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sgbdave
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Visitor
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Registered: ‎07-04-2018

Evaluation board suitable for low temperature ops?

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Hello,

Currently pursuing a technology demonstration mission with an evaluation board (FPGA) as part of a high-altitude balloon test. The FPGA will be doing basic image processing/machine learning, as well as camera control, but it needs to operate at temperatures as low as -40 C and survive -50 C (Or mid-upper Troposphere in Ontario).

I was wondering which evaluation board is best suited for this kind of mission. (Considering eval board due to time-to-develop constraint)

Other constraints:

- Board size has to be <= 10 cm x 10 cm

- Must have USB input (for Camera), SD Card slot and a dedicated processor (i.e. no MicroBlaze)

 

Based on my own search I have Arty A7 100T (I know it has a microblaze processor but I had trouble finding a board that meets all temperature requirements)

Another is a heater-attached to a ZYBO Z7 or ZynqBerry. I have experience with these boards from before, but never in upper atmosphere conditions or with a heater.

Open for suggestions and ideas.

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joancab
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Scholar
417 Views
Registered: ‎05-11-2015

We have similar problems for a similar project. What you should really worry about is condensation. That means water, that may not be much harmful if you think of DC conductivity or corrosion, but a droplet between two near pins of a high-speed differential pair can become a capacitor and spoil all the signals. So, an enclosed chamber purged with N2, dry air or CO2 may be necessary. Or else, some heating keeping the temperature above the dew point.

About temperature itself, the risk is just if the FPGA can start or not. Once it boots and runs, it will probably keep warm enough to operate. You need to carry out some thermal analysis with thermal conductivities, convection coefficients, etc. They are not easy, highly empirical. If you are not short on energy, I would suggest a controlled heating system (independent of the FPGA, software-less if possible (yes, once upon a time there was smart electronics with just dumb transistors, ask the gray-haired old grumpy ones...). Keep temperature at, say, 15 - 20C if your enclosure has normal (humid) air, or at the minimum temperature for the FPGA to start if you use a dry gas.

If you go for the airtight dry gas chamber, be aware of the pressure difference with the exterior. It's actually simpler an open enclosure but you must keep a higher temperature to prevent condensation, what means energy, so that's quite a key to choose the solution.

Hope that helps!

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drjohnsmith
Teacher
Teacher
430 Views
Registered: ‎07-09-2009

The general answer, 

   is to put the parts in a well insulated case

        and chuck in a few  hand warming pads like these,

    weight a lot less than a heater with batteries.

https://www.amazon.co.uk/Little-Hotties-Pocket-Warmers-Winter/dp/B001G6SQMG/ref=asc_df_B001G6SQMG/?tag=googshopuk-21&linkCode=df0&hvadid=205188093108&hvpos=&hvnetw=g&hvrand=10099300596036231697&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvloc...

 

These guys have a range of industrial temperature boards that might fit,

https://shop.trenz-electronic.de/en/Products/Trenz-Electronic/

 

 

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sgbdave
Visitor
Visitor
428 Views
Registered: ‎07-04-2018

Will propose it to the team. Thank you for the recommendation and the trenz-electronic link. Really helps

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joancab
Scholar
Scholar
418 Views
Registered: ‎05-11-2015

We have similar problems for a similar project. What you should really worry about is condensation. That means water, that may not be much harmful if you think of DC conductivity or corrosion, but a droplet between two near pins of a high-speed differential pair can become a capacitor and spoil all the signals. So, an enclosed chamber purged with N2, dry air or CO2 may be necessary. Or else, some heating keeping the temperature above the dew point.

About temperature itself, the risk is just if the FPGA can start or not. Once it boots and runs, it will probably keep warm enough to operate. You need to carry out some thermal analysis with thermal conductivities, convection coefficients, etc. They are not easy, highly empirical. If you are not short on energy, I would suggest a controlled heating system (independent of the FPGA, software-less if possible (yes, once upon a time there was smart electronics with just dumb transistors, ask the gray-haired old grumpy ones...). Keep temperature at, say, 15 - 20C if your enclosure has normal (humid) air, or at the minimum temperature for the FPGA to start if you use a dry gas.

If you go for the airtight dry gas chamber, be aware of the pressure difference with the exterior. It's actually simpler an open enclosure but you must keep a higher temperature to prevent condensation, what means energy, so that's quite a key to choose the solution.

Hope that helps!

View solution in original post