PID gone mad?!?

[imark]

Checked my brewpi this morning and it seems like the pid is gone mad in it. It's been heating and cooling my fermenting beer by 2C every hour. The overshoot and undershoot seem to be excessive. I think something has gone wrong with one of the parameters. Any idea what I need to change to restore this to correct behaviour?

[imark]

False alarm  .No sooner had I posted than I realised I should check the probe was attached to the bucket. Was surprised I could swing the beer tempo that much. So had a look and low and behold it was hanging loose. Attached to bucket now so back in business.

[DEMPSEY]

 

[Damien M]

IF that was a genuine response: reducing  the P term by halves ( or Doubling depending on the calc that is used)  until it gets back into control.

[imark]

Cheers Damien. Useful to know.
It freaked me out until I realised there was no way my fermentation fridge could swing the temperature of 20L wort that quickly.

[Dr Horrible]

If you've got a PID controller, it would be well worth your while to tune it correctly for your system.  I've attached a little guide which I always find handy whenever I have to get involved in the black art of tuning.  I'd be really interested in seeing the data for the first 2-3 days of a fermentation when there's a sharp rise in temperatures, and seeing how well the fridge deals with it.