555 Timer IC is one of the commonly used IC among students and hobbyists. There are a lot of applications of this IC, mostly used as vibrators like, ASTABLE MULTIVIBRATOR, MONOSTABLE MULTIVIBRATOR and BISTABLE MULTIVIBRATOR. You can find here some interesting circuits based on 555 Timer IC by using these different operating modes.

The basic circuit operates at a frequency determined by R1, R2 and C1 and has a pulse width range of 0 to 100 percent.

The following diagram shows a basic circuit with an open collector output that would require a pull up resistor at its output. The parts values are the nominal values of the components used.

In this Instructable, I first demonstrate how to build the complete circuit on a breadboard using two NPN transistors and two LEDs. Once that circuit is built, I demonstrate how we can break the circuit out onto a circuit we will draw with your CircuitScribe pen!

Although its name is “Clap switch”, but it can be turned ON by any sound of about same pitch of Clap sound. The main component of the circuit is the Electric Condenser Mic, which has been used as a sound sensor.