RVGs

Mini Project-06 JAM - Just A Minute Circuit

GOVT. COLLEGE OF ENGINEERING KANNUR

MINI PROJECT REPORT

ON

JUST A MINUTE (JAM) CIRCUIT

SUBMITTED BY

SUJESH.NLATHEESH.T

MANORANJ KK.NAJUMUDDEEN NP

RAHUL V GOPINATH

DEPARTMENT OF ELECTRONICS & COMMUNICATION

KANNUR2006

Dept. Of Electronics & Communication Engg. GCE Kannur


GOVT.COLLEGE OF ENGINEERINGKANNUR

CERTIFICATE

This is to certify that the mini project report entitled JUST A MINUTE (JAM) CIRCUIT is an authentic report of the work done by LATHEESH.T , MANORANJ K.K., NAJUMUDDEEN N.P, RAHUL.V.GOPINATH and SUJESH.N, at GOVT. COLLEGE OF ENGINEERING, KANNUR during their Sixth semester in partial fulfillment of the requirement for the award of the B.Tech degree course in ELECTRONICS & COMMUNICATION ENGINEERING, of Kannur university.

HEAD OF THE DEPARTMENT Guided By

Mrs.GEETHARANJINI Mr. MOHAMMED SALIH Head of the Department Lecturer Dept of Electronics & comm. Dept of Electronics&comm. Govt. College of Engg. Govt. College of Engg.

Kannur. Kannur.



CONTENTS

ABSTRACT

CIRCUIT DIAGRAM Power supply JAM Circuit

CIRCUIT DESCRIPTION

PCB LAYOUT Power supply section JAM Circuit

MAKING OF PCB

SOLDERING

COMPONENTS & PRICE LIST

ADVANTAGES & DISADVANTAGES

DATASHEET IC 74LS00 IC 74LS04 IC 74LS30 IC 74LS373 IC 74LS147 IC 7805

BIBLIOGRAPHY

CONCLUSION



ABSTRACT

Just A Minute (JAM) circuit contains additional display circuit by which it overcomes all the disadvantages of Ordinary Quiz Buzzer. Just A Minute (JAM) Circuit has the same purpose as that of Ordinary Quiz Buzzer. But it will overcome all the disadvantages of Ordinary Quiz Buzzer. JAM circuit contains display sections, which will show the number of the contestant pressing his button before the others. Simultaneously, a buzzer will also sound. The circuit given here permits up to eight contestants with each one allotted a distinct number (1 to 8). This JAM circuit can be used in quiz contest wherein any participant who presses his button (switch) before the other contestant gets the first chance to answer a question. Now we can find out which one of the participants pressed the buzzer switch at first, by checking that displayed number. Only the participant pressed the buzzer switch first will be displayed.. Thus use of JAM circuit is more accurate when two or more participant teams simultaneously presses their buzzer switches.



CIRCUIT DIAGRAMS

2.1 Power Supply

2.2 JAM Circuit



CIRCUIT DESCRIPTION

JAM circuit has mainly two sections.

Power supply section Buzzer and Display section

Power Supply section

This section contains TRANSFORMER 230/6-0-6 DIODES IN4001 CAPACITOR REGULATOR IC 7805

Buzzer and Display Section

This section contains BUZZER D FLIP FLOPE IC 74373 NAND IC 7400, 7430 PNP TRANSISTOR CK100 DISPLAY FND 507 DISPLAY IC 7447 PRIORITY ENCODER IC 74147 NOT IC 7404 RESISTOR CAPACITOR SWITCHES



CIRCUIT OPERATION

The working of the circuit can be explained as1 DC voltage generation2 Buzzer Display operation

DC voltage generator

This unit will generate +5 volt & ground from the AC supply, which is used for driving all ICs. This generator contains 230/6-0-6 volt transformer, bridge rectifier circuit (using 1N4001diodes) & 7805-voltage regulator IC. Transformer secondary output is applied to bridge rectifier .The bridge rectifier will produce a DC voltage. To remove ripples of the bridge rectifier output; a capacitor (C1) is connected across the bridge output. To remove the remaining ripples regulator IC 7805 used. Then +5V & ground are obtained from 7805.

Buzzer Display operations

Initial Condition

Initially when the power supply is switched on all the inputs of IC1 (74373) are connected to Vcc via resistors R1 through R8. Thus all the outputs of IC1 go logic HIGH. Since all the outputs of IC1 are connected to inputs of IC2 (7430) the outputs of IC2 becomes logic LOW which causes outputs of both gate N1 & N2 to go logic HIGH state the output of gate N2 is applied to latch enable pin of IC1. Thus all the outputs of IC1 will be latched to logic HIGH. Since the outputs of N1 are logic HIGH the buzzer cannot be drived.

All eight outputs of IC1 are also connected to inputs of IC3 (74147) with all input pins of IC3 being logic HIGH its BCD output is 0000 which is applied to 7 segment decoder driver IC5 (7447) after inversion hex inverter gates inside IC4 (7404). Thus when power supply is switched on the display shows 0 without a buzzer sound .



When any of the switch is pressed

When any of the push to on switches S1 through S8 is

pressed, the corresponding output line of IC1 is latched at logic LOW level

and the display indicates the corresponding number associated with specific

switch .At the same time output of IC2 becomes logic HIGH which causes

output of both N1and N2 to go to logic LOW. Logic LOW output of N2

inhibits IC1 and thus pressing any of the other switches S1 through S8 has

no effect. Thus, the contestant who presses his switch first, jams the display

to show only his number. In the unlikely event of simultaneous pressing

(within few nano-second difference) of more than one switch, the higher

priority number(switch no) will be displayed. Simultaneously the logic LOW

output of gate N1 drives the buzzer via PNP transistor CK100 (T1). The

buzzer as momentary pressing of reset switch S9 so that next round can reset

well the display may start.



PCB LAYOUT



MAKING OF PCB

A PRINTED CIRCUIT BOARD is popularly known as PCB. A PCB ensures that various circuit components are interconnected as per the circuit diagram after they are placed on the PCB in their proper position and subsequently soldered.

PCB Fabrication

Different steps involved in the fabrication of a PCB are follows1. Components layout designing 2. PCB layout designing3. Transferring the PCB layout design onto the PCB laminate4. Developing for etching the PCB.5. Other operations like drilling, cutting, tinning etc

Components Layout designingComponents layout designing is the placement of different

components with their inter connections as per the circuit diagram on the PCB. This exercise usually begins with an estimate of the size of the PCB (length & breadth) needed to accommodate various circuit components. Having placed all the components, the inter connections can be made by drawing lines (known as Tracks).

PCB Layout designingPCB Layout designing is the mirror image of components layout. The

component layout is drawn looking from the components side whereas the PCB layout is drawn looking from the copper side. It is obtained by taking a

carbon copy of the components lay out by placing a reversed carbon underneath the paper.

Transferring PCB lay out on to PCB laminate First the PCB laminate is chosen. The copper side of the laminate is thoroughly cleaned with petrol to make it completely free from contaminants. The PCB lay out is drawn on the copper side. Care should be taken to mark the position of holes. The same is redrawn giving proper width to different tracks and leaving proper space using permanent marker.



Etching In this process, all excess copper is removed leaving behind only the drawn pattern. To do etching the aqueous solution of ferric chloride with the quantity depending upon the size of the PCB to be etched is then poured in the tray. The etching process may take about half an hour. The laminate is now thoroughly washed in water after etching is completed. The mark is then removed with alcohol.

Drilling-Tinning After etching the process employed is drilling of holes. The diameter of holes varies from component. It is 1mm per IC pins, 1.25mm for resistors and capacitors 1.5mm for diodes and even larger mounting presets. Using a soldering iron can do the oxidation of copper portions can be prevented by tinning that.



SOLDERING

Soldering is the process of joining metals by lower melting metal to wet or alloy with adjoined surfaces.

SOLDER Solder is the joining material that melts below 427 degree Celsius.

Soldered joints in electronic circuits will establish string connection between components leads .The popularly used solders are alloys of tin & lead that melts below the melting point of tin.

FLUXES In order to make the surfaces accept solder readily, the component

terminals are made free from oxides and other obstructing films. The leads are cleaned chemically or by abrasion using blades or knives. Small amounts of lead coating are done on the clean portion of leads using soldering iron. This process is called tinning. Zinc chloride or ammonium chloride separately or in combination are used fluxes. These are in available in petroleum jelly as paste flux. The residues which remain after soldering is washed out with more water accompanied by brushing.

SOLDERING IRON It is the tools used to melt the solder apply at the joints in the

circuits. It operates in 230volts mains supply. The iron bit at the tip of it gets heated up with in few minutes. 50W and 25W soldering irons are commonly used soldering purpose.

PROCEDURE

1. The layout of the connection of the components in the circuit is taken. The chord of the soldering iron is plugged to the main supply to get it heated up.

2. The component leads are straightened and cleaned using blade or knife. Then a little flux is applied on the leads. A little solder is taken on soldering iron and is applied on molten solder on the leads. Care is taken to avoid the components getting heated up.

3. The components are mounted on the PCB by bending the leads of components using nose pliers.

4. Flux is applied on the joints to solder it. To avoid dry soldering and heating up of the components, it is done in minimum time.

5. The residues are removed using water and brush.



COMPONENTS & PRICE LIST

ITEM NO.

COMPONENT SPECIFICATION QUANTITY PRICE(Rs.)

1 Transformer 230/6-0-6V, 1A 1 43.002 Diode IN 4001 4 04.00

3 Resistor10KΩ 9 04.502.2KΩ 1 00.501KΩ 1 00.50560Ω 7 03.50

4 Capacitor1000 μ F, 25V 1 06.000.1 μ F 1 01.000.01 μ F 1 01.00

5 IC

74373 1 25.0074147 1 20.007447 1 15.007430 1 15.007404 1 12.007400 1 15.007805 1 10.00

6 Switch Push to on 9 27.007 Display FND 507 1 20.008 Buzzer 5V 1 15.009 Transistor CK 100 1 15.0010 PCB 2 150.0011 Wires Single strand 17.50

Total Price 420.50



ADVANTAGES & DISADVANTAGES

Advantages

Good accuracy in use. Easy to operate and handle. High Efficiency

Disadvantages

It is costly compared to ordinary quiz buzzer.



DATA SHEETS

1) IC 74LS00

DescriptionThese devices contain four independent 2-input NAND gates.



2) IC 74LS04

DescriptionThese devices contain six independent NOT gates.



3)IC 74LS30

DescriptionThese devices contain a single 8 input NAND Gate.



4)IC 74LS373

DescriptionThese 8-bit registers feature 3-state outputs designed specifically for driving highly capacitive or relatively low-impedance loads. Thehigh-impedance 3-state and increased high-logic-level drive provide these registers with the capability of being connected directly to anddriving the bus lines in a bus-organized system without need for interface or pullup components. These devices are particularly attractive for implementing buffer registers, I/O ports, bidirectional bus drivers, and working registers. The eight latches of the ’LS373 and ’S373 are transparent D-type latches, meaning that while the enable (C or CLK) input is high, the Q outputs follow the data (D) inputs. When C or CLK is taken low, the output is latched at the level of the data that was set up.The eight flip-flops of the ’LS374 and ’S374 areedge-triggered D-type flip-flops. On the positive transition of the clock, the Q outputs are set to the logic states that were set up at the D inputs.Schmitt-trigger buffered inputs at the enable/clock lines of the ’S373 and ’S374 devices simplify system design as ac and dc noise rejection is improved by typically 400 mV due to the input hysteresis. A buffered output-control (OC) input can be used to place the eight outputs in either a normal logic state (high or low logic levels) or the high-impedance state. In the high-impedance state, the outputs neither load nor drive the bus lines significantly. OC does not affect the internal operation of the latches or flip-flops. That is, the old data can be retained or new data can be entered, even while the outputs are off.





5)IC 74LS147

Description

These TTL encoders feature priority decoding of the inputs to ensure that only the highest-order data line is encoded. The ’147 and ’LS147 devices encode nine data lines to four-line (8-4-2-1) BCD. The implied decimal zero condition requires no input condition, as zero is encoded when all nine data lines are at a high logic level.Cascading circuitry(enable input EI and enable output EO) has been provided to allow octal expansion without the need for external circuitry. For all types, data inputs and outputs are active at the low logic level. All inputs are buffered to represent one normalized Series 54/74 or 54/74LS load, respectively.



6)IC 74LS47

DescriptionThe 74LS47 feature active-low outputs designed for driving common-anode LEDs or incandescent indicators directly.74LS47 circuit incorporate automatic leading and/or traling-edge zero-blanking control .Inputs and outputs are entirely compatible for use with TTL logic outputs.

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7)IC 7805

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BIBLIOGRAPHY

1. www.electronic-circuits.com

2. www.alldatasheet.com

3. E F Y Magazine



11. CONCLUSION

JAM circuit overcomes all the disadvantages of ordinary quiz buzzer. Thus use of JAM circuit in the quiz program competition is more suitable. This project costs only about Rs. 450/-. The commercial production reduces the cost to around Rs. 300/-.




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