Automatic 2 second 240v mains interruption using relays - how?

Tom Smith's picture


Joined: Feb 09, 2020

Replies: 0
Automatic 2 second 240v mains interruption using relays - how?
February 9, 2020 - 5:36pm

Hi guys and gals

Absolute beginner here doing a small project at home. I require the following functionality for an aspect of my project:-

Constant power to a device at all times (240v supply) with a momentary button that disconnects the supply circuit for 2 seconds and restores it automatically.

I was thinking a normally closed relay that when triggered, opens, stays open for 2 seconds, then closes again. How can I achieve this?  It needs to be 1 button press with the 2 second hold and then the close happening automatically in a sequence. Not sure if I require 2 relays with delays to achieve this and how I'd wire it up, or wether there's an off the shelf solution? Any help greatly appreciated. 

Many thanks in advance


Debasis Parida's picture


Joined: Aug 22, 2019

Replies: 125

Hi Tom, for this you can use a 555 timer circuit along with a relay.When you push the button that activates the 555 timer which will trigger the relay.After a certain time, it will again restored.Hope it helps!!!

Sourav Gupta's picture


Joined: Feb 12, 2018

Replies: 646

You can also use RC time constant and a transistor to achieve this one.

Muhammad Umar's picture


Joined: Apr 09, 2020

Replies: 55

Hi Tom Smith! There are various methodologies you can adopt to complete your project. First you can make a RC circuit according to which you can set your required time (i.e., t = R*C) for disconnection. Also, you can use a commonly used IC NE555 by using which you can set the frequency/time in any of its 3 modes. And the smart way for this is you can use a micro-controller by using which you can set a condition for the relay to activate and deactivate the supply connection. You can use any of the above methods.