Time Delay Relay

A time delay relay is a relay that stays on for a certain amount of time once activated. This time delay relay is made up of a simple adjustable timer circuit which controls the actual relay. The time is adjustable from 0 to about 20 seconds with the parts specified. The current capacity of the circuit is only limited by what kind of relay you decide to use.

Schematic

Parts

Part Total Qty. Description Substitutions R1 1 1 Meg Pot R2 1 10 K 1/4 Watt Resistor C1 1 10uf 25V Electrolytic Capacitor C2 1 0.01uf Ceramic Disc Capacitor D1,D2 2 1N914 Diodes U1 1 555 Timer IC RELAY 1 9V Relay S1 1 1A 120V SPST Switch MISC 1 Board, Wire, Socket For U1

Notes

1. R1 adjusts the on time.
2. You can use a different capacitor for C1 to change the maximum on time.
3. S1 is used to activate the timing cycle. S1 can be replaced by a NPN transistor so that the circuit may be triggered by a computer, other circuit, etc.