I finally got my control working.
PC running Linux with my own software.
Ethernet connected to a Wago ethernet coupler
A temperature module connected to a sensor that touches bean mass
A digital output connected to an SSR that controls the heating elements
A logger every 3/10 sec
It works like a million bucks, no need of my watching the temperature, to turn either on/off the heating elements.
It is done automatically.
Future enhancemnets:
1. open the door with a stepper motor when temperature reaches the drop temperature.
2. Turn off the exhaust until coffee has dried out (around 308 F)
3. Independent control of the 4 pairs of heating elements, so very small amount of coffee can be roasted.
4. Add my big cooler (1 HP shop vacuum, the one used for wood shavings) to the roaster
5. Control the cooler when coffee drops
6. Turn off roaster after it has cool down (safe shutdown)
My big question is:
I would like to use the code for a PID controller posted above, for drying coffee only. But I can't seem to get it to work. It keeps turning on and off too fast.
Any ideas...Thanks,
Monito
P.S. Pictures will follow...