I’m using a fresh install of BrewBlox and set up my fridge via the fridge wizard. For now, the beer temperature is directly controlled, while the fridge temperature sensor is not used. Beer temp is perfectly stable, but the fridge temp swings around it a lot and there is quite some unnecessary heating and cooling.
I think both your heater and cooler are a bit too aggressive.
The integral seems fairly steady, so that’s not the problem.
Try to just divide Kp by 2 for both. Maybe the heater a bit more, because it raises the fridge temp pretty quickly. I don’t know what your current value is, but Td should be roughly the expected overshoot duration.
You could also increase Td for both, to decrease the output when it is moving in the right direction quickly.
To block the heater and cooler from alternating, you can increase the lock time in the mutex constraints. Please note that it can now also be set in the individual constraints, which will override the default fallback set in the target mutex block.