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L24, Simple Clap Switch Circuit

The interesting clap switch circuit shown here can be used in stairways and passages for illuminating the premise momentarily through clap sound. The circuit is basically a sound sensor circuit with an enclosed amplifier stage. The clap sound or any similar sound is detected by the mic and converted into minute electrical pulses. These electrical pulses are suitably amplified by the subsequent transistor stage.

The Darlington stage shown at the output is the timer stage which switches in response to the above sound interaction and illuminate the connected LEDs for some period of time defined by the 220K resistor and the two 39 K resistors. After the time lapses the LEDs are switched off automatically and the circuit returns to its original state until the next clap sound is detected.


  • Resistors = 180E, 100E, 100K, 39K, 33K,4K7,2K7, 1K

  • Capacitors = 47 & 220 microfarad

  • Micro condenser

  • LEDs

  • Transistors BC547, BC557

  • 12volt DC power supply

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