Comment by jauntywundrkind
4 days ago
Amazing project, great write-up. Would love to see a temperature graph as well! I'm wondering how good the PID controller here is working.
For future improvements, a cheap but effective win might be to put a temperature sensor on the oscillator (or two or three in various places). And use that to drive the PID loop.
Even if just experimental & not long term, it would be nice to have data on how strong the correlation is between the cpu & oscillator temperatures. To see their difference and how much that changes over time. Another graph! CPU vs txco (vs ambient?) temperatures over time.
> put a temperature sensor on the oscillator
At that point, couldn't we just use the temperature value to compensate for the drift?
You can do that as well, but (in theory) the correction will be smaller than it otherwise would need to be if the temperature is regulated within a narrower range.
I for sure thought I included one, updating with that in a min!
Others have mentioned the temperature compensation. I've done it and it sounds like I should do that for the next writeup. A simple DS18B20 close to the Pi produces reasonable results.