Simple Clap On off switch using 4017 IC

Clap On off switch with 4017 IC and BC547 Transistor

This is the circuit of a very sensitive clap switch. It switches ON/OFF a White LED or electrical appliances through claps. The circuit can sense the sound of claps from a distance of 1-3 meters. Condenser Mic picks up sound vibrations c by the clap.

Circuit Diagram

Clap on off switch with ic 4017

These sounds vibrations are given to the Base point  of transistor BC 557 (a PNP transistor). It amplifies the sound collected by the Mic. Transistor collector point is connected with IC point 14 which is clock point. When clock e is received from Amplifier Transistor BC557.
IC 4017 is a decade counter IC which is wired as a toggle switch. That its outputs 1 and 2  becomes high and low when the input pin 14 receives pulses.  output4 (pin4) is connected to the reset pin 15 so that further counting restricted. The high output from IC 4017 passes through resistor to the base of switching transistor BC557. When BC557 conducts, Red LED (indicator LED) turns on.  A 6V 100 ohms relay is connected to the points marked (A and B), the relay turned on and 220v AC pass through the relay and bulb or any other electrical appliance Switched on. In the next clap output pin 2 becomes low and relay and indicator LED switched off.


  1.  Prototyping board (Roughly 1″ by 1″) or bread board.
  2. 9v connector
  3. BC 547 transistor (npn)
  4. BC 557 Transistor (pnp)
  5. IC 4017
  6. 22k resistor
  7. 470 ohm resistor
  8. 1k resistor
  9. 6v relay
  10. 9v battery