# Photo Cell question



## craigdj87 (Oct 11, 2016)

We installed a small outdoor Led light and added the Intermatic K4200 photo cell to it. The light stays on all the time and is wired correctly. Do photo cells shut power of completely or just reduce the voltage? Maybe there is just enough voltage for the led to stay on. I looked on the specs and it says nothing about leds. Are there Led compatible photo cells?


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## frenchelectrican (Mar 15, 2007)

craigdj87 said:


> We installed a small outdoor Led light and added the Intermatic K4200 photo cell to it. The light stays on all the time and is wired correctly. Do photo cells shut power of completely or just reduce the voltage? Maybe there is just enough voltage for the led to stay on. I looked on the specs and it says nothing about leds. Are there Led compatible photo cells?


That is a three wire photo cell unit and it should complety shut off when it go in daytime mode.

there is no minuium load to run this type of photocell.

The red conductor should be go to the LED luminaire and the neutral should be tied in that location and the black is the line side.

useally they dont go bad often but if they do go bad they will go either full off or full on mode in fault mode. so try a other model to see if that clear up.


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## MikeFL (Apr 16, 2016)

Photocells use 1800's technology. 

Enter Willoughby Smith, the Godfather of photoconductivity. 

Is your photocell exposed to sunlight or installed in a location where it does not get direct exposure to the sun? 

Many instruction sheets, as well as ANSI C136.10, say to install a photocell facing north, and that's been debated aplenty. It's the cause of why lights are on 15+ hours per day and cycle on and off as clouds go over. Face them south and you do a little better, maybe.

Do you have a sliding lens cover on your installation? Did you open it all the way?


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## telsa (May 22, 2015)

You either screwed-up or it's defective.

You decide.


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## gnuuser (Jan 13, 2013)

photo cells used for an outdoor light are usually photo resistors (resistance gets higher as more light is detected) (at least those used in street lamps and dusk to dawn type)
If the lamp is full on when light is shining on the photo sensor then the relay in the sensor module may be damaged


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## wildleg (Apr 12, 2009)

https://www.intermatic.com/-/media/inriver/10039-9030.ashx/K4200-Specifications


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## daveEM (Nov 18, 2012)

wildleg said:


> https://www.intermatic.com/-/media/inriver/10039-9030.ashx/K4200-Specifications





> K4251 and K4253 Models are designed for spot/flood type fixtures


Looks like a EK4236S works...
https://www.intermatic.com/en/photocontrols/fixed-mount-electronic-photocontrols/ek4236s


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