Why aren't your signs working? Matrix displays, Raspberry PI, and low temperatures

Why aren't your signs working? Matrix displays, Raspberry PI, and low temperatures

I've worked in the electronics industry for years... primarily in the radio communications sector, so most of the time I have a pretty good grip on how to work with things in this flashy-blinky hobby.

It was the cold snap of late 2022 when I was shocked to hear from viewers that a few of my P5 matrix signs were not working.  Sure enough, no display - did a cursory check of power and connectivity into FPP by browser and while it was sluggish to respond, it was communicating on port 80.  FPP just refused to run the local scheduler or working playlist from the master.  If I manually started FPP, it would just run for a second and stop. 

I briefly considered working more on it, but decided it was way to cold to mess with it.  After all, it was around -14F with the wind, even colder.  It was at that point I had a flash back to a CISCO SIAD problem our company had many years ago where the SIAD actually experienced a hardware failure due to cold temperatures.  Yes, you read that right, not only did a commercial piece of equipment fail under cold temps, it was an unrecoverable failure!  Not to take a longer rabbit trail, but it was tracked back to a single component and Cisco lost a ton of money swapping the defective units out because they didn't meet their own whitepaper specs... but I digress....
Most of my failing signs were PI Zero 2 W's with a HUB75 compatible "Hat".

What are the whitepaper operating temps for a RaspPi zero you ask?  0C - 85C or 32F - 176F for those in the USA or still in denial of the metric system. 

At the time, we were at -23C/-10F. 

So, I brought a 6 panel sign indoors and let it warm up.  Sure enough, the PI stopped being sluggish and the sign came to life on it's own.  Clearly a temperature issue.
So, what to do about this?  In my old field days, we'd just put a high wattage incandescent light bulb in an outdoor cabinet for a little heat, but these enclosures were a little tight on space.  Need a small form factor heat source - ideally to run off 120v AC since that would be the most efficient use of power in my application, on a low temp thermostat.

I ended up sourcing some 4" long, 120v, inductive heat strips and wired them up to an inexpensive DIN rail thermostat.  Some preliminary tests I did using a chest freezer show these little guys can maintain enough heat to keep the PI's in working range. 

Next step will be to outfit the rest of our signs with these in preparation for any additional harsh seasons ahead. 

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