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IC555 delay timer for controlling the on-off time of AC devices

Hello engineers, In this article, I will explain how to control AC appliances ON-OFF time using the IC555 Delay timer circuit that I have already discussed in the previous article. The delay timer ON-OFF circuit is similar and has just a few more components. So, Let’s Starts with the materials required and diagram followed by explanation and video for simulation.so let’s start IC555 DELAY TIMER Control AC appliances ON-OFF time.


  • IC555-1Pcs
  • R1&R2 10K-2Pcs
  • C1 470uf-2200uf 16Vmax(any capacitor 1 pcs)
  • PCB Relay – 12V
  • Push-button-1Pcs
  • D1 1N4007-1Pcs
  • Battery or power supply 12-14v max.
  • PCB

CIRCUIT Diagram for IC555 Delay timer ON-OFF circuit

ic555 delay timer

The circuit for the delay timer is quite simple and similar to the one IC555 delay timer I have already discussed just the additives are D1 diode 1N4007 which will be a protection to the circuit from flybacks by the relay coil and 12v relay. The delay time is decided by capacitor C1 that has to be checked either by simulation or by testing first on a breadboard.

This design shows how the Counter Timer can be used to measure the
the pulse width of a simple 555 monostable.

The timer is set to operating in timer mode, whilst the 555 output controls its clock enable input. The count thus advances whilst the output is high.

The reset edge is set to high->low such that the timer is reset when the
the button is released.

When pin3# signal output is high the relay is turned ON and com is connected to the NO and the device is connected to the AC supply. After the time completes (capacitor discharges) the IC’s pin3# output goes off and the relay is also turned off and com again Connects to NC.

The delay time is varied by varied the changing capacitor values .470ufcapacitor gives approximately 5.161 seconds and the 2200uf capacitor approximately 45 seconds.

Applications of the delay timer

This kind of circuit can be used in soda machines that have a fixed delay timer to fill glasses when button pressed, Automatic turn off a water tap system, and a bit more modification can make us use it in an auto turn off door system, etc.

Below is the simulation video as

For a realtime practical testing video for Delay timer circuit without relay only with an LED, click here.

I hope you guys liked it. If you guys liked it please let me know in comments and for any doubts or suggestions please comment below.

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Aabhishek Sharma is a Computer Science Engineer and a Digital Marketing Trainer and Consultant. Aabhishek Sharma also loves working on Electronics Projects and working with microcontrollers and Designing Home automation Gadgets.

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