Hello,

I wish to operate a circuit with contactor.
I have problem of switching between the circuits.
I have UPS power and wish to utilise this power when the light goes off..
i want to make contactor like this when light goes off the contactor will automatically give ups power.

 

Hello,

I wish to operate a circuit with contactor.
I have problem of switching between the circuits.
I have UPS power and wish to utilise this power when the light goes off..
i want to make contactor like this when light goes off the contactor will automatically give ups power.

You dont need to use a lamp to see if the power goes off. You can make a circuit to sense the mains voltage and when it goes off then the relay will turn on. However, you can simplify the circuit a lot if you have a relay with a 240 VAC coil and connect it to the mains supply. This will always activate the relay until the power goes off. Then the relay will turn off and connect your circuit to the power source by its normally on contact.

If you want to use a lamp you can make a dark detector by using an LDR, a few resistors and a transistor.

 

Could you post a possible diagram, or at least an idea. I'm imagining that you are referring to a relay, but I don't have a clue.

 

If your application is to switch the UPS, that function should be built into the UPS already. It should switch between the line and the inverter automatically.