If you get to regulating fan/motor speed then the SCR type controls are the only way to go.
This depends on the type of motor you're controlling, for a P1 a variac does a very nice job of controlling the fan speed.
I've been manually variac'ing the fan for years (my one Wearever's done perhaps 350 lbs), but I'm considering an Arduino PID project that would control both fan and heater. Worse, I'd like to make the thing capable of controlling gas flow from a standard backyard LP/NG regulator, as well. Electrical and gas would have wildly varying requirements (mostly due to thermal inertia and latency, I'd suppose -- and depending so much on roaster design), but that's precisely where it's nice to have code doing the work.
I just want, finally, to join those who've been enjoying automation.
One thing I'd like to do is develop a bean flow sensor for poppers -- some method to determine whether there's a loft stall -- or an imminent one. With poppers, max heater current alone is not a sufficient "rail" -- ya need to keep the circulation near minimum for maximum heat, and with too much flow the beans may not even roast all the way (Yada yada . . . no one reading this doesn't know that). I temperature spike would sufficiently indicate that, but it'd be nice to anticipate that rather than let the beans weather it . . .
