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Topic: Board-behavior in vacuum, low/high temperature ranges and vibrations? (Read 906 times) previous topic - next topic

romolos_de

Mar 10, 2011, 02:50 pm Last Edit: Mar 10, 2011, 04:12 pm by romolos_de Reason: 1
Hi,

we are considering using Arduino for our ROMOLOS project www.romolos.de. It's a reentry capsule released in 100km altitude and re-entering earth atmosphere.

So the capsule will be exposed to a low (-60°C) and high (300°C) temperatures, low pressure (0.0001 bar and less) and high vibrations during start.

We'll do a shaker tests, that's for sure, but I couldn't find informations of the temperature and pressure ranges Arduino can handle.
The given values are for the capsule hull. Inside it won't be as high temperatured. It's designed for 0-10°C at the 100km peak, and for 40°C and 50° for a short time during re-entry.
Pressure will be important, because the capsule won't be sealed, so the board and electronics shouldn't degas.
And the Vibrations will be there as well, that's hard to predict.

We don't need a space-approval for Arduino, but we must have some further details where the limits are in respect to "never exposing" and "just exposing for some short times".

Best regards, Andreas
--
www.romolos.de

johnwasser

You probably don't need a full Arduino in space.  For instance, are you going to have a PC connected to the USB port?  If not you can develop the software on the Arduino and switch to a perfboard implementation with just the chip and maybe a crystal and two small capacitors.  That reduces to three the components you need to check for rated temperature range.  Look a the data sheets for Absolute Maximum Ratings.  For example the ATmega168 has an operating temperature range of -55°C to +125°C.  Your expected conditions seem to be well within the operating range.

Of course all of the sensors and peripherals must be checked for their operating temperature range.

You should be able to greatly reduce the risk of failure due to vibration by encapsulating the circuit.  Make sure whatever connector you use to connect to it includes the 6 signals of the ICSP header if you ever want to update the software in the encapsulated system!
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kg4wsv

Few common ICs are rated to 300C (none that I've seen).  IIRC Arduinos use commercial temperature rated parts, which are typically in the  0C - 70C operating range.

I would at the very least put the flight hardware together from a kit and substitute automotive rated parts (usually -40C to 125C).

If this is a sub-orbital flight and the arduino will be operating continuously I wouldn't expect cold to be a problem, especially for an automotive part, because self-heating will help.

If the parts will see 300C, though, you'll need some thermal management of some sort.

-j

felis

Also, make sure no heat is generated by components. With such a low pressure, parts would transfer heat by radiation only and radiation is very weak at temperatures you specified. I used to design circuits to work in vacuum and it was amazing to see 1/4w resistor overheating by 1ma current. With PTH components the usual trick is leave leads uncut to give larger area. In any case, find a way to test your circuit in vacuum before sending it.
/felis

Si

I would imagine that it is as much about how you encase the board, as the bare board itself.

Felis, I would never have thought of that.

How about if you have a good old fashioned potting box with epoxy resin. Presumably that would allow heat transmission by contact rather than radiation and solve the overheating probs. Then perhaps insulate it to prevent low temperature problems? I'm guessing now.

Interesting problem though.
--
My New Arduino Book: http://www.arduinobook.com

felis

Epoxy is not very good heat conductor. There is a product called "Arctic Silver Epoxy" and it conducts heat extremely well. It is expensive, however, you probably don't want to fill your whole enclosure with it.
/felis

Udo Klein

If timing is not critical get rid of the crystal as well. The Atmel chips can run on the internal RC oscillator. Gets rid of more components, especially of the crystals. Unless tested I would not trust any crystal under such conditions. As already recommended the atmel chip should be replaced by an automotive rated chip. Not much more expensive. Especially compared to your overall project.

Udo
Check out my experiments http://blog.blinkenlight.net

thebigphish


Epoxy is not very good heat conductor. There is a product called "Arctic Silver Epoxy" and it conducts heat extremely well. It is expensive, however, you probably don't want to fill your whole enclosure with it.


cut directly from the Arctic Silver interwebs...

Even though Arctic Silver Thermal Adhesive is specifically engineered for high electrical resistance, it should be keep away from electrical traces, pins, and leads. The cured adhesive is slightly capacitive and could potentially cause problems if it bridged two close-proximity electrical paths.


it was a nice idea at the start. If you had a significant heat source, what if that source had a simple heat pipe on it to a radiator?
yes, have some.

felis

Arctic Sivler Epoxy capacitance doesn't matter for 16MHz AVR clock. This statement appeared on Arctic Silver website after people reported issues while gluing heatsinks to 2GHz clock video memory chips.

The problem with vacuum is that any part which bears any current is a heat source so you need a heat pipe for every part. It's worth noting that parts have heat capacity as well so exposure time is also a factor - heating up a big part to a high temperature with a small current may take quite some time.
/felis

Si

'Arctic Silver Epoxy' - what a great name for a product!

I think I need some.

I keep telling people about the factlet from felis - the resistor overheating on a tiny current, because there is no thermal conduction.

My though that this is really interesting is not apparently shared by the majority of people. When will I learn?
--
My New Arduino Book: http://www.arduinobook.com

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