Description: Here’s a simple DIY clap switch circuit. The circuit is mainly composed of an audio frequency and a bistable trigger circuit.

Q1 and Q2 together form an amplifier circuit. MK1 (electret microphone) accepts Clap/Audio signal and that enters to transistor Q1 through the coupling capacitor C1 and enters to Q2 base through collector directly after getting amplified. And it obtains a negative square-wave which used to trigger the bistable circuit from Q2’s collector. 

R1 and C1 restrict the frequency response of circuit to 3kHz which is in a high sensitivity range. Q4 is cutoff while Q3 is saturated and D3 is off when the power is on. When MK1(electret microphone) obtains the control signal, a negative square-wave is output after amplification and negative pulse is added to Q3 base through D1 after differentiation processing. The power flips rapidly and D3 is switched on at this time. The power flips again when MK1 obtains the control signal at the second time and the LED D3 goes off. A cable terminal J1 can be added on PCB which used for connecting external control equipment. It can realize the sound control function on other equipment by connecting J1 and relay.

A diode should be connected reversely at the ends of relay when connecting the relay. You can learn about relay from this link.

This circuit works with 6V-9V power supply. The circuit consumes 3mA when the LED is off, and it takes 6mA when the LED is on.

Schematic: 

Documents:

1. Assembly Tutorial

Watch the video: