LED Outdoors

[Robert Reed]

I have used LEDs many times for pilot and indicator lamps. But this time I want to mount one on an outdoor unit. Any problems I should be aware of? The very worst case temperature in our area is -20F to +105F, but that is extremely rare. In an average ten year period, -5F to +95 would be the extremes. Also this would not be in direct summer sunlight.

[sofaspud]

I can say I'm not aware of any likely problems. As far as I know, they use the same epoxy material for LEDs from IR to UV so indirect
sunlight shouldn't be an issue. The two storage temp specs I have are both -40C to +85C; the operating temps are the same. To keep
out moisture/humidity, I'd apply some sealant where the leads enter the LED case, just to help put my mind at ease.

[MrAl]

Hi Robert,


Yes, moisture could be a problem where you get electrolysis between the LED leads which would lead to one of the leads being dissolved over time. Perhaps some sort of potting compound.

Also, with extreme changes in temperature the LED voltage could change significantly. This would mean the drive circuit would be best as a constant current source or at the very least run at less current than usual at 20 deg C.

[jollyrgr]

No problem using and LED outside unless the circuit gets wet. I have numerous solar powered yard lights with LEDs and most still work; some are almost ten years old now. (The NiCad batteries have been replaced at least once.) The ones that don't work were the ones that got wet and the circuit boards corroded; not a problem with the LED but with the circuit itself.

For what it's worth LED modules are used in road signs, traffic lights, and on tail lights of vehicles. Many of the "third brake light" modules are LEDs. On many trucks the brake/turn signal are LEDs. These work fine at -25F to 100F.

[Robert Reed]

Okay, so it looks like temperature is no real problem here. The LEDs will be press fit from the rear into a plastic housing and then hot melt glue to the back side of the panel to insure mounting stability and moisture sealing so that I won't be concerned about moisture problems. the whole circuit assembly gets mounted in a weatherproof case about 5' from grade. Thanx for inputs.

[haklesup]

Forget the hot glue, its a mess and dosen't work as well as one might think. Its ok for mounting but won't work as well as something like liquid nails. I find hot glue easily delaminates from smooth surfaces like PC boards over time when temp cycling is involved.

Just clean the board good and bake it dry, then spray on a conformal coating made up of clear urethane or acrylic spray paint from the hardware store. Its the same stuff used by electronic manufacturers to seal out moisture. If you ever need to remove it, a wash in acetone will get it right off.

[Robert Reed]

UH-OH
I just did it 3 hours ago, but thanks for the warning and I will be sure to keep my eye on it.

[haklesup]

I'm sure it will be fine, its not like you live at a salt water marina