One-shot multivibrator using IC 555
Oscillateurs   /    Oscillators
Électronique / Electronic

In this project, you're going to build a one-shot multivibrator using IC 555.

A trigger pulse drives the one-shot multivibrator into the ON state, which continues for a predetermined period of time.

When you finish wiring, turn power ON and give S1 a quick push.

Upon push of S1, the one-shot multivibrator is triggered, so that LED 1 lights for some time before it goes out.

The control volume is intended to vary the lighting period of LED 1. Turn the control volume clockwise and press S1. You'll see LED 1 lights for a longer period. The lighting period should be shorter when you turn the control volume counterclockwise.

When IC 555 receives an L pulse at the TR terminal, it is triggered with the fall of the pulse, so its output turns ON.

The period of time, T, over which 555's output stays ON, is determined by 555's add-on components:

The control volume (50K) + R1 (1K), and C1 (100 µF).

T = 1.1R x C sec.

In equation, T is given as in which R = control volume + R1, and C = C1.