This circuit is a compact timer circuit that will keep the headlights of your car ON for about 1.5 minutes and then turns it OFF.This circuit incorporated to your car will help you to access dark places with out the need to come back and turn OFF the head lights.

When the push button switch P1 is pressed the capacitor C1 is charged to the full battery voltage.As a result the transistor Q1 is turned ON ,which in turns ON Q2 which in turns drives the relay K1 to glow the head lights.The relay K1 will remain activated until the capacitor C1 is fully discharged.The time delay of the circuit depends on values of C1 & R1 and here it is set to be 1.5 minutes.

Circuit diagram with Parts list.



  • Assemble the circuit on a good quality PCB or common board.
  • The time delay of the circuit can be varied by varying the values of R1&C2.
  • At most care must be taken while wiring this circuit to your car because a wrong connection could cost you a lot of money.
  • The capacitor C1 must be rated at least 15V.


  1. From the way the circuit function, This circuit behaves like a monostable, please tell me, is it wired as a monostable?

  2. James Gyore

    This is fantastic! Exactly what I was looking for. May I ask about R1 and C1 values. What calculations can be made to vary the delay time. Particularly interested in increments of 5 seconds from 5 seconds to 60 seconds.

    Many thanks for the circuit.

  3. shadrack mittage,TANZANIA,Dar es salaam institute of technology

    the circuit i have taken so that i can try building on a breadboard.later i will feedback you.

  4. shadrack mittage,TANZANIA,Dar es salaam institute of technology

    we need more simple circuits that can boost our studying at the institute.