A simple Continuous to Momentary Contact Relay Circuit

by Mike Holderfield, Dothan, AL

This circuit was designed to convert a continuous closure to a momentary closure. 

For example, it might be used to provide remote starts from a console 
with on/off switches that do not provide momentary closures. 

Or, it could be a transmitter re-start circuit (after a power failure) for those that don't have one.
Just substitute a 12 volt wall wart for the switch. When power returns, you get a momentary closure to re-start.

Here's How it works: 

Closing the switch fires the relay. The R-C circuit times out and the relay closure is then opened. 

The closure time of the circuit is determined by the value of the capacitor. 1000 uF should give a .X second pulse. Varying the value will increase or decrease the timing. For example: at 500 uF, the circuit will drop out at .0X seconds.

Our thanks to Mike Holderfield for sharing this circuit.