Temperature Controlled rasPi 3B

[Achim Gratz]

So, just before I left last week I managed to finally set up a
temperature controller on my rasPi 3B using three sha512sum processes
that get individually stopped and continued by the temperature control
loop every 100ms to create a load between 0% and 300% and put it into
another cardboard box and bubblewrap.  I still have to add an integral
term to the control loop in order to make the residual zero and add a
few other things to enable changing the setpoint while it's running and
improve the logging, but it already converges to within 0.2K of the
target temperature and keeps the 5 minutes average temperature to within
20mK or so (unless something else loads the cores for more than just a
few seconds, like compiling a new NTPsec version).  Since I was away I
have data for nine days of uninterrupted and undisturbed performance:

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The average heating power is too low at the moment, so I will have to
reduce the thermal isolation when the weather gets warmer.

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The rasPi 2B that I had set up the same way unfortunately had only
intermittent GPS lock.  It appears these problems were due to RF
interference, so I've removed the GPS module from the box now and put it
outside.  I will also have to check the GPS settings or swap in one of
my spare modules the next time I take the system down as the other
modules seem to work better in the same spot.  It also had a jump in the
crystal aging that was probably caused by moving the system and having
it switched off for a few hours.  Since I had to pry the GPS out anyway,
I've (moderately) overheated the system for some time and it looks like
I'm back to the original aging transient.  Without these issues it
appears that the performance should have been very close to the one of
the rasPi 3B (not very surprisingly).  At the level of performance I'm
expecting now it takes about a week to gather meaningful data.


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Samples for the Waldorf Blofeld:
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