PID keeps firing heating element although already over target

Troubleshooting
1

Hi,
during heating up the HLT and BK for mash in, I do repeatedly experience that one of the heating elements keeps turned on although the actual temperature is already way over the target.

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Any ideas what could be wrong?

Didn’t experience this behaviour while mashing with the HLT setpoint driver…

Kind regards
Wolfgang

2

Your i is still at 2048, while it already overshot target temperature.

Elco happened to explain this pretty recently: Still cooling even though past beer set temperature (you want positive Kp values as you’re heating)

3

For a hlt heating element, you probably want Kp to be at least 50.

4

I have Kp set at 100 and that works well for my setup.

Have a read through this: https://pid-tuner.com/pid-control/

5

Bob’s hint about the “I” being 2048 did the trick. I deleted the value and let Brewblox set it automatically and the heating element settled at the target temperature.

But I have no clue how the value 2048 did get there. I am absolutely sure I didn’t enter it deliberately. I had activated the preset “Kettle heating element” once I found it after one of the recent release updates.

Is there any chance brewblox sets this value internally?

Cheers
Wolfgang

6

Yes, the i value is calculated. If you open the PID settings in the Spark page, or by clicking on the cooler/heat r in the builder layout, you can see the calculation.

It being too high is likely caused by the Kp being too low. The i value slowly builds up to compensate.

7

And 2048 (2k) is the maximum? :wink:

As I mentioned in my previous post: I am using the preset “Kettle heating element” which sets the PID values like this:

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I didn’t touch any of the values because I wanted to see how the system works with this preset. Seems to work quite well for my setup in terms of heating rate etc. but if “I” is constantly rising I guess that something must be wrong.

My Kp is 50, just as the preset sets it. If this is too low, prehaps the preset should be changed.

8

I’d have to dig up some values, but 2048 may well be the max.

We reached the same conclusion about presets, and have some changes ready for next release. This includes adjusting PID settings based on whether the fermentation fridge is using beer or fridge mode. The Kp for beer mode is significantly higher.

I’ll also double check whether we already updated the PID presets.