buckmartin:
I am developing a concept of a temp controller device that takes an analog input from a temp sensor input and setpoint from a UI then turns the heat source knob with a DC Motor and potentiometer as the feedback/encoder using a PID (or portion of) control to maintain the setpoint.
If your application requires fine granularity, you may want to consider "fuzzy logic" techniques and applications. Sample-and-hold can cause quite wide temperature swings.
It depends on your application, of course.