Astable multivibrator using op amplifier LM324
Electronic

We've already learned how a multivibrator circuit works. In this project, we're going to make an LED flash on and off with an astable multivibrator using an operational amplifier. The astable multivibrator is used in LED flashers and similar electronic devices.

IC 324 acts as the astable multivibrator. Remember that the output of a multivibrator is a square wave?

The circuit shown in the schematic has an oscillating frequency of about 0.5 Hz and makes LED 1 light up and go out repeatedly. This continues over and over again at intervals of about 2 seconds. (That means the half of the intervals in a second -- 0.5 Hz, OK?)

The output of the multivibrator is sent to transistor Q1. Q1 amplifies current to light up LED 1. This experiment is super-easy.....just switch power ON, and LED 1 flashes on and off.

See how the oscillating frequency changes by changing C (10µF) and R (100 k ohms) to different values.