PID overshoot

[cyan trout]

I tweaked a Vibiemme Domobar with Gaggiuino, and for temperature control I use a PID. I autotuned the PID after the machine is warmed up and I flush some water to completely fill the boiler (during warmup under 100 degrees celsius a 2WV releases pressure into the water reservoir). Whatever I do the temperature always overshoots with 2 or 3 degrees, and takes a few minutes to cool down a bit. How can I autotune correctly to get the temperature spot on? Or what settings can I change to get a more precise temperature? Thanks in advance!

[agile plover]

What's the PID model? Would like to take a look at the manual if possible. You should also be able to purge to get to your desired temperature pretty quickly I would imagine but I know that's not ideal.

[cyan trout]

It’s a QB-T7100.

[agile plover]

If you can adjust the parameters, you should theoretically be able to adjust the proportional temperature gain to help mitigate overshoot, you can really fine tune this but I would take care to note where you started so if you get deep in the weeds you can get back to where you started. Adjusting P will probably extend the length of time to reach your max temperature, but it could make your final temperature more accurate. There may be a better way to go about adjusting but from my admittedly still growing knowledge, this should get you the results you're looking for. It's not a flaw so much as a result of the algorithm just doing what it does. This could also be hardware limitations of your actual heater. It's difficult to say for sure.

Can't find a manual with some cursory searching, but I'll keep looking when I can

Although I'm not really familiar with Gaggiuino or how it may interact with the PID controller. There may be some level of programming or UI I don't know about, so apologies if this is old news to you or generally unhelpful.

[cyan trout]

Sorry for the poor quality, but I made photos of the manual

Gaggiuino doesn’t interact with the PID, I put 2 thermocouples in the same place so Gaggiuino measures the same temperature as the PID.

I will try to play with the P setting tomorrow. Thanks for the tip!

[runic rampart]

2-3 degrees for warmup is pretty good already. What matters most is how it responds to using the machine / flushing

Personally I’d look into having gaggiuino control it since that’s a more fancy and customizable control loop

[cyan trout]

I've been down that road, Gaggiuino heating algorithm is made for a small boiler. With the bigger boiler of the Domobar it took ages to become stable no matter the settings....