Would it be sensible, feasible, to place an Ardunio in a good box and keep it at a decent temperature (above 0°C) using a heating resistor (if such a thing exists).
The setup would be powered externally, so there'd be no problems with energy consumption.
Is this a normal technique for electronics at low temperatures? Or did I dream that I'd heard of it somewhere?
I imagine a temperature sensor and a solid state switch (or maybe a relay) which would swicth on the heating coil when the temperature fell too much.
Quite reasonable...we've done this before. If you have a well sealed box it doesn't take much power to heat a power resistor and keep the inside of the enclosure above 0C. I'd suggest using multiple resistors in series/parallel to spread the heat around the edges of the enclosure (preferably not touching the enclosure).
You don't need a special "heating resistor", just a regular wirewound power resistor will do fine, for example:
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The MegaRAM shield: add 128 kilobytes of external RAM to your Arduino Mega/Mega2560
RuggedCircuits:
Quite reasonable...we've done this before.
On an Arduino project! Magic!
Searching on about this idea I came across the fact that there is an industrial ATMEGA328. Presumably using one of those helps (guaranteed to -40°), but also, presumably, the other components on the Arduino board are NOT guaranteed at -40°...
That's correct, unless you know specifically which parts are used you cannot be sure that ALL the parts on the Arduino are rated down to -40C. Most likely they are not, as such parts cost more (in general).
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The Ruggeduino: compatible with Arduino UNO, 24V operation, all I/O's fused and protected
We've used industrial/automotive rated components to make arduino compatible circuits that work fine at low temperatures. On one particular experiment I flew a commercial (0C) rated RTC, and the clock stopped reporting at about -40C. It was apparently still ticking, as it reported the correct time once it warmed up. All other parts on that flight had a -40C rating and worked as designed.
I would use specially made resistive heaters from minco. Go with kapton flexible heaters and place a few around the inside. you can purchase ones with adhisive backing and matching the power rating with your voltage source.
I sent an Arduino Mini to the edge of space. It was at least -40 before my temperature sensor started getting errors. You can read more on my site or by searching this forum.
Very impressive edge of space experiment! You should compete in the AAPT apparatus competition. Your kids should at least present this in their school.
On the other hand, for extended exposure in cold weather, the solder junctions may get brittle and fail. The fiber glass board may have different thermal expension rate than solder so expose in cold for too long they may break apart too.
How high do you have to fly to reach -40C (or was this in a particularly cold place?)
We were going up - this was a high altitude balloon experiment. As best I recall, it's about 40k ft where the really cold temps usually begin. -40C is typical, -70C is possible going to 100k ft.
