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General PID explanation

Glossary

  • Error

    Difference between setpoint and current measured temperature. For example, if setpoint is 25.0 and current temperature is 23.8, error is 1.2.

PID parameters

  • P - Proportional term.

    This does not depend on time. Error will be multiplied to this value each pid_sample_period to get this term. So, its value is depended on pid_sample_period.

    Generally speaking, it is responsible for the basic sinus.

  • I - Integral term.

    This term depends on time and responsible for the error compensation during timeline.

  • D - Derivative term.

    Usually not need in high inertia system like room heating/cooling.

Tuning PID parameters

  1. First start with some small P. Set I and D to 0.
  2. Wait some time and check history graph. You should get stable sin() form on the target_sensor graph.
  3. Adjust P to get minimal sin() period.
  4. Set some initial I.
  5. Check the history graph and adjust I until you will see stable straight line on the graph.

NOTE: Be ready to spend 1-2 days during tuning high inertia system, like water-heating floor. Be patient and final result will be amazing! :)

PID regulation case: water heating floor + room sensor

  • Heating floor has very high inertia.
  • We have external heating floor thermostat, which was added to HA with climate domain. We can directly adjust floor temperature with it by setting climate setpoint.
  • We have room temperature sensor and want to have some constant room temperature.

I solved this case with:

pid_sample_period: 00:00:05
pid_params = 0.1, 0.001, 0

First graph is floor temperature, second is room temperature.

You can see on the graph, that after few hours room temperature was stabilized on setpoint 23.5:

PWM PID regulation case: water heating floor (PWM mode)

  • Valve for heating floor collector with open time around 3 mins and close time around 2 mins. It is visible as switch entity in Home Assistant.
  • DS18B20 sensor inside heating floor connected to ESPHome, with scan period 10 seconds.
pid_params: 10, 0.004, 0
pid_sample_period: "00:00:05"
pwm_period: "00:05:00"