What would cause this to swing like this?

My brewpi has been really solid for a while but I just had a beer that started to swing by 1 full degree. I have the newest version of Legacy installed.

Mine has picked up a tendency to do this too… Any hints or tips much appreciated.

Please show a zoomed in chart, a copy of your settings and the details of your setup.

Even though you have the latest version of legacy, please not that the latest version on the BrewPi Spark has much better control algorithms and we do not recommend using Arduino for new builds. The legacy firmware has not been updated for over a year and will not be updated either.

Brand new BrewPi user here, but there’s a visible correlation between room temperature decrease and fridge temperature increasing to compensate (and vice versa) which didn’t happen in the first few days.

Something right between 26/7 and 27/7 screwed with the algorithm?

Here is the additional info you asked for, it is running on, I have been using this build for a while and this has never happened before.


Your fridge temperature is following the fridge setpoint just fine, so that’s not the problem.

There is a lot of lag in the beer temperature. You can try reducing the filtering on the beer temperature in advanced settings. This will make the fridge setting a bit more jumpy, but it is really smooth now.

You can also try increasing Kd, to for example 3. Try reducing Ki a bit, to 0.125.

Ok it seems to be just fine while I am using Beer Constant while I have active fermentation but then 4 days in, boom everything goes wild. IT also is running my fridge a lot more and swinging by 1 degree not .1 like normal. Trippy.

I also made the adjustments you told me to but it si still acting the same way,

Ok I seemed to have kind of solved this issue. It seems to only go crazy after 4 days and only when I run in beer constant mode. Using beer profile seems to work fine. Not really sure why but that does solve my problem.