Alternating between heating cooling

Brewbot · January 22, 2018, 7:34am

Hi. My setup alternates between heating and cooling and doesn’t seem to r ache correct set temp.

What setup should I try to change? Standard settings is used.

Thanks

adempewolff · January 22, 2018, 7:21pm

Two requests:

Could you explain what setup you are using for heating and cooling?
Can you zoom in on a period of a few hours so it’s easier to judge the magnitude and period of the oscillating fridge temps? (It’s easier to zoom in using a laptop/desktop browser than the phone browser)

It seems like both your heat and cooler (especially your heater) are somewhat overpowered. This can be compensated to some extent with PID tuning (lowering Kp, changing the PWM period, etc.) but it might be more effective to just address the root cause (ie. install a less powerful heater). It will be easier to give you specific advice after you’ve provided the information requested above.

Best,
Austin

Brewbot · January 22, 2018, 9:53pm

Thanks Austin for your reply!

It’s a quite small fridge which can hold 25L bucket. A 200W heater inside. This type:

Thanks

adempewolff · January 23, 2018, 3:16am

Well, my first reaction is that 200W is waaaaay too much. I think most people use a heater in the range of 60W. I use a ~30W reptile heating pad which works really well. It looks like you can adjust the power of the heater, your first step should be to turn it to the lowest setting. I would do that before starting to tune the PID.