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I'm going to use my Raspberry Pi and Wifi router on my terrace (roof covered, no direct rain, but low temperatures, down to -15 celsius in winter and high humidity are possible) and I need to power the equipment.

I have already one wall socket on terrace, but power supplies I have are designed for indoor-only usage (according to the warning labels.)

Could it be dangerous to use it outside on my terrace? Can they begin to burn or get shot circuit? Is there any way to protect against this?

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  • \$\begingroup\$ I would suggest using a sealed box with some sort of heating mechanism coupled with a temperature sensor to keep the temperature well maintained for smooth operation of the Pi... About the power supply, It should be fine outdoors as long as you keep it away from direct sunlight and rain. \$\endgroup\$ Mar 1, 2017 at 7:29

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Add a low power, incandescent lamp or heater to the box to ensure that the components remain dry. The heat will prevent temperature fluctuations that causes condensation. In most electrical junction boxes the heaters run at about 40 celsius and have no temperature control.

Putting the power supply inside the box will warm it a little and also reduce the possibility of condensation. You might be able to get away with no heating element.

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Some salts and chemicals always remain on the PCB after manufacture. When water condenses on it, it becomes slightly conductive, but not enough to cause problems like short-circuits. The worst that can happen is increased leakage current, which will only disturb high-impedance circuits.

At low voltages, what destroys your PCB is simple electrolysis: consider two exposed solder joints or copper pads, with a voltage between them. Add water with some ions... the metals will be corroded by electrolysis, until the circuit stops working.

At high voltages (ie, mains), ionized water can cause lots more trouble, especially if the creepage distances in your chineesium USB charger are like 0.5mm! It could arc or leak dangerous voltages to the secondary.

Note that this only applies to powered equipment. If it's not powered, it can be wet, as long as it has time to dry before you power it.

Conformal coating spray can protect your PCB, but since it is insulating, if some of it gets inside your connectors... they'll stop connecting. If you use a mains powered supply outside, it's a good idea to spray the circuit board, and while you do that, check on the creepage distances, also check the XY caps are really XY caps... as a precaution... some of these "usb chargers" have crap ceramic discs which are absolutely not rated for XY use!

As said by skvery above, you want to keep the water as a vapor and not let it condense. You can insulate the box with styrofoam so dissipation from the PSU and Pi keeps it warm.

If all you want is WiFi on your terrace, you could also keep the Pi and router inside, and simply route a coax to an antenna outside.

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