Photocell question

[ichimo23]

This is probably a stupid question, but for photocell operated luminaires when the photocell is mounted ON the fixture; why doesnt the light emitted from the lamp actuate the photocell and turn the fixure off? Is a photocell only sensitive to rays in the spectrum that are not produced by 'artificial' light, or is there some other reason. Thanks

 

[iwire]

Generally the photo cell is not aimed into the fixture so the photo cell only sees the reflected light from the fixture which is not strong enough to shut it down.

 

[Rewire]

I have had photo eyes than had to be turned away from light sources because they would turn off.

 

[iwire]

I got the impression he is asking about something like this.

A fixture with a photocell.

 

[drbond24]

This is probably a stupid question, but for photocell operated luminaires when the photocell is mounted ON the fixture; why doesnt the light emitted from the lamp actuate the photocell and turn the fixure off? Is a photocell only sensitive to rays in the spectrum that are not produced by 'artificial' light, or is there some other reason. Thanks

As far as I know, photocells don't care what kind of light they get. I've used them in the lab under flourescent lights and the outdoor kind obviously work on sunlight.

If you are referring to the type of fixture that iwire posted pictures of, then it is just as simple as what iwire said; there isn't any light from the fixture shining directly into the photocell, so there isn't a problem.

 

[SiddMartin]

if you are asking about a wallpack light like the one pictured above, usually those p/c's are recessed in. It doesn't matter what light either, you can get one to turn off w/ a flashlight.

w/ this in mind, if you mount a p/c and have another light source near-by or pointed at the light, it may shut it off

(I've seen stubs of 1/2" nm-sealtite on the button p/c's to sheild from stray lights, but bugs usually make a nest in these)