Temperature control behaviour changed since 1st March


I’ve been using Brewpi for the last week and a half. It’s been keeping the beer within 0.05C of the set temp which is excellent. However, since the 1st of March, the control cycle seems to have changed and I’m getting much bigger oscilations in the temperature. This can be seen in the two graphs (one showing full run, the other showing a zoom around 1st march):

Any ideas what might have caused this?

There is a lot of delay between the fridge temp and the beer temp.
I wonder if it is because fermentation stopped and the beer is not ‘stirred’ anymore?

The behavior of the fridge setting seems correct for the temperature at that moment, but you are overshooting a bit due to the beer responding much later.

Try increasing beer-to-fridge Td to anticipate that overshoot.

Thanks Elco,

I suppose I was a little bit puzzled why it would change so drastically when it had been tracking so close for a week and a half.

I also found this post after I posted Brewpi: Solved losing precicse control. I tried resetting the Kp, Ki and Kd values to the ones suggested.This seems to have tightened up the control over the last day (Now back within 0.02C)

I’ll look at increasing the Td as well.