After the first tests with the SoftPWM on a breadboard, I now soldered everything together and pressed it into an old PSU case of an old PC. Actually this is a prototyping case, but I know how long those things are lasting usually. I guess, if it works, I will just improve it slightly, but leave it ;)
Technically it looks pretty good. As you can see in the video, I can set a temperature, which my simple regulation in CODESYS tries to hold. I published the data and the control element in a web visualization, so that I can control the smoker from my smartphone.
I tried to keep the regulation circuit as slow as possible. But I defined myself a tolerance which the circuit should compensate in a given time. The regulation should react on a deviation of 5 degrees after 10 seconds. But currently this is just a mind game, and I will for sure know more after the next weekend ;)