line is brought to thelogic zero state, extra cycles called WAITcycles are introduced to wait for theslower chips to input or output data.Since most modern chips can accom-modate a Z80 CPU at 4MHz, this line canalso be tied to the 5V rail with a 1Kresistor.

The final CPU input is the BUSRQ.This line, when brought to logic zero,causes the CPU to shut itself off. The ad-dress bus, data bus, and control bus areplaced in the high impedance state and the

39

INTRODUCING:THE NEW STANDARD

FOR IBM PC/XTCOMPATIBILITY

The ACS -1000 Super Computer

INTRODUCING:THE NEW STANDARD

FOR IBM PC/XTCOMPATIBILITY

The ACS -1000 Super Computer1 Megabyte On -Board Memory

Built-in Disk Controller- up to 4 Floppies- SASI Hard Disk Interface

54 KB User Definable ROM Switchable: 4.77 or 8 MHZ Built-in Multifunction Board

- Parallel Printer Port- 2 Serial Ports- Time -of -day Clock

Seize Control of YourHardware Destiny

If you are using board level microcom-puters you can have greater power, versatilityand reliability by using the ACS -1000 singleboard SuperComputer.

The ACS -1000 is compatible with bothsoftware and hardware designed for the IBMPC/XT. It even has the same mounting holesand the same power supply connections. Thedifference is that the ACS -1000 offers a muchhigher level of integration and costs less than$600 when ordered in quantity.

Save your Expansion Slots for true ex-pansion. Disk Controllers, I/O ports and ex-tensive memory are already built-in, simplif-ing production and freeing the 6 expansionslots to take on specialized work of your pro-cess control, CAD/ CAM or office automa-tion applications. There's even a special portfor a low cost piggyback modem.

See for yourself. We are offering asystem evaluation kit for $995.00. The 128Ksystem includes bios, documentation, and anXT compatible power supply.

Special introductory offer onperipherals and chips.

Shugart SA 455 Floppy Drives $185.00,IBM Compatible cases $65.00, 130 WattPower Supplies $220.00, Keyboard$200.00, Chips 64K $3.00, 256K $14.00.

To order call 604-888-2606 or write:Soheck Industries Inc.9274 - 194th Street

Surrey, B.C. V3T 4W2

Computing Today

CPU then acknowledges this state by out-putting a low on the BUSAK output. Dur-ing this state other devices, such as CPUsor DMA (Direct Memory Access) con-trollers, can access the memory and I/Odevices controlled by the Z80. In this statethe CPU is completely idle and any inter-rupts incurred will be ignored.

at a logic level one until the appropriatecycle drives two of the outputs low. Table2 summarizes the four different machinecycles. The MREQ signal indicates amemory read/write cycle and the IORQindicates an input/output cycle. Finally,the RD and WR signals indicate read andwrite operations respectively. Most Z80

Fig. 3 Z80 CPU clock circuit using the 74L504 Hex inverter

Z80 Output PinsGenerally, the HALT output is used to in-dicate to a peripheral device that the CPUis waiting for data and it should interruptthe CPU when it has the data ready.Apart from that, this output line is nottoo useful.

The RFSH output is used to indicatea memory refresh cycle which is used bydynamic RAM chips to refresh its datacontents. During this cycle the lower sevenbits of the address bus contain a refreshaddress used by the dynamic RAM. Thiscycle is provided to reduce the number ofchips necessary to connect dynamic RAMto the Z80 CPU. In instances when noRAM is required, this line can bedisregarded.

The MI signal is a multi -purposeoutput line, which when used with MREQand IORQ outputs, can indicate an in-struction fetch, reset cycle, and interruptcycle. Table 1 illustrates the differentcombinations.

The next set of output pins is calledthe control bus, and consists of MREQ,IORQ, RD, and WR. All of these signalsare active low; this means that they are all

Fig. 5 Decoder for the control bus.

peripheral chips use these four outputsand decode the proper signal internally.However, older 8080 peripheral chipsneed decoding to indicate what cycle is be-ing performed. Fig. 5 shows a typicaldecoding circuit used to indicate what cy-cle is being performed.

There are sixteen address lines label-ed AO through A15, giving the Z80 thecapability to address 65536 differentmemory locations. When addressing anI/O port, only the lower 8 bits of the ad-dress bus is used, allowing the Z80 CPUto address up to 256 different I/O ports.

The final set of pins make up the databus. These lines, labeled DO through D7,are bidirectional, i.e., data can be input oroutput from the same lines. To determinethe direction of the data, the RD or WRcontrol lines are used.

BufferingSince there are thousands of transistorsinside the Z80 CPU, not only is the sizereduced, but also the drive capability ofeach transistor. Buffers are needed whenthe load placed on the CPU exceeds themaximum ratings. The maximum currentwhich the CPU can handle for one outputpin is 1.8mA in the logic zero state and250mA in the logic one state. This meansthat each output is capable of driving onestandard TTL load. Table 3 shows a list oftypical loads placed on the Z80 CPU. Forsmall microprocessor projects (one ROMchip, one RAM chip, and a PIO) no buf-fers are needed. In fact, the buffers woulddraw more current from the CPU than theoriginal chips.

Fig. 6 shows how to connect a bufferto the data bus using a 74LS245 bidirec-tional buffer. The WR signal is connectedto pin 1 on the 74LS245, controlling thedirection of data flowing from the buffer.Pin 19 is connected to the BUSAK signal

40

A01Z80CPU Alt

A216

A3,15

A413.4 14

A55 13

12

A713711

BUSA

18

17 741...S

245

1213

4

6

8

> AO

> AlBuffered

> A2 Bus> A3

> A4

A5

A6

A7

Fig. 7 Address and controlbus buffer.

Z80CPU DO

17DI .

D21216

D3

D4 7

D519

D6

D7

BUSAK

18

IS

14 6 >D413 1

2 1

> D5>D6

II I 9> D7

DO3

74LS BufferedDI

245 4 DataD2Bus

1-5--> D3

Fig. 6 Data Bus buffer.

Food for thought . . .

In the Third World there is ashortage of schools, desks,equipment, teachers, money. Yeteducation today puts food on thetable tomorrow. USC Canadaprovides literacy programs foradults and working children,management trainingcooperatives, secondary schoolscholarships, vocational trainingand builds and upgrades villageprimary schools. Write fordetails.

Please send contributions to:

USC Canada56 Sparks Street Ottawa, Ontario, K1 P 5B1(613) 234-6827Registration number 006 4758 09 10 i'lrrERS°Founded by Dr. Lotta Hitschmanova in 1945

Electronics Today June 1985

coming form the CPU, insuring that thedata bus buffer is shut off when the databus on the CPU is turned off.

Fig. 7 illustrates how to connect buf-fers to the control and address buses.Again a 74LS245 buffer is used, but thistime pin 1 on the buffer is tied to groundbecause direction on the address bus doesnot change. The 74LS245 is not the onlybuffer that can be used; however, thisbuffer is preferred because of the simplelayout of the pin connections.

Pin Name Description Type

GND, VCC Power InputCLK Clock Frequency InputReset Power -on Reset InputNMI, INT Interrupts InputWAIT Wait Cycle Request InputBUSRQ Bus Request InputBUSAK Bus Request

Acknowledge OutputHALT CPU Halt Executed OutputRFSH Memory Refresh

Cycle OutputM 1 Machine Cycle I OutputMREQ, IORQRD, WR Control Bus Output, tristateAO -A15 Address Bus Output, tristateDO -D7 Data Bus I/O, tristate

MI MREQ IORQ Type of Cycle

0 I 0 Reset0 0 I Instruction Fetch0 I 0 Interrupt Acknowledge

Table 1

MREQ IORQ RD WR Type of Cycle

0 I 0 1 Memory read0 I I 0 Memory writeI 0 0 I I/O Read1 0 I 0 1/0 write

Table 2

Logic "I" Logic "0"Z80 CPU Drive Current 250uA I .8mAStandard TTL (i.e. 74(0) 40uA I.6mALow power TTL (i.e.74L500) 40uA 0.4mAEPROM (i.e. 2716) 10uA 10uARAM (i.e. 2128) 10uA 10uAZ80 PIO 10uA 10uAZ80 CTC 10uA 10uA

Table 3.

Next month, we discuss ROM chips andhow to connect them to the Z80 CPU. IN

41

Designer's NotebookPower Amp Design:Cutting through thesuperstition and hype ofpower amplifier design.

By John Linsley Hood

A CONSIDERABLE amount of mystiquesurrounds the whole field of audioamplifier design, particularly poweramplifiers, and a vast amount of time isspent in labs and listening rooms sortingthe good from the not -so -good. Howmuch of this mystique is justified is aspeculative question.

My own feelings in this matter, par-ticularly in respect to hifi devotees, arehighly ambivalent. On one hand, I amconvinced that much of the stock in tradeof hifi journals, reviewers, and manufac-turers who follow in the train of their ap-proval, is built on the identification andexaggeration of differences which are, inreality, fairly small. On the other hand, Iknow that there are sound differences bet-ween differing designs. Contributing fac-tors undoubtedly reside in a gray area oftechnology not yet clearly defined.

Output PowerBecause of the nature of the sensitivity ofthe human ear, doubling the power fed toa speaker does not make the resultantsound twice as loud. In reality, this is alogarithmic relationship, in which ap-parent increases in sound loudness areted to power by by the equation W = k.log

P2/P1. While precision in this field is dif-ficult because the loudness/power rela-tionship varies with level and frequency,one can say roughly that ten times thepower doubles the loudness; in otherwords, 3W, 30W, and 300W are in-crements corresponding to doublings ofloudness. One can see that very big stepsin amplifier power are required to getsignificant gains in sound level. The con-verse is also true, that microscopicamounts of sound power, like the buzzingof a fly's wings or amplifier noisevoltages, are still quite audible.

Power is related to the square of thevoltage or current; if an output power of100W is required into 8 ohms, the RMSoutput voltage must be 28.3V. This cor-responds to an 80V peak -to -peak swing.Allowing for voltage drops in the outputtransistors, emitter resistors, etc., the sup-ply should be closer to 100V. Now let ussuppose that the loudspeaker impedancedrops to 2 ohms at I5KHz. 100W will thencorrespond to 10A peak current. Ouramplifier, to meet this spec, would require28.3V RMS and 10A peak currentcapability. Fortunately, it usually doesn'trequire them simultaneously.

Power BandwidthThe audio spectrum is assumed to lie bet-ween 20Hz and 20KHz, but with averagelistening rooms, average listeners, andaverage program material, 45Hz to15KHz is more realistic. Happily, thereisn't much program energy above 10KHz,so we don't need to cater for maximumpower in this region unless the equipment

Series)is going to be reviewed. There is also notmuch very low frequency content fromprogram material or loudspeakers. Unfor-tunately, if the amplifier cannot operatewell below 30-40Hz it may sound thin andwill probably overload on record rumbleand the like.

Some listeners with acute hearing canundoubtedly hear the difference when HFresponse is curtailed even if this is abovetheir ear's frequency response, because ofthe absence of beat -note effects due to theinteraction of HF sounds within thenon-linearities of their own ears. A betterHF response may not make things soundbetter, but it can make them sound dif-ferent.

This is where the first of the needs tocompromise occurs. With typical powerjunction transistors, which are fairly slug-gish devices, increased HF power band-width can only be obtained a the expenseof loop stability in a negative feedbackamplifier. If loop stability is poor, theamplifier transient response is bad, andthis can introduce some pretty drasticdistortions into pulse type signals such asdrum beats or cymbal clashes. Anamplifier with good loop stability is usual-ly much more pleasant to listen to, andwill certainly be less critical about thespeaker load characteristics.

Feedback and StabilityNegative feedback is the comparison ofthe input signal with the output and thegeneration of a corrective adjustment tothe input signal to make sure input andoutput are closely identical. It is the majortool of circuit designers, but there aresnags.

We need to make sure that our use offeedback does not make the whole systemunstable, and this is particularly the casefor amplifiers which have to drivespeakers, since these are notoriously com-

0

SETTLING ITIMEIii

===

SETTLINGI- TIME

10kHz INPUT SIGNAL

OUTPUT FROMAMPLIFIER OF FIG.1

OUTPUT FROMAMPLIFIER OF F10.2

50uS

TIME

100uS

Fig. 1 Gain/phase or Bode diagram for conditionally stable feed -back Fig. 2 Influence of gain and phase margins of NFB amplifiers and settlingamplifier (a change of load might make this amplifier oscillate at 30-50 kHz). time.42 Electronics Today June 1985

plex in their impedance and delayedresponse characteristics. It is also essentialto remember that a feedback path is justwhat its name suggests: a means by whichsignal components can be fed back fromthe speaker to the input. Since speakerscan generate signals of their own becauseof internal cabinet echoes and inadequate-ly damped reflections, we have to watchthis point.

With regard to loop stability, thisfield was investigated by Bode and Ny-quist many years ago in respect toclosed -loop servomechanisms. I find theBode diagram of Fig. 1 the easiest tofollow and explain. In this, the gain andphase shift are shown as a function of fre-quency. If the amplifier has a gain of 1 ormore at a frequency where the feedback isin phase with the input (feedback shift of180 deg.) it will oscillate. The reason forthis is simple: the feedback path is pro-viding an input signal of the right size andphase to generate the actual outputwithout the need for any other signal at all(the circuit starts by amplifying its own in-herent noise). If the gain is more than uni-ty, the output will continue to increase un-til some other effect such as clippingreduces it to unity.

It isn't sufficient merely to ensurethat the amplifier doesn't oscillate onload. There must be an adequate marginof gain or phase at the unity gain point tomake sure that the amplifier is not trig-gered into misbehaviour during transientsin the input signal. In particular, the settl-ing time, or time required following an in-put voltage excursion for the circuit to set-tle to the new value, depends solely on thesystem's speed and stability margin, asshown in Fig. 2. I would very much muchlike reviewers of audio amps to measurethis value for a step input with a real livespeaker load, since this is one of the areaswhere the pursuit of very low THD figuresat the top end of the audio spectrum canlead to circuit design characteristics whichare bad for the transient handling qualitiesof the amplifier and make it fussy aboutthe speaker with which it is used. It seemspointless to try to reduce .1 percent distor-tion at 20KHz to .01 percent if the priceyou pay is 20 to 50 percent distortion ontransient signals.

In a typical audio amplifier, the ma-jor factor which dominates the gain andHF phase shift characteristics is therelative slowness of the output transistors.The faster the response of these, the easierit is to design a good, stable amp. Thecatch is that fast junction output tran-sistors are also more fragile and requiremore restrictive protection circuitry. Thismakes the amp less good at driving lowimpedance loads. The answer, and a vir-tually complete one too, is to use powerMOSFETs. Some of the recent ones havealmost instantaneous response and areElectronics Today June 1985

more linear than either tubes or junctiontransistors. They too have drawbacks, ofwhich the main one is that they are par-ticular about the phase characteristics oftheir loads, but there's a simple designanswer to this. It is possible to designMOSFET amplifiers that are ten timesbetter than their forerunners.

DistortionNot all distortions are equal in theirunpleasing effects, and the characteristicof distortion can be greatly influenced bythe relative phases of the signal com-ponents. This effect has relevance to thebehaviour of multi -driver speakers, whichcan jumble up the phases of a signal and

AMPLIFIER HAVING FTAT LEAST 10to ANDSTABLE AT UNITY GAIN

Fig. 3 Feedback amplifier having good gainand phase margins.

thereby alter the nature of the amplifiernasties. Our efforts in the design exerciseshould be aimed at removing componentsof distortion which can be so transform-ed.

Obviously it is helpful if we can keepthe distortion of the amplifier as low aspossible before feedback is applied, inthat low feedback leeds to better loopstability. A useful design yardstick, cribb-ed from servo theory, is to determine thetime constants of the bits of the circuitwhich lead to HF rolloff, and then makeone of these ten times the size of the rest.This isn't as arbitrary as it seems; if wewish to end up with an ideal Bode plot, wemust remember that the phase shift due toan RC element begins one decade belowthe -3dB rolloff point. In this way, thesystem will behave as though it had only asingle phase -shifting component.

Another useful design approach is to

limit the system to no more than twostages within the loop, adding more loopsif necessary. This isn't always possiblewith power amps, so other approaches,such as the phase -lead generating stepnetwork, may be necessary. One canalways put in a an internal loop operatingonly at HF where transistor trouble is like-ly to arise, and include only two gainstages.

The aim of the designer should be toproduce an amplifier in which the har-monic distortion is as low as possible, andthe gain bandwidth is as high as possible,before the application of feedback. Thefeedback should be used mainly to controlthe gain and output impedancecharacteristics rather than as a way oflowering distortion.

As far as the feedback path is con-cerned, it is best not to use a parallelcapacitor across the feedback resistor asthis can make the amplifier sound lessgood on some speaker units. It is alsohelpful if a small resistor in the range of0.15 to 0.33 ohms is added in series withthe output to act as one element of an at-tenuator. Against the much lower outputimpedance of the amplifier, this will assistin attenuating signals originating from thespeaker itself. (Editor's note: this goesagainst thestandard dogma of having thelowest possible output impedance to raisethe damping factor. Comments fromdesigners are invited.)

A final thought with regard toamplifier sound. The human ear is not aparticularly good judge of distortion inthat a number of randomly chosen peo-ple, all reasonable aware of sound quality,either preferred the addition of 0.3 per-cent third harmonic distortion, or had nospecific preferences. Similar work hasbeen done by other investigators. Thistends to cast doubt on the value of suchjudgements, where the listener may ac-tually prefer inferior equipment because itadds a wanted colouration to the sound.

A Practical DesignMy preference for power MOSFETs asthe output devices is definite, but not justsimple source followers where they requirean output inductor in the speaker lead to

E,n0--A/VV

--3dB0 \\\ GAIN

to -10- I

\I

-2o -.1

Eoot

7 0V

PHASE

-20dB

fol100 to/10 to 10fo

FREQUENCY

10010

-90°

180°

Fig. 4 Gain/phasediagram for a simpleRC attenuator; thecharacteristics of theamplifier in Fig. 2would be similar tothis.

43

Designer's Notebook

INPUT

C10.47u

R3100R

Q2

R24k7

8122k

4-44

R510OR

25OR

R7lkO

C3

2mA

R833R

R10250R

Vs*Ill

tcs

R13680R

R622k

10mA R1422k

5 09

Q6 010

R4 R11270R 56R

I Vs 111

Fig. 5 Power amp. driver stage.

prevent VHF oscillation due to thedevice's own small lead inductance. If thepower MOSFET is used in combinationwith a bipolar small -signal transistor asshown, this small inelegance can be avoid-ed without degradation of the fastresponse of the MOSFET. The onlynecessary device protection can then be anoutput fuse or a current -limited DC supp-ly.

A typical small -signal voltageamplifier to drive this output stage isshown. Because small -signal transistorsare cheap I have been lavish in using themto confer some practical benefit to the cir-cuit. R2 and C2 roll off the response at33KHz to prevent very fast transientsfrom affecting the circuit. RI defines thezero -volts DC level. Q5 and Q6 are acompound constant -current source, set-ting lmA each through Q1 and Q4, andminimizing noise pickup through thenegative supply. PRI allows the outputDC voltage (offset voltage) to be set toprecisely zero.

I have chosen to use a current mirror,Q2 and Q3, as the load for the differentialamp in order to combine the signals fromthe two input transistors and optimize theinput stage gain. From this, the signal isfed to the second stage PNP amplifier Q8,again loaded by a constant current sourceto ensure high AC gain and low distor-tion. R11 is chosen to give a collector cur-rent of 10mA in order to lessen the effectof variable drive current into the outputstage and to push the maximum slewingrate possible with C4 up to a high value.

RIO, bypassed by C5, provides the

NFBC-4I

NOTE01,4,5,6,10 ARE NPN 50V WKG02,3,7 ARE PNP 50V WKGQ8,12 ARE PNP 100V WKG 1600mWI09,11 ARE NPN 100V WKG (600mW)

R15lkO

R161k0

011

Q12

ZD1

R17270R

R18270R

ZD2

R20022R

(ALL SUPPLY LINESBYPASSED TO OVBY CAPACITORS/

Vs+12)

013P -CHANNELMOSFET

R190.22R

R220.22R

R218R

C6

T''"014N -CHANNELMOSFET

Vs 121

LS1

0 OV

Fig. 6 MOSFET output stage.

2.5V bias to set the output stage at 100mAquiescent current.

Under overload conditions, Q9 and10 limit the current which can be drawnfrom the -Ve line to 10mA. Q7 and R8provide a similar protective function forQ8.

R9, R7 and C3 provide the negativefeedback path from the output stage tostabilize the AC gain to 27 which allowsmaximum output (in this case, 50W) from0 VU or .77V input. C4 provides HFstabilization by means of an internal HFfeedback loop enclosing the two stagesQ1/4 and Q8, which gives a goodwell -damped transient response, especial-ly with reactive loads. Eight ohm speakersmost definitely do not behave likeresistances.

R12 and R13 serve the useful func-tion of preventing temporary latch -up ifthe amplifier is driven into clipping; intheir absence clicks and bangs are pro-longed and sound louder.

The output stage is unusual in that ituses MOSFETs in a compound emitterfollower configuration with Q11 and Q12as the input devices. Excess voltage acrossthe gate/source junctions is prevented byZD1 and ZD2, while R15/16 and R16/18limit the AC gain of the output to 5.

R22 is the resistor which attenuatessignals returned from the speaker unit,and R21 /C6 is the Zobel network whichprevents the output from seeing an opencircuit if the speaker is removed.

The power supplies are shown withtwo numbers; if two channels are used, itis advantageous to use two separate power

supplies to prevent interaction, particular-ly to prevent power supply nasties fromintruding into the sensitive input stages.You could always run the inputs from aregulator, since it draws only 12mA; youcan then use a single large power supplywith protective fuses in the speaker lines.

This article is meant as a design exer-cise; I am not going to fill in all the smalldetails of power supplies, PCB, and soon. Designers may wish to do a bit of"fine-tuning" to make sure it as good aspossible in all the various conflicting re-quirements of the system.

44 Electronics Today June 1985

Almost Free Software

ALMOST FREE SOFTWARE

OFFER

MoorsheadPublications

Almost Free Software #1, #2 and #3 are forCP/M and are available in a variety of for-mats: Apple // + CP/M, 8 inch SSSD*, Ac-cess Matrix, Morrow Micro Decision, Super -brain, Xerox/Cromemco*, Epson QX-10VD,Sanyo MBC 1000, Nelma Persona, Kaypro II,Osborne and double densities, Televideo, DECVT -180, Casio FP -1000, Zorba.

Modem 7. Allows you to communicate with anyCP/M based system and download files. Completedetails were in Computing Now! November 1983.

PACMAN. You can actually play PACMAN withoutgraphics, and it works pretty fast.

FORTH. A complete up-to-date version of FIGFORTH, complete with its own internal DOS.

DUU. The ultimate disk utility allowing you torecover accidentally erased disk files, fix gorched files,rebuild and modify your system. A real gem.

D. A sorted directory program that tells you how bigyour files are and how much space is left on the disk.

USQ/SQ. Lets you compress and uncompress files.You can pack about 40% more stuff on a disk withthis system.

Almost Free Software (CP/M) #1

Finance. A fairly sophisticated financial package writ-ten in easily understandable, modifiable MicrosoftBASIC.

BADLIM. Ever had to throw out a disk with a singlebad sector? This isolates bad sectors into an invisiblefile, making the rest of the disk useable.

DISK. Allows you to move whole masses of files fromdisk to disk without having to do every one by hand,you can also view and erase files with little typing.

QUEST. A "Dungeons and Dragons" type game.

STOCKS. This is a complete stock management pro-gram in BASIC.

SEE. Also known as TYPEI7, will TYPE any file,squeezed for not allowing you to keep documents incompressed form while still being able to read them.

Order as AFS #1,and specify system

$19.95 eachExcept for 8" disks and those with two diskswhich are marked with an asterisk (*) abovewhich are:

$22.95'single density formats require two disks. The packagecost for these formats is $22.95.

Almost Free Software (CP/M) #2

.

.............ir

"""."'""'.II.1.1.01/11

''..".":*. ... /matt

... I III .4131

II ......1,11. .............

BISHOW The ultimate file typer, BISHOW version3.1 will type squeezed or unsqueezed files and allowyou to type files which are in libraries (see LU, below).However, it also pages in both directions, so if youmiss something, you can back up and see it again.

LU Every CP/M file takes up unneccessary overhead.If you want to store lots of ata in a small space, you'llwant LU, the library utility. It permits any number ofindividual files to be stored in one big file and crackedapart again.

MORTGAGE This is a very fancy mortgage amortiza-tion program which will produce a variety of amor-tization tables.

NSBASIC Large disk BASIC packages, such as

MBASIC, are great . . . and very expensive. This one,however, is free . . . and every bit as powerful as manycommercial programs. It's compatible with North StarBASIC, so you'll have no problem finding a manualfor it.

RACQUEL Everyone should have one printer picturein their disk collection.

7.30ASM This is a complete assembler package whichuses true Zilog Z80 mnemonics. It has a richvocabulary of pseudo-ops and will allow you to usethe full power of your Z80 based machine . .. muchof which can't be handled by ASM or MAC.

VFILE Easily the ultimate disk utility, VFILE showsyou a full screen presentation of what's on your diskand allows you to mass move and delete files using atwo dimensional cursor. It has heaps of features, abuilt-in help file and works extremely fast.

ROMAN This is a silly little program which figuresout Roman numerals for you. However, silly pro-grams are so much fun . . .

CATCHUM If you like the fast pace and incrediblerealism of Pacman, you'll go quietly insane over Cat -chum . . . which plays basically the same game usingASCII characters. Watch little "C'"s gobble periodswhile you try to avoid the delay "A's" . .. it's ascream.

Order as AFS #2and specify system

$19.95 eachExcept for 8" disks and those with two diskswhich are marked with an asterisk (*) abovewhich are:

$22.95*single density formats require two disks. The packagecost for these formats is $22.95.

Electronics Today June 1985 See Order From Page 51 4.5

OIL. This is an interesting simulation of the workingsof the oil industry. It can be approached as either agame or a fairly sophisticated model.

CHESS. This program really does play a mean gameof chess. It has an on -screen display of the board, achoice of colours and selectable levels of look ahead.

DEBUG. The DDT debugger is good but this offersheaps of facilities that DDT can't and does symbolicdebugging... it's almost like being able to step, traceand disasemble through your source listing.

DU87. The older DUU program does have somelimitations. The version overcomes them all and addssome valuable capacities. It will adapt itself to anysystem. You can search map and dump disk sectors orfiles. It's invaluable in recovering damaged files too.

ELIZA. This classic program is a micro computerhead shrinker... it runs under MBASIC, and with verylittle imagination, you will be able to believe that youare conversing with a real psychiatrist.

Almost Free Software (CP/M) #3

LADDER. This is... this program is weird. It'sDonkey Kong in ASCII. It's fast, bizarre and good forhours of eye strain.

QUIKKEY. Programmable function keys allow you tohit one key to issue a multicharacter command. Thistiny utility allows you to define as many functions asyou want using infrequently used control codes and tochange them at any time... even from within anotherprogram.

RESOURCE. While a debugger will allow you todisassemble small bits of code easily enough, only atrue text based disassembler can take a COM file andmake source out of it again. This is one of the bestones available.

Order as AFS #3and specify system

Almost Free Apple DOS Software

$19.95 eachExcept for 8" disks and those with two diskswhich are marked with an asterisk (1 abovewhich are:

$22.95single density formats require two disks. The packagecost for these formats is $22.95.

Almost Free Apple DOS Software . . . .#1

While CP/M is a wonderful thing in its ownright, the Apple computer can also, and usuallydoes, operate under DOS. For this reason,there's a multitude of programs available forit. Below, we offer a mini -multitude of ourown.

The following programs will operate onany Apple //+, //e, //c, or true compatibleoperating under DOS 3.3. Apple usersoperating only under ProDOS may have tomake alterations to some programs.

Picture Coder: All Apple HiRes pictures take up 36sectors in their binary form. This program creates atext file of a program in memory, squeezing out thezero bytes, that can later be EXECd into memory. Thetext file often takes up less room on the disk.

DNA Tutorial: Operating under Integer BASIC, thisprogram might appeal to 'clone' owners. In actuality,though, it's an interactive low-res graphics tutorial ofDNA in its inherent forms. And you thought your Ap-ple was only good for games...

Toad: Speaking of games, this program is an Ap-plesoft BASIC implementation of 'Frogger' that canbe controlled with either a joystick or the keyboard.The user's high scores are saved to disk.

Function Plotter: A fairly extensive Applesoft BASICprogram that takes any inputted function and plots iton the HiRes Screen.

Data Disk Formatter: Apple DOS disks need not bebootable to be useful. This binary program formats adisk without setting DOS on the tracks, conservinguseful disk space.

BASIC Trace: A program for the advanced Applesoftprogrammer, this file, when EXECd, displays the hex-adecimal locations of each Applesoft line number of aprogram in memory.

Gemini Utility: A word processor pre -boot forGemini printer users, this BASIC program initialisesthe printer's font or pitch before you boot your wordprocesser.

Payments: This BASIC program allows you to keeptrack of payments and credits to and from up to 100accounts on a single disk. A sample account is includ-ed.

Databox: A small but useful database program in Ap-plesoft BASIC. Sample files are included to get youstarted.

Nullspace Invaders: A quick BASIC HiRes gametesting coordination and judgement as you manipulatea monolith through mysterious gates.

Fine Print: The majority of this software has been obtainedfrom on-line public access sources, and is therefore believed tobe in the public domain. Any remaining programs were writtenin-house. The prices of the disks defer the cost of collecting theprograms, debugging them, reproducing and mailing them,plus the cost of the media they're supplied on. The softwareitself is offered without charge.

Moorshead Publications warrants that the software is

readable, and if there are any defects in the medium, we willreplace it free of charge. While considerable efforts has beenmade to ensure that the programs have been thoroughly debug-ged, we are unable to assist you in adapting them for your ownapplications.

Order as AFAD #1and specify system

Each disk is

$19.95or, as an introductory offer you

can order all three for

$39.95

Software Services Moorshead Publications

46 See Order Form Page 5125 Overlea Boulevard, Suite 601, Toronto, Ontario M4H 1B1

Electronics Today June 1985

MoorsheadPublications

Amort: A monthly amortization program thatcalculates monthly payments to an inputted figure,calculates principle, interest on every balance, andprints out the resulting chart.

Voiceprint: An unusual program that uses the HiResscreen to sample sounds inputted through the cassettejacks at the back of your Apple. Sampling rate andother variables can be controlled, and two sounds maybe compared side -by -side.

Cale NOW!: Written in BASIC, this spreadsheet pro-gram is somewhat slower than VisiCalc, but still offersthe power you expect from a spreadsheet. With samplefiles.

Cavern Crusader: A mix of BASIC and binary pro-gramming, winning this HiRes game is difficult, to saythe least. For every wave of aliens shot in the cavern,there's always a meaner bunch in the wings.

Newcout: With source file. This binary programreplaces the I/O hooks in the Apple with its own soyou can operate your Apple through the HiRes screen.Comes with a character set.

Almost Free Apple DOS Software . . . . #2

Charset Editor: A utility to help you create your owncharacter sets to use with Newcout.

Calendar: A BASIC utility useful for finding a par-ticular day of any inputted month and year, or forprinting out any given year.

LCLODR: With source. This binary utility BLOADsany given file into the 16K language card space at$D000. The source is useful in showing how to useDOS commands through assembly language.

Cristo Rey: An animated HiRes BASIC programshowing Cristo Rey by moonlight. For apartment --bound romantics.

ATOT: That's an acronym for 'Applesoft to Text'.EXEC this text file to produce a text file of your pro-gram.

Applesoft Deflator: This program takes a textfilemade by ATOT and squeezes it, replacing PRINTstatements with '?' and removing unnecessary spacesfrom the listing.

Almost Free PC Software

Order as AFAD #2and specify system

Each disk is

$19.95or, as an introductory offer you

can order all three for

$39.95

Almost Free PC Software #1

Our Almost Free Software disks, volumes onethrough three, for systems running CP/Mhave been so thunderingly popular that wehave assembled a volume for IBM PC users.The considerably greater power of a sixteen bitsystem, coupled with its larger capacity diskdrives, have enabled us to offer a collection ofprograms that will knock the socks off virtual-ly any sentient life form booting the disk. Bewarned... wear sandals when you unwrap thisthing.

This software will run superbly on ge-nuine IBM PC's and compatible systems.

PC -WRITE While not quite Wordstar for nothing,this package comes extremely close to equalling thepower of commercial word processors costing five orsix bills. It has full screen editing, cursor movementwith the cursor mover keypad, help screens and all thefeatures of the expensive trolls.

SOLFE This is a small BASIC program that playsbaroque music. While it has little practical use, it'sjust a kick to toodle with. It's also a fabulous tutorialon how to use BASICA's sound statements.

PC -TALK Telecommunications packages for theIBM PC are typically intricate, powerful and huge.This one is no exception. It has menus for everythingand allows full control of all its parameters, even thereally silly ones. It does file transfers in both ASCIIdump and MODEM7/XMODEM protocols andcomes with... get this... 119424 bytes of documenta-tion.

SD This sorted directory program produces displayswhich are a lot more readable than those spewed outby typing DIR. It's essential to the continuedmaintenance of civilization as we know it.

Electronics Today June 1985

FORTH This is a small FORTH in Microsoft BASIC.It's good if you want to get used to the ideas and con-cepts of FORTH... you can build on the primitives in-tegral with the language.

LIFE This is an implementation of the classic ecologygame written in 8088 assembler. While you may growtired of watching the cells chewing on each other, intime the source will provide you with a powerful ex-ample of how to write code.

MAGDALEN This is another BASIC music pro-gram. We couldn't decide which of the two we've in-cluded here was the best trip, so we wound up puttingthem both on the disk. Ah... the joys of double sideddrives.

CASHACC This is a fairly sophisticated cash acquisi-tion and limited accounting package written inBASIC. It isn't exactly BPI, but it's a lot less expen-sive and suitable for use in most small business ap-plications.

DATAFILE This is a simple data base manager writ-ten in... yes, trusty Microsoft BASIC.

UNWS Wordstar has this unusual propensity for set-ting the high order bits on some of the characters inthe files it creates. Looks pretty weird when you try todo something other than Wordstar the file, doesn'tit... Here's a utility to strip the bits and"unWordstar" the text. The assembler source for thisone is provided.

HOST2 This is a package including the BASIC sourceand a DOC file to allow users with SmartModems toaccess their PC's remotely. It's a hacker's delight.

Moorshead Publications warrants that the software willbe readable. If defects in the medium prevent this, we willreplace your disk at no cost. While we have made every effortto assure that these programs are completely debugged, we areunable to assist you in adapting them for your application.

See Order Form Page 51

The disk also includes various support anddocumentation files needed to run the software.

We can provide the Almost Free PC SoftwareDisk volume one on either one standard double sideddisk or on two single sided ones.

Order as AFDC #1and specify system.

Only

$19.95or $22.95

for two single sided disks.

continued from page 15 Distortion Meter

C274n7

R35 330k

R36 100k100H:

R37 33k 300Hz

*--AAA/17-1-0tH,R3813k

n3s 3 1kHz

R40 1k8 20k Hz

R41 27k

IC5e

OV

C284n7

R42 330k

100HzR43 100k

00HzR44 33k

3645 10k wim

R46 33:32521kHz

R47 1k8 20kHz

R48 27k

R491k5

THI

IC5b

5

OV

650 220R

R51 22k600mV

60mV652 10k

6.11V

R531006

SIN8

RV62k5

NOTE:IC5 - TL072THI - RA53

SK4

OSCILLATOROUTPUT

Fig. 5 The final circuit diagram of the spot frequency oscillator.

C29 +100u

IC6

C30 t -1000u

R54470R

D6 D8

15

C31 +100u

IC7

C32 IL,1000u

3

R551k0

11

SW9L

NOTE:IC6 - 7815IC7 = 7915

-I-CASE

Fig. 6 The circuit diagram of the stabilized power supply.

Internal view of the prototype. A number of modifications have been incorporated inthe final version, so don't try and follow this wiring too closely!48

Fig. 7 A dual supply from a battery (top) andchanges in the circuit to suit this method.

However, if the supply voltagechosen is the plus and minus 4V5, a pro-blem would arise because the notchamplifier circuit would overload at the 3VRMS required from ICs 2 and 3 for FSDon the measuring instrument. It istherefore necessary to downgrade this abit by cutting out R19 (2k33) so thatSW2b is that shown in Fig. 7. This gives aminimum sensitivity of 1 percent. This re-quires only a IV swing from the notchamplifier.

The Wien BridgeIt is not a difficult matter to generatequite a good notch in a frequencyresponse and tune it to the test waveform,and there are several circuit choices fordoing this. Of these, the two most conve-nient are the RC Twin -T and the Wienbridge.

The interesting thing about the Wienbridge is that it has zero phase shift and anattenuation of just three at one specificfrequency. If one makes the resistors ad-justable, this frequency can be altered. Ifthe capacitors are not quite the same, theattenuation will not be exactly three, butthis can be adjusted by altering the valuesof the resistors.

In the circuit I have chosen, theamplifier is used to simply invert the phaseof the signal and amplify it by 2x. Thisutilizes the feature of the Wien bridge thatthe impedance of one leg is twice that ofthe other when the phase shift producedby each leg is equal. So, if the amplifierapplies a signal to the upper half which isexactly twice that of the lower, the outputwill come to a null at some frequency

Electronics Today June 1985

r.... . .. .. .... . ... .... .... ... .... - .... . . .... ..I grand scheme of things. But without them the grand scheme of things wouldn't work.

They're the unsung heroes. The folks with jobs you never think about. Jobs that are small in the

The guy who spent hours to get you that important software package. Or the teacher who put their

Iown money into ensuring your school has a computer. Don't they deserve more than a slap on the back?

If you agree, please just write a few lines about them. And they could be rewarded with an

Iadvertisement about them and their achievements. As well as a gift from Moorshead Publications. Thereward. Just mail your story to: Moorshead Publications "Reward", Suite 601, 25 Overlea Boulevard,Toronto, Ontario, M4H 1B1. Please be sure to include your name and address. As well as the name,

Iaddress and a snapshot of the person(s) you want to reward.

IMMI 111111111 IN= MEM

oes someone you know deservea special reward?

MoorsheadPublications The reward.

Distortion Meter

dependent on the values chosen. Thisamplifier method eliminates the problemof requiring a very well-balanced dif-ferential amplifier.

If we just want to remove the inputsignal frequency without attenuating theharmonics, the skirts of the notch must bemuch steeper than those of an ordinaryWien bridge. However, we can sharpenthe notch by applying some negative feed-back around the bridge.

To tune the notch frequency so that itexactly coincides with the input frequen-cy, we need to be able to adjust either theCs or the Rs in the network. Since theoperating frequency is given by the equa-tion

1

F0- 21r Ci C2 R3 R4

the values for C are too large to allow theuse of a variable ganged capacitor unless avery high impedance circuit is used. Infact, if the Rs were 10k each, thecapacitors would have to be 16nF for a1KHz notch frequency, and lower fre-quencies would require proportionatelylarger values of capacitors.

It is possible to make such a systemwith an air -spaced twin -gang capacitor,but the necessary high values of R makethe whole unit very sensitive to humpickup. Overall, I think it is better to usevariable resistors, which are easier to getand a lot more compact.

The necessary slow-motion adjust-ment can be obtained by the use of tworesistors in series, one ten times the valueof the other, when the high value resistors(as ganged pairs adjusted together) can beused as the coarse adjustment and thelower ones for fine trimming. This princi-ple could be extended, of course, toemploy three such resistors in series toallow a very fine adjustment indeed.

Since the resistor which adjusts thegain of the Wien amplifier is a singlepotentiometer, a ten -turn type can be us-ed in this position to adjust the gain ofthis leg so that a complete notch is obtain-ed with no residues of the input frequencyremaining.

The final part of the system will be awide bandwidth millivoltmeter to displaythe value of the distortion and noiseresidues remaining when the inputsinewave is removed.

Since we live in the real world andthere will inevitably be some hum pickupsomewhere in the system we are testing, itis useful to incorporate a 60 Hz filterwhich can be switched in. Also, while weare doing that, we might as well includesome HF filtering options so that we don'tmeasure the THD over too wide a fre-quency window, with its associated noisecomponents.

Finally, it is very helpful in tests

The prototype, looking much the way most prototypes do at this stage in theirdevelopment!

BALANCE(10 TURNS)

INPUT

SENSITIVITY

0v

ClSET FREQUENCY

R3a (COARSE)

R3b(FINE)

OUTPUTTOSCOPE

Fig. 8 Wien network with negative feedback to produce a sharper notch.

where one is taking the measuring instru-ment to the gear being tested, to have abuilt-in signal source of adequate quality.

There are two versions of the aboveinstrument in this project; one alaboratory standard instrument operatedfrom the AC line, and a somewhat simplerversion operated from a single 9V battery,which will be somewhat easier to make, ifthe demands made upon it are less str-ingent.

I like battery operated instrumentsmyself because they are highly portableand don't cause problems with groundloops. However, if one wants high perfor-mance, it is impractical to demand muchlower power consumption at the sametime. If one then accepts a higher batterydrain, say, 10-25mA, it is expensive if oneforgets to switch off the instrument afteruse, while any auto -off circuit may switch

it off in the middle of a measurement,which is infuriating.

Hence the two versions of the instru-ment. I have deliberately tried to make thebattery -operated system as economical inuse as possible without resorting to exoticICs, and in both cases I have organizedthings so that the millivoltmeter isavailable as a separate input so that it andthe oscillator can be used on their own asa means, for example, of measuring fre-quency response.

PCBs and constructional details will ap-pear next month.

50 Electronics Today June 1985

Fig. 9a and b - Two possible arrangements of the Wien network.

OUTPUT

1.0

0.9

0.6

0.5

0.0

NOTCH SHARPENED UP BY NFB

NOTCH GIVEN BYWIEN NETWORK

FREQUENCY

Ito/10) 110101

Fig. 10 The notch produced using the arrangement of Fig. 9b.

Fig. 11 Examples of the waveforms obtained by using a notch filteron distorted sine -waves.Electronics Today June 1985

Moorshead Publications

Order FormSubscriptions:Please complete reverse side of order form to start orrenew a subscription.

Back Issues: $4.00 each; Ontario residents add 7% sales tax.Please circle issues desired.

1977 February July1978 April May September November December1979 February March April May July

August September October November1980 January February May June November December1981 January February March April June July

August September October November December1982 January March April May June

July August September October November December1983 January February March April May June July

August September October November December

1984 January February March April May June July AugustOctober November December

On the following items please add $1.00 for postage and handlingplus 7% Ontario provincial sales tax.

Special Publications:QTY ITEM AMOUNT

Hobby Projects $3.95Electronic Circuit Design $3.95Projects Book No. 2 $3.95Personal Computer Guide $3.9550 Top Projects $4.95Your First Computer $3.95Computers in Small Business $3.95 $

Binders: Electronics Today; Computing Now!Moorshead Publications

$9.25 each plus 7% P.S.T.

BOOKSHELFORDER FORM

Code Title Price(e.g. BP12) (Short -form is O.K.)

$

$

$

SOFTWAREORDER FORM

Sub Total $Tax (Ontario Residents) $

Postage $Total Enclosed $

Orders from the Bookshelf are tax exempt. Please add $1.00for postage. Remember to put your name and address onreverse side. See over for mailing details.

Do you currently subscribe to Electronics TodayDo you currently subscribe to Computing Now!Do you currently subscribe to Computers in EducationDo you currently subscribe to Software Now!

Yes NoYes NoYes NoYes No

BE SURE OF YOUR ISSUE EACHMONTH. SUBSCRIBE TODAY.

Electronics*Today

":40I°4".r \ \ ":97Tys fn. APO.

se

PIDCP''SMgA

BOOKS, BACK ISSUES, SPECIALPUBLICATIONS, BINDERS - SEE OVER

Moorshead PublicationsSuite 601, Overlea Blvd., Toronto, Ontario M4H 1B1.

MERCHANDISE ORDER Please fill oul,form overleafSUBSCRIPTIONS: NEW SUBSCRIPTION RENEWALElectronics Today

One year (12 issues) $19.95 0 Two years (24 issues) $34.95.Computing Now!

_ One year (12 issues) $22.95Computers in EducationO One year (10 issues) $25.00Software Now!O One year (12 issues) $19.95

O Two years (24 issues) $37.95

Two years (20 issues) $45.00

O Two years (24 issues) $34.95

For U.S. please add $3.00 per year other countries add $5 per year

NAME

ADDRESS

TOWN/CITY PROVINCE/STATE

CODE DATE

POSTAL CODE

O Cheque enclosed DO NOT send cash

O Mastercard Account No.

O Visa Account No

O American Express Account No

Expiry Date

Signature

Disk FormatConversion Service

There are a lot of computers on this particular planet and, if you're like quite afew users of several of them you'll have noticed that no two seem to have cornpatible disk formats.

The data on your disks . . . and possibly the programs as well . . . might wellbe useable on a whole variety of systems. However, getting the files from onedisk format to another is often where things get a bit tricky.

We have the facilities to move files between a whole variety of popular computers. We can end your data compatibility problems in a few seconds . . .

without having to enrich the national debt on your behalf.Here's the rub . . .

If you have files on a disk in any of the formats listed below you can send usthe disk and some money . . the details of which are also listed below. Tell uswhat format you want the data in. We'll send you back your old disk plus a newone in the format of your choice.

Nothing could be simpler . . at least, not without several governmentedicts.

The details:We will move all the files on a disk to any of the formats listed here. It is up to youto make sure that the files will he useful under the new format. Note that pro-grams moved from format to format may or may not work in their new en-vironments. For example, CP/M based programs will not work under MS-DOSbased systems.

We only undertake to make sure that the files make the trip intact and uncor-rputed.

We cannot move files on copy protected disks.While we will take every precaution to ensure the safety of your disks, we

cannot be responsible for disks or data lost or damaged in the mail. Please don'tsend us original disks . .. make backups.

If the disk you send us contain more data than will fit on one disk in the for-mat you want it transferred to we will copy only those files that will fit unless youallow for the cost of two disks.

We can only copy complete disks.

The formats we are currently able to support are:

Apple CP/M"IBM MS-DOS 1Actrix DSDD'Chameleon'H/Z ICO ZDOS SSDDIdea BitelexKaypro 11/2'Osborne 4 DSDD'PMC Mcromate Superbrain DSDD'Cromemco DSDD'Nelma PersonaEpson Mulhiont DSDD'Groupil III CP/M DSDD'Lobo Max 80512Morrow MD 2NEC PC -8001A SSDDOlympia EX 100 DSDD'TRS80 III HurricaneTRS80 IV Mont MicroTurbo DOS DSDD'Zorba 40 trk SSDD

Apple DOS IBM MS-DOS 2'Avatar TC10'Columbia CPM80'H/Z 100 ZDOS DSDD'ISM CP/M DSDD'LNW-80'Osborne OsmosisReynolds & ReynoldsTI Professional CP/M 86Cromemco SSDDDavidge DSDD'Espson OX- I 0*H/Z 100 CP/M DSDD'MP ral 9050 DSDD'Morrow MD 3 DSDD'NEC PC -8001A DSDD'Osborne SSDDTRS80 III Mem. MerohTeletek 40 trkWang Maws CP/M'

IBM CPMActrix SSDDCasio FP -100Cromemco CDOSHeath MagnoliaInsight 10-120Lobo Max -80'Otrona CP/M Sanyo CP/M TRS-80 FEC SSDDDEC VT180Digdog Fujitsu Micro I6s'1-1/2 100 CP/MMorrow MD 1INCR Decision Mt 5'Olympia ETX IITRS80 FEC T805TRS80 IV CP/M+Toshiba TIOOXerox 82011

Financial matters:The base cost is $25.00 for the hrst disk of any format and 10.00 for each additional dsk inthe same order plus the applicable surcharges. This includes shipping and the cost of a newdisk.

Add $3.00 per disk, Add $10.00 per disk, Add $12.00 per disk.Add $3.00 per disk if the contents of your source disk will not fit onto a single disk in the for-mat of your destination.

Moorshead Publications Disk File Conversion Service25 Overlea Boulevard, Suite 601

Toronto, Ontario M4H 1B1

52 Electronics Today June 1985

Project

Anti PhaserThe Anti Phaser is aphaser with a difference:the notch filters sweepin opposite directions.Suitable for anyamplified instrwnent.

By D Bradshaw

DESIGNING a notch filter is not dif-ficult, and there are several standard con-figurations to choose from. The situationis rather more difficult where a tunablenotch filter is required, and much moredifficult in an application such as thiswhere the filter must be voltage controlledso that it can be swept by a low frequencyoscillator. The main difficulty is thatnotch filters tend to require that severalfilter resistances or capacitances are variedin value and remain accurately matched inorder to give usable results over a widefrequency range.

There are two conventional solutionsto the problem. The most common one isto use a series of voltage controlled phaseshifters, and to then mix the shifted andunshifted signals. At frequencies wherethe signals are out of phase they tend tocancel each other out and produce the re-quired notches of high attenuation in thefrequency response. Two phase shiftersper notch are required, and matching ofthe two voltage controlled resistors (usual-ly JFETs) is unnecessary. The othermethod is essentially the same but uses adifferent system to obtain the anti -phasesignals. Rather than phase shifters ananalogue delay line is utilised.

These days there are practical alter-natives to the conventional systems, and itis one of these that is used in this unit. It isbased on four operational transconduc-tance amplifiers, two being required foreach notch filter. Fig. 1 shows the blockdiagram for the Anti-phaser.

Transconductance amplifiers caneasily be used to act as bandpass, low-pass, or high pass filters, and it is thebandpass configuration which is usedhere. This is, of course, the exact oppositeof what is required here, but a bandpassElectronics Today June 1985

ovBIAS 0

IN 0-/NANN--Ra

+OP AMP

e-AAAA-Rb

d BANDPASSVCF

INVERTER

Rd

BANDPASSVCF

0 OUT

LFTRIANGULAROSCILLATOR

FREQUENCY

Fig. 1 The block diagram of the Anti-Phaser. This is for one notch filter. Two are used.

response can be converted to a notch typesimply by using the filter in the feedbackpath of an inverting mode operationalamplifier circuit. Fig. 2 shows the basic in-verting mode circuit, and the two resistorscontrol the voltage gain of the circuit. Thevoltage gain of the operational amplifieritself is extremely high, being typicallyabout 100,000 times at low frequencies.What it is actually amplifying is the voltagedifference across its two inputs, with theoutput going positive when the non -inverting ( + ) input is at the highervoltage, or negative when it is at a lowervoltage than the inverting (-) input. Dueto the very high voltage gain of the deviceonly a very small voltage difference of

typically under 1 millivolt is needed inorder to send the output fully positive ornegative.

In the circuit of Fig. 2 the negativefeedback from the output to the invertinginput results in the inverting input beingmaintained at the same potential as thenon -inverting input. If an input signalwas to take the inverting input slightlypositive, this would unbalance the inputsand send the output negative. The coupl-ing through R2 would result in the inver-ting input being taken negative, counter-acting the positive input signal and main-taining the balance. Just how negative theoutput has to go for a given input voltagedepends on the values of R1 and R2. If we

R2

OVBIAS

OUT

Fig. 2 The basic circuit which inverts the bandpass response into a notch type response.53

Product Mart Where Buyers Find Sellers

HP -85, Model -A, 16K RAM. Variety of ac-cessories including ROM drawer 82936A,three interfaces and 16K memory module.$4500.00 (value $8500.00). GENTIANELECTRONICS LTD., Box 1240, Stittsville,Ontario KOA 3G0 (613) 836-3987.

2068 USER! Now available, CharacterFont Generator and Text Centrer utilities,plus more! Write for free information toBEAVER COMPUTER PRODUCTS, 781Adamdell, Winnipeg, R2K 2B2.

TS2068 OWNERS. We now carry a largeselection of excellent software for the un-modified TS2068. Write for brochure to: E.MCGHEE, suite 557-21 10405 JasperAvenue Edmonton. Alberta.

"DISK Drives aligned and repaired, allmakes. Most home and personal com-puters repaired. Reasonable rates. Fastturnaround. Call evenings: FM COM-PUTERS, Toronto 281-2151."

TECHNICAL BOOKS. Metalworking,woodworking, electronics, plans, science.Large catalogue $1.00. ERIC KEATS &COMPANY, P.O. Box 796, Station A, Scar-borough, Ontario, M1K 5C8.

CONSTRUCT your own Satellite TV Anten-na for under $100.00. Easy to follow plans$24.95 or send $2.00 for information,refundable on purchase. To: SOTHISSATELLITE SYSTEMS, Box 6637. Station"A", Saint John, N.B. E2L 4S1.

J&J ELECTRONICS Ltd., Box 1437E, Win-nipeg, Manitoba R3C 2Z4. Surplus andSemiconductor Specialists. Do you getour bargain flyer? Send $1.00 to receivethe current literature and specials and tobe placed on the mailing list for futurepublications.

ELECTRONIQUE MASTER VOX LIMITEE,400 rue St -Jean, Longueil, Que. J4H 2X6(514) 670-1550. The largest electronicpart's supplier on Montreal South Shore.

PAY TV in Canada gives schematics anddetails for all systems $11.95. Terrificselection of 4GHZ Microwave TV DishSystems from $79.95 complete. Includesschematics. Complete product catalogue#2, SHOJIKI ELECTRONICS CORP., 1327Niagara St., Niagara Falls, N.Y. 1403C.O.D.s are O.K. 716-282-1001.

DIGITAL Organ and Drum Kits from$475.00, Demo LP $8.00 (Plus $2.00 P/H),Professional 4 to 16 channel Mixer Kitfrom $675.00. Free Infromation fromSELTRON INSTRUMENTS, 35 South-bridge St., Leamington, Ont. N8H 4N4.

ELECTRONIQUEWE DON'T SELL COMPUTERS.WE JUST SELL THE PARTS!

Send your name and address along with$1.00 to: 7454 Langelier, St. LeonardMontreal, Que. H1S 3A7.Tel: (514) 259-5581.

OPENING SPECIAL: Service Centre andRetail Outlet. Computer parts, Interface,Monitor, Printer, Drive, Diskette, system.FORTRESS ELECTRONICS INC. 4429,Sheppard Ave., East, Scarborough,416-293-2266.

BRIDGE Game Software. 1 to 4 players ...$39.95, IBM colour and Monochrome, Ap-ple, Adam, TI99/4A/16K TRS80-1/3/4/CoCo/CoCo2, Commodore 64/C16/+ 4/VIC-20.ALLAN'S MICROCOMPUTING, Box 313,Azilda, Ontario, POM 1130, (705) 983-4341.

CANADIANS; Smashing values; Surplus,closeouts, buyouts; Video, Computer,Cable TV, Telephone, Scanners, RadarDetectors, Wireless Microphones, Parts &Accessories, 60 miles from Montreal. Set ofcatalogs $2.00 ETCO, Box 777, Champlain,N.Y. 12919.

MPF III Apple Ile Compatible $1395.00 64KSlim Drive, Z80, Printer Card, 80 ColumnsAmber or Green Monitor, Shipping $10.00.Send SASS for catalog. RAITRONIC'S,6650 Ross St., Vancouver, B.C. V5X 4B2.

PRINTED CIRCUITS for E.T.I. projects orfrom your artwork are available fromWENTWORTH ELECTRONICS, R.R. #2Burlington, Ontario, L7R 3X5. Write foryour free catalogue!

FOR $10 per kit $2 handling, receive freeflyer and any of the following. #1: 1000asst'd pcs, choke - capacitor - resistor

transistor - hardware - etc.Capacitor specials: #2: 200 asst'd ceramic- #3: 100 asst'd silver mica - #4: 100asst'd mylar - #5: 50 asst'd tantalum -#6: 50 asst'd electrolytic - #7: 50 asst'dfeed -through - #8: 50 asst'd metallicsilver mica (Elmenco) #9: 25 asst'dvariable. All new material. Unconditionalguarantee. Repco Module for portableradio available at special price. SURPLUSELECTRO QUEBEC, 2264 Montee Gagnon,Blainville, Quebec J7E 4H5.

PRIVATE Sale Tektronics 453A-1Oscilloscope. Dual 60 Meg in perfect con-dition includes paraphernalia. Bestreasonable offer. Paid $2200 15 monthsago. After 6 416-654-3356 Toronto.

CERESIST, the guaranteed line of drytransfers for direct etching of PCBs (alsofor layouts on mylar film etc.) comes inover 65 patterns, including 1:1 and Sym-bols too. 1 -of -a -kind and assortmentpackages available. Send stamp for freecatalog w/sample, or $3 for our SP -6 Hob-by Pak with 100s of symbols. Mailing ad-dress only: CERES, 866 Bloor St. W.,Toronto, M6G 1M5.

ZX81, 2068 Disk Drive Controller Card. UseShugart SA 455 or compatible drive. 160KB per disk, ZK DOS on EPROM $119.95.LARKEN ELECTRONICS, RR #2 NauanOntario, KOA 2S0, 613-835-2680.

Advertising in the Product Mart section allows you to reach over 30,000 Canadian readers nation wide for $1.50 per word (minimum 25words). Please contact us for further details on the various sizes and styles available. Moorshead Publications, Suite 601, 25 OverleaBlvd., Toronto. Ontario M4H 1B1, (416) 423-3262.

54 Electronics Today June 1985

Anti Phaser

349

TO IC5PINS 7AND 6

3

IC

R347k

C22u2

IN OUT

+1 R2C 1 3,k,

TOOu

SKIIN

R510k

O 614 3

7 R7lk

0447k

NOTES.IC 1.3 741C1C2.4 LM13600N

TO ICS

015220k

11

C2.

9-12NA/V-. 5

O 847k

6

C3 au..1009

Fig. 3 The signal processing stages of the circuit.

assume that they have the same value thenany increase in voltage at the input willproduce and identical but opposite changein the output voltage. If R2 is made higherin value than RI it becomes necessary forthe output voltage to change by a largeramount in order to maintain the inputvoltage balance by what is really just asimple potential divider action.

What is of greater importance is thisapplication, if R2 is made lower in valuethan RI, the output has to change by asmaller amount than any change at the in-put in order to maintain the balance. Thecircuit can therefore provide both voltagegain and attenuation, depending on thefeedback resistor values. The voltagegain/attenuation of the circuit is simplyequal to the value of R2 divided by thevalue of RI. For instance, if RI and R2had values of (say) 100k and lk respective-ly, this would give a gain of 1/100, ofsome 40dB of attenuation if you prefer.

Returning to the block diagram ofFig. 1, each bandpass filter is connected inthe feedback path of an inverting modeoperational amplifier circuit. In effect thebandpass filters replace R2 of Fig. 2. Atpass frequencies the filter provides a lowresistance, and consequently a very lowlevel of voltage gain. Outside the pass -band it provides a very high feedbackresistance and therefore a very highvoltage gain. In this application we onlyrequire a low level of gain within thefilter's passband, and about unity gainrather than high gain at other frequencies.Rb and Rd are therefore used to limit thefeedback resistance to a suitable level sothat the response of the circuit as a wholeis tamed to an acceptable degree.

The sweeping of the filters is ac-complished using a low frequencyoscillator having a triangular outputwaveform. The sweep frequency is con-tinuously variable from about 0.1Hz to10Hz. One of the notch filters is driven

Electronics Today June 1985

The

27k

R1747k

0166k6

2

3

IC3

7

819474

C6tL10.

OUT

29211

SK2OUT

R1947k

1120104

TO 1C41

62911116

R211k

3

02214

R2322k

11

IC41

6

026224

0261k

4

R27 14..AA

1k

IC44

10

ANION/OFF/

co I . C9MOE 100u

16

12

two notch filters each use two ICs and are identical.

direct from output of the oscillator, butthe other is driven by way of an inverterstage which provides the anti -phase opera-tion of the second filter.

Circuit OperationFig. 3 shows the circuit diagram of thesignal processing stages while theoscillator/inverter circuit diagram appearsin Fig. 4.

Taking Fig. 3 first, RI, and R2 andCl provide a centre tap on the supply rail,effectively giving dual 4V5 supplies fromthe single 9 volt input. The circuit is infact powered from a 9 volt battery and thecurrent consumption is only about 7 mili-amps.

The two notch filters are essentiallythe same, one utilizing IC1 and IC2 whilethe other is built around IC3 and IC4. Wewill consequently only consider the opera-tion of the first filter. The two trans -conductance amplifers of IC2 are con -

coloop

024Ski

R26224

1009C7 ulm, 030

NMI

61Iv

nected in a standard transconductanceamplifier state variable filter configura-tion. Lowpass filtering is produced at theoutput of IC2b, and the bandpass filteringneeded here is obtained at the output ofIC2a. This bandpass filtering is connectedin parallel with feedback resistor R4,which is the equivalent of Rb in Fig. 1.The two transconductance amplifiers areused here as voltage controlled resistorswhich act as lowpass filters in conjunctionwith filter capacitors C3 and C4. Feed-back through R9 and R14 is used to con-vert the response at the output of IC2a tothe required bandpass type.

SW2 provides a means of bypassingthe unit and switching out the effect. Inpractice this is a heavy duty push buttonswitch so that it can be operated by foot.

Turning to Fig. 4 now, IC5 is used asa conventional triangular/square-waveoscillator with IC5a acting as the MillerIntegrator and IC5b being used as the

R3122k

2

3

8

IC5o

4

C102u2

R3215k

1

RV12M2

R3322k

5

TO R29

TO R1,R2, me.

IC5b

6

r 3

2

IC6

7

4

NOTES:IC5 LM358106 CA3140E

0+9V

R34100k

VSAA,RV3220k

TO R16

0 VE

Fig. 4 Part of the circuit, showing the operation of ICS, the L.M. 358.55

Anti Phaser

Schmitt Trigger. RV1 controls thecharge/discharge rate of timing capacitorCIO and it acts as the sweep frequencycontrol. IC6 is used as the inverter stage,and its voltage gain can be varied bymeans of RV3. The bias voltage at thenon -inverting input can also be adjustedwith RV2 providing the adjustablevoltage. This enables the sweep range ofthe first filter to be set so that it exactlymatches the sweep range of the secondfilter.

ConstructionThere are few difficulties here, but do notoverlook the four link wires. Also, IC6 isa MOS input type and therefore requiresthe usual MOS antistatic handling precau-tions to be taken. Use an 8 pin DIL ICsocket for this device, do not fit it intoplace until the unit is otherwise finished,and handle it as little as possible.

C10 must be good quality non -polarised component (ie not an elec-trolytic or a tantalum type), and theprinted circuit board is designed to take aprinted circuit type having 15mm leadspacing. However, it should be possible tofit other types onto the board without toomuch difficulty, but the component usedin the CIO position must be physicallyquite small.

When all the link wires and com-ponents have been fitted onto the boardconnected the battery clip and fit pins atthe points where connections to the otheroff -board components will be made.

CaseSW2 and RV1 are mounted on the top ofthe case (which in this case is the panel op-posite the removable one). SW2 must be aheavy duty component since an ordinarypush button type is unlikely to stand up tofoot operation for long, SK1 is mountedslightly high of a central position on oneof the long sides of the case, and SK2 isfitted opposite this on the other long sidepanel. On the prototype SK1 is a typewhich has DPDT contact, and two ofthese contacts are used as make typeswhich act as on/off switch SW1. The unitis therefore automatically switched onwhen a plug is inserted into SKI, and swit-ched off again when the plug is removed.This is a quite common practice withmusical effects units, but a separate switchcan of course be used for SW I if prefer-red.

After the hard wiring has been com-pleted the printed circuit board ismounted inside the case. There are printedcircuit guide rails built into the case, butthe board will not fit directly into these. Itmust be fitted into the guide rails via a setof four plastic adaptors which enable it tobe mouted at right angles to the rails. Thisadaptors are not normally supplied with56

Fig. 5 The PCB layout. Assembly is straightforward, but see the note in the text about C10.

the case and must be purchased separate-ly. The board must be mounted as lowdown in the case as possible so that it isnot obstructed by the sockets or controls.An alternative method of mounting theboard would be to simply bolt it to thebase panel of the case, using short spacersto keep the connections on the undersideof the board clear of the metal panel.There are plenty of small spaces on theboard where mounting holes can be drill-ed.

There is sufficient space for a 9 voltbattery at one end of the case, and somefoam material can be used to trap the bat-tery firmly in place there. Four small

cabinet feet are fixed to the base panel ofthe case to prevent the unit from slippingwhen SW2 is operated.

In useThe electric guitar or other instrumentconnects to SKI by way of the usualscreened jack lead, and as explainedpreviously, the unit is automatically swit-ched on and off as the plug is inserted intoand withdrawn from SKI. The outputsignal is taken from SK2, and again, anormal screened jack lead is used to takethe output to the amplifier (or whatever).

RV2 and RV3 should be set at aroughly mid setting initially, and the unit

Electronics Today June 1985

Resistors(All 1/4W 507e carbon)RI, 2 3k9R3, 4, 8, 17, 18, 19 47kR5, 20 10kR6, 7, 12, 13, 21, 22, 26, 27 lkR9, 11, 14, 23, 25, 28, 31, 33 22kRIO, 16, 24, 30 5k6R15 220kR29 1M5R32 15kR34 100k

PotentiometersRV1 2M2

linearRV2 22k

0.1W horizontal presetRV3 220k

0.1W horizontal preset

CapacitorsCl, 9 100uF 10V

radial electC2 2u2 63V

radial electC3, 4, 6,7 100pF

ceramic plateC5 10uF 25V

radial elect

C8 10Onfceramic

C10 2u2polyester or carbonate

SemiconductorsICI, 3 741C

op ampIC2, 4 LM13600N or LM13700N

dual transconductance ampIC5 LM358

dual op ampIC6 CA3140E

MOS op amp

MiscellaneousSKI Standard jack with DPDT

contactsSK2 Standard jackSW1 Part of SKISW2 Heavy duty DPDT push

button switchB1 9 volt

150 by 80 by 50mm diecast aluminium box;printed circuit board; control knob, four guiderail adaptors; battery connector; for 8 pin DILIC holders; two 16 pin DIL IC holders;Veropins, wire, etc.

PC/XT Compatible

ECS1-PC/XT11111111 .,$1295.00

. '

8088 processor optional Intel 8087numeric coprocessor 64K memory exp.to 256K on board double sided doubledensity disk drive detachable keyboard colour -graphic board 130 watt powersupply support PC software 90 daywarranty. 8 slot Mother board.

ECS4 Systems

Special

$995.00

it. dual processor 6502 and Z80 64KRAM controller card disk drive Hi.res lilt amber monitor colourgraphics detachable keyboard withspecial function 90 days war:anty

UNIOMODEM 1200 HC1200/300 BPS Intelligent

Modem Hayes Compatible

The UNIQMODEM 1200 HC isHayes Compatible, a high quality,low cost modem for use with per-sonal computers, stand-alone ter-minals, or other intelligent com-munications devices or systems.

$395.00

XT/PC MAIN PERIPHERALMother Board 8 Slot $295.00Color Graphic Card 5169.00Multifunction $169.00Monochrome Card $149.00Monochrome Graphic 5269.00Game Port $ 49.00RS232 Card 69.00Parallel Interface 69.00Disc Controller Card $ 99.00Case $ 75.00Keyboard (Cherry) 5125.00Power Supply 130 Watts 5149.00Printer Cable 25.00RS232 Cable 25.00Disk Drive Cable $ 15.00Moving Message Board .$495.00TTL and CMOF test Card .$ 99.00150 Watt Power Supply . .$159.00

ELECTRONIC CONTROL SYSTEMSirma Awe Aril1590 Matheson Boulevard. Sure 1 8. 2 Mississauga. Ontario L4W 1J1

(416) 625.8036 Hours - Mon. to Fri. 10-6. Sat. 10.2

Circle No. 23 on Reader Service Card

should then provide the anti -phase phas-ing effect. However, the two notches willalmost certainly cover different frequencyspans and will not exactly complementone another. By adjusting RV2 and RV3,using a process of trial and error, it shouldbe possible to set the range of the firstfilter so that it matches that of the second.This adjustment is probably most easilyaccomplished with RV1 adjusted to give amiddle modulation frequency of about1Hz. It is also easier if the input signalcontains a wide range of frequencies (alow frequency squarewave or a noisesignal for example) since the phasing ef-fect is then most apparent. Of course, youcan use any settings for these two presetsthat given an effect you like, and you donot have to adjust them for matchedsweeps.

The sweep range of the first filtershould be satisfactory, but if necessary therange of frequencies covered can be mov-ed up by making R29 lower in value orshifted down by using a higher valueresistor here.

WHY SPEND A FORTUNE ON ADIGITAL CAPACITANCE

METER?The MC100A comes completely assembl-ed and calibrated and at $89.95 is anoutstanding value. The extensive range of1 pF to 9,999 uF (no external meters re-quired) and true hand held portable size(only 4Y." x 2V2" x 17/) make theMC100A an extremely practical and easyto use instrument for the hobbyist techni-cian or engineer.CHECK THESE OTHER FEATURES Basic accuracy 1% (It one count) onpF, nF ranges, 3% ± one count) on uFrange.'Uses single 9V battery (not included).'Decimal points light up when battery islow or when capacitor is overrange_Futl 4 digit high efficiency LED displayuses special circuitry to save on batteries.'Constructed with a tough impact resis-tant plastic case.

ONE YEAR PARTS &LABOUR WARRANTY

DAETRON935 THE OUEENSWAYBOX 641TORONTO ONTARIO M8Z 5Y9(416) 255-9701DEALER ENQUIRIES INVITED

$89.95PLEASE SEND ME

(Quantity) MC100A(s)4 $89.95 s_Ontario residents add 7% PSTPostage - S1.85 (per instrument)(C.O.D. orders ad.:181.591

I ENCLOSE CHEQUE L MONEY ORDER T BILL MY VISA TOTAL 6_VISA CARD NO.

EXPIRY DATE SIGNATUREImmediate shipping on orders with money orders, VISA or certified cheque.Personal Cheques pleaSe allow 2 to 3 weeks for clearance.NAMEADDRESSCITY PROV. POSTAL CODE

MAIL TO DAETRON 935 THE OUEENSWAY BOX 641 TORONTO ONTARIO M8Z 5Y9

Circle No. 7 on Reader Service Card 57

OSCILLOSCIP111 ou5

Test Cable -

Coaxial test cable; length 1.15m, charac-teristic impedance 50 OHM, cable capacitance12pF. Input voltage max. 500Vp. $10.40

Coaxial test cable; length 1.2m, characteristicimpedance 50 OHM, cable capacitance 126pF.Input voltage max. 500Vp,

$9.48

Two 4mm binding posts (19mm betweencenters) to standard BNC male plus. Inputvoltage max. 500Vp.

$11.50

For terminating systems with 50 OHMcharacteristic impedance. Maximum load 2W.Max. voltage 10Vms.

$26.17

Carrying CasesFor HM203-1 and HM203-3 HZ42For HM312, HM412, HM512,and HM705 HZ43 $48.00For HM307, HZ62,and HZ64 HZ44 $39.00For HM103 HZ45 $39.00For HM203-5, HM 204and HM605 HZ46 $73.50

$66.00

For HM203, HM204, HM208, HM605, HM705,HM808, HM312, HM412, HM512, and HM812

$14.00 ea.

For checking the Y amplifier, timebase, andcompensation of all probes, the HZ60 providesa crystal -controlled, fast -rising (typ.3ns)square -wave generator with switchable fre-quencies of 1, 10, 100kHz, and 1MHz. ThreeBNC outputs provide signals of 25mVpp into 50OHM, 0.25Vpp (open circuit for 10X and 100Xprobes); accuracy ± 1 %. Battery -powered orAC supply operated (optional). $63.75

Indispensable for trouble -shooting in elec-tronic circuits. Single component and in -

circuit tests are both possible. The HZ65operates with all scopes, which can be switch-ed to X -Y operation (ext. horizontal deflection).Non-destructive tests can be carried out onalmost all semiconductors, resistors,capacitors, and coils. Two sockets provide forquick testing of the 3 junction areas in anysmall power transistor. Other components areconnected by using 2 banana jacks. Test leadssupplied.

Examples of Test Displayno lunc,gn E Z4cde <Bs/

LIST $75.00

LIST $1550.00

60MHz Multifunction OscilloscopeY: 2 channels, DC -60 MHz, max. 1 mV/cm, delay line;

triggering up to 80 MHz; var. hold -off time; Component Tester.X: 2.5s/cm -5 ns/cm incl. x10 magnification, delayed sweep;

The new HM605 is a truly versatile scope satisfying a wide variety ofexacting requirements in laboratory, production, and service. Themaximum input sensitivity of 1mV/div. facilitates the display of extremelylow-level signals. Despite their high sensitivity, the HM 605's verticalamplifiers are of excellent stability and low drift design with not more than1 % overshoot.

The built-in delay line permits viewing of the trigger edge at all times. Theoverscan feature indicates if any part of the trace passes the vertical limits ofthe CRT screen. An analog Y -output, switchable to Channel I or II, allowsfurther processing of the signal.

Reliable triggering is ensured up to at least 80 MHz, and trigger facilitiesinclude vertical mode alternate triggering, line trigger and single sweepoperation. Other trigger features are variable hold -off time, RF- and LF-filtersat any sweep speed for TV frame and line displays, as well as normal andautomatic peak -value triggering. An LED indicates when the sweep istriggered. Sweep ranges from 5ns/div. to 2.5s/div. ensure optimum resolu-tion of slow and fast signals. The variable sweep delay facility enables anysection of the waveform to be expanded by 1000 and more for detailed signalanalysis. A rectangular 14kV CRT with illuminated graticule provides excep-tionally bright and sharp displays.

A unique feature for scopes in this price range is the built-in switchable1 kHz/1MHz squarewave generator providing 0.2V and 2V calibration sig-nals with a risetime <5ns. It is now possible to self -test instantly the transientresponse of the vertical amplifiers and compensation of modular attenua-tion probes for utilization of the full bandwidth of scope and probe.

A Component Tester is also incorporated. The HM 605's outstandingprice/performance capability is not likely to be matched by similar productsin the near future.

ELECTRON ICSLIMITED

980 Ainess St. Unit 7,Downsview, Ontario

M3J 2S2(416) 661-5585

TELEX 065-28169Mon -Fri 8-5 pm, Sat 10 am -1 pm

Circle No. 21 on Reader Service Card

58 BCS Electronics Limited, 980 Alness St., Unit 7, Downsview, Ont. M3J 2S2 (416) 661.5585

Circuit Ideas 1:1Ar884:1LTO °

Crescendo AlarmBy A.N. CollinsonThis circuit is designed for the benefit ofthose who find the start of the day a littletoo alarming. It can be coupled to analarm clock or almost any other timingmechanism, and produces a output whichbuilds up from nothing to full volume.The sleeper is thus awakened by the veryminimum volume necessary.

The input can be an oscillator oralmost any other audio source, such asmusic from a clock radio. R1 and R2 pro-vide attenuation and the signal is then fedto IC1, a transconductance amplifierwhose gain is controlled by the currententering pin 5. Q1, DI, D2 and RI I pro-

vide a constant current of about 1 uAwhich is used to charge capacitor C5. Theconstant current ensures that the voltageacross C5 rises linearly, full charge beingreached after about 3 or 4 minutes. Thisvoltage is passed to IC1 via IC2; R3 andR5 are included to compensate for IC2'soffset. Some experimenting may benecessary with R5 if the offset causes anoutput when you don't want one.

The output of IC1 is coupled via R10and C4 to the audio amplifier IC3 andthen to the loudspeaker. If a poweramplifier output is not required, IC3 canbe deleted and the output taken from C4.Constant current source QI can be anysmall -signal PNP general purpose tran-sistor.

SIGNALINPUT

-50-500mV

NOTE.IC1 = CA3080IC2 = 741IC3 IS LM38001 = 2N370201,2 = 1N4148

Cl R1100n 10k

100nC4 R10

R5100k

4k7

R74-12V 363

+12V

OV

R9560k

01

D2

01

R6

OV10k

C3,±R8<,, C5-10uT 22u-

R0k11

1

IC3 8

2+ 7

.t

7C0u+6..

IC3PINS3,4,5,10, c(11,12

0.12V

LS18R

Coy

Expanding Ex -Or GatesBy L RobertsonExclusive -OR gates are only obtainable in2 -input packages, and simply cascadingtwo gates does not give the correct truthtable. Any application, therefore, whichrequires an Ex -OR gate with three ormore inputs is going to require sometricky logic combinations.

In the first circuit, inputs A and B arefed into gate 1 and the output of the gateis combined with input C at gate 2. Thisarrangement satisfies every part of thetruth table except A = B = C = 1, where theoutput from gate 2 will be 1 instead of 0.To overcome this problem, inputs A andB are also fed to gate 3 so that when bothare high the consequent high output from

Electronics Today June 1985

that gate will disable gate 4 and so pro-duce a final output of 0.

If a four -input arrangement is re-quired, the expansion can be achieved bytreating inputs C and D in the same way asinputs A and B in the first circuit. Thus, inthe second circuitt gate 5 performs asimilar function to gate 1 and gate 6behaves in the same way as gate 3.

The final permutation is a six -inputgate, shown in simplified form in the thirdcircuit diagram. The three -input Ex- ORgate shown as gate 4 is made up as shown

continued on next page

toz

Circle No. 22 on Reader Service Card 59

Circuit

in the first diagram above and the pairs ofinputs AB, CD, EF are combined in threeNAND gates and fed to three of the inputsof the final AND gate.

Walking Ring Sequencer

By S.P. GilesThis circuit is useful for generatingvoltages for note sequences, gating, con-trolling filters, etc. A 555 timer is used as asimple voltage controlled clock with the 5meg pot determining sequence speedalong with the voltage at the control

Ideasvoltage input. This input will vary thespeed with a positive voltage applied. Thisfunction is non-linear, has a 3:1 range andincreases speed as the voltae decreases.The range is 2Hz to 7KHz; the outputsoverlap so the final output is apparent asfour steps. Negative inputs should not beapplied without the optional gate protec-tion circuit. The 1u0 cap and switch pro-vide a slide function.

NOTE.IC1 = 555IC2 - 7474ZD1 = 5V1 ZENER01.7= 1N4148

CONTROLVOLTAGE

0-VNA/R1160

ZD1

-45V0

4

RI 7

IC1

160 6

R2160

C1 RV122n 5m0

C247n

OV

GATE

4-5V

01

4 114PR

IC2a

D

PIN 4IC2a

5

12

IC2d

O

D1 D7

RV2506

OV

RV3506

OV

7. OV

R V4

5°kLOG

OV

1V550kLOG

OV

D2

01

D3

01

D4

IiH

D5

4GATE

D6OPTIONAL GATE

OV PROTECTION CIRCUIT

RV6506LOG

V

C31u0

-4-0V

0 OUTPUT

Oscilloscopes Best Price in CanadaOSCILLOSCOPE 33330 - Chan.Mode -33330 Dual Trace Scope 20Z

20 mHz Built-in Compon Bandwidth 5mV vert. Sensitivity

Sale Price $529.00 probes included

DMM 60131/2 Dig. 025%0.1mV. 100ADC0.1uV. 2A AC/DC

$63.90

DM 6010

(same as 601) except:10A MP AC -DC $69.50

A-1 Electronics5062 Dundas St. W., Toronto, Ont.

M9A 1B9 (416) 231-4331Order by Mail, Chargex or Mastercharge

Mail Orders add 5% for shipping.60 Circle No. 34 on Reader Service Card

(Mt.'

-% icaid lyThe world of electronics is changing, not year -by -year, butday-by-day. Our future depends heavily on thedevelopments in the electronics field: computers to speedthe flow of information and to remove the drudgery from ourlives, control systems to improve productivity in our fac-tories and offices and to reduce energy wastage. Entertain-ment is also now largely electronic: TV, VCR's, Hi-Fi and in-formation systems such as Telidon.

Defence, communications, navigation ... the list goes onand on.

We are living in an electronic world and Electronics Todayreflects this, keeping you in touch with what is happeningand what is changing. Each month Electronics Today reportson new products and applications as well as presenting cir-cuits and state-of-the-art projects.

Features: A vast range of subjects are covered in themagazine, from microwave ovens to music synthesizers tosatellite communications, but this gives only a glimpse at thetrue scope.

Projects: Each month Electronics Today describes at leasttwo electronic projects, a high proportion of them designed,built and tested in ETI labs. Almost all build into attractiveunits using printed circuit boards available from severalsources.

Circuits and Design: Most months Electronics Today carries a"Circuits" feature, which either describes a multitude ofapplications for a particular device, or different circuits for agiven application. These are invariably written by profes-sional circuit designers.

I If f fl I If II/Elf ffl l I I l ft/ I, If If I, II 41, 4

I I

411111111111117.11111111111111111111w

Microcomputers: Each issue of the magazine has a computerreview as well as a regular column "Computing Today" plusseveral other articles and frequently projects for the advanc-ed microcomputer user.

SAVE UP TO 55%To: Electronics Today Subscriptions, Moorshead Publications,

25 Overlea Blvd., Suite 601,Toronto, Ontario, M4H 1B1 (416) 423-3262

YES, I want to subscribe to Electronics Today. I understand that Imay cancel my subscription at any time and receive a refund onthe unexpired portion.0 Please send me a full year of Electronics Today (12 issues) atthe special rate of $19.95, a 48% saving off the newsstand rate.111 I would prefer two years (24 issues) at $34.95, a saving of 55%from the newsstand rate.

For US add $3.00 per year, other countries add $5.00 per year.

0 Cheque/Money Order enclosed. Visa 0 MasterCard ID Am. Exp

Card No Expiry Date

Name

Address

City

LProvincePost Code

111

J

Electronics Today June 1985 61

COF1PUTERringss J Lit 11-1.11\0_

316 College St.Toronto, Ontario M5T 1S3

INC.

Toll Free Orders Only1.800-387-1385

Order Checking (416)925-8291Technical Data (416)925-1105

AMP IC SOCKETSAs you know AMP makes the best ICsockets. With a double wipe action and avery wide open target for easy insertion,the best.6, 8, 14, 16, 18, 20, 24, 28, 40Pin in stock at only1.50 PER PIN

ASCII KEYBOARDS

160141,06VOL1110 NSW. +. 3,0 in OriVitIPV.,,a, %A.:a ,5"."SescAh 111

Now, we have a new keyboard, micro con-trolled with 3 levels of pre -coded func-tions for Basic, CPM etc. and at the sameold price as before.Function Keyboard, Numeric $89.95Function Keyboard, Standard 5n.95

This is a high quality Hall Effect keyboardmade by Microswitch of Canada for AESdata and now bought by us for 10% of the$169.00 that AES paid for them in 10,000lots. They are a very good word process.ing keyboard with both serial and paralleldata outputs for use with APPLE and IBMtype systems and come complete with aribbon cable connector and complete pin -out. $24.95

KEYTRONICSPUOCRAIMINIMB 11111110111111D

An excellent ASCII Keyboard, fully AppleCompatible. Full sire with numeric pad.I ully programmable key switches with lulldata /MPS

POWER!SUPPLYGSA APPROVOur Famous "BLACK BEAUTY" power supply, now reduced in price but not in quality.Our ratings are 5V -5A, 121/2.5A, SA -1/2 Ai.121/1/2A for real $7995

SOLID ABSCASE /

NUMERIC$59.95

WIRED CARDS16K $ 45.00 Applaext 128K .$140.00128K no IC $ 34.95 Sprite gr. $ 69.95128K OK ..$ 55.00 TMS9918AIC $ 18.9512864K...S 99.00 DISC SHMRCK $ 45.00128K 128K .5150.00 80 Column $ 65.00MC3242 IC $ 12.00 80 Col. Sof sw 5 69.00DISC $ 45.00 Grippler 50.007-80 $ 45.00 Grip cable . 19.95Applacard 5150.00

SOLDERLESS

111

BREADBOARDSolderless prototyping boardsare the best way to quickly bread-board up a circuit. The holes aremade especially for IC's,resistors, and other small partswith 22-28 gage wire leads, takesWW pins too.

WB-106 $42.953 IC strips, 5 power strips4 Binding posts, Aluminum plateWB-104-3 $29.952 IC strips, 1 power strip2 Binding posts, aluminum plateWB-108 $59.954 IC strips, 7 power strips4 Binding posts, aluminum plateWB-104 $33.952 IC strips, 4 power strips2 Binding posts, aluminum plate.

NEW LOW BAREPCB PRICES*

Real time clock PIA card Rana 4 drive EPROM 9 V Music WILD CARD Disc Controller SAM TALKS Disc Controller COMMUNI-

(Shamrock) CATIONSGROUP 2 $9.00 each

Grippler RGB 80 Column Sprite graphics 80 Column Soft APPLACARD 128K

Switch ADD ON Z-80

GROUP 3 $11.00 each SSM MODEM APPLACARD AP-PARAT EPROM PROG 16K 128KAll boards come with a parts list andplacement diagram. We have all the partsof the PCB's iust ask for them.Prices so low we require payment with

OUR 6502 BOARDNow only $29.95 still with allthe versatility of the originaland a full 8 slots.

APPLE' DETACHEDKEYBOARD 5159.00

cr,Z,LtUd:::7H:1-7117 .r

The excellent MAK)II Apple detachedkeyboard using serial cata fIBM) format.Plugs direcily into Apple PCB

GREATDEALTHE GREAT DEALCARRIES ON FOREVERAND GETS BETTEROur proven 6502 motherboard plus a

numeric case plus a black beauty power -supply plus a numeric function keyboardplus any 4 bare pub for 5225.03

MEMORY FLASH256K-150Ns DRAM 519.7564K-150Ns DRAM S 2.4964K-200Ns DRAM S 2.119Prime stock, limited quantity.

EXTENDED 80 COLUMN for Apple Ileiii

ADDS 64K TO THE IleADDS BO COLUMN ALSO

-NICE PRINT- APPLE II . , Ile CARDAn APPLE Ilk. APPLE Ile precision parallel printer card for usewith EPSON and GEMINI (and similar) to generate multiple fonts.sizes and near letter quality ',Noting The printer steppers are conrolled to give multiple and incremental strike capability tochieve the above

COMPLETE WITH CABLE 5119.00

FANS FANS FANS

Has your IBM look -a -like system startedto make funny grinding noises as theTaiwanese fan bearings start to run out ofoil, if you have oil -no problem, but unlessyou do something the neighbours willsoon call the police. We got some niceAmerican fans, in 3" and 41/2" sizes 110Volt new and like new HOm equipment(checked)3" NEW $14.9543/a" NEW $14.953" USED $ 9.9541/4" USED $ 9.95

Since they are American they last forever.

IBM POWERSUPPLY

One of the nicest open frame IBM typeswitching power supplies we haveever seen. Came from the defunctNCR IBM compatible. runs the wholething, has +5V -7A, + 12V -3A, -5,-12-1/4A. A very good unit for startersystem. Will not run hard disc system.A real Steal at $49.95

mowsI 8.4V

'14A.H7 "D"

. I.-. CELLS 1 pus pus of I brand nu, GENKADSminOav al A, nous Each

is IN an<1Oparaies us, WU asSV backup 1nconon 2005 Gus I

Auriga...aura SUM

TItARSPORIVIRINAI Maks an 011.1 !maw sup. Q.. I OMO Ws. Tnn unn p.m20AnNO 12, 10A0USn0 - 5 izIa.,. V. pus Ina p.m forma. 12451110VACSAW COSICIOVAC SA 25VAC CT .2 AA 110,12VAC WU.* 2 SOIE12VAC &Amps .112451,1500 WATT ISOLADONISTEP vpr

DOWN 110720 201.11rent US OSIG112VACUTO 1.

SV12A 25VCT. AA 22V AA ma. for1111y S 100 sNn

SWITCHINGPOWER SUPPLY

Another great bargain from PARTS GALORE, Asmall power supply switching style that give+ 5v - 4A; ±12v 1A and -5v (adjustable) on acompact 4x8" open frame PCB. Cost NorthernTelecom $50.00 when they bought 5000 pieces.We got em when a subcontractor went belly up for10% of that price and we are selling em for

$18.95 NEW IN BOX TESTED

AC power cable (3 Wire) for above $2.50

CONNECTORS

DB SERIESDB-25 M solder 51.95DB25 F solder SIASD(325 M IDC. Flat cable 55.95DB-25 F IDC, Flat cable 15.95D1325 M Right angle PCB $4.95DB-25 F Right angle PCB pissDB-25 Shell $1.00D8.15 M solder $1.950615 F solder $1.95DB 15 F IDC, flat cable $395DB15 k4 right angle PCB $2.95D13-15 F right angle PCB 52.9513B-15 Shell $1.00DB-9 M solder $1.751313.9 F solder $1.75DB.9 M right angle PCB $2.50DB-9 F right angle PCB $2.50DB-9 Shell $0.75

DRIVE CONNECTORS50 Pin Edge C. 8" drive $5.9540 Pin Edge C. $4.9534 Pin Edge C. 5114" drive $59520 Pin Edge C. Hard drive $49534 Pin Fern header 17 x 2 $3.5026 Pin Fem header 13 x 2 93.0020 Pin Fern header 10 x 2 $290

ASSORTED SEMI-CONDUCTORS AND

OTHER STUFF(A) RED LED SfM/L 1051.00(B) GREEN LED S/M/L 8/91.00(C) AMBER LED S/M/L 8191.00(DI PIN PHOTODIODES.INFRARED 231.00(E) PHOTO TRANSISTOR,NPN VISIBLE 241.00(F) LDR (LIGHT DEP RESISTOR) . . $1.00(G) FET ELECTRET MIKE.TINY 10MM $2.00(hl) 1144601 10/91.00(1)154004 8/91.00(J)1N4007 941.00(K)25AMP.600V BRIDGE 92.95(L) 25AMP-600V BRIDGE $3.50(MI 6AMP.200V BRIDGE $1.50(N)3AMP-200V BRIDGE $1.00(0) DIODE 3AMP-600V 341.00(1111N914/1N4148 Silicon diode 10/91.00(0)7805 1AMP-5V regulator 2/51.00(RI 7812 lANIP-12V regulator 90.75(S( 78M 12 At AMP12V regulator ...2/31.00(T) LM317 Variable LAMP regulator .91.50(UI LM323 5V 3AMP regulator 5295(N) LM350 Variable 3AM P reg $395(W) 21/2" 80hm mini speaker $1.500/I MINI TOGGLE SWITCH SPDT 91.95(Y) MINI PUSH BUTTON SWITCH,NO $0.50

62 Circle No. 19 on Reader Service Card Electronics Today June 1985

(A) Color Graphics (Persyst)(B) Monochrome graphics(C) Disc controller(0) Disc controller + Printer(El Disc controller + Game(F)10 + 21/0 clock etc(G) Mull if unction card 11 function(H) AST SIXPACK COPY(I) Parallel printer(J) RS-232card(K) Simple modem card(LI Disc fix above(8)512K card

316 College St.Toronto, Ontario M5T 1S3

Toll Free Orders Only1 -800-387-1 385

Order Checking (416)92 5.8291Technical Data (416)925.1105

MAIL ORDERS: We accept VISA; MC.AMEX; credit cards. Money orders, che-ques (2 week wait) are also OK. Minimumpacking and handling fee 55.00 or 5%,whichever is larger. The only COD we useis via CANPAR (Add $4.00 COD fee) ormotor freight. We do not use postal CODat all. All Ont. res add 7%. All prices aresubject to change without noticeReturns are subject to a 20% restockingcharge

CHERRY IBM - !C124.00STYLE KEYBOARD

At last a good low cost keyboard for the IBMPC, XT or Compatible machine. Usescapacitive keys, has a very good feel", andhas TYPEWRITER LAYOUT for easy word-processing at the very low price of 112400

MBE -XTAN IBM'

Kr Compatible8 Slot motherboard

MBE.XT BARE PCB WITHMANUAL AND SCHEMATICS.

$49.95LAZY BOARD

What is your time worth. We have had abunch of MBE -XT boards stuffed andwave soldered so you can save all thatlime soldering them up. All you need arethe IC's memory and BIOS and you areset lo go 160.00

FULLY WIRED AND TESTED WITH64K ON BOARD WITH MEGABIOS

AND MANUAL

$36500

8088 16 Bit Microprocessor 8087 Math Processor Optional Up to 256K Dram on Board Has Digital Delay Line for Error Free Memory

Refresh B IBM Compatible Expansion Slots 4 DMA and Timer Channels 6411/128K Eproms Jumper Selectable Will run any Compatible BASIC IBM Power Plug Compatible Same PCB size as IBM XT Runs PC -DOS and GPM -86 Compatible BIOS in stock

MEGAThe amazing MEGABIOS. from DTCof Dallas. A fully rewritten BIOS thatallows you to make a fully compatiblelegal system. Note they do not askMEGABUCKS,' for it, only ...529.95

BIOSTAIWAN BIOS, not as good or 100%compatible but it will get you runningand save you bucks $19.95

TAIWAN BASIC, in 4 2764 EPROMS$49.95

IBM BARE PCB527.95 (N) 256K short card $19.95$24.95 (0) IBM 6" extender for service $19.95$17.95 IP1 WW Proto, full sized with DB-9 8$24.95 0825 footprint $24.95$24.95 (0) WW Memory proto, full sized with$24.95 256K (1Meg) memory laid out on one$24.95 end with DB-9. DB25 footprint 529.95$34.95 (RI 512K Mapping PROM $12.95$17.95 (S) Mult if unction PROMS(2) $24.95$17.95 (T)2732 for color graphic $10.00$17.95

8.00$24.95

All cards come with a detailed parts list andplacement drawing, we also have all parts neededfor them

IBM CASE

We have the nicest case of all the various com-peting cases, ask any friend who has boughtsomeone else's case and then has seen ours. Thelid is hinged with pushbutton access. The back iscut for 8 XT slots and it comes with all the caseback inserts for cards, card guides, blind discfiller plates, standoffs, feet, screws, all for .589.95Please specify back or side cutour for power sup-ply.

We also have an economy version ABS case,visually exactly the same, but of cheaperbuild $69.95

We also have an IBM B Slot/6502 Board dual dutycase for making IBM look -a -like 6502systems 569.95

PVCcr.:E'40:trTKxrtUNICAT PINS

ConnectorsEnalartgal.

IL17:;n771710a)

VE11 Mena -Byte Pam CONOWen beard,Pnr6PPrrrr

Y. tin. Kr, inK MtnYAK enn

MBE -XTMBEXT Motherboard, wave soldered with no IC's atall with manual and schematics $189.00

As above with 64K, no BIOS, tested with all IC's andfully burned In, 8 Slots 1325.00

BASIC SYSTEM, MBE -XT, A 8 T with 256K with one360K drive 8 controller with power supply, hinged lidcase and MEGA -BIOS 5895.00

MBE.XT SYSTEM 4., The fully loaded MBE -XT systemwith 256K on board, BIOS, Cherry keyboard, colorgraphics, 2.360K DSDD Drives with controller andserial, parallel ports, calendar, clock and many moresmall features, fully tested, ready to go 11599.00

MEGABOARD CASE, similar to the above, but nopushbuttons or hardware, from DTC in DallasTexas. A stronger US made case, but lessfinishing parts. Fits the MEGABOARD exactlywith side cut extender, for back powersupply $99.00

PARTS, PARTS, PARTS, PARTS, PARTSHard to get parts for yourIBM computable (8088)systems and peripherals8088 CPU $14.958087 Math Processor 5219.008237A-5 Prog. DMA Cntrl. 914.958250 serial Port $11.508253A-5 Prog. Interval timer $7.508255A-5 P.I.A. M.958259A Prog. Interrupt Cntrl, 99.958284A ADC clock gen & driver $7.758288 Bus Controller 915.508272 Floppy Disk Controller 914,95NEC 765 Floppy Disk Controller(equivalent 1o8272) $14.95Set of 8088, 8255A-5, 8237A-5, 8288, 8284, 82538-5and 8259A $09.00

All parts (except NEC785) are prime parts made byIntel.

DELAY LINES100ns delay line $4.007ns delay line $13.95

62 pin edge con (high quality) $2.405 pin Din conn $1.25Power conn $1.25Dip switch B pot. $2.494.7k x6 sip 4.894.7k x 8 Pin sly .898.2k or 10k 16 pin Resistor or network $ .9933ohm x 8 network $1.10Small speaker $1.99.1 ut 501/ high quality bypass capacitors $ .10

LS for IBMSystems00 50.3502 90.3904 50.3906 50.3910 $0.4520 $0.4527 00.4530 00.4532 50.8074 50.50138 $0.70158 $0.75175 00.80243 $1.20244 51.25245 51.50273 $1.50322A 06.00323 53.50373 51.40374 $1.40377 51.25670 $1.757407 TTL 51.00

S SERIESsoo 10.75SO2 50.75SO4 S0.75SO8 $0.75S74 saes5138 51.755157 51.855158 51.855374 53.25

Trimcap $ .9934 pin card edge con. 55.95 PAI I SCfor your floppy controller 75477 51.25

Electronics Today June 1985

Hard to get parts for your6502 Systems and AppleCompatible Peripherals.6502 C PU6845 CRT controller68845 CRT controllerZ80A CPU (4 MHz)MC324274L536774LS25974LS1617457474S17474L5323Card edge connector (50 pin)RCA lack PC mount6 pin power square connectorPhono lack (small)MPSA 13 trans2N3904 trans2N3906 transMPSLI51 trans2N4258 transistor or riot&1K SIP 10 pin1K SIP 8 pin10K SIP 10 pin4 pos dip sw20 pin female header for disk drive20pin male50 pi trim cap220 ohm trimpot20 conductor ribbon cable

5.509.509.95

$ 489011.95

.821.39

.99

.82I 1.70$ 4.55

2.49.89.99

9 .99.55.19

$ 2779

5 89$ .695 69

75S .95

1.795 1.89S .890 .89

$ .8911t

ONLY!

$99

Olt6e

nowirt

J,Pon6r

11066 PrOneBer

80617 nurnennPio i

support C.cuite

ORDER ROWE, I

Boar EraitaRien nowt Me

MEGABOARDMEGABOARD Motherboard, Wave soldered with no IC'sat all with pans list and schematics 51 95.00

MEGABOA RD Motherboard, Wave soldered with all IC'sand 64K on board, with schematics and test data, noBIOS but 1 ully burned in and tested with one s390.00

BASIC SYSTEM, MEGABORO, A & T with 256K (256KDRAMS) with one 3606 DSDD DflVe & controller withpower supply and hinged lid case, and megabios

5995.00

MEGABOARD SYSTEM + The fully loadedMEGABOARD with 640K on board (25611 8 64K DRAM)with 2.360K DSDD droves and controller, color graphicsboard, with serial. parallel, clock, calendar, and manysmall features fully tested and ready to go sing 00

SWITCHING POWERSUPPLY

110V, 60Hz with Fan and tworear switched outlets.

lnese power supplies tit our cases100 WATT 5v -10A; + 12y -3.5A; z 12V -112A

8139.00130 WATT +5V -14A; + 12v -4.2A; s 12Y -1/2A

1169.00Please specify, side or back switch

8" DRIVESWITCHING

POWER SUPPLY

$3995

ire0,49

010111iite1i

The greatest 8" Drive supply we have ever found. Has24V -2.2A 5V -3A and -12V-.17A. All you need for a dual 8"Drive system. A switching power supply by ASTEC _539.95

MONOLITHIC CAPSMONOLITHIC CERAMIC CAPSWe bought 100,000 of em din cheap, they are verygood quality, 63V, 0.2" lead spacing. Now only 10e N.SO pcs. $ 5.00100 pcs. 9.001000 pcs. 585.00more? ask!

WE'VE GOT EM!5-1/4"HALF SIZE DRIVES!For IBM PC, TI PC,XEROX 820

Shugart/Panasonic 1/a sizeSA455-3A E C $189.00

TEAC (A Cadillac Drive) 1/2

size FD55B $189.00

Canon MDD210 2/3 size, areal buy with, red/green led,head load and door relay.With all data $129.00

40 Track per side 48 TPI Double -sided, double

density Same as SA455 Latest head & drive

technology Fast access time

TEACTEAC the nicest driveFD55F $219.00with free DOS patch for 80track.

80 Track per side 96 TPI Double sided, quad density Same as SA465 Latest head & drive

technology Fast access time

Circle No. 20 on Reader Service Card

1 EPA1IIIIN

warmsFEINIMRE

NitlaW1111.1101\711k

111010.0W \ 1la1 IBRIMNU U111.11M1111.111111111\110101

101' WIL111111MM11111111111111WILINIMInilliUMWINKIN

_ IRS I. lilaMr

1.11. ill111111 II IS II II

-11iiiltaA111111111111111111,..,,,.ja-ia 111111411111111011 "A'pm aiiialliiliUIUli4Mr..-vorommums $3 -

We've Put aLocal Area Networkon a Disk

Corporate Information Sharing. It's been describedas the key to increasing a company's productivity. It'salso why large networks of PC's are becoming moreand more common In the workplace...in spite of thefact that they're costly, difficult to install, and incompat-ible with much existing software.

Finally, there's a solution to this corporate dilemma.Its name is LANLinkl.m

A Software -Driven LAN That Uses Standard,RS -232 Ports. A major breakthrough in local area net-works, LANLinkTM uses your computers' existing serial portsand runs under PC -DOS.

Because all of the intelligence the network requires ison the server and satellite diskettes, expensive networkinterface boards aren't required.

A Powerful Network That's Cost -Conscious. Ifyou've been pricing board -driven LAN's, you alreadyknow that they can cost over $1,000 per workstation.

LANLinkTM is different.Boasting a data transfer rate in excess of '100,000 BPS,

LANLinkTM is compatible with a wide range of programs.And because special boards aren't required, installa-tion costs are one-third that of a traditional network.

A Network Designed the Way Business Works. WithLANLinkl,m you're able to customize your network alongdepartmental lines using a data -sharing hierarchy andpassword -protected access.

Get Started With LANLinkrm TODAY. Call The SoftwareLink TODAY for complete details and the authorizeddealer nearest you. The LANLinkTM Starter Kit, priced at$745, comes complete with network software for both aserver and a satellite computer. For a limited time, 50feet of RS -232 cable will be included free of charge.

LANLinkTm is immediately available and comes witha money -back guarantee. VISA, MC, AMEX accepted.

\\1Circle No. 39 on Reader Service Card.

TM

CL/ THE SOFTWARE LINK, INC.Developers of MultiLinkTM and MultiLink AdvancedTM

400 Esna Park Drive, Suite 18, Toronto (Markham), Ont. L3R 3K2

CALL: 416/477-5480Dealer Inquiries Invited

MultiLink, MultiLink Advanced & LANLink are trademarks ofThe Software Link, Inc. PC -DOS is a trademark of IBM Corp.