GitHub: https://github.com/Colahall/tiny85fancontrol/tree/main/schem... Codeberg: https://codeberg.org/Colahall/tiny85fancontrol/src/branch/ma...
Seems like something similar should already exist, but I haven’t been able to find anything that is a close enough fit.
Couple of gotchas that I ran across. I found that on Linux, desktop PC fan control support is pretty abysmal. The sensor library that everyone relies on, lm_sensors, is semi-abandoned and didn't recognize sensors on my relatively popular, 7 year old ATX motherboard and GPU. It also requires having Perl installed.
About GPU cooling in particular - modern NVidia cards in particular seem to have a built-in minimum of 30% fan speed when controlling them manually. The connectors are also a different, smaller connector (perhaps a JST PH?).
This is mainly because the companies that make the “super io” controller chips (ITE and others) are deluded and think that they have some sort of cutting edge tech and their chip documentation must be super secret.
Years ago there was someone at a mobo manufacturer who would leak the datasheets, but they left or got found out, and there hasn’t really been a source for that info since.
bArray•6mo ago
[1] https://andrey.mikhalchuk.com/2011/06/20/reading-attiny85452...
[2] https://github.com/micronucleus/micronucleus
MisterTea•6mo ago
gosub100•6mo ago
MisterTea•6mo ago
numpad0•6mo ago
bArray•6mo ago
Yeah... It's either overkill, or there is some decent power going through it and it will affect thermal measurements anyway. Not to mention what it might do to the reference voltage.
> [..] mentions I2C is bit banged [..]
They possibly bit banged it? But it wouldn't have been needed given the hardware support...
> [..] yet completely left out circuit schematics [..]
Yeah, which is far more important that anything else.
> [..] which incidentally includes freewheel diode for the fan.
This may have been sensible to be fair, especially if you happen to rapidly change the delta PWM signal, you could end up with a decently sized back-EMF. But I think even better would be to sink it into something, rather than back into the power supply of sensitive components...
> PCB getting in the way isn't going to matter in this instance.
Agreed.
bArray•6mo ago
The compensation might be needed, and the internal thermal sensor also needs tuning in any case if you read the specs, but it's close enough that you could use it out of the box and only be out by a few degrees. Chip temperature with regular sleeps isn't going to be a significant factor.
There is enough code space on the ATtiny85 that you could actually build a model that takes measured temperature T at time t (T_t), the goal temperature of G (G_t) and produce a predictive model for M(T_t, G_t) = T_{t+n}. You could then do something a little smarter than a PID controller that takes in some profile considerations, i.e. slow (low noise, low RPM, likely for normal usage), fast (high noise, high RPM in bursts, likely for gaming).
ashafq•6mo ago
USB Bootloader is interesting, but I already had a few ISP loaders. You can make an ISP loader with Arduino as well. [1]
[1] https://docs.arduino.cc/built-in-examples/arduino-isp/Arduin...
bArray•6mo ago
It's kind of better than ambient, it would reach the temperature of the GPU if thermally coupled. The sleep-mode thing would just be a case of lots of micro sleeps to discount the temperature of the chip, could have even under-clocked too.
> USB Bootloader is interesting, but I already had a few ISP loaders. You can make an ISP loader with Arduino as well.
The benefit of USB is being able to get debug data from the fan controller as it runs, and be able to re-flash it whilst in the PC by attached to an internal USB bus.
This way you could also log out what the GPU reports, vs what you measure, vs what the ATtiny85 measures.