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

Time Delay Relay-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


  • R1 adjusts the on time.
  • You can use a different capacitor for C1 to change the maximum on time.
  • 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.