One-shot multivibrator using op amplifier
LM324
Oscillateurs   /    Oscillators
Électronique / Electronic

When you finish wiring, turn power ON.

Flick the key S1, and watch what happened to LED 1. It should light for approx. 1.5 seconds.

You can guess that the key you pressed triggered the one-shot multivibrator. Now, try to press S1 and hold it down. LED 1 should have lit in the same way as before. From these, you know that the one-shot multivibrator is triggered once at the moment when the key is pressed.

The (+) terminal of the OP amplifier U1A is connected to C1 and R2 provided for trigger pulsation.

The other terminal, (-), is at approx. 0.6 V as it is clamped by a diode, so the output of U1A is L.

C2 and R4 of the (-) terminal serve to determine the duration of pulse. When S1 is pressed, a positive differential wave is applied to the (+) terminal, the output of U1A changes to H, Q1 turns ON, and therefore LED 1 lights.

When C2 is charged until the level at the (-) terminal goes above that at the (+) terminal, LED 1 goes out.