2. › 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. 

3.  For the next clap the light turns OFF. This circuit works with 12V voltage.Therefore a step-down transformer 12V/300mA is employed.  The working of this circuit is based on amplifying nature of the transistor, switching nature of transistor, and relay as an electronic switch

4.  12V battery  Two way Switch- 1  Condenser microphone  Red LED’s  Transistors (BC547)- 4  Diodes(IN4148) -2  Capacitors:  1000 microfarad-1  10 microfarad- 3  100 microfarad -1  Resistors”  330 ohms- 3  1K – 3  5.6K – 2  33K -3

5.  2.2.1 INTRODUCTION OF 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

7.  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.  A capacitor (formerly known as condenser ) is a passive electronic capacitor consisting of a pair of conductors separated by a dielectric (insulator). When a potential difference (voltage) exists across the conductors, an electric field is present in the dielectric.

9.  semiconductor is a material that has an electrical conductivity between that of a conductor and an insulator. This means roughly in the range 10 3 Siemens per centimeter to 10 −8 S/cm. Devices made from semiconductor materials are the foundation of modern electronics, including radio, computers, telephones, and many other devices. Semiconductor devices include the various types of transistor, solar cells, many kinds of diodes including the light-emitting diode, the silicon controlled rectifier, and digital and analog integrated circuits.

10.  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.

12.  In electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. The term usually refers to a semiconductor diode, the most common type today. This is a crystalline piece of semiconductor material connected to two electrical terminals. A vacuum tube diode (now little used except in some high-power technologies) is a vacuum tube with two electrodes; a plate and a cathode.

13.  INTRODUCTION OF TRANSISTORS :  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.computers cellular phones electronic devices

15.  INTRODCTION OF 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.

16.  If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (V S ) is in proportion to the primary voltage (V P ), and is given by the ratio of the number of turns in the secondary (N S ) to the number of turns in the primary (N P ) as follows:load

17.  Vs/Vp = Ns/Np  By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be "stepped up" by making N S greater than N P, or "stepped down" by making N S less than N P. alternating current (AC)

18.  Step down transformers are made from two or more coils of insulated wire wound around a core made of iron. When voltage is applied to one coil (frequently called the primary or input) it magnetizes the iron core, which induces a voltage in the other coil, (frequently called the secondary or output). The turns ratio of the two sets of windings determines the amount of voltage transformation.

19.  INTRODCTION OF RELAYS:  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.switchelectrical circuitJoseph Henryamplifier

20.  All relays operate using the same basic principle. Our example will use a commonly used 4 - pin relay. Relays have two circuits: A control circuit (shown in GREEN) and a load circuit (shown in RED). The control circuit has a small control coil while the load circuit has a switch. The coil controls the operation of the switch.

22.  Current flowing through the control circuit coil (pins 1 and 3) creates a small magnetic field which causes the switch to close, pins 2 and 4. The switch, which is part of the load circuit, is used to control an electrical circuit that may connect to it. Current now flows through pins 2 and 4 shown in RED, when the relay is energized.

24.  When current stops flowing through the control circuit, pins 1 and 3, the relay becomes de-energized. Without the magnetic field, the switch opens and current is prevented from flowing through pins 2 and 4. The relay is now OFF

27.  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 Q1. Transistor Q1 is used as common emitter circuit to amplify weak signals received by the microphone. Amplified output from the collector of transistor Q1 is then fed to the Bistable Multivibrator circuit also known as flip-flop.

28.  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 2 nd transistor 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.

29.  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 Q4 which is a common emitter circuit. Output of Q4 is connected to a Relay (Electromagnetic switch), works like a mechanical switch. With

30.  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 12Volt eliminator with the help of Transformer T1, Diode D1 and capacitor C1.It is a half wave rectifier.

31.  INTRODUCTION OF CONDENSER MICROPHONE:  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. 

32.  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.

33. 9. 4.1 CONDENSER MICROPHONE

35. Dynamic MicrophoneCondenser Microphone Do not have flat frequency response but rather tend to have tailed frequency response for particular applications Have a flat frequency response Operate with the principle of Electromagnetism as it does not require voltage supply. Employs the principle of electrostatics and consequently, require voltage supply across the capacitor for it to work They are suitable for handling high volume level, such as from certain musical instruments They are not ideal for high volume work as their sensitivity makes them prone to distortion The signal produced are strong therefore making them sensitive The resulting audio signal is stronger than that from a dynamic. It also tends to be more sensitive and responsive than dynamic

36.  This circuit can be used to switch on and off a light, a fan, a radio or a t.v. by the sound of a clap

37.  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 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. 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.

38.  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, a t.v. etc using this converted electrical energy which is used to turn on relay (an electronic switch).

39.  http://www.kpsec.com: Country circuits, the Electronics club  Alex Pounds, “Electronics Tutorial” Denenberg University,  http://www.ffldusoe.edu/faculty/Denenberg/topics/Electr onics/AlexPounds.htmls. Retrieved May 5,2007.  http://www/the 12volt.com.SPDT automobile Relays, 2004  http://www/starmicromics.com/components/mics.html: Microphone series  The Audio Forum “How Microphones Work”, www.mediccollege.com  Tony Van Roon (VA3AVR) “Relays and Relay Drivers” www.starcounter.com  December 6, 2006.  The Electronics Clubs, “Transistor Circuit”, www.kspec.com  www.mccsemi.com. NPN Silicon Amplifier Transistor