Thread: Need to control physical hot plate knob - Instrument Control (GPIB, Serial, VISA, IVI) - NI Discussion Forums

Now I just need to build the contraption. I'm thinking to get a couple of gears, and attach a tight-fitting removable sleeve to the hot plate knob, and I think I've got the idea for the mount design -- won't firm it 'til I've all the supplies in hand. An electronics-minded classmate suggested the ~$10 DC "hobby motor" over the cheaper one, and I think I can pin it through parallel.   I know one power supply...

I've never tried this but it should be possible.-- Tie the thermistor to the feedback of a ring oscillator.  The resistance of thermistor will vary with temperature. Therfore the ring oscillator frequency will change. Your PC probably has a MIC input record the tone and adjust the heat as needed.      

Following on Jeff's suggestion, you may want to include limit switches at both ends of knob travel to cut power to the motor in the offending direction. This will prevent stalling the motor in a locked rotor condition, stripping the knob from the shaft, or damaging the heater control.   -AK2DM      

Fallowing on to Analogkid: place a diode in parallel to each of the limit switches so the motor can be pulled off the switch but not run into the stop.   Instead of putting in 2 relays a motor  2 limit switches and 2 diodes and wiring all that up why not put one bigger relay in the power line and control the on/off time with it. Would be a lot simpler than trying to deal with the heat/cool time constants in adjusting the control which...