This post is part of the series IC 555 Tested Mini Projects
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This is a special application of IC555 clap switch with timer mini project. It uses a condenser mic to pickup the clap like sharp sound and trigger the IC 555 designed as monostable multivibrator, as shown in the following circuit.
Working of the circuit
The circuit uses one condenser mic to receive the clapping sound and IC 555 is used as one shot timer circuit. When power supply is connected to the circuit, pin-2 of IC 555 is held at +ve supply and so its output at pin-3 remains LOW and the LED D2 remains OFF.
When a sharp clapping sound is produced in front of the condenser mic MIC1, it gets quickly discharged into the base of transistor T1 (preferably BC549B, as tested in our lab), and T1 gets momentarily switched on. So pin-2 receives a short -ve pulse and IC 555 is triggered.
So the output at pin-3 becomes HIGH and the LED lights up. At the same instant, capacitor C1 starts charging through resistor R1. When voltage across the capacitor becomes equal or slightly greater than 2/3 of the battery voltage i.e. about 6V, the output of the IC becomes LOW and the LED turns OFF.
Capacitor C1 gets quickly discharged into pin-7 and the circuit becomes ready for the next clapping sound.
If again a clap sound is produced in front of the mic, same action is repeated.
The circuit is easy to construct even on a veroboard, but the lab tested actual size PCB layout of the circuit is given below.
If you have any difficulty in the circuit, during or after construction, you can contact our expert faculty. You can also refer our most popular article about the details of IC 555. To adjust the timing of one shot multivibrator of IC 555, you can refer to the online IC 555 calculator at this link. For more mini projects of IC 555 refer our special archive.
Continue reading this series:
IC 555 Frequency Shift Keying mini Project