Quiz Buzzer

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APROJECT REPORT

ON

SCHOOL / COLLEGE QUIZ BUZZER

SUBMITTED IN PARTIAL FULFILLMENT OF THE

REQUIREMENT FOR THE AWARD OF THE DEGREE

OF

BACHELOR OF ENGINEERING

INELECTRONICS AND COMMUNICATION ENGINEERING

Guided by: - Submitted by: -

Mr. Nilesh Parihar Sumit Kumar Dahiya

Lecturer (E.C.E) Narendra Bagoria

Final year (E.C.E.)

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

SOBHASARIA ENGINEERING COLLEGE, SIKAR

UNIVERSITY OF RAJASTHAN

2007-08

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CANDIDATE DECLARATION

This is to certify that work, which is being presented in the project entitled SCHOOL /

COLLEGE QUIZ BUZZER submitted by undersigned students of final year B.E. in

Electronics & Communication Engineering in partial fulfillment for award of degree of

bachelor of engineering is a record of our own work carried out by us guidance and

supervision of Mr. Nilesh Parihar (Lecturer), Department of Electronics &

communication Engineering.

This work has not submitted elsewhere for award of any other degree.

Date: 12/ 12/ 2007 ( )

Place: S.E.C.,Sikar Name: Sumit Kumar Dahiya

Enroll. No. 04/13030

( )

Name: Narendra Bagoria

Enroll. No.04/13050

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CERTIFICATE

THIS IS TO CERTIFY THAT THE WORK, WHICH IS BEING PRESENTED IN THE

PROJECT SCHOOL/COLLEGE QUIZ BUZZER SUBMITTED BY SUMIT

KUMAR DAHIYA AND NARENDRA BAGORIA, STUDENTS OF FINAL YEAR

B.E. IN ELECTRONICS & COMMUNICATION ENGNEERING AS A PARTIAL

FULFILLMENT FOR THE AWARD OF DEGREE OF BACHELOR OF ENGINEERING

IS A RECORD OF STUDENTS WORK CARRIED OUT BY HIM UNDER MY

GUIDANCE AND SUPERVISION.

THIS WORK HAS NOT BEEN SUBMITTED ELSEWHERE FOR THE AWARD OF

ANY OTHER DEGREE.

DATE: 12/ 12 / 2007 (----------------------)

PLACE: S.E.C., SIKAR PROJECT GUIDE

(Sh. NILESH PARIHAR) (Sh.K.B.SINGH)PROJECT INCHARGE (H.O.D OF E.C.E. DEPTT.)

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ACKNOWLEDGEMENT

Expressing gratitude is not just a ritual that has to be carried out. Rather it is an

opportunity to sincerely thank all those who extended their much-needed help.

It gives us immense pleasure in acknowledging the help we have received during

our tenure at Sobhasaria Engineering College. We owe our all the obligations and our

sincere feelings to our guide Mr. Nilesh Parihar (Lecturer, ECE) to provide us valuable

guidance and encouragement through out the stages of presentation of our project as well

as preparation of report. We regard him for all time he could devote for the project and for

helping us grasps the technical wiz-a-wiz of the SCHOOL / COLLEGE QUIZ

BUZZER. We gladly appreciate the time and patience they could spare their busyschedule.

We are highly obliged to Mr. K.B.Singh (H.O.D., ECE) for their appreciation.

At last but the most we would like to extend our thanks to all faculty members of

Department of Electronics & Communication Engineering, faculty ofCommunication

Lab, our friends and colleague for their support and cooperation.

( )

Sumit Kumar Dahiya

( )

Narendra Bagoria

(Final Year ECE)

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ABSTRACT

Manual buzzers used for quiz competitions in schools and colleges create a lot of

confusion in identifying the first respondent. Although there are circuits using PCs and

discrete ICs, they are either too expensive or limited to only a few numbers of players.

The quiz buzzer circuit given here can be used for up to eight players, which is

maximum in any quiz com-petition. The circuit uses IC 74LS373 and a few passive

components that are readily available in the market. The circuit can be divided into two

sections: power supply and quiz buzzer. Fig. 1 shows the power supply section. The

regulated 5V power supply for the quiz buzzer section is derived from AC mains. The

230V AC mains is stepped down to 7.5V AC by transformer X1, rectified by bridge

rectifier BR1, filtered by C1 and regulated by regulator IC1. Capacitor C2 bypasses ripples

in the regulator output.Fig. 2 shows the quiz buzzer section. At the heart of this section is

IC 74LS373, an octal latch that is used to transfer the logic state at data input pins D0

through D7 to the corresponding Q0 through Q7 outputs. Data pins D0 through D7 are

normally pulled low by resistors R1 through R8, respectively.One terminal of push-to-on

switches S1 through S8 is connected to +5V, while the other terminal is connected to the

respective data input pins.

The switches are to be extended to the players through cord wire. The torch bulbs

BL1 through BL8 can be housed in boxes with the front side of the boxes covered with a

white paper having the name or number of the contestant written over it for easy

identification. Place the boxes above the head level so that these can betseen by the

audience also.

When the power is switched on using switch S9 (provided terminals A and B of

both the power supply and quiz buzzer sections are interconnected), the circuit is ready to

use. Now all the switches (S1 through S8) are open and Q0 through Q7 outputs of IC

74LS373 are low. As a result, the gates of silicon-controlled rectifiers SCR1 through SCR8

are also low. As soon as a contestant momentarily presses his respective switch, the

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corresponding output data pin goes high. This triggers the corresponding SCR and the

respective bulb glows.

At the same time, the piezobuzzer (PZ1) sounds as transistor T1 conducts.

Simultaneously, the base of transistor T2 becomes high to make it conduct. Latch-enable

(LE) pin 11 of IC2 is tied to ground to latch all the Q0 through Q7 outputs. This restricts

further change in the output state due to any change in the state of switches S1 through S8

by any other contestant. Only one of the eight torch bulbs glows until the circuit is reset by

on/ off switch S9.

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INDEX

Chapter 1 Introduction 11.1 School / College Quiz Buzzer

1.2 Basic terms

Chapter 2 Component description 2-13

2.1 Introduction

2.2 7805 IC Voltage Regulator

2.2.1Definition of 741 pin function

2.3 74LS373 IC

2.3.1Definition of pin functions

2.3.2 Operating modes

2.3.2.1 Monostable mode

2.3.2.2 Astable mode

2.4 Silicon Controlled Rectifier (SCR)

2.5 Resistor

2.6 Transistor

2.6.1 Types of BJT transistor

2.6.1.1 NPN transistor

2.6.2.2 PNP transistor

2.6.2 Region of operation

2.7 Capacitor

2.8 Diode

2.9 Light Emitted Diode (LED)

Chapter 3 Versatile intercom system 14-16

3.1 The circuit

3.2 Construction

Conclusion 17-18

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References 19

Chapter: 1

INTRODUCTION

1.1 School / College Quiz Buzzer

The attraction of any game show depends on the visual effects. The way in which

they present different rounds makes the game shows effective. The good Quiz show always

contains one or more buzzer rounds.

The buzzer makes a round of a Quiz show 'fastest finger first '. The active buzzer

makes the team to first respond to the question. A common question will be asked for all

the teams in these rounds. The team which presses the buzzer first gets first chance to

answer. To avoid confusion of the teams to be answered when one or more team presses the

buzzer almost simultaneously, buzzer circuits are used.

Instead of just showing who pressed the buzzer using some LED or electric bulb, if

has some visual effects, audio effects and different options that makes the show entice. So

our approach is to make this possible which includes all the features. This project makes

the show attractive and easy to operate. This Quiz buzzer is built with the view of making

the game show priority less.

This project uses PC parallel port to input user's response from the switches

placed in the participant's table. Response of the teams can be projected on to a screen.

Number of all the teams will be displayed in the screen in order of the response.

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Chapter: 2

COMPONENT DESCRIPTION

2.1 Introduction

When a beginner to electronics first looks at a circuit board full of components

he/she is often overwhelmed by the diversity of do-dads. An electronic circuit is made up

of electronic component. Electronic components are classified as active or passive.

Passive component is one that contributes no power gain (amplification) to a circuit

or system. It has no control action and does not require any input other than a signal to

perform its function. Examples are resistors, capacitors, inductors.

Active components are those that are capable of controlling voltages or currents and

can create a switching action in the circuit. Examples are transistors, diodes, etc.

2.2 IC 7805 Voltage Regulator

It is very easy to get stabilized voltage for ICs by using a three terminal voltage

regulator.The power supply voltage for a car is +12V - +14V. At this voltage, some ICs can

not operate directly except for the car component ICs.

In this case, a three terminal voltage regulator is necessary to get the required

voltage. The three terminal voltage regulator outputs stabilized voltage at a lower level than

the higher input voltage.

A voltage regulator cannot put out higher voltage than the input voltage. They are

similar in appearance to a transistor. On the left in the photograph is a 78L05. The size and

form is similar to a 2SC1815 transistor. The output voltage is +5V, and the maximum

output current is about 100mA. The maximum input voltage is +35V. (Differs by

manufacturer.)

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Fig. 2.2.1 IC 7805 Voltage Regulator

On the right is a 7805. The output voltage is +5V, and maximum output current is 500mA

to 1A. (It depends on the heat sink used) The maximum input voltage is also +35V.

There are many types with different output voltages.

5V, 6V, 7V, 8V, 9V, 10V, 12V, 15V, 18V.

Component Lead of Three Terminal Voltage Regulator

Example of 78L05

Part number is printed on the flat face of the regulator, and indicates the front.

Rightside:Input

Center : Ground

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Leftside:Output

2.3 IC 74LS373

The SN54 / 74LS373 consists of eight latches with 3-state outputs for bus organized

system applications. The flip-flops appear transparent to the data (data changes

asynchronously) when Latch Enable (LE) is HIGH. When LE is LOW, the data that meets

the setup times is latched. Data appears on the bus when the Output Enable (OE) is LOW.

When OE is HIGH the bus output is in the high impedance state.

The SN54 / 74LS374 is a high-speed, low-power Octal D-type Flip-Flop featuring

separate D-type inputs for each flip-flop and 3-state outputs for bus ori- ented applications.

A buffered Clock (CP) and Output Enable (OE) is common to all flip-flops. The SN54 /

74LS374 is manufactured using advanced Low Power Schottky technology and is

compatible with all Motorola TTL families.

Eight Latches in a Single Package

3-State Outputs for Bus Interfacing

Hysteresis on Latch Enable

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Edge-Triggered D-Type Inputs

LOGIC DIAGRAMS SN54LS / 74LS373

2.4 Silicon Controlled Rectifier (SCR):

The TYN 204-1004 family of Silicon Controlled Rectifier uses a high performance

glass passivated technology.

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This general purpose family of silicon controlled rectifier is designed for power

supplies up to 400 Hz on resistive or inductive load.

Fig. 2.4.1 Silicon Controlled Rectifier

2.5 Resistors:

A resistor is a two-terminal electrical orelectronic component that resists an

electric current by producing a voltage drop between its terminals in accordance with

Ohm's law: The electrical resistance is equal to the voltage drop across the resistor divided

by the current through the resistor. Resistors are used as part of electrical networks and

electronic circuits.

The resistance of a resistor is given by the formula

where:

is the resistivity of the material that the resistor is made from

l is the length of the resistive material, between the end contacts

A is the (presumed uniform) cross sectional area of the resistive material

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Fig 2.5 symbolic representation of resistor

2.6 Transistor

A transistor is a semiconductor device, commonly used as an amplifier or an

electrically controlled switch. The transistor is the fundamental building block of the

circuitry in computers, cellular phones, and all other modern electronic devices. Transistors

are the basic devices providing control of this kind. Modern transistors are divided into two

main categories: bipolar junction transistors (BJTs) and field effect transistors (FETs).

Application of current in BJTs and voltage in FETs between the input and common

terminals increases the conductivity between the common and output terminals, thereby

controlling current flow between them

A bipolar junction transistor (BJT) is a three-terminal device constructed of

doped semiconductor material and may be used in amplifying or switching applications.

Bipolar transistors are so named because their operation involves both electrons and holes.

A BJT consists of three differently doped semiconductor regions, the emitter region, the

base region and the collector region. These regions are, respectively, p type, n type and p

type in a PNP, and n type, p type and n type in a NPN transistor. Each semiconductor

region is connected to a terminal, appropriately labeled: emitter (E), base (B) and collector

(C).

The base is physically located between the emitter and the collector and is made

from lightly doped, high resistivity material. The collector surrounds the emitter region,

making it almost impossible for the electrons injected into the base region to escape being

collected, thus making the resulting value of very close to unity, and so, giving the

transistor a large . A cross section view of a BJT indicates that the collectorbase junction

has a much larger area than the emitterbase junction.

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The bipolar junction transistor, unlike other transistors, is usually not a symmetrical

device. This means that interchanging the collector and the emitter makes the transistor

leave the forward active mode and start to operate in reverse mode. Because the transistor's

internal structure is usually optimized to forward-mode operation, interchanging the

collector and the emitter makes the values of and in reverse operation much smaller

than those found in forward operation; often the of the reverse mode is lower than 0.5.

The lack of symmetry is primarily due to the doping ratios of the emitter and the collector.

The emitter is heavily doped, while the collector is lightly doped, allowing a large reverse

bias voltage to be applied before the collectorbase junction breaks down. The collector

base junction is reverse biased in normal operation. The reason the emitter is heavily doped

is to increase the emitter injection efficiency: the ratio of carriers injected by the emitter to

those injected by the base. For high current gain, most of the carriers injected into the

emitterbase junction must come from the emitter.

2.6.1Types of BJT

BJT is basically of two types: NPN and PNP.

2.6.1.1 NPN transistor

NPN is the bipolar transistor, in which the letters "N" and "P" refer to the majority

charge carriers inside the different regions of the transistor. Most bipolar transistors used

today are NPN, because electron mobility is higher than hole mobility in semiconductors,

allowing greater currents and faster operation.

Fig 2.6.1.1 NPN transistor symbol

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NPN transistors consist of a layer of P-doped semiconductor (the "base") between

two N-doped layers. A small current entering the base in common-emitter mode is

amplified in the collector output.

The arrow in the NPN transistor symbol is on the emitter leg and points in the direction of

the conventional current flow when the device is in forward active mode.

2.6.1.2 PNP transistor

The other type of BJT is the PNP with the letters "P" and "N" referring to the

majority charge carriers inside the different regions of the transistor. Few transistors used

today are PNP, since the NPN type gives better performance in most circumstances.

Fig 2.6.1.2 PNP transistor symbol

PNP transistors consist of a layer of N-doped semiconductor between two layers ofP-doped material. PNP transistors are commonly operated with the collector at ground and

the emitter connected to a positive voltage through an electric load. A small current

flowing from the base allows a much greater current to flow from the emitter to the

collector.

The arrow in the PNP transistor symbol is on the emitter leg and points in the

direction of the conventional current flow when the device is in forward active mode.

2.6.2Regions of operation

Bipolar transistors have five distinct regions of operation, defined mostly by applied

bias:

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Forward-active (or simply, active): The emitter-base junction is forward biased and

the base-collector junction is reverse biased. Most bipolar transistors are designed

to afford the greatest common-emitter current gain, f in forward-active mode. If

this is the case, the collector-emitter current is approximately proportional to the

base current, but many times larger, for small base current variations.

Reverse-active (or inverse-active or inverted): By reversing the biasing conditions

of the forward-active region, a bipolar transistor goes into reverse-active mode. In

this mode, the emitter and collector regions switch roles. Since most BJTs are

designed to maximise current gain in forward-active mode, the f in inverted mode

is several (2 - 3 for the ordinary germanium transistor) times smaller. This transistor

mode is seldom used, usually being considered only for failsafe conditions and

some types of bipolar logic. The reverse bias breakdown voltage to the base may be

an order of magnitude lower in this region.

Saturation: With both junctions forward-biased, a BJT is in saturation mode and

facilitates high current conduction from the emitter to the collector. This mode

corresponds to a logical "on", or a closed switch.

Cutoff: In cutoff, biasing conditions opposite of saturation (both junctions reverse

biased) are present. There is very little current flow, which corresponds to a logical

"off", or an open switch.

Avalanche breakdown region

2.7 Capacitor:

A capacitor is a passive electronic component that stores energy in the form of an

electrostatic field. In its simplest form, a capacitor consists of two conducting plates

separated by an insulating material called the dielectric. Capacitance is directly

proportional to the surface areas of the plates, and is inversely proportional to the plates'separation. Capacitance also depends on the dielectric constant of the dielectric material

separating the plates. The capacitor's capacitance (C) is a measure of the amount ofcharge

(Q) stored on each plate for a given potential difference or voltage (V) which appears

between the plates:

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The standard units of Capacitance,

farad: F

microfarad: F (1 F = 10-6 F)

nanofarad: nF (1 nF = 10-9 F)

picofarad: pF (1 pF = 10-12 F)

2.8 Diode:

In electronics, the word diode describes 2 classes of device:

a device that passes current in one direction much more readily than in the other Some other devices with structures related to silicon diodes (eg Diac).

Most diodes have 2 terminals, and most are used for their unidirectional current

property, but neither of these applies to all diodes.

The directionality of current flow most diodes possess is sometimes generically called the

rectifying property). The most common function of a diode is to allow an electric current to

flow in one direction (called the forward biased condition) but to block it in the opposite

direction (the reverse biased condition).

Most modern diodes are based on semiconductorp-n junctions. In a p-n diode,

conventional current can flow from the p-type side (the anode) to the n-type side (the

cathode), but cannot flow in the opposite direction

A semiconductor diodes currentvoltage, or IV, characteristic curve is related to

the transport of carriers through the so-called depletion layerordepletion region that exists

at thep-n junction between differing semiconductors. When a p-n junction is first created,

conduction band (mobile) electrons from the N-doped region diffuse into the P-doped

region where there is a large population of holes (places for electrons in which no electron

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is present) with which the electrons recombine. When a mobile electron recombines with

a hole, both hole and electron vanish, leaving behind an immobile positively charged donor

on the N-side and negatively charged acceptor on the P-side. The region around the p-n

junction becomes depleted ofcharge carriers and thus behaves as aninsulator.

However, the depletion width cannot grow without limit. For each electron-hole

pair that recombines, a positively-charged dopant ion is left behind in the N-doped region,

and a negatively charged dopant ion is left behind in the P-doped region. As recombination

proceeds and more ions are created, an increasing electric field develops through the

depletion zone which acts to slow and then finally stop recombination. At this point, there

is a built-in potential across the depletion zone.

If an external voltage is placed across the diode with the same polarity as the built-

in potential, the depletion zone continues to act as an insulator preventing a significant

electric current. This is the reverse bias phenomenon. However, if the polarity of the

external voltage opposes the built-in potential, recombination can once again proceed

resulting in substantial electric current through the p-n junction. For silicon diodes, the

built-in potential is approximately 0.6 V. Thus, if an external current is passed through the

diode, about 0.6 V will be developed across the diode such that the P-doped region is

positive with respect to the N-doped region and the diode is said to be turned on as it has

a forward bias.

2.9 Light Emitted Diode (LED):

An LED is a special semiconductor which emits light when current is passed

through it. There are many different physical styles. The emitted color spectrum is usually

very narrow. It can generally be specified as a specific wavelength in the electromagnetic

spectrum. The emitted color selection is somewhat limited. The most commonly available

colors are red, green, amber, yellow, blue and white. The red, green, yellow and amber

have a working voltage of approximately 1.8 volts. You can refer to the data sheet for each

LED to find the exact value. The actual working voltage is determined by the breakdown

voltage of the particular semiconductor material.

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Fig 2.9.1 Schematic Symbol Fig 2.9.2 Description

2.7.1 IV characteristics of a P-N junction diode

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Chapter: 3

SCHOOL / COLLEGE QUIZ BUZZER

Manual buzzers used for quiz competitions in schools and colleges create a lot of

confusion in identifying the first respondent. Although there are circuits using PCs and

discrete ICs, they are either too expensive or limited to only a few number of players.












switches S1 through S8 is connected to +5V, while the other terminal is connected to the

respective data input pins.

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audience also.






corresponding output data pin goes high. This triggers the corresponding SCR and therespective bulb glows.






on/ off switch S9.

3.2 Construction:

Suggested PCB layout is shown in Fig. 3.2 and the corresponding components

layout in Fig. 5. Care should be taken when wiring DPDT switch S1. Suggested cabinet

layout is shown in Fig.6. Note that the transformer is mounted in a separate enclosure and

placed at a minimum distance of 20 cm from the main enclosure containing the condenser

mic, PCB etc. If transformer and diode are mounted inside the same enclosure it will result

in howling because of air pressure variation which is very difficult to control.

Using a 2-core shielded cable is recommended with the shield connected to the

ground as it will also avoid electrical noises. A regulated power supply will give good

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audio reproduction. The circuit diagram of suggested power supply is shown in

Fig3.2.1There must be separate power supplies for each station.

Fig. 3.2.1 Supply

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Fig. 3.2.2 Circuit

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CONCLUSION

Manual buzzers used for quiz competitions in schools and colleges create a lot ofconfusion in identifying the first respondent. Although there are circuits using PCs and

discrete ICs, they are either too expensive or limited to only a few number of players.












switches S1 through S8 is connected to +5V, while the other terminal is connected to therespective data input pins.





audience also.






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corresponding output data pin goes high. This triggers the corresponding SCR and the

respective bulb glows.






on/ off switch S9.

REFERENCE

Books:

1. Electronics for you

2. Integrated circuits:- Ramakant A Gaykward

3. Principle of Electronics:- V.K. Mehta

Sites:

1. www.datasheetarchive.com

2. www.electronicsforu.com

3. www.centralsemi.com

Date post:	30-May-2018
Category:	Documents
Upload:	narencool05
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