HASmartThermostat

Smart Thermostat with PID controller for Home Assistant

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.

Installation:

I recommend using HACS for easier installation.

Install using HACS:

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.

Manual installation:

1. Go to default /homeassistant/.homeassistant/ (it's where your configuration.yaml is)
2. Create /custom_components/ directory if it does not already exist
3. Copy the smart_thermostat folder into /custom_components/
4. Set up the smart_thermostat and have fun

Configuration:

The smart thermostat can be added to Home Assistant after installation by adding a climate section to your configuration.yaml file.

Configuration example:

configuration.yaml

climate:
  - platform: smart_thermostat
    name: Smart Thermostat Example
    unique_id: 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 : 5
    ki : 0.01
    kd : 500
    pwm : 00:15:00

Usage:

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 settles over 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 = target_temp - 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.

Outdoor temperature compensation

Optionally, when an outdoor temperature sensor entity is provided and ke is set, the thermostat can automatically compensate building losses based on the difference between target temperature and outdoor temperature. An external component E is added to the PID output: E = Ke * (target_temp - outdoor_temp)
output = P + I + D + E
Output is then limited to 0% to 100% range to control the PWM. The Ke gain depends on the insulation of the building, on recent buildings with good insulation, a gain of 0.6 is recommended. This compensation will act like the integral of the PID, but with faster response time, so the integral will be more stable.

Autotune (not always working, not recommended to use):

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 and set the desired temperature on the thermostat. The autotuner will then start analyzing your heating system, measure the sampling rate of the sensor, control the heater switch and monitor the temperature changes.

Wait for the autotune to finish by checking the autotune_status attribute for success. The Kp, Ki and Kd gains will then be computed and set according to the selected rule and the thermostat switches to PID.
The Kp, Ki and Kd gains are also computed using the other rules, and all values are shown in the Home Assistant log like this: "Smart thermostat PID Autotuner output with ziegler-nichols rule: Kp=######, Ki=######, Kd=######".
You should then save for reference the gains computed by the autotuner for future testing.

Warning: The thermostat set point can't be changed once the autotuner has started monitoring the temperature. The temperature regulation will work as a basic hysteresis thermostat based on set point and noise band. If your heating system and temperature monitoring is slow, reducing the noise band will reduce the temperature oscillations around the set point. If the sampling rate of your temperature sensor is too fast (few seconds) or noisy (frequent temperature changes) increase the noise band for system stability.

Warning: The autotuner result is saved in the entity attributes and restored after Home Assistant is restarted.
However, it is recommended to save the new gains in the YAML configuration file to keep it in case of Home Assistant database's is corrupted.

Services

Services can be used in Home Assistant to configure the thermostat.
The following services are available:

Set PID gains: smart_thermostat.set_pid_gain
Use this service to adjust the PID gains without requiring a restart of Home Assistant. Values are saved to Home Assistant database and restored after a restart.
Please consider saving the final gain parameters in YAML configuration file when satisfied to keep it safe in case of database corruption.
Optional parameters : kp, ki and kd, as float.
Example:

service: smart_thermostat.set_pid_gain
data:
  kp: 11.8
  ki: 0.00878
target:
  entity_id: climate.smart_thermostat_example

Set PID mode: smart_thermostat.set_pid_mode
Use this service to set the PID mode to either 'auto' or 'off'.
When in auto, the PID will modulate the heating based on temperature value and variation. When in off, the PID output will be 0% if temperature is above the set point, and 100% if temperature is below the set point.
Mode is saved to Home Assistant database and restored after a restart.
Required parameter : mode as a string in ['auto', 'off'].
Example:

service: smart_thermostat.set_pid_mode
data:
  mode: 'off'
target:
  entity_id: climate.smart_thermostat_example

Set preset modes temperatures: smart_thermostat.set_preset_temp
Use this service to set the temperatures for the preset modes. It can be adjusted for all preset modes, if a preset mode is not enabled through YAML, it will be enabled. You can use any preset temp parameter available in smart thermostat settings.
Please note the value will then be saved in the entity's state in database and restored after restarting Home Assistant, ignoring values in YAML.
Example:

service: smart_thermostat.set_preset_temp
data:
  away_temp: 14.6
  boost_temp: 22.5
target:
  entity_id: climate.smart_thermostat_example

Clear the integral part: smart_thermostat.clear_integral
Use this service to reset the integral part of the PID controller to 0. Useful when tuning the PID gains to quickly test the behavior without waiting the integral to stabilize by itself.

Parameters:

• name (Optional): Name of the thermostat.
• unique_id (Optional): unique entity_id for the smart thermostat.
• heater (Required): entity_id for heater switch, must be a toggle device. Becomes air
• conditioning switch when ac_mode is set to True.
• invert_heater (Optional): if set to true, inverts the polarity of heater switch (switch is on while idle and off while active). Must be a boolean (defaults to false).
• target_sensor (Required): entity_id for a temperature sensor, target_sensor.state must be temperature.
• outdoor_sensor (Optional): entity_id for an outdoor temperature sensor, outdoor_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 (float, default 100).
• ki (Recommended): Set PID parameter, integral (i) control value (float, default 0).
• kd (Recommended): Set PID parameter, derivative (d) control value (float, default 0).
• ke (Optional): Set outdoor temperature compensation gain (e) control value (float, 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).
• min_cycle_duration (Optional): Set a minimum amount of time that the switch specified in the heater option must be in its current state prior to being switched either off or on (useful to protect boilers). Can be float in seconds or time hh:mm:ss (default 0s).
• min_off_cycle_duration (Optional): When min_cycle_duration is specified, Set a minimum amount of time that the switch specified in the heater option must remain in OFF state prior to being switched ON. The min_cycle_duration setting is then used for ON cycle only, allowing different minimum cycle time for ON and OFF. Can be float in seconds or time hh:mm:ss (defaults to min_cycle_duration value).
• min_cycle_duration_pid_off (Optional): This parameter is the same as min_cycle_duration but is used specifically when PID is set to OFF. Defaults to min_cycle_duration value.
• min_off_cycle_duration_pid_off (Optional): This parameter is the same as min_off_cycle_duration but is used specifically when PID is set to OFF. Defaults to min_cycle_duration_pid_off value.
• 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.
• cold_tolerance (Optional): When PID is off, set a minimum amount of difference between the temperature read by the sensor specified in the target_sensor option and the target temperature that must change prior to being switched on. For example, if the target temperature is 25 and the tolerance is 0.5 the heater will start when the sensor equals or goes below 24.5 (float, default 0.3).
• hot_tolerance (Optional): When PID is off, set a minimum amount of difference between the temperature read by the sensor specified in the target_sensor option and the target temperature that must change prior to being switched off. For example, if the target temperature is 25 and the tolerance is 0.5 the heater will stop when the sensor equals or goes above 25.5 (float, default 0.3).
• 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).
• preset_sync_mode (Optional): If set to sync mode, manually setting a temperature will enable the corresponding preset. In example, if away temperature is set to 14°C, manually setting the temperature to 14°C on the thermostat will automatically enable the away preset mode. Should be string either 'sync' or 'none' (default: 'none').
• boost_pid_off (Optional): When set to true, the PID will be set to OFF state while boost preset is selected, and the thermostat will operate in hysteresis mode. This helps to quickly raise the temperature in a room for a short period of time. Should be a boolean (default: false).
• away_temp (Optional): Set the default temperature used by the "Away" preset. If this is not specified, away_mode feature will not be available. The temperature can then be adjusted using the set_preset_temp service, new value being restored after restarting HA.
• eco_temp (Optional): Set the default temperature used by the "Eco" preset. If this is not specified, eco feature will not be available. The temperature can then be adjusted using the set_preset_temp service, new value being restored after restarting HA.
• boost_temp (Optional): Set the default temperature used by the "Boost" preset. If this is not specified, boost feature will not be available. The temperature can then be adjusted using the set_preset_temp service, new value being restored after restarting HA.
• comfort_temp (Optional): Set the default temperature used by the "Comfort" preset. If this is not specified, comfort feature will not be available.
• home_temp (Optional): Set the default temperature used by the "Home" preset. If this is not specified, home feature will not be available. The temperature can then be adjusted using the set_preset_temp service, new value being restored after restarting HA.
• sleep_temp (Optional): Set the default temperature used by the "Sleep" preset. If this is not specified, sleep feature will not be available. The temperature can then be adjusted using the set_preset_temp service, new value being restored after restarting HA.
• activity_temp (Optional): Set the default temperature used by the "Activity" preset. If this is not specified, activity feature will not be available. The temperature can then be adjusted using the set_preset_temp service, new value being restored after restarting HA.
• sensor_stall (Optional): Sets the maximum time period between two sensor updates. If no update received from sensor after this time period, the system considers the sensor as stall and switch to safety mode, the output being forced to output_safety. If set to 0, the feature is disabled. Can be float in seconds or time hh:mm:ss (default 6 hours).
• output_safety (Optional): Sets the output level of the PID once the thermostat enters safety mode due to unresponsive temperature sensor. This can help to keep a minimum temperature in the room in case of sensor failure. The value should be a float between 0.0 and 100.0 (default 5.0).
• initial_hvac_mode (Optional): Forces the operation mode after Home Assistant is restarted. If not specified, the thermostat will restore the previous operation mode.
• 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): length of the autotune buffer for the signal analysis to detect peaks, can be float in seconds, or time hh:mm:ss (default 2 hours).
• 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

Credits

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