At the moment, I'm using the PID as a simple on-off control, connected to a thermocouple in the chaff collector. If the thermocouple gets too hot, then the PID cuts power to the Burkert, shutting off the gas.
The big red button switch on the side of the box also cuts power to the valve. Not visible is the regular on/off switch for the box, PID, and the valve. The visible toggle switch selects either using the computer or the knob for control.
(There are also a separate electrical/master kill switch and manual gas turn-off located a few feet away from the roaster.)
What I'm interested in is my worst espresso being fantastic - James Hoffmann