Switch Clap is an interesting amateur circuit that turns on the lights with an applauded sound. Although its name is "Clap switch", but it can be activated by any sound of approximately the same Clap sound tone. The main component of this clap switching circuit is the Electric Condenser Microphone, which has been used as a sound sensor. Mic Condenser basically converts the energy of sound into electrical energy, which in turns is used to trigger 555 timer IC, through a transistor. And the activation of 555 IC would turn on the LED, which will turn off automatically after some time. I have made this circuit as simple as possible, you can find many complex Clap switches (using 555 IC) with some more components in it, and simply doing the same thing. Even making things simpler requires more effort than making it complex.
Explanation of work
Here we are using Microphone Electric Condenser to detect the sound, transistor to activate the 555 IC timer and 555 IC to turn on the LED through a low voltage trigger.
Components
Microphone Condenser
555 IC Timer
Transistor BC547
Resistors (220, 1k, 47k, 100k ohms)
Condenser (10uF)
LED and battery (5-9v)
Circuit diagram and explanation
You can see the circuits and connections in the above schematic diagram of the clap switch. Initially the transistor is OFF because there is not enough (0.7v) base-emitter voltage to turn it on. And point A is at high potential, and point A is connected to trigger 2 of 555 IC, as a result. Trigger 2 is also at high potential. As we know, to activate the IC 555 via the activation PIN 2, the voltage of the PIN 2 must be below Vcc / 3. So in this stage the LED is off.
Now, when we produce sound near the condenser microphone, this sound will turn into electrical power and increase the potential at the base, which will activate the transistor. As soon as the transistor is turned ON, the potential at point A will go low and will activate the 555 IC due to the low voltage (below Vcc / 3) at trigger 2 and the LED will turn on. We have connected the LED to the 555 IC PIN Output 3 through a 220ohm resistor.
After some time, the LED will turn off automatically because we are using the 555 timer in Monostable Mode. The LED will remain lit for 1.1 * R1 * C1 seconds. Thus we can see, with these formulas, that we can change this duration by changing the value of resistance R1 or / and capacitor C1. We can modify this circuit using Relay to control electronic devices (120 / 220V AC). The 555 Timer IC control pin 5 must be grounded through a 0.01uF capacitor.