Solar Photo Cell Question

I have some solar lights that fail to turn off during the day.
Are photo cells prone to failure? I also had one that wouldn't work at all until I swapped the photo cell out. Can anyone provide some insight into this phenomenon.

I placed this thread here because solar lights get discussed occasionally.

Thanks.

Dave

dirty lens perhaps?

Marduke said:

dirty lens perhaps?

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I don't think so. The exterior is clean, however frosted from weathering, I would think it would let light through, as others in the same condition operate.

phenwick said:

I don't think so. The exterior is clean, however frosted from weathering, I would think it would let light through, as others in the same condition operate.

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I don't think it's the frosted lens. Try swapping the cells and see if the problem moves. If the problem stays with the lamp rather than the cell, it's probably a bad sensing circuit and not the cell itself. Cadmium-sulfide cells are pretty rugged and not normally prone to failure.

phenwick said:

I have some solar lights that fail to turn off during the day.
Are photo cells prone to failure? I also had one that wouldn't work at all until I swapped the photo cell out. Can anyone provide some insight into this phenomenon.

I placed this thread here because solar lights get discussed occasionally.

Thanks.

Dave

Click to expand...

I've worked in camera repair for over 30 years. CDS cells are definitely prone to failure. Well they would be if anyone still used them in cameras. What happens is during manufacture they are sealed to keep out moisture. Once the seal is compromised, the substrate absorbs moisture from the humidity in the air making it more conductive. Not all cells fail because some use better sealing methods than others. Certain types have almost 100% failure. It takes years for this to happen normally.

As it relates to your question, the problem is the artificially low resistance makes the device think it's always daylight. A cell going bad in that manner would cause the light to never turn on, not to fail to go off.

They are fairly delicate so an open circuit is possible. A simple test would be to put a clip lead across the photo cell (avoid electrocution). After plugging back in it should be off.