Switch between power sources

Thread Starter


Joined Jul 20, 2022
I have two power sources supply 230 volts, The main source occasionally has power outage while the secondary source has power 24/7. I want to connect a light to both sources with a switch that when the main source drops power it must automatically switch over to the secondary source.


Joined Jan 27, 2019
Welcome to AAC.

What is the function of the light? Is it for illumination or indication?

Generally, an ATS (Automatic Transfer Switch) is used to switch mains voltage to an alternative. BUt, because they are usually for critical applications, they are not cheap.

You’ll need to provide a lot more detail to get good help. For example:

What does the light do?
What are the two sources?
Is the power going to be used for anything else?
Do you want to build or buy something?
What is your budget?

And anything else that can give a better pi true of what you are trying to do and why.


Joined Aug 7, 2020
Power relay energized by the primary source.
When power is lost the relay trips out and connects to the backup power source.
Exactly how it’s usually done.
But don’t forget to use a double-pole relay to switch both live and neutral, as you don‘t want to connect the neutrals together. Then also make sure that you can guarantee earth continuity when the first supply is lost, but do not switch the earth.