Clap Switch

ABSTRACT  This paper presents the design of a clap activated switch device that will serve well in different phono-controlled applications, providing inexpensive key and at the same time free from false triggering. This involves the design of various stages consisting of the pickup transducer, low frequency, audio low power and low noise amplifier, timer, bistable multivibrator and switches. It also consists of special network components to prevent false triggering and ensure desired performance objectives. A decade counter IC serves the bistable function instead of flip-flop.

PREFACE

The primary purpose of switch is to provide means for connecting two or more terminals in order to permit the flow of current across them, so as to allow for interaction between electrical components. The motivating force behind this design is based on the desire to alleviate the problem faced by the aged and physically challenged persons in trying to control some household appliances. It also takes into considerations the illiterates that may have problems operating some “complex” hand-held Remote Control Units (RCUs). Therefore this paper provides an introductory study on the basic principles involved in utilizing acoustic energy to control switching process. This is achieved by converting the energy generated by the “handclap” into electrical pulse, which is in turn used to drive an electronic circuitry that includes a relay, which in turn switches ON/OFF any appliance connected through it to the main.

TABLE OF CONTENTS

INTRODUCTION

BLOCK DIAGRAM

BLOCK DIAGRAM EXPLANATION

CIRCUIT DIAGRAM

COMPONENT STUDY

CIRCUIT DESCRIPTION

PRINTED CIRCUIT BOARD(PCB) LAYOUT

COMPONENTS REQUIRED

APPLICATIONS

CONCLUSION

PHOTOS OF THE FINAL PRODUCT

APPENDIX- DATA SHEET

INTRODUCTION

The operation of the circuit is simple. Clap and the lamp turns on. Clap again and it

turns off. The condenser microphone picks up the sound of your claps, coughs, and the

sound of that book knocked off the table. It produces a small electrical signal which is

amplified by the succeeding transistor stage. Two transistors cross connected as a

bistable multivibrator change state at each signal. One of these transistors drives a

heavier transistor which controls a lamp. This circuit can switch on and off a light, a fan

or a radio etc by the sound of a clap. This working of this circuit is based on amplifying

nature of the transistor, switching nature of transistor , relay as an electronic switch .

BLOCK DIAGRAM

BLOCK DIAGRAM EXPLANATION

INPUT TRANSDUCER

The sound of your claps is picked up

using a condenser microphone. This microphone has a stage of amplification built in. The

power for this built in amplifier is supplied by connecting a resistor to a positive source

of voltage, and the changes in current get reflected as changes in voltage across this

resistor according to the familiar relation V = I*R. A larger resistor will give you a larger

voltage, but then, the current into the device gets reduced which brings down the gain.

The value of 5600 ohms (usually abbreviated to 5.6K, and written down in schematics

as 5K6) seems to work all right.

AMPLIFIER

A transistor stage, biased near cut-off amplifies the signal from the microphone. The

output of the microphone is coupled to the base of the transistor using an electrolytic

capacitor (note: using a better capacitor here will not work). The first time the

microphone output goes positive, however, (because somebody clapped) this change

gets coupled to the base entirely due to the action of the capacitor. This causes the

current through the transistor to increase, and this increase in current causes the

voltage at the collector, which was sitting near the supply voltage, to fall to nearly zero.

This is not a high fidelity audio amplifier. Its function is to produce no output for small

sounds and large output for (slightly) bigger sounds, so the customary biasing network

can be omitted.

BISTABLE MULTIVIBRATOR STAGE

Two cross connected transistors in a bistable multivibrator arrangement make up a

circuit that remembers. You can set it to one of two possible states, and it will stay in

that state until the end of time. When one transistor conducts, its collector is near

ground, and a resistor from this collector feeds the base of the other. Since this resistor

sees ground at the collector end the base at the other end receives no current, so that

transistor is off. Since this transistor is off, its collector is near supply potential and a

resistor connects from this to the base of the other transistor. Since this resistor sees

voltage, it supplies the base with current, ensuring that the transistor remains on. Thus

this state is stable. By symmetry, the other state is, too.

CHANGING STATE

On a clap, the state of the bistable changes. The output of the amplifier is converted to

a sharp pulse by passing it through a (relatively) low valued capacitor. This is connected

through "steering" diodes to the base of the transistor which is conducting. This

transistor stops conducting, and the other transistor was not conducting anyway. So at a

clap, both transistors become off.

Then, those two capacitors across the base resistors come into

action. The capacitor connecting to the base of the transistor which was ON has voltage

across it. The capacitor connecting to the base of the transistor which was OFF has no

voltage across it.

OUTPUT STAGE

An incandescent lamp of 60watt is connected in the output stage through a relay.

CIRCUIT DIAGRAM

COMPONENT STUDY

CAPACITOR

The capacitor plays a crucial role in electronics -- it stores electrons for when they're

needed most. Capacitors consist of two conducting plates placed near each other.

Inside the capacitor, the terminals connect to two metal plates separated by a dielectric.

The dielectric can be air, paper, plastic or anything else that does not conduct electricity

and keeps the plates from touching each other..

They can store electric charge for later discharge. Direct current

through a capacitor will charge the capacitor for a short time, and then stop flowing.

Alternating current, because of the changing electric fields it generates, can “flow”

across a capacitor.

BATTERY

If you look at any battery, you'll notice that it has two terminals. One terminal is marked

(+), or positive, while the other is marked (-), or negative. In an normal flashlight

batteries, the ends of the battery are the terminals. In a large car battery, there are two

heavy lead posts that act as the terminals. Electrons collect on the negative terminal of

the battery. If you connect a wire between the negative and positive terminals, the

electrons will flow from the negative to the positive terminal as fast as they can (and

wear out the battery very quickly -- this also tends to be dangerous, especially with large

batteries, so it is not something you want to be doing). Normally, you connect some type

of load to the battery using the wire.

Inside the battery itself, a chemical reaction produces the electrons. The speed of

electron production by this chemical reaction (the battery's internal resistance) controls

how many electrons can flow between the terminals. Electrons flow from the battery into

a wire, and must travel from the negative to the positive terminal for the chemical

reaction to take place. That is why a battery can sit on a shelf for a year and still have

plenty of power unless electrons are flowing from the negative to the positive terminal,

the chemical reaction does not take place. Once you connect a wire, the reaction starts.

CONDENSER MICROPHONES

A condenser microphone is essentially a capacitor, with one plate of the capacitor moving in response to sound waves.

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.

DIODE:

An electronic device that restricts current flow chiefly to one direction. An electron tube

having a cathode and an anode. A two-terminal semiconductor device used chiefly as a

rectifier.

LEDs and diodes used in the circuit cost 10 rupees.

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, 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 small area.

BC 549 and BC 548 transistors are used in this circuit.

IC555

555 Timer IC is an integrated circuit (chip) implementing a variety

of timer and multivibrator applications. The IC was designed by Hans R.

Camenzind  in 1970 and brought to market in 1971 by Signetics (later acquired

by Philips).

IC4017

The 4000 series (originally: CD4000 series, but now includes HEF4000 series, etc.) is a

family of industry standard integrated circuits which implement a variety

of logic functions using Complementary Metal–Oxide–Semiconductor technology. They

were introduced byRCA as CD4000 COS/MOS in 1968, as a lower power and more

versatile alternative to the 7400 series of TTL logic chips.

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. It 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, to be a form of an

electrical amplifier.

CIRCUIT DESCRIPTION

The amplified signal provides negative pulse to pin 2 of IC1 and IC2, triggering both the

ICs. IC1, commonly used as a timer, is wired here as a monostable multivibrator.

Trigging of IC1 causes pin 3 to go high and it remains high for a certain time period

depending on the selected values of R7 and C3. This ‘on’ time (T) of IC1 can be

calculated using the following relationship: T=1.1R7.C3 seconds where R7 is in ohms

and C3 in microfarads On first clap, output pin 3 of IC1 goes high and remains in this

standby position for the preset time. Also, LED1 glows for this period. The output of IC1

provides supply voltage to IC2 at its pins 8 and 4. Now IC2 is ready to receive the

triggering signal. Resistor R10 and capacitor C7 connected to pin 4 of IC2 prevent false

triggering when IC1 provides the supply voltage to IC2 at first clap. On second clap, a

negative pulse triggers IC2 and its output pin 3 goes high for a time period depending

on R9 and C5. This provides a positive pulse at clock pin 14 of decade counter IC 4017

(IC3). Decade counter IC3 is wired here as bistable. Each pulse applied at clock pin 14

changes the output state at pin 2 (Q1) of IC3 because Q2 is connected to reset pin 15.

The high output at pin 2 drives transistor T2 and also energizes relay RL1. LED2

indicates activation of relay RL1 and on/off status of the appliance. A free-wheeling

diode (D1) prevents damage of T2 when relay de-energizes

PRINTED CIRCUIT BOARD LAYOUT

COMPONENTS REQUIRED

No. Component Name Value Quantity

1 IC1,IC2 555 2

2 IC3 4017 1

3 Diode IN4001 1

4 Capacitor (C1,C4,C5,C6) 0.01µF 4

5 Capacitor (C2) 0.1µF 1

6 Capacitor (C3) 10µF, 25V 1

7 Capacitor (C7) 2.2µF, 15V 1

8 Resistor (R1,R5) 3.3 K 2

9 Resistor (R2) 4.7K 1

10 Resistor (R3) 2.2M 1

11 Resistor (R4,R7) 270K 2

12 Resistor (R6,R10,R13) 10K 3

13 Resistor (R8,R12) 1K 2

14 Resistor (R9) 100K 1

15 Resistor (R11) 470K 1

16 LED (LED 1) RED 1

17 LED (LED 2) Green 1

18 Transistor (T1) BC549 1

19 Transistor (T2) BC548 1

20 Condenser Microphone .. 1

21 Relay (RL1) 9V 1

APPLICATIONS

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, a TV. etc using this converted electrical energy which is used to

turn on relay (an electronic switch). The major advantage of a clap switch is that you

can turn something (e.g. a lamp) on and off from any location in the room (e.g. while

lying in bed) simply by clapping your hands. The primary application involves an elderly

or mobility-impaired person. A clap switch is generally used for a light, television, radio,

or similar electronic device that the person will want to turn on/off from bed. The major

disadvantage is that it's generally cumbersome to have to clap one's hands to turn

something on or off and it's generally seen as simpler for most use cases to use a

traditional light switch.

CONCLUSION

After the successful working of the project, it can be concluded that this project is suitable to switch ON and OFF the household appliances just by clapping hand. As a team we tried our level best to bring out the best , even though this is not a very innovative project , within our limitations we think we did justice to this project.

The final product.

The circuit that makes it happen.

Appendix- Data Sheet