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Streetlight PCB and electronics is open to the air...is this a problem?

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Flyback

Well-Known Member
Hello,
We took apart a mains connected streetlight “head” from China.
The head had a hole which was for sliding onto the vertical pole (lamp post).

This hole was quite a tight fit to the pole, but obviously not an absolutely perfect seal…so in other words, air and moisture and small dust particles would be able to get inside the head through this tiny gap between pole and “head-hole”.

Now, inside the streetlight head was the LED driver inside a plastic enclosure. We noticed that the plastic enclosure was not totally enclosed, but had air gaps around the connectors at each end of the plastic box….so in other words, the LED driver PCB and electronic components were in fact “open to the air”.

Given this “Open-air” nature, do you think that the LED driver PCB would need to be conformal coated?
I mean, for example, we noticed that there was a TO220 switching FET in the LED driver enclosure which had straight legs into its PCB footprint (and so not much clearance between drain and source pins)

Or do you think that it would even need potting to prevent dust and moisture from ingressing into and around the PCB and electronic components? (obviously some way would need to be found to prevent the potting compound from escaping while it cures during the potting procedure)
 

gophert

Well-Known Member
Most Helpful Member
It is a problem unless all connectors are corrosion resistant (proof) and the board is properly encapsulated. More detail would be needed to know for sure.
 

Flyback

Well-Known Member
The board is just a standard PFC'd Offline LED driver of 70W. Its coated in solder resist, but no conformal coating. Sorry i dont understand what is meant by a board being "properly encapsulated"?
 

dknguyen

Well-Known Member
Most Helpful Member
The board is just a standard PFC'd Offline LED driver of 70W. Its coated in solder resist, but no conformal coating. Sorry i dont understand what is meant by a board being "properly encapsulated"?
Dunked into a block of epoxy. It is the same as what you called potting.
 

ronsimpson

Well-Known Member
Most Helpful Member
If the board is level (flat) water will pool on the board. Vertical boards are batter.

Here if you live down wind from a coal burning plant the sulfur in the air will eat up the parts. I assume if you are near large amounts of salt water there will be the same problem.
 

RODALCO

Well-Known Member
Just reading your post, had one of these potted units fail on a streetlight. Vented near the blue device, I think it was a Capacitor.2018-09-11_12-03-10.png Where the yellow arrow is, something near the blue device vented.
This is an epoxied, encapsulated unit.
 
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