How to build 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.

Circuit diagram

C1 10uf 16V Electrolytic Capacitor
C2 0.01uf Ceramic Disc Capacitor
R1 1 Meg Pot
R2 10 K 1/4 Watt Resistor
D1,D2 1N914 Diodes
U1 555 Timer IC
RELAY 9V Relay
S1 Normally Open Push Button Switch
MISC Board, Wire, Socket For U1

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.


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