A simple Push ON/Push Off Control Circuit

by Mike Callaghan, KIIS, Los Angeles

This circuit was designed at the request of Carl Hanson at KNX-FM.
He needed it for their automation system..

(If you don't like my hand-drawn schematic, then click on it !!)

This circuit was submitted to and became the National First Prize Winner for Broadcast Management and Engineering Magazine's 'Great Idea Contest" for 1987..

Here's How it works: 

When power is first applied to the circuit, the parallel combination of C1/R2 is charged to 1/2 VCC through the voltage divider R1/R2.
When PB1 is closed, C1 discharges through the coil of RL1. This pulls in the relay , and the wiper is held in by the current through RL1 and R1.

Any charge remaining on C1 discharges through R2, so when PB1 is pressed again, C1 (representing a short this time) makes the relay drop out, returning the circuit to its original condition.

So, it provides a toggling 'Push-On / Push-Off' action using two resistors, a capacitor, and a relay. And because of the simplicity, it's virtually foolproof...

Our thanks to Mike Callaghan for sharing this with us.