I realise you get a lot of these questions but I haven’t been able to glean much direction from other posts.
I’m attempting to configure the PID settings for my BIAB setup. It’s a 70L pot with a 5500W element and recirculating pump. I wrote a post about my setup a couple of years back:
I did a water test last night with 35L of water (I aim for 30L into my fermenter). The temperature control does not appear as stable as I would have hoped. These are the PID settings (default from wizard):
I tried a number of different temperatures and tried to leave it for 15-30 minutes at each temperature to stabilise. Here’s a summary graph (note there was a loss of data from 21:18 to 21:45, as my Raspberry Pi dropped off the network for some reason):
It looks like the Differential portion seems to be contributing quite a lot. Also I suspect Kp is too high?
I also tried boiling. Boil was reached when the probe was measuring 98°C. From what I can see the controller didn’t detect boil so the “minimum output when boiling” was never reached. Is this an indication that my probe needs calibrating? Can the “Boil Temperature Setting” be -ve?
The D portion should be all but inactive during steady state. You can try disabling Td entirely, and then configuring Kp / Ti to keep temperature steady.
Afterwards you’ll have to tune step response separately - the D portion is relevant to avoid overshoot there.
There’s no harm in calibrating your sensor, but boil temperature does indeed vary, based on altitude (pressure) and mineral content of the water.
You can set a negative value for boil point adjustment. If you set that to -5°C, then boil mode will kick in for every setpoint >=95°C. You can then use a setpoint setting of 97-98°C.
Graphs are downsampled based on how much data would be yielded for their period. The policy is chosen for each new query (whenever a graph is loaded). I assume your Session View graph is showing a significantly longer period than your live view?
We don’t currently have UI settings to override the algorithm that selects the most appropriate downsampling policy for a query.
There is an auto pid in craft beer pi that someone wrote. Could that code be useful in brewblox. It’s deadnuts every time. U just have to transfer over the parameters…
Slightly different topic, but I also have some questions about my fermentation chamber setup. I think from reading the guide here:
that I should not be using a dynamic fridge setpoint, and instead control the beer temperature directly from the heater and cooler PIDs. My fermenter is only about 25mm from the fridge evaporator. I use a tube heater under my fermenter with a fan:
The fridge sensor is currently in the fridge control box at the top left, as that was the most convenient place to mount it.
If using this setup wouldn’t there need to be different PID settings when switching between Constant Beer and Constant Fridge modes? I also use the chamber for bottle conditioning/storage and yeast starters so often switch between these 2 modes.
All settings currently being used are the defaults from the wizard:
I’m now trying a typical ale profile with 30L of water in my fermenter using the beer sensor. Will see how it goes (thermowell right in the center of the fermenter).
