relay coil rating/protection for AC lighting proj.

Thread Starter


Joined Oct 24, 2013
Hi Folks,
New to the forums, great resource, thanks for sharing your knowledge!

I've done some looking around but can't quite seem to find an answer to my question. I'm considering a project using a 120vAC 100W max input signal to activate a relay to turn on a couple 120vAC garage lights (400 - 500W max). The input signal source would come from the lamp socket on a garage door opener with a max rating of 100W. I'd rather not damage the opener or burn up the relay: <> so I have the following questions.

The coil voltage rating is 120vAC @ 60 Hz; Coil current rating is 7.5 milliamps. What does this represent? Is this the draw of the coil when energized? Would the output from the garage door opener lamp socket provide too much/little current?

I've also read quite a bit about adding a diode for EMF protection. Would this be necessary in this situation?

Thanks for the help!



Joined Oct 15, 2009
The load (relay) will only "draw" as much current as it needs (7.5mA @120V)
A diode across the coil should not be used with AC.

Word of caution.. AC/Mains voltages are dangerous.. Be careful


Joined Jul 18, 2013
The relay load of 7.5ma is insignificant so you can power it from the 100w socket if you wish.
If you did add protection it would be in the form of an AC resistor/capacitor snubber.
Do not use a diode.