Control Analysis needed

[merkur]

Hi - I have BrewPi running on a Raspberry Pi with the Arduino Uno and it is used to control my Fermentation Chamber which is a freezer. The heat source is a 100W lamp in a paint can. Typically control is +/- 0.5 degrees. Is this a normal profile or can it be tweaked? All the settings are stock and I have been reluctant to change them.

Paul.

[Elco]

You are only showing the beer temperature, not the fridge temperature and fridge setpoint. My analysis will be very limited:

• You have a lot of fluctuation in your beer temperature. I assume you are not using a thermowell and have taped the beer sensor to the carboy. You should fix that first. You are not measuring your beer temperature, you are measuring a combination of fridge air and beer temperature.

[merkur]

Thanks Elco! Great response time. Yes I am using a thermowell inside a 5 gallon batch.

Here is the full profile:

The spike was when we dry-hopped and removed the thermowell and is understood.

Paul

[Elco]

Please zoom in a bit more, so we only see a few oscillations.

[merkur]

How does this look Elco? Thanks for doing this.

Paul

[Elco]

You beer takes some time to respond to the fridge temperature.

I don’t remember very well what the defaults are on Arduino, but I think you should: decrease Ki to let the integrator build up slower, increase Kd to take more overshoot into account.

[merkur]

Thanks. These are the current, default settings:

Paul

[Elco]

You need to hit those update buttons, so you don’t have zero’s in those fields.

[merkur]

Sorry about that. Here you go: