According to our local POCO's trouble guys (who handle streetlight repairs) the bi-metal PE switches are still the most common and tend to fail due to lightning surges which flashover internally and burn things up. From the pic that ELA posted you can see there's not much clearance inside. (Even the twistlock style is built pretty compact like in the pic. )
Why does a photoeye stop working?
- Thread starter Kdog76
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Hameedulla-Ekhlas
Senior Member
- Location
- AFG
There are many reasons but see below reasons.
How many of you have ever experienced fog in your bays so thick that you couldn't see someone standing 10 feet away? This is a very common problem in locations where cooler temperatures during the winter months combined with hot water put extreme demands on your sensors. Most photo-eyes would fail under these circumstances.
The number one reason for photo-eye failure is contamination
The next common reason why so many photo-eyes fail is vibration. Have you ever seen a car or truck wash facility devoid of vibration? With arches turning on and off, and other assorted wash components in constant motion, vibration is certain to occur.
Last, but certainly not least, water leakage can cause photo-eyes to perform intermittently at best, or fail altogether at worst. As water leaks into the housing of the photo-eye, the internal components become damaged and condensation begins to form on the inside of the lens, fogging up glass and plastic lenses alike.
ELA
Senior Member
- Occupation
- Electrical Test Engineer
There were some posts here about facing them north and I had always heard that and thought it presented the best exposure for turn on /off times of day.
As mentioned by other posts there are other possible considerations.
An interesting thing about the Bi Metallic units is that the cell varies its resistance over a very wide range (900k - 0.5K in a unit I tested) depending upon the light present. When dark the heater is dissipating very little heat. As the amount of light increases the heat dissipation goes up as the cell resistance goes down.
It seems possible that these types might also fail earlier when exposed to excessive direct light into the cell.
Under these conditions the heater is dissipating the most heat (> 1.5Watts).
As mentioned by other posts there are other possible considerations.
An interesting thing about the Bi Metallic units is that the cell varies its resistance over a very wide range (900k - 0.5K in a unit I tested) depending upon the light present. When dark the heater is dissipating very little heat. As the amount of light increases the heat dissipation goes up as the cell resistance goes down.
It seems possible that these types might also fail earlier when exposed to excessive direct light into the cell.
Under these conditions the heater is dissipating the most heat (> 1.5Watts).
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