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View Thread » DATALOGGERS - CONTROLLERS - RATE OF RISE METERS » Dataloggers/Controllers/Rate of Rise Meters
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Quest Control - TC4 Interface

since a very long time I do have several hobbies. One is about everything related to coffee and the other is about making things.
So it was just a matter of time until these two hobbies are merging into a project.

I'm roasting already quite a while, the last years with my Quest M3 which is really a nice little roaster with a perfect size for a small household. Although I'm really happy with it, as time goes by and reading in this forum the idea grew to automate it.

After browsing the web and especially this forum, I decided to make my project based on the TC4.

Now my project has finished and before I'm asking for some help related to PID here some pictures first:

First prototype board:

The "Quest Control" works pretty fine. I've done already some automations with Artisan alarms and my whole setup now is really cool.

My next step is to understand the PID functionality. Even if I don't think that its possible to reroast an existing profile, I'm trying to ensure a defined temperature load of the roaster using PID.

Here are my current artisan settings. As you can see, I'm using ET as a reference, which in case of the Quest usually is the MET probe.

And this is the result, which is not really satisfying. Ist there any experience related to a small drum roaster?

Thanks already for helping...


P.S. if you are able to read in German language here my project in the German "Kaffee-Netz":
Edited by Piezo on 07-24-2018 04:30
You need to tune your PID, read about Ziegler-Nichols method.
Or, if you are familiar with Arduino programing, use the Auto-Tune library made by same author as the PID.
Yep, that looks like the PID parameters are off. I've made an autotuning sketch for the TC4, that has Ziegler-Nichols and a few other methods integrated:
Very nice project Thomas!

KKTO Roaster.
I love the control box! Looks very neat and professional! Also love the 3D printed parts, especially the SSR cage.

mg512 wrote:
I've made an autotuning sketch for the TC4, that has Ziegler-Nichols and a few other methods integrated:

The Quest uses phase angle control for the fan. Does your autotune support that now?
Brett autotune (and the associated forks) controls the heater only.

You should run AT multiple times with various fan manual settings, to find how the airflow change the machine dynamics.
Also, AT should be ran with beans in the machine, an empty machine response is wildly different.

Even the AT various methods give significantly different results, enough to fool a beginner. To quote Brett:

"I’m not the biggest fan of Autotune. I’ve often said, and still believe, that a moderately trained person will beat an Autotuner every day of the week. There’s just so much that can go wrong without the algorithm knowing about it. That being said, Autotune is a valuable tool to help the novice get into the ballpark."
Edited by renatoa on 07-26-2018 20:57
Thanks already for your answers. I already tried the Ziegler-Nichols method, but unfortunately without success.
But the autotuning sketch sounds really promissing. I‘ll try out asap, but it just might still last a couple of days (weeks).
I‘ll inform about the results...
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greencardigan wrote:

I love the control box! Looks very neat and professional! Also love the 3D printed parts, especially the SSR cage.

Thanks, also the control box is a 3d print :-)
The Ziegler-Nichols tuning creates a "quarter wave decay". This is an acceptable result for some purposes, but not optimal for all applications.
This tuning rule is meant to give PID loops best disturbance rejection.
It yields an aggressive gain and overshoot – some applications wish to instead minimize or eliminate overshoot, and for these this method is inappropriate.

You can check also my past posts against PID approach/usage, as not appropriate for a roasting scenario.
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