Photo cell failure

[Classic Lighting]

Why is it that photo cells fail in the "on" position. I've come across 3 this month and they have all been "on".

[steveparrott]

Originally Posted by Classic Lighting

Why is it that photo cells fail in the "on" position. I've come across 3 this month and they have all been "on".

The default state of a photocell is a closed circuit (lights on). When the photo receptor is energized with light, a current goes to a relay that opens the circuit (lights off).

If the receptor window is dirty or if the sensing circuit has been damaged, then the relay is not triggered and the lights stay on.

[INTEGRA Bespoke Lighting]

Another question would be: Why can't anyone seem to make a quality photocell? They have been at it for long enough, you would think they would have it right by now. Horrible, unreliable things.