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  • Clap Switch Circuit

  • Created: Sep 17, 2014

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The clap switch or clapper is a sound activated switch, it is triggered by sharp sounds or noise such as coughing, a dog barking, a door being closed, laughter, yelling, banging, knocking, and even from televisions and speakers. The load (e.g. lights and appliances) can be any device that consumes an AC power directly to the household outlet.

This device is a switch simply installed in between the power source and the load. a condenser microphone acts as a sound sensor and converts the sound into electrical signal. The first BC548 transistor amplifies the signal from the microphone for a more enhanced signal. The amplified signal is then inputted to the Bistable multivibrator using another two BC548 transistors (flip-flop circuit). In the flip-flop circuit, the two BC548 transistors will be switched/triggered in opposite state (e.g. Q2=ON: Q3=OFF). When a signal is detected, the state of the two transistors will change and remain stable continuously until another signal is detected.

The BC368 transistor will then amplify the output signal (logic 0 or 1) of the flip-flop. This transistor will also act as the switch of the Electromagnetic relay ON or OFF. The relay will CLOSE or OPEN the circuit loop of the AC power source and the appliance (load).



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