His solution for controlling the thermostat from afar was to take advantage of the GSM network and implement a SMS-based heater controller ... [kohleick] connected two temperature sensors ...

and an Arduino. There’s also an LCD display and a FET to control the heater. The idea behind a PID controller is that you measure the difference between the current temperature and the desired ...

Done. R5 is now “reasonably well” calibrated for a CCW to CW span of zero to 130 o C above room temp. Thermal coupling of the chosen length of sensor/heater wire to the desired thermal load (e.g., ...