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187 lines
6.4 KiB
ReStructuredText
187 lines
6.4 KiB
ReStructuredText
SCD4X CO₂, Temperature and Relative Humidity Sensor
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===================================================
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.. seo::
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:description: Instructions for setting up SCD4X CO₂ Temperature and Relative Humidity Sensor
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:image: scd4x.jpg
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The ``scd4x`` sensor platform allows you to use your Sensirion SCD4X CO₂
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(`datasheet <https://sensirion.com/media/documents/E0F04247/631EF271/CD_DS_SCD40_SCD41_Datasheet_D1.pdf>`__) sensors with ESPHome.
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The :ref:`I²C Bus <i2c>` is required to be set up in your configuration for this sensor to work.
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.. figure:: images/scd4x.jpg
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:align: center
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:width: 80.0%
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.. code-block:: yaml
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# Example configuration entry
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sensor:
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- platform: scd4x
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co2:
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name: "Workshop CO2"
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temperature:
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name: "Workshop Temperature"
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humidity:
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name: "Workshop Humidity"
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Configuration variables:
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------------------------
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- **co2** (*Optional*): The information for the CO₂ sensor.
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- All options from :ref:`Sensor <config-sensor>`.
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- **temperature** (*Optional*): The information for the Temperature sensor.
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- All options from :ref:`Sensor <config-sensor>`.
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- **humidity** (*Optional*): The information for the Humidity sensor.
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- All options from :ref:`Sensor <config-sensor>`.
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- **temperature_offset** (*Optional*, float): The temperature offset can depend
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on various factors such as the SCD4x measurement mode, self-heating of close
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components, the ambient temperature and air flow. This variable allows the
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compensation of those effects by setting a temperature offset. Defaults to
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``4°C``.
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- **automatic_self_calibration** (*Optional*, boolean): Whether to enable
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automatic self calibration (ASC). Defaults to ``true``.
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- **ambient_pressure_compensation** (*Optional*, int): Enable compensation
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of measured CO₂ values based on given ambient pressure in mBar.
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- **altitude_compensation** (*Optional*, int): Enable compensating
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deviations due to current altitude (in metres). Notice: setting
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*altitude_compensation* is ignored if *ambient_pressure_compensation*
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is set.
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- **measurement_mode** (*Optional*): Set measurement mode for scd4x.
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- ``periodic``: The sensor takes a new measurement every 5 seconds. This is the default mode.
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- ``low_power_periodic``: The sensor takes a new measurement every 30 seconds. Make sure ``update_interval`` is at least 30 seconds.
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- ``single_shot``: A measurement is started in every update interval. A measurement takes 5 seconds. This mode is only available on scd41 and useful if low power consumption is required.
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The automatic self-calibration is optimized for single shot measurements performed every 5 minutes.
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To reduce noise levels, you can can perform several single shot measurements in a row and average the output values using a :ref:`sensor-filters`.
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- ``single_shot_rht_only``: A measurement is started in every update interval. A measurement takes 50 ms. Only humidity and temperature is measured. CO2 is reported as 0 ppm. This mode is only available on scd41 and useful if low power consumption is required.
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- **ambient_pressure_compensation_source** (*Optional*, :ref:`config-id`): Set an external pressure sensor ID used for ambient pressure compensation.
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The pressure sensor must report pressure in hPa. the correction is applied before updating the state of the co2 sensor.
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- **address** (*Optional*, int): Manually specify the I²C address of the sensor.
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Defaults to ``0x62``.
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- **update_interval** (*Optional*, :ref:`config-time`): The interval to check the
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sensor. Defaults to ``60s``.
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Actions:
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--------
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.. _perform_forced_calibration_action:
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``perform_forced_calibration`` Action
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---------------------------------------------
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This :ref:`action <config-action>` manually calibrates the sensor to the provided value in ppm.
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Operate the SCD4x in the operation mode later used in normal sensor operation (periodic measurement, low power periodic measurement or single shot) for > 3 minutes in an environment with homogenous and constant CO2 concentration before performing a forced recalibration.
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As of April 2022 the average fresh air Co² concentration is 419 ppm.
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.. code-block:: yaml
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on_...:
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then:
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- scd4x.perform_forced_calibration:
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value: 419 # outside average April 2022
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id: my_scd41
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value can also be a template, for example to define a Home Assistant calibration service:
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.. code-block:: yaml
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api:
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services:
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- service: calibrate_co2_value
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variables:
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co2_ppm: int
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then:
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- scd4x.perform_forced_calibration:
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value: !lambda 'return co2_ppm;'
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id: my_scd41
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.. _factory_reset_action:
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``factory_reset`` Action
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--------------------------------
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This :ref:`action <config-action>` triggers a factory reset of the sensor. Calibration settings are restored from factory settings.
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.. code-block:: yaml
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on_...:
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then:
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- scd4x.factory_reset: my_scd41
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Pressure compensation
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---------------------
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A static ambient pressure value can be set with `ambient_pressure_compensation` or `altitude_compensation`. It can also be changed dynamically with :ref:`lambdas <config-lambda>` using `set_ambient_pressure_compensation(<mBar>)`, or by pointing `ambient_pressure_compensation_source` to a local pressure sensor.
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Example with a local sensor
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***************************
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Note: remember your pressure sensor needs to output in mBar
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.. code-block:: yaml
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sensor:
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- platform: bme280
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pressure:
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name: "Ambient Pressure"
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id: bme_pressure
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- platform: scd4x
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measurement_mode: low_power_periodic
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ambient_pressure_compensation_source: bme_pressure
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temperature_offset: 0
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co2:
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name: "CO2 level"
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Example with a remote sensor
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****************************
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This example creates a service `set_ambient_pressure` that can be called from Home Assistant:
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.. code-block:: yaml
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api:
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services:
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- service: set_ambient_pressure
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variables:
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pressure_mbar: int
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then:
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- lambda: "id(my_scd41)->set_ambient_pressure_compensation(pressure_mbar);"
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sensor:
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- platform: scd4x
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id: my_scd41
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measurement_mode: low_power_periodic
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temperature_offset: 0
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co2:
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name: "CO2 level"
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See Also
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--------
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- :ref:`sensor-filters`
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- :doc:`absolute_humidity`
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- :doc:`scd30`
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- :apiref:`scd4x/scd4x.h`
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- :ghedit:`Edit`
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