Trigger a relay when a DC light bulb is screwed in

I'm trying to do something a little tricky and am looking for some guidance.

I have a 12VDC light bulb that I will be screwing into a light fixture that is wire to a 12VDC power supply.

I would like to have a relay output to trigger when the bulb is screwed in and the circuit is completed. The output should turn off when the bulb is unscrewed.

Any ideas?

by outcida
September 24, 2018

Put in a series resistor that drops say 100mV at the normal lamp current at the ground end, then use a comparator to detect this and drive your relay.

In theory a relay could be used directly, but it has to work on the lamp current without dropping too many volts.

by mikerogerswsm
September 27, 2018

Thanks Mike. Do you think something like this will work?

by outcida
September 27, 2018

Yes, no reason why not, though it does far more than you need.

by mikerogerswsm
September 27, 2018

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