Hi,
Ive used the wizard to setup my ferment dashboard and havent touched any of the default figures. Im using a thermowell in my fermenter. My previous batch seemed to track the temperature much better, and the 18deg setpoint on this batch was tracked alot closer. When i raised to 22deg. it started OKish but then had cooling overshoots. Ive extracted the blocks (i think that gives you all the settings info?) any suggestions on what i can tweak?
Your mutex times are only 20 minutes and 29 minutes. This is too short.
You should set them to something like 3 hours to avoid alternating between heating and cooling.
You want to cool and let it rise naturally, so the cooler should block the heater for a much longer time after cooling.
When you share the graphs, increase the period, so we can see where it oscillates. The part you shared is just the heater running at full power.
I think Td is very high on both PIDs. When Td is high, we automatically select a slow filter, but more filtering comes with more delay. This probably results in the D value lagging so much that it comes too late. I would decrease Td. You can also manually select a filter for the derivative since the last release.
If you share the graphs I can give more detailed suggestions.
I assume this is a fermenter in a fridge, is that correct?
Its actually a chest freezer, albeit quite old which maybe isnt helping. It also has quite a large wooden collar on it due to needing more height to acomodate fermzilla hop bong! Possibly less than ideal insulation is having a impact?
I’ll adjust the mutex.
Td is 1800 (30m) on cool and heat.
I’ll admit to not having done any tweaking from the wizard, this is a reset up as i’ve started brewing again, previously (with no wooden collar?) it was withh 0.1 deg all the time.
Kp at 50/-50 means it will run at 50% when the beer is 1 degree too high/low.
What is your derivative filter set to?
The current setting is pointless, it only has a spike on each bit flip of the sensor.
It needs more filtering or you can set Td to zero to not use the differential part at all.
Derivative filter is derived from Td and is 15m, Td is 30m what should i look to decrease that to? Is 15minutes meaning if outside of a mutex period it will still wait for the filter period before heating or cooling to smooth any spikes?
Re Kp, is that set based on the heating/cooling power of the appliances? chest freezer and greenhouse tube heater? Its -50 on the cooling but actually 100 on the heat side, and as you are saying 50 is too high im guessing 100 is very high!
It really depends on how powerful your heater/cooler is.
When cooling, it seems to drop a lot quickly, so I think -50 is too much. Try -25.
For heating, I don’t see much overshoot.
Start with Td at zero for both.
And mutex on 3 hours for both.
Regarding filtering: filtering is similar to averaging. Because you can only average values in the past, more averaging will give more delay. It is not actively waiting and is unrelated to the mutex. For example if you take the average value over the last half hour, you will have less spikes and see less effect of bit flips, but your filtered value is lagging the actual value.
