AC Mains interrupt activate relay on DC

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kevinloh

New Member

• Oct 30, 2012

• #1

I would like a simple schematic of a circuit that will trigger a relay through DC (from batteries) when the mains current is interrupt. Sort of like those emergency lighting that turns on when the mains is cut.

Thanks

 

Last edited: Oct 30, 2012

alec_t

Well-Known Member

Most Helpful Member

• Oct 30, 2012

• #2

It might be simpler just to use a relay having a mains-voltage coil and change-over contacts to connect a DC load when the relay drops out?

 

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kevinloh

New Member

• Oct 30, 2012

• #3

That would be great except that I would like to use what I have right now with me. Which is just a simple relay 12V on one side and 2 terminals on the other side.

 

alec_t

Well-Known Member

Most Helpful Member

• Oct 30, 2012

• #4

Something like this? Q2 type, and resistor values, depend on how much current your relay coil needs. Q2 can be a 2N3904 or similar for coil currents up to ~150mA.
View attachment 68351