Strange heating behaviour - oscillation? [Arduino]

Any ideas on this strange minor oscillation that seems to have started after a day sitting at 24C constant.

Up to the point it starts the beer seems to be very stable +/- 0.06C around the setpoint. Then it seems to fluctuate further - 0.25C

Running on a super cheap Arduino / RPi setup so I’m aware it’s old firmware etc.

Do I need to change the PID settings?

Many Thanks

I think you should increase Kp. It looks like you are relying on the integrator too much. This causes the fridge setting to lag behind.

The Arduino version of BrewPi does not heat if the beer is already above the setpoint, which is why the fridge temp is allowed to drop.

Thanks Elco. I will give that a try - have just been running “stock settings” so far an it’s been excellent.

Thanks for all your work on this project.