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I have built a device based on Raspberry Pi who have to be located on a house's roof. I use an IP67 enclosure with IP69 pressure compensation element with gore-tex membrane. I add silica gel before closing the enclosure.

I have seen that 3 chips are very hot (+-30°C more than ambient temperature) in normal external temperature (power regulator, ethernet and arm chip). I will add a passive heat sink on those three components.

I will underclock the ARM to match with performance needs.

Do you have another idea to avoid premature failure of electronics due to humidity/temperature?

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  • \$\begingroup\$ Use a metal IP67 enclosure and bond the heatsinks to the enclosure? \$\endgroup\$ Jul 17, 2013 at 9:33
  • \$\begingroup\$ I use a Pi Camera inside the box to take pictures. The box has to be in clear poly-carbonate. \$\endgroup\$
    – hotips
    Jul 17, 2013 at 10:09
  • \$\begingroup\$ Then I guess it it will inevitably get hot inside there. Thats how they make solar ovens isn't it? Maybe you can find an enclosure with a metal half and a polycarbonate half (or window) - just a thought. \$\endgroup\$ Jul 17, 2013 at 10:11
  • \$\begingroup\$ That was my feeling but it seems that I have to build it by myself... \$\endgroup\$
    – hotips
    Jul 17, 2013 at 10:23
  • \$\begingroup\$ Similar things may exist \$\endgroup\$ Jul 17, 2013 at 10:24

3 Answers 3

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This box has suffered 80F-plus direct sun exposure, survived weeks buried under ice and snow, even several days completely submerged. The heatsink was robbed from a Pentium II processor and mounted to the box with the screws tapped into the plastic. "25 Year" Silicon seals the heatsink to the plastic case. The internals show no sign of contamination.

Controller

"Silicone," now THAT'S funny!!! (grin)

This box has a "vent." Inside this cabinet is a 12VDC 500W, fan cooled power supply.

Vented

In the upper right hand corner I placed a right-angle cable "box-end" connector. Inside the connecter is a round patch of Scotch-Brite dish scrubber (http://www.scotch-brite.com/wps/portal/3M/en_US/Scotch-BriteBrand/Scotch-Brite/Products/Product-Catalog/~/Heavy-Duty-Scour-Pad?N=4337+3294631680&rt=rud) - helps keep the tiny critters out.

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    \$\begingroup\$ Actually, "Silicone sealant" is correct, rather than Silicon. It's not silicon at all, but a family of polymers. \$\endgroup\$ Jul 17, 2013 at 13:25
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One thing is worth considering and I think this is quite important. Here's the story: -

An IP69 product that was shipped to China for taking measurements of metal contaminants on a food line. It was switched-off every evening after the last shift. After about a year it failed to power up one morning. Upon opening the bottom panel (which housed the switch-mode power supply and some customer terminations), it was obvious why it had failed. There was about 1" of water slopping around.

Now bearing in mind this was IP69 rated, we immediately thought its seals had gone. No, the simple answer was that during the day, the bottom panel got warm and forced air out of the box through pressure and at night, when the unit was switched-off, the air inside the box cooled and dragged the humid air into the enclosure. After about 365 days of doing this it had accumulated enough water to reach the power supply.

Try putting a small drain and vent hose from a hole on your box to prevent this happening. Obviously it needs to be placed underneath and it needs to have a small hose from it to stop rain splashes getting in. Maybe even consider a one-way valve so positive pressure always expels.

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    \$\begingroup\$ He has already dealt with this by using the gore-tex membrane. \$\endgroup\$ Jul 17, 2013 at 13:40
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Can you drill two holes (so that air flows from Bottom to Top) and use a PTFE vent membrane to allow circulation and equalization of pressure?

@see http://machinedesign.com/news/good-vents-make-good-housings

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