Monday, January 10, 2011

Clap Controlled Electronic Switch

This electronic switch allows you to control an electronic device by only clapping your hands twice. It is based on three integrated circuits; 741 Op-Amp, 555 timer, and 4013 dual D flip-flop.
A 9V battery is ample to operate the circuit.
When you first clamp your hands, mic detects the sound and triggers the 555 timer via the operational amplifier. The timer stretches the signal and applies it to the clock input of the flip-flop. Because of the three state arrangement of the flip-flop , one more clamp is needed to change the output state. Second clamp sets the flip-flop output to high and this forward biases the 2N2222 BJT. Relay closes so the device connected to the relay switches on. Same procedure applies for the opposite. When you clap your hands twice, relay closes and turns off the device connected to it.
R3 trimpot adjusts the sensitivity of the circuit. You should turn it till the room noise does not effect the switch operation.

IC1: 741 Op-Amp
IC2: 555 Timer
IC3: 4013 Dual D Flip-Flop
Q1: 2N2222 NPN Transistor
C1, C2, C3, C4: 0.1uF Ceramic Capacitor
C5: 47 uf Electrolytic Capacitor
R1, R2, R4, R5, R10: 10 KOhm
R6: 150 KOhm
R7, R9: 100 KOhm
R8: 1 MOhm
R11: 220 Ohm
R3: 100 KOhm Trimpot
B1: 9 Volt Battery,
K1: SPST Reed Relay 5 Volt DC Coil
MIC: Electret Microphone


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