Tuning the PID
The PID controller uses a feedback loop with Proportional, Integral, and Derivative components to control the power output. These must be balanced via constant multipliers to fit the system under control. Tuning is critical to getting the results as close as possible to the desired goal. Ideally it will reach a new goal as quickly as possible if the goal is changed. In this case, we are more concerned with its ability to compensate for external temperature changes. A modified form of the Ziegler–Nichols method (with some manual tweaking) was the method used to set the tuning constants.
Here different constants (Kp, Ki, Kd) were used as well as a variation of the cycle time. The cycle started at 3 minutes and eventually dropped to 25 seconds.
The large 50% power block in the middle is just an artifact of graphing while no testing was being done.
