INTRODUCTION

This circuit can switch on and off a light, a fan or a

radio etc; by the sound of a clap.

This circuit is constructed using basic electronic

components like resistors, transistors, relay,

transformer, capacitors. This circuit turns 'ON' light

for the first clap. The light turns ON till the next

clap. For the next clap the light turns OFF. This

circuit works with 12V voltage. Therefore a

stepdown transformer 12V/300mA is employed.

The working of this circuit is based on amplifying

nature of the transistor, switching nature of

transistor, relay as an electronic switch.

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ABSTRACT

This circuit that can switch on and off a light, a

fan, a radio or a T. V. etc., by a sound of a clap.

The sound of clap is received by a small micro-

phone (condenser) that is shown by resistor r1 in

the circuit. The signal is further amplified by

transistors Q1, Q2, Q3. The relay contact is

connected to the power line and hence turns

on/off any electrical device at output socket.

The components included are resistors 15k, 2M,

270K, 3K, 27K, 1K, 10K. 2K. Capacitors 0.01uf,

0.047uf, 1000UF/16V. Transistors Q1234-BC 149,

Diodes IN 4002, IN 4148. Transformer of

12v/300mA, condenser mic , 12v single charge

over relay.

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CIRCUIT DIAGRAM

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COMPONENTS USED

RESISTORS:

R1 15K

R2, 5 ,12 2.2M

R3 270K

R4 3.3K

R6, 10 27K

R7, 11 1.5K

R8, 9 10K

R 13 2.2K

CAPACITORS:

C1 0.01UF

C2, 3 0.047UF

C4 1000UF/16V

SEMI CONDUCTORS:

Q 1, 2, 3, 4 BC 149

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D1 IN 4002

D2, 3, 4, 5 IN 4148

TRANSFORMER 12V / 300mA

CONDENSER MIC

RELAY 12 V single charge over relay

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COMPONENTS DESCRIPTION

RESISTOR:

A resistor is a two-terminal electrical or electronic

component that resists an electric current by

producing a voltage drop between its terminals in

accordance with Ohm's law: R=V/I 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.

CAPACITOR:

An electric circuit element used to store charge

temporarily, consisting in general of two metallic

plates separated and insulated from each other

by a dielectric. Also called condenser.

DIODE:

An electronic device that restricts current flow

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chiefly to one direction . An electron tube having

a cathode and an anode . A two-terminal

semiconductor device used chiefly as a rectifier.

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.

Because of its fast response and accuracy, the

transistor is used in a wide variety of digital and

analog functions, including amplification,

switching, voltage regulation, signal modulation,

and oscillators. Transistors may be packaged

individually or as part of an integrated circuit,

some with over a billion transistors in a very

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small area

TRANSFORMER:

A device used to transfer electric energy from

one circuit to another, especially a pair of

multiply wound, inductively coupled wire coils

that effect such a transfer with a change in

voltage, current, phase, or other electric

characteristic.

RELAY:

A relay is an electrical switch that opens and

closes under the control of another electrical

circuit In the original form, the switch is operated

by an electromagnet to open or close one or

many sets of contacts. If was invented by Joseph

Henry in 1835. Because a relay is able to control

an output circuit of higher power than the input

circuit, it can be . considered, in a broad sense,

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to be a form of an electrical amplifier

CONDENSER MIC:

Condenser means capacitor, an electronic

component which stores energy in the form of an

electrostatic field. The term condenser is actually

obsolete but has stuck as the name for this type

of microphone, which uses a capacitor to convert

acoustical-energy into electrical energy.

Condenser microphones require power from a

battery or external source'. The resulting audio

signal is stronger signal than that from a

dynamic. Condensers also tend to be more

sensitive and responsive than dynamics, making

them well-suited to capturing subtle nuances in a

sound. They are not ideal for high-volume work,

as their sensitivity makes them prone to distort.

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OPERATION

Here is a circuit that can switch on & off a light,

Fan, Radio etc. by the sound of clap. The sound

of clap is received by a small microphone that is

shown biased by resistor R1 in the circuit. The

microphone changes sound wave in to electrical

wave which is further amplified by Q 1. Transistor

Q 1 is used as common emitter circuit to amplify

weak signals received by the microphone.

Amplified output from the collector of transistor

Q 1 is then feed to the Bistable Multivibrator

circuit also known as flip-flop.

Flip flop circuit is made by using 2 Transistor, in

our circuit Q2 & Q3. In a flip-flop circuit, at a time

only one transistor conduct and other cut off and

when it gets a trigger pulse from outside source

then first transistor is cutoff and 2nd transistor

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conducts. Thus output of transistor is either logic-

0 or logic-1 and it remains in one state 0 or 1

until it gets trigger pulse from outer source.

The pulse of clap which is trigger for flip-flop

makes changes to the output which is

complementary (reverse). Decision of flip-flop

which is in the low current form is unable to drive

relay directly so we have used a current amplifier

circuit by using Q 4 which is a common emitter

circuit. Output of Q 4 is connected to a Relay

(Electromagnetic switch), works like a

mechanical switch. With the help of a relay it is

easy for connecting other electrical appliance.

The relay contact is connected to the power line

and hence turns on/off any electrical appliance

connected all the way through relay.

For power supply, we have made 12 Volt

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eliminator with the help of Transformer T 1,

Diode D1 and capacitor C 1. lt is a half wave

rectifier.

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APPLICATIONS

This circuit can be used to switch on and off a

light, a fan, a radio or a TV by the sound of a clap

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CONCLUSION

Hereby we would like to conclude that this circuit

is very much useful to switch ON and OFF the

household appliances just by clapping hand. This

circuit functions on using the sound energy

provided by the clap which is converted into

electrical energy by condenser mic. This circuit

turns on and off a light, a fan, a radio or a TV etc.

using this converted energy which is used to turn

on relay (an electronic switch)

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