GVC Systems Pvt LtdElectronics - Embedded - Entreprenurship

Agenda

About me

About Embedded & Electronics

About You

Why I am here

Inviting you to work with us

Me - ProfessionalVinay Chaddha. Electronics Hobbyist. Author. Innovator. Passionate about learning and sharing.

Filed 3 patents, Shared five successful commercial projects. Many copy rights.

Developed over 200 comemrcially successful projects.

CONSTRUCTION

44 ELECTRONICS FOR YOU ! APRIL '99

CMYK

Caller-ID Unit UsingMicro-controller

T he facility of knowing yourcaller’s telephone number beforeanswering the call, which has

been available to cellular phone usersonly in India so far, has now been ex-

tended to the normal telephone usersalso in Delhi, Mumbai and some othercities of India through MTNL and DoTsince 1st January.

MTNL/DoT telephone exchanges

transmit the telephone number of call-ing party just before the first ring whilein systems used in USA and China, thedata relating to the calling number issent between first and the second rings.The number of calling party in India istransmitted by MTNL/DoT exchangesin DTMF codes.

Two documents containing stan-dards and specifications issued by DoT’sTelecommunications Engineering Cen-tre (TEC) in the form of ‘Generic re-quirements’ and ‘Interface require-ments’ for ‘Subscriber service unit forcalling line identification presentation(SSU for CLIP)’ are available from TEC,Khursheed Lal Bhawan, Janpath,

VINAY CHADDHA

C O N S T R U C T I O N

A.P.S. DHILLON

Fig. 1: Complete circuit diagram of caller-ID unit

CONSTRUCTION

52 ELECTRONICS FOR YOU ! SEPTEMBER '99

Remote-controlledAudio Processor UsingMicrocontrollerVINAY CHADDHA

Most hi-fi audio CD systemsnowadays are available withremote control. However, no

such circuit is available for adding tothe AF power amplifiers made as hobbyprojects. The design of such an add-oncircuit along with remote control is pre-sented here. It can be used by hobby-ists as an attachment to their audiopower amplifiers.

This design is based on audio con-troller TDA7315 from SGS-THOMSONand Motorola microcontrollerMC68HC705KJ1. The microcontroller,after programming with the specificsoftware code for the current applica-tion, has been renamed GVC-AUD-257. Other construction projects bythe author using the same series ofmicrocontrollers, which can be referredto for additional details, have been pub-lished in EFY in Jun. ’97 (Set-Top Con-verter) and Apr. ’99 (Caller ID). In ad-dition to audio controller andmicrocontroller the circuit comprisesthe following standard parts that areused in any normal system:

1. Power supply2. LED indicator panel to indicate

status/keys pressed3. Relay to switch on/off the supply

to the power amplifier or the main unitThe following parts are used in re-

mote systems for VCR, TV, etc:1. Memory (24C02).2. Remote handset with 12 keys3. IR receiver for remote operationFunctionality of these parts is ex-

plained below with reference to Figs 1

G.S. SAGOO

and 3.

DescriptionMemory. 24C02 is an I2C bus compat-ible 2k-bit EEPROM, organised as 256x 8 bits. It can retain data for a periodof more than ten years, including thecurrent settings of volume, treble, bal-ance, bass, as well as the on/off statusof the main amplifier unit or the relaystatus. The various audio parameterscan be stored in just six bytes.

Mains power failure is quite com-mon in India. This does not allow thelast settings of volume, tone and bal-ance to remain intact. To overcome thisthe microcontroller unit (MCU) muststore all audio settings of the user inmemory (EEPROM). The memory en-sures that even after a power trip, theMCU will read the latest saved settingsfrom the EEPROM.

Using two lines, SCL (serial clock)and SDA (serial data), the microcon-troller can read and write six bytes forall the audio parameters. For more de-tails on I2C bus and memory interfac-ing, please refer to Caller ID construc-tion project in Apr. ’99 issue of EFY.

At power ‘on,’ the last-saved audiosettings are read by the MCU. In casememory IC cannot be read by themicrocontroller, volume LED will blinkthree times to indicate the problem. Thepossible reasons could be either a badmemory IC, or a discontinuity/shortingof its tracks, or improper insertion ofthe IC in its socket.

Under the circumstances, the unitwill still work, but it will not remem-ber the last settings and will select the

centre values of treble, balance andbass. Volume will be set at 50 per centof the maximum value and the relaywill be off. Loudness and mute will alsoremain in the off mode. A remote hand-set can be used to change the settingsas desired.

Audio controller. TDA7315 is asingle-chip I2C bus-compatible audiocontroller which is used to control allfunctions of the audio amplifier. Stereoaudio input from the preamplifier is fedto the IC input. A microcontroller can

PARTS LISTSemiconductors:IC1 - TDA7315 digitally controlled

audio processorIC2 - MC68HC705KJ1CP Motorola

microcontroller (GVC-AMP-257)

IC3 - 24C02 I2C serial EEPROMIC4 - 7805 fixed regulator +5VIC5 - 7809 fixed regulator +9VIC6 - µPD6121 infrared remote

controlT1,T2,T3 - BC547 npn transistorT4 - 2SC2001 npn transistorD0-D7 - Red LEDD8, D10-D11 - 1N4007 rectifier diodeD9 - 8.2V,0.5W zenerD12 - IR LED

Resistors (all 1/4W, ± 5% metal/carbon film,unless stated otherwise)

R1,R2,R15,R16- 10-kilo-ohmR3,R4,R14 - 1-kilo-ohmR0,R5-R9,R12,R13 - 330-ohmR10,R11 - 5.6-kilo-ohmR17 - 2-ohm, 0.5WR18,R19 - 200-kilo-ohmCapacitors:C1 - 10µF, 16V electrolyticC2-C4,C7,C19,C20 - 0.1µF ceramic discC15,C16,C9,C10,C11,C13 - 0.1µF polyesterC5,C6 - 33pF ceramic discC8 - 22µF, 25V electrolyticC12,C14 - 2.7nF polysterC17,C18 - 2.2µF, 16V electrolyticC21,C22 - 220pF ceramic discC23 - 10µF, 50V electrolyticMiscellaneous:RL1 - 12V, 150 ohm, SPST relay

OEN Pt. No. 57DP-12-1C6XTAL - 4MHz quartz crystalY - 455kHz, ceramic resonator

- Battery 1.5V, pencil cell- IR sensor module- Remote control handset,

complete with keyboard- Connectors for audio input-

output and power supply- 12V DC, 250mA battery

eliminator

The author is the proprietor of GVC Systems,Noida. He can be approached through e-mailat gvc@vsnl.com

CONSTRUCTION

E L E C T R O N I C S F O R Y O U • O C T O B E R 2 0 0 6 • 7 7W W W . E F Y M A G . C O M

CMYK

Beverage vending machines arecommonplace at railway sta-tions, airports, fast-food restau-

! VINAY CHADDHA

SANI T

HEO

rants and even in companies. Press aswitch and the machine delivers a hotcup of your favourite drink.

This looks quite a simple operationbut has a very complex logic behind

it: It involves use oftwelve precision timersand four counters apartfrom physical devices likedisplay, solenoid and mo-tor to deliver water andpremixed tea/coffee/souppowder in exact quantityfor better taste and in ex-act sequence.

This has become pos-sible because of the use ofmicrocontrollers, which

allow compact size, higher reliability,lower cost and multiple functionalities.

This tea/coffee/soup vending ma-chine controller uses Freescale’s latestMC908JL16 microcontroller chip. Thecontroller is programmable and user-friendly. You can set the quantity ofthe beverages through a button switchprovided on the front panel of the con-troller as per your requirements. Thus,cups of any size can be filled at anytime.

The hardware

Fig. 1 shows the block diagram of thevending machine controller. It com-prises the following sections: powersupply, microcontroller, relays, relay

driver, alphanumericdisplay, keyboard andmemory. The powersupply circuit is shownin Fig. 2.

The control unituses low-cost, readilyavailable components.The temperature con-trol section has notbeen included in thedesign as the parts re-quired are expensiveand not easily avail-able. However, a low-cost thermostat used inwater heaters can beused in the unit.

Power supply. Therelays need 12V DCand the microcontrollerand memory need 5VDC for operation.Bridge rectifier, capaci-tive filter and regulatorICs 7812 and 7805 arethe standard parts usedin the power supply.

Microcontroller.We need individually

BEVERAGE VENDING

MACHINE CONTROLLER

Fig. 1: Block diagram of the beverage vending machine controller

Fig. 2: Power supply circuit

The prototype of beverage vending machine controllerdeveloped by the author

C O N S T R U C T I O N

ELECTRONICS FOR YOU OCTOBER 200250

C O N S T R U C T I O N

VINAY CHADDHA*

Security is a prime concern in our day-to-day life. Everyone wants to be asmuch secure as possible. An access-

control system forms a vital link in a secu-rity chain. The microprocessor-based digi-tal lock presented here is an access-control system that allows only authorisedpersons to access a restricted area.

System overviewThe block diagram of the access-controlsystem is shown in Fig. 1. The systemcomprises a small electronic unit with anumeric keypad, which is fixed outside theentry door to control a solenoid-operatedlock. When an authorised person enters apredetermined number (password) via thekeypad, the relay operates for a limited timeto unlatch the solenoid-operated lock so thedoor can be pushed/pulled open. At the endof preset delay, the relay de-energises andthe door gets locked again. If the enteredpassword is correct the unit gives threesmall beeps, and if the entered password iswrong it gives a longer beep of one second.

The system uses a compact circuitrybuilt around Motorola’s MC68HC705KJ1microcontroller and a non-volatile I2CEEPROM (ST24C02) capable of retaining

SUNIL KUMAR

ible 2048-bit (2-kbit) EEPROM is organisedas 256x8 bits. It can retain data for morethan ten years. Using just two lines (SCLand SDA) of the memory, themicrocontroller can read and write thebytes corresponding to the data requiredto be stored.

(Note. For details of the microcontrollerand programming of I2C EEPROM, you mayrefer to the article ‘Caller ID Unit UsingMicrocontroller’ published in April ’99 is-sue of EFY and the article ‘Remote-con-trolled Audio Processor UsingMicrocontroller’ published in Sep. ’99 is-sue of EFY. For additional data on Motorolamicrocontrollers, refer to EFY-CDs of thisyear’s January and February issues. Theinformation pertaining to I2C EEPROM isavailable on STMicroelectronics’ Website.)

Power supply. The power supply unitprovides a constant 5V supply to the en-tire unit. This is a conventional circuit us-

the password data for over ten years.The user can modify the password as

well as relay-activation time duration fordoor entry. This version of softwareenables use of the unit even without theI2C EEPROM. (However, without EEPROM,the password and relay-activation timeduration will be reset to default valueson interruption of the power supply.)

Hardware detailsFig. 2 shows the access control circuit. Itsmain components are a microcontroller,I2C memory, power supply, keypad, relay,and buzzer.

Microcontroller. The 16-pinMC68HC705KJ1 microcontroller fromMotorola has the following features:

• Eleven bidirectional input/output(I/O) pins

• 1240 bytes of OTPROM programmemory

• 64 bytes of user RAM• 15-stage multiple-function timerOut of eleven I/O pins, seven lines

have been used for the keyboard, one forthe buzzer, one for relay operation, andtwo (SCL and SDA, i.e. serial clock andserial data lines) for communication withI2C EEPROM.

I2C memory. A two-wire serial EEPROM(ST24C02) isused in thecircuit to re-tain the pass-word and therelay-activa-tion time du-ration data.Data storedremains in thememory evenafter powerfailure, as thememory en-sures readingof the latestsaved settingsby themicrocontroller.

This I2Cbus-compat-

MICROCONTROLLER-BASEDACCESS CONTROL SYSTEM

F ig . 1: B lock diagram of the access-control system

PARTS LIST

Semiconductors:IC1(U1) - MC68HC705KJ1

microcontrollerIC2 (U2) - ST24C02 I2C EEPROMIC3 (MN1) - MN1280 reset stabiliserIC4 (Reg1) - 7805 +5V regulatorT1, T2 - BC547 npn transistor(Q1, Q2)D1, D2 - 1N4007 rectifier diodeLED1 - Red LED

Resistors (all ¼-watt, ±5% carbon, unlessstated otherwise):R1-R6 - 10-kilo-ohmR7-R9 - 1-kilo-ohm

Capacitors:C1, C2 - 33pF ceramic diskC3, C4,C6, C7 - 0.1µF ceramic diskC5 - 10µF, 10V electrolytic

Miscellaneous:Xtal (Y1) - 4MHz quartz crystalPZ1 (BZ1) - Ceramic piezo buzzerCon1 - Power-supply connectorCon2 - 2-pin male/female Berg

connectors- 7-pin male/female Berg

connectorsSW1-SW12 - Tactile keyboard switchRL1 (RLY1) - 1C/O, 12V, 250-ohm

miniature relay

Me - PersonalMarried. Stay in Noida with Wife Geeta, Daughter Upasana and Pet Maggie.

When I got married - I did not own shoes - made millions - lost every thing - did not give up - asked for help - now back to profits.

About Embedded

Today for each PC there are 49 small tiny size micro controllers.

Every thing from Lamps, Fans, Chimneys to Bikses, Cars, Traffic Lights, Elevators, Battle Tanks, Missiles use them.

There is a huge demand for local/regional products. This can not be supplied by large companies/imports.

More about embedded

This needs three things

- Electronics

- Software

- Creativity - Imaginations

How will it help youThis is part of your project. You need to it.

Knowledge will be useful in which ever field you work. You will be using embedded devices.

Skills are required if you wish to join core technical company.

ProblemsNew models of PC, Mobiles, Cars ... are available every year.

Unfortunately, college syllabus stills includes obsolete devices that I read 31 years back.

In a job with embedded company, your boss may ask you to unlearn what ever you know and then start learning again.

Why I am here

To share about a project

and ask you to work with me

Joy-n-Freedom

We use electonics for luxury and convenience.

Persons who are differently abled or sick or old have limitations.

They and their familis are under stress.

We wish to work on creating electronics projects for them and add Joy-n-Freedom in their life

What we have done

Participated in two events

First one at National Blind School, Delhi.

Second at Viklang Kendra, Allahabad

Interacted with persons with disability, their family members and NGOs.

There is a need and no supplies.

Imported devices are too expensive

Invitation

Work me with me on projects.

Work alone, as a team, in technical field, non-technical field, just support, feedback, share the concept, develop website or what ever you can.........

Embedded PlatformEmbedded devices are available from multiple sources like Philips, Motorola, Renesas,ST Micro, Micro chip and so ....

We can use of any of them, however each device needs specific tools and compilers and and some time on learning specific details.

More than technicals it is the support from supplier of embedded devices that is critical.

Our ChoiceI have work on NXP (Philips), Freescale (Motorola), Renesas(Hitachi), Microchip, ST, Zilog , Atmel.

My choice is Freescale(Motorola) and Atmel.

Both of them offer good developent support. You get quick results.

Freescale

Freescale has some India Specific Micro controllers.

Compilers is Code warrior 6.3

Devices are 9S08IA, 9S08IB and 9S08IC

ATMEL

Compiler is ARDUINO

Devices are ATMEGA168

Demo boards are available locally.

Projects to be made

Interfacing landline with TV

Talking clock

Universal remote for lights, fan, tv, air con, telephone, mobile

Audio Visual Alerts for medicines

Collection of Vital Stats and updating records. Alerts in case of serious issue

Contact mename and email address by SMS to

9811074026

Send email to

vinay@joy-n-freedom.com

Visit my lab at

Amity Incubator, Amity University, Noida

Thanks for your valuable time.....

CONSTRUCTION

44 ELECTRONICS FOR YOU ! APRIL '99

CMYK

Caller-ID Unit UsingMicro-controller

T he facility of knowing yourcaller’s telephone number beforeanswering the call, which has

been available to cellular phone usersonly in India so far, has now been ex-

tended to the normal telephone usersalso in Delhi, Mumbai and some othercities of India through MTNL and DoTsince 1st January.

MTNL/DoT telephone exchanges

transmit the telephone number of call-ing party just before the first ring whilein systems used in USA and China, thedata relating to the calling number issent between first and the second rings.The number of calling party in India istransmitted by MTNL/DoT exchangesin DTMF codes.

Two documents containing stan-dards and specifications issued by DoT’sTelecommunications Engineering Cen-tre (TEC) in the form of ‘Generic re-quirements’ and ‘Interface require-ments’ for ‘Subscriber service unit forcalling line identification presentation(SSU for CLIP)’ are available from TEC,Khursheed Lal Bhawan, Janpath,

VINAY CHADDHA

C O N S T R U C T I O N

A.P.S. DHILLON

Fig. 1: Complete circuit diagram of caller-ID unit

CONSTRUCTION

52 ELECTRONICS FOR YOU ! SEPTEMBER '99

Remote-controlledAudio Processor UsingMicrocontrollerVINAY CHADDHA

Most hi-fi audio CD systemsnowadays are available withremote control. However, no

such circuit is available for adding tothe AF power amplifiers made as hobbyprojects. The design of such an add-oncircuit along with remote control is pre-sented here. It can be used by hobby-ists as an attachment to their audiopower amplifiers.

This design is based on audio con-troller TDA7315 from SGS-THOMSONand Motorola microcontrollerMC68HC705KJ1. The microcontroller,after programming with the specificsoftware code for the current applica-tion, has been renamed GVC-AUD-257. Other construction projects bythe author using the same series ofmicrocontrollers, which can be referredto for additional details, have been pub-lished in EFY in Jun. ’97 (Set-Top Con-verter) and Apr. ’99 (Caller ID). In ad-dition to audio controller andmicrocontroller the circuit comprisesthe following standard parts that areused in any normal system:

1. Power supply2. LED indicator panel to indicate

status/keys pressed3. Relay to switch on/off the supply

to the power amplifier or the main unitThe following parts are used in re-

mote systems for VCR, TV, etc:1. Memory (24C02).2. Remote handset with 12 keys3. IR receiver for remote operationFunctionality of these parts is ex-

plained below with reference to Figs 1

G.S. SAGOO

and 3.

DescriptionMemory. 24C02 is an I2C bus compat-ible 2k-bit EEPROM, organised as 256x 8 bits. It can retain data for a periodof more than ten years, including thecurrent settings of volume, treble, bal-ance, bass, as well as the on/off statusof the main amplifier unit or the relaystatus. The various audio parameterscan be stored in just six bytes.

Mains power failure is quite com-mon in India. This does not allow thelast settings of volume, tone and bal-ance to remain intact. To overcome thisthe microcontroller unit (MCU) muststore all audio settings of the user inmemory (EEPROM). The memory en-sures that even after a power trip, theMCU will read the latest saved settingsfrom the EEPROM.

Using two lines, SCL (serial clock)and SDA (serial data), the microcon-troller can read and write six bytes forall the audio parameters. For more de-tails on I2C bus and memory interfac-ing, please refer to Caller ID construc-tion project in Apr. ’99 issue of EFY.

At power ‘on,’ the last-saved audiosettings are read by the MCU. In casememory IC cannot be read by themicrocontroller, volume LED will blinkthree times to indicate the problem. Thepossible reasons could be either a badmemory IC, or a discontinuity/shortingof its tracks, or improper insertion ofthe IC in its socket.

Under the circumstances, the unitwill still work, but it will not remem-ber the last settings and will select the

centre values of treble, balance andbass. Volume will be set at 50 per centof the maximum value and the relaywill be off. Loudness and mute will alsoremain in the off mode. A remote hand-set can be used to change the settingsas desired.

Audio controller. TDA7315 is asingle-chip I2C bus-compatible audiocontroller which is used to control allfunctions of the audio amplifier. Stereoaudio input from the preamplifier is fedto the IC input. A microcontroller can

PARTS LISTSemiconductors:IC1 - TDA7315 digitally controlled

audio processorIC2 - MC68HC705KJ1CP Motorola

microcontroller (GVC-AMP-257)

IC3 - 24C02 I2C serial EEPROMIC4 - 7805 fixed regulator +5VIC5 - 7809 fixed regulator +9VIC6 - µPD6121 infrared remote

controlT1,T2,T3 - BC547 npn transistorT4 - 2SC2001 npn transistorD0-D7 - Red LEDD8, D10-D11 - 1N4007 rectifier diodeD9 - 8.2V,0.5W zenerD12 - IR LED

Resistors (all 1/4W, ± 5% metal/carbon film,unless stated otherwise)

R1,R2,R15,R16- 10-kilo-ohmR3,R4,R14 - 1-kilo-ohmR0,R5-R9,R12,R13 - 330-ohmR10,R11 - 5.6-kilo-ohmR17 - 2-ohm, 0.5WR18,R19 - 200-kilo-ohmCapacitors:C1 - 10µF, 16V electrolyticC2-C4,C7,C19,C20 - 0.1µF ceramic discC15,C16,C9,C10,C11,C13 - 0.1µF polyesterC5,C6 - 33pF ceramic discC8 - 22µF, 25V electrolyticC12,C14 - 2.7nF polysterC17,C18 - 2.2µF, 16V electrolyticC21,C22 - 220pF ceramic discC23 - 10µF, 50V electrolyticMiscellaneous:RL1 - 12V, 150 ohm, SPST relay

OEN Pt. No. 57DP-12-1C6XTAL - 4MHz quartz crystalY - 455kHz, ceramic resonator

- Battery 1.5V, pencil cell- IR sensor module- Remote control handset,

complete with keyboard- Connectors for audio input-

output and power supply- 12V DC, 250mA battery

eliminator

The author is the proprietor of GVC Systems,Noida. He can be approached through e-mailat gvc@vsnl.com

CONSTRUCTION

E L E C T R O N I C S F O R Y O U • O C T O B E R 2 0 0 6 • 7 7W W W . E F Y M A G . C O M

CMYK

Beverage vending machines arecommonplace at railway sta-tions, airports, fast-food restau-

! VINAY CHADDHA

SANI T

HEO

rants and even in companies. Press aswitch and the machine delivers a hotcup of your favourite drink.

This looks quite a simple operationbut has a very complex logic behind

it: It involves use oftwelve precision timersand four counters apartfrom physical devices likedisplay, solenoid and mo-tor to deliver water andpremixed tea/coffee/souppowder in exact quantityfor better taste and in ex-act sequence.

This has become pos-sible because of the use ofmicrocontrollers, which

allow compact size, higher reliability,lower cost and multiple functionalities.

This tea/coffee/soup vending ma-chine controller uses Freescale’s latestMC908JL16 microcontroller chip. Thecontroller is programmable and user-friendly. You can set the quantity ofthe beverages through a button switchprovided on the front panel of the con-troller as per your requirements. Thus,cups of any size can be filled at anytime.

The hardware

Fig. 1 shows the block diagram of thevending machine controller. It com-prises the following sections: powersupply, microcontroller, relays, relay

driver, alphanumericdisplay, keyboard andmemory. The powersupply circuit is shownin Fig. 2.

The control unituses low-cost, readilyavailable components.The temperature con-trol section has notbeen included in thedesign as the parts re-quired are expensiveand not easily avail-able. However, a low-cost thermostat used inwater heaters can beused in the unit.

Power supply. Therelays need 12V DCand the microcontrollerand memory need 5VDC for operation.Bridge rectifier, capaci-tive filter and regulatorICs 7812 and 7805 arethe standard parts usedin the power supply.

Microcontroller.We need individually

BEVERAGE VENDING

MACHINE CONTROLLER

Fig. 1: Block diagram of the beverage vending machine controller

Fig. 2: Power supply circuit

The prototype of beverage vending machine controllerdeveloped by the author

C O N S T R U C T I O N

ELECTRONICS FOR YOU OCTOBER 200250

C O N S T R U C T I O N

VINAY CHADDHA*

Security is a prime concern in our day-to-day life. Everyone wants to be asmuch secure as possible. An access-

control system forms a vital link in a secu-rity chain. The microprocessor-based digi-tal lock presented here is an access-control system that allows only authorisedpersons to access a restricted area.

System overviewThe block diagram of the access-controlsystem is shown in Fig. 1. The systemcomprises a small electronic unit with anumeric keypad, which is fixed outside theentry door to control a solenoid-operatedlock. When an authorised person enters apredetermined number (password) via thekeypad, the relay operates for a limited timeto unlatch the solenoid-operated lock so thedoor can be pushed/pulled open. At the endof preset delay, the relay de-energises andthe door gets locked again. If the enteredpassword is correct the unit gives threesmall beeps, and if the entered password iswrong it gives a longer beep of one second.

The system uses a compact circuitrybuilt around Motorola’s MC68HC705KJ1microcontroller and a non-volatile I2CEEPROM (ST24C02) capable of retaining

SUNIL KUMAR

ible 2048-bit (2-kbit) EEPROM is organisedas 256x8 bits. It can retain data for morethan ten years. Using just two lines (SCLand SDA) of the memory, themicrocontroller can read and write thebytes corresponding to the data requiredto be stored.

(Note. For details of the microcontrollerand programming of I2C EEPROM, you mayrefer to the article ‘Caller ID Unit UsingMicrocontroller’ published in April ’99 is-sue of EFY and the article ‘Remote-con-trolled Audio Processor UsingMicrocontroller’ published in Sep. ’99 is-sue of EFY. For additional data on Motorolamicrocontrollers, refer to EFY-CDs of thisyear’s January and February issues. Theinformation pertaining to I2C EEPROM isavailable on STMicroelectronics’ Website.)

Power supply. The power supply unitprovides a constant 5V supply to the en-tire unit. This is a conventional circuit us-

the password data for over ten years.The user can modify the password as

well as relay-activation time duration fordoor entry. This version of softwareenables use of the unit even without theI2C EEPROM. (However, without EEPROM,the password and relay-activation timeduration will be reset to default valueson interruption of the power supply.)

Hardware detailsFig. 2 shows the access control circuit. Itsmain components are a microcontroller,I2C memory, power supply, keypad, relay,and buzzer.

Microcontroller. The 16-pinMC68HC705KJ1 microcontroller fromMotorola has the following features:

• Eleven bidirectional input/output(I/O) pins

• 1240 bytes of OTPROM programmemory

• 64 bytes of user RAM• 15-stage multiple-function timerOut of eleven I/O pins, seven lines

have been used for the keyboard, one forthe buzzer, one for relay operation, andtwo (SCL and SDA, i.e. serial clock andserial data lines) for communication withI2C EEPROM.

I2C memory. A two-wire serial EEPROM(ST24C02) isused in thecircuit to re-tain the pass-word and therelay-activa-tion time du-ration data.Data storedremains in thememory evenafter powerfailure, as thememory en-sures readingof the latestsaved settingsby themicrocontroller.

This I2Cbus-compat-

MICROCONTROLLER-BASEDACCESS CONTROL SYSTEM

F ig . 1: B lock diagram of the access-control system

PARTS LIST

Semiconductors:IC1(U1) - MC68HC705KJ1

microcontrollerIC2 (U2) - ST24C02 I2C EEPROMIC3 (MN1) - MN1280 reset stabiliserIC4 (Reg1) - 7805 +5V regulatorT1, T2 - BC547 npn transistor(Q1, Q2)D1, D2 - 1N4007 rectifier diodeLED1 - Red LED

Resistors (all ¼-watt, ±5% carbon, unlessstated otherwise):R1-R6 - 10-kilo-ohmR7-R9 - 1-kilo-ohm

Capacitors:C1, C2 - 33pF ceramic diskC3, C4,C6, C7 - 0.1µF ceramic diskC5 - 10µF, 10V electrolytic

Miscellaneous:Xtal (Y1) - 4MHz quartz crystalPZ1 (BZ1) - Ceramic piezo buzzerCon1 - Power-supply connectorCon2 - 2-pin male/female Berg

connectors- 7-pin male/female Berg

connectorsSW1-SW12 - Tactile keyboard switchRL1 (RLY1) - 1C/O, 12V, 250-ohm

miniature relay