[App_rpt-users] Frozen repeater -- Deep Freeze test

[David McGough]

Hi Mike (& Everyone),

I ran an "experimental" freezer test over the last 10 hours or so. My test
setup is a "bare" BBB (no case or anything) with URI plugged in, sitting
in a ceramic dinner plate on the 2nd shelf from the top of the
deep-freezer. I'm powering the contraption using an Adafruit 5V2A
wall-wart located outside the freezer, with the small power cord running
thru the freeze door seal.

An uncalibrated analog thermometer inside said about -20 degrees
Fahrenheit just now. The typical range on this thermometer is about -15 or
lower.

I brought an industrial "point and shoot" IR thermometer back from my 
office and checked the BBB at various spots. The CPU/SoC was the warmest 
at about -2 degrees. Other spots ranged as low as -9. When I pointed the 
IR thermometer at my old analog one, the IR said -17 (analog says -20). 
The plate, BBB and thermometer are in the air stream from the freezer 
circulating fan--that should be a worst case scenario!

I'm already getting some dirty looks about "commandeering" the freezer!  
I'll going to conclude this phase of testing before lunch! HiHi!


73, David KB4FXC



On Fri, 21 Nov 2014, David McGough wrote:

> 
> Hi Mike,
> 
> Was the URI green LED flashing (I guess not...)??
> 
> I'm rather amazed that the BBB or URI was directly the cause of the 
> lock-up, even with really cold conditions. The simplest low-power-budget 
> solution to keep this hardware warm is a simple Styrofoam container. 
> Even with the minuscule BBB power consumption, Styrofoam should do the 
> job fine.
> 
> I'll mention here, again, that the ONLY scenarios I've seen where BBB's 
> have locked-up were due to 5VDC power woes. I completely stable 5V power 
> source is critical. And, the 5VDC regulator might be a source of problems 
> in extreme cold, too.
> 
> If you don't already have it, I recommend adding a cheap digital 
> thermometer to your cabinet that records all-time temperature extremes, 
> including time/date. Or, if you want to get fancier, the BBB AllStar 
> release already includes support for a USB attached thermometer (see the 
> "pcsensor" command) which will log temperature to a file, etc. Note that 
> if you decide to go the USB thermometer route, a bug was found in the code 
> in the 1.2.1 release. This has already been patched, but, you'll need the 
> patch (contact me off list or search the arm-allstar list for more 
> details).
> 
> Any idea how cold it got and for how long??? And, what is your power 
> source??
> 
> I'm preparing to put a "test" BBB and URI in my deep-freezer (about -15
> degrees Fahrenheit) for this weekend. I'll put it in there completely
> unprotected.
> 
> My problems in the past with such extreme cold have been issues directly
> with the radio hardware (like VCO's that unlock, etc.).  This type of
> extreme thermal shock can also destroy transmitter PA's, in short order by
> cracking ceramic substrates in power modules, etc. (I've got a few of 
> those Tee-shirts, too!).
> 
> 73, David KB4FXC
> 
> 
> 
> 
> On Thu, 20 Nov 2014, Michael Lussier wrote:
> 
> > 
> > I went up on the mountain Wednesday morning. The repeater was powered up as well as the BBB. No action from the repeater. 
> > Any thoughts on low power way to keep the BBB and the URI warm ? I can use 12vdc 
> > 
> > Sent from an iPhone 5 iOS 8
> > 
> > Mike.Lussier at gmail.com
> > AE4ML at arrl.net
> > AE4ML at amsat.org
> > 
> > 
> > 
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