I am wondering exactly how a thermostat program would work and wanted to see if anyone had a better opinion on it. From what I know, there are a few control algorithms that could be used, some being Bang-Bang (On/Off), Proportional Control Algorithms, and PID Control. Looking on Wikipedia, there is a great deal of explanations for all three in which I understand completely. However, when trying to implement a proportional control algorithm, I feel that I am missing the need or the use of the proportional gain (K) and the output. Since today's thermostats do not include the need to vary power or current, how do I manipulate the output so that I can trigger the controls ON/OFF of the thermostat? Also, what is the value of the proportional gain or K?
The issue is overshooting the setpoint temperature.
If you simply run the device until the set point temperature is reached, you will overshoot, wasting energy (and possibly doing damage, depending on what the thermostat controls.)
You need to "ease up to" the setpoint so that you arrive at the set point just as the device is shutting down so that no more energy goes in to rise above the set point.
Thermostat Control Algorithms