Re:Tune Your PID Controller
by trench0 on Wednesday May 26, 2021 @07:48AM
(#27289259)
Can confirm. We use PIDs in espresso machines to control the temperature of the water used in brewing. Some machines have simple thermostats that over/under shoot ideal brewing temperature and a PID will help keep a consistent temperature or even let you override the temperature (if your machine runs too hot or too cold).
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Do you have any insight on why PID controllers are used for this application? PID assumes a system with a continuous control input, but water boilers usually have an on/off switch. Is the input something like a PWM value?
My temperature controlled kettle does a way-more-than-optimal amount of switching when it's near the setpoint. That's consistent with using a PID controller into a PWM input.
Maybe there is a market opportunity for a water boiler that uses control techniques better suited to on/off inputs :)
A resistive electric heater can be PWM'ed to provide variable output. If you want to maintain a narrow temperature band, you can do that better by feeding the water temperature into your PID loop and have it control the PWM duty cycle, rather than to a simple on-off thermostat.