Create a virtual thermostat with accurate and reactive temperature control through PID controller. Principle of the PID controller. Any heater or air conditioner unit with ON/OFF switch or pilot wire can be controlled using a pulse width modulation that depends on the temperature error and its variation over time.
I recommend using HACS for easier installation.
Go to HACS, select Integrations, click the three dots menu and select "Custom repositories". Add the path to the Github repository in the first field, select Integration as category and click Add. Once back in integrations panel, click the Install button on the Smart Thermostat PID card to install. Set up the smart thermostat and have fun.
- Go to default /homeassistant/.homeassistant/ (it's where your configuration.yaml is)
- Create /custom_components/ directory if it does not already exist
- Copy the smart_thermostat folder into /custom_components/
- Set up the smart_thermostat and have fun
The smart thermostat can be added to Home Assistant after installation by adding a climate section to your configuration.yaml file.
climate:
- platform: smart_thermostat
name: Smart Thermostat Example
heater: switch.on_off_heater
target_sensor: sensor.ambient_temperature
min_temp: 7
max_temp: 28
ac_mode: False
target_temp: 19
keep_alive:
seconds: 60
away_temp: 14
kp : 75
ki : 0.001
kd : 70000
pwm : 00:15:00
The target sensor measures the ambient temperature while the heater switch controls an ON/OFF heating system. The PID controller computes the amount of time the heater should remain ON over the PWM period to reach the temperature set point, in example with PWM set to 15 minutes, if output is 100% the heater will be kept on for the next 15 minutes PWM period. If PID output is 33%, the heater will be switched ON for 5 minutes only.
By default, the PID controller will be called each time the target sensor is updated. When using main powered sensor with high sampling rate, the sampling_period parameter should be used to slow down the PID controller refresh rate.
By adjusting the Kp, Ki and Kd gains, you can tune the system response to your liking. You can find many tutorials for guidance on the web. Here are a few useful links:
- PID Control made easy
- Practical PID Process Dynamics with Proportional Pressure Controllers
- PID Tuner
- PID development blog from Brett Beauregard
- PID controller explained
To make it quick and simple:
- Kp gain adjusts the proportional part of the error compensation. Higher values means stronger reaction to error. Increase the value for faster rise time.
- Ki gain adjusts the integral part. Integral compensates the residual error when temperature settles in a cumulative way. The longer the temperature remains below the set point, the higher the integral compensation will be. If your system settles below the set point, increase the Ki value. If it overshoots the set point, decrease the Ki value.
- Kd gain adjusts the derivative part of the compensation. Derivative compensates the inertia of the system. If the sensor temperature increases quickly between two samples, the PID will decrease the PWM level accordingly to limit the overshoot.
PID output value is the weighted sum of the control terms:
error = set_point - current_temperature
di = temperature change between last two samples
dt = time elapsed between last two samples
P = Kp * error
I = last_I + (Ki * error * dt)
D = -(Kd * di) / dt
output = P + I + D
Output is then limited to 0% to 100% range to control the PWM.
You can use the autotune feature to find some working PID parameters.
Add the autotune: parameter with the desired tuning rule, and optionally set the noiseband and lookback duration if the
default 2 hours doesn't match your HVAC system bandwidth.
Restart Home Assistant to start the thermostat in autotune mode, make a step on the set point (positive for heating,
negative for cooling) and wait for the autotune to finish by checking the autotune_status attribute for success.
The Kp, Ki and Kd gains will be shown in the attributes and shown in the log like this: "Set Kp, Ki, Kd. Smart
thermostat now runs on PID Controller." followed by the three computed gains Kp, Ki and Kd respectively.
Warning: I'couldn't yet save the settings to the configuration.yaml file. The PID parameters set by the autotune won't be stored and the process restarts everytime Home Assistant is restarted.\ To save the parameters read attributes or log after autotune has finished, manually copy the values in the corresponding fields and remove the autotune parameter in the YAML configuration file before restarting Home Assistant.
- name (Required): Name of the thermostat.
- heater (Required): entity_id for heater switch, must be a toggle device. Becomes air conditioning switch when ac_mode is set to True.
- target_sensor (Required): entity_id for a temperature sensor, target_sensor.state must be temperature.
- keep_alive (Required): sets update interval for the PWM pulse width. If interval is too big, the PWM granularity will be reduced, leading to lower accuracy of temperature control, can be float in seconds, or time hh:mm:ss.
- kp (Recommended): Set PID parameter, proportional (p) control value (default 100).
- ki (Recommended): Set PID parameter, integral (i) control value (default 0).
- kd (Recommended): Set PID parameter, derivative (d) control value (default 0).
- pwm (Optional): Set period of the pulse width modulation. If too long, the response time of the thermostat will be too slow, leading to lower accuracy of temperature control. Can be float in seconds or time hh:mm:ss (default 15mn).
- sampling_period (Optional): interval between two computation of the PID. If set to 0, PID computation is called each time the temperature sensor sends an update. Can be float in seconds or time hh:mm:ss (default 0)
- target_temp_step (Optional): the adjustment step of target temperature (valid are 0.1, 0.5 and 1.0, default 0.5 for Celsius and 1.0 for Fahrenheit)
- precision (Optional): the displayed temperature precision (valid are 0.1, 0.5 and 1.0, default 0.1 for Celsius and 1.0 for Fahrenheit)
- min_temp (Optional): Set minimum set point available (default: 7).
- max_temp (Optional): Set maximum set point available (default: 35).
- target_temp (Optional): Set initial target temperature. If not set target temperature will be set to null on startup.
- ac_mode (Optional): Set the switch specified in the heater option to be treated as a cooling device instead of a heating device. Should be a boolean (default: false).
- away_temp (Optional): Set the temperature used by the "Away" preset. If this is not specified, away_mode feature will not be available.
- eco_temp (Optional): Set the temperature used by the "Eco" preset. If this is not specified, eco feature will not be available.
- boost_temp (Optional): Set the temperature used by the "Boost" preset. If this is not specified, boost feature will not be available.
- comfort_temp (Optional): Set the temperature used by the "Comfort" preset. If this is not specified, comfort feature will not be available.
- home_temp (Optional): Set the temperature used by the "Home" preset. If this is not specified, home feature will not be available.
- sleep_temp (Optional): Set the temperature used by the "Sleep" preset. If this is not specified, sleep feature will not be available.
- activity_temp (Optional): Set the temperature used by the "Activity" preset. If this is not specified, activity feature will not be available.
- autotune (Optional): Set the name of the selected rule for autotune settings (ie "ziegler-nichols"). If it's not set, autotune is disabled. The following tuning_rules are available:
| ruler | Kp_divisor, Ki_divisor, Kd_divisor |
|---|---|
| "ziegler-nichols" | 34, 40, 160 |
| "tyreus-luyben" | 44, 9, 126 |
| "ciancone-marlin" | 66, 88, 162 |
| "pessen-integral" | 28, 50, 133 |
| "some-overshoot" | 60, 40, 60 |
| "no-overshoot" | 100, 40, 60 |
| "brewing" | 2.5, 6, 380 |
- noiseband (Optional): set noiseband for autotune (float): Determines by how much the input value must overshoot/undershoot the set point before the state changes (default : 0.5).
- lookback (Optional): duration of the signal analysis for the autotune, need to have 5 cycles (temperature crossing the set point) included in the analysis period, can be float in seconds, or time hh:mm:ss (default 2 hours).
This code is a fork from Smart Thermostat PID project:
https://github.com/aendle/custom_components
The python PID module with Autotune is based on pid-autotune:
https://github.com/hirschmann/pid-autotune