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178 lines
8.7 KiB
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VEML7700 and VEML6030 Ambient Light Sensors
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===========================================
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.. seo::
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:description: Instructions for setting up VEML7700 / VEML6030 ambient light sensors in ESPHome.
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:image: veml7700.jpg
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:keywords: VEML7700, VEML6300
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The ``veml7700`` sensor platform allows you to use the Vishay VEML7700 and VEML6030 ambient light sensors with ESPHome.
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Communication with the device is over :ref:`I²C <i2c>`, which must be present in your configuration. VEML7700 and VEML6030
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are basically the same but in different packages. The VEML7700 uses a fixed address of ``0x10``, while the smaller VEML6030
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can be configured to use either ``0x10`` or ``0x48``.
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The VEML 7700/6030 devices are available on breakout boards from a number of vendors including `Adafruit`_, `SparkFun`_,
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`DFRobot`_, and others.
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.. _Adafruit: http://www.adafruit.com/products/4162
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.. _SparkFun: https://www.sparkfun.com/products/15436
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.. _DFRobot: https://www.dfrobot.com/product-1620.html
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.. figure:: images/veml7700-full.jpg
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:align: center
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:width: 70.0%
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VEML7700 Ambient Light Sensor on a board and standalone sensors.
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.. figure:: images/veml7700-ui.png
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:align: center
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:width: 60.0%
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VEML sensor in Home Assistant UI.
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The sensor is a high accuracy ambient light digital 16-bit resolution sensor with dynamic range from 0 lux to about 120,000 lux.
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Its wide range of measurements is enabled by four configurable *gain* levels and six different *integration time* options.
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Higher gain values are typically used for lower light conditions.
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The sensor has two photodiodes with different spectral response represented by two channels: an *ALS* channel and a *WHITE* channel.
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The *ALS*, or *Ambient light* channel follows a so-called human eye curve very closely. The *WHITE* channel covers a much wider wavelength/spectrum, capturing quite a lot of near-infrared radiance.
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.. figure:: images/veml7700-spectral.png
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:align: center
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:width: 100.0%
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ALS and WHITE channels spectral response
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Using this component's automatic measurement mode is advised; in this mode, proper *gain* and *integration time* are automatically selected by the component after
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taking several measurements. To do so, it follows a process recommended by the manufacturer.
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Should you desire to manually control those parameters - please note that:
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- Gain levels of 1/8 and 1/4 shall be used in most cases.
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- Gain levels of 1 an 2 are only intended to be used in low light conditions < 100 lux. For very high illuminations it shows high non-linearity.
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- In the range of 0 lux - 1000 lux the sensor measurements are stricly linear for Gain 1/4 and 1/8, after 1000 lux it shows non-linearity.
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A lux compensation formula is used to get better readings in bright conditions.
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However, it gives quite high error in very bright direct sunlight (instead of 100-120 kilolux it might give 150-200k+).
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This Wikipedia `article <https://en.wikipedia.org/wiki/Lux>`__ has a table of some lux values for comparison.
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Automatic measurement mode
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--------------------------
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In automatic measurement mode the component starts from Gain 1/8 and 100 ms (*default*).
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- If illuminance is higher than 46 lx (100 counts) it gradually reduces integration time to get good reading (best in range 100 - 10,000 counts).
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- In case of low illuminance (less than 46 lx) it tries to gradually increase gain and only then increase integration time.
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Please note, that in low light conditions measurement process might take several seconds due to long exposure periods and sensor reconfigurations.
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Starting values can be overriden by setting ``gain`` and ``integration_time`` parameters. The gain value gets adjusted first if possible.
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Lux compensation
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----------------
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Lux compensation is done as recommended by the manufacturer, however it can be turned off by
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setting ``lux_compensation: false`` in your device's configuration.
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.. math::
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\displaystyle \begin{array}{l}
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lux & = & counts \times resolution(time, gain)\\
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lux_{comp} & =& 6.0135e \times 10^{-13} \times lux^4 - 9.3924e \times 10^{-9} \times lux^3\\
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& & + 8.1488e \times 10^{-5} \times lux^2 + 1.0023 \times lux\\
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\\
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\text{Where:} & & \\
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counts & - & \text{sensor readings, counts}\\
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resolution & - & \text{sensor resolution for given integration time and gain, lx/counts}\\
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lux & - & \text{calculated illumination, lx}\\
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lux_{comp} & - & \text{compensated illumniation, lx}\\
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\end{array}
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Available data
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--------------
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The implementation offers seven sensors:
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- Two providing *lux* value,
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- Two unitless data measurements directly from the device,
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- Two actual *gain* and *integration time* values used for the measurement (useful in automatic mode), and
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- One fully artificial, somewhat representing near-infrared part of spectrum.
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- **ambient_light**: Illuminance value for *ALS* channel representing human eye, lx
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- **full_spectrum**: Illuminance value for *WHITE* channel with wide spectrum, lx
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- **infrared**: Calculated illuminance value (*WHITE* minus *ALS*) representing near-infrared spectre, lx
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- **ambient_light_counts**: Raw 16 bit reading from *ALS* channel, counts
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- **full_spectrum_counts**: Raw 16 bit reading from *WHITE* channel, counts
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- **actual_gain**: The actual gain value being used for values reported, multiplier
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- **actual_integration_time**: The actual integration time being used for values reported, ms
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Example configuration
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---------------------
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.. code-block:: yaml
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# Example configuration entry
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sensor:
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- platform: veml7700
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address: 0x10
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update_interval: 60s
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# short variant of sensor definition:
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ambient_light: "Ambient light"
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# longer variant of sensor definition:
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actual_gain:
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name: "Actual gain"
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Configuration variables:
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------------------------
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- **auto_mode** (*Optional*, boolean): Automatic gain and integration time selection. Defaults to ``True``.
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- **integration_time** (*Optional*, :ref:`config-time`):
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The amount of time the sensor is exposed. Valid values are ``25ms``, ``50ms``, ``100ms`` *(default)*,
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``200ms``, ``400ms``, ``800ms``. *In automatic mode it sets starting value*.
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- **gain** (*Optional*, string): The gain the device will use for the internal ADC. Valid values are
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``1/8x`` *(default)*, ``1/4x``, ``1x``, ``2x``. Higher values are better in low-light conditions.
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*In automatic mode it sets starting gain value*.
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- **lux_compensation** (*Optional*, boolean): Lux compensation formula is used as per manufacturer.
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Defaults to ``True``.
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- **glass_attenuation_factor** (*Optional*): The attenuation factor of glass if it's behind some glass
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or plastic facia. Default is ``1.0`` means ``100%`` transmissivity. ``2`` means ``50%`` transmissivity etc.
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- **update_interval** (*Optional*, :ref:`config-time`): The interval for checking the sensors.
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Defaults to ``60s``.
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- All other options for I²C devices described at :ref:`I²C Bus <i2c>`.
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The sensor supports bus modes "standard" and "fast": 10 kHz to 400 kHz.
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Sensors
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.......
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You can configure all or any subset of the sensors described earlier.
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Each configured sensor is reported separately on each ``update_interval``.
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All options from :ref:`Sensor <config-sensor>` are supported.
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However, if you don't need any other options, you can just use shorthands like this: ``ambient_light: Ambient light``.
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- **ambient_light** (*Optional*): Illuminance for visible light (*ALS channel*), lx.
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- **full_spectrum** (*Optional*): Illuminance for the full spectrum sensor (*WHITE channel*), lx.
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- **infrared** (*Optional*): Calculated illuminance for the Near-IR spectrum (*WHITE* minus *ALS*), lx.
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- **ambient_light_counts** (*Optional*): The reading for visible light (*ALS channel*), counts.
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- **full_spectrum_counts** (*Optional*): The reading for the full spectrum sensor (*WHITE channel*), counts.
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- **actual_gain** (*Optional*): The value of gain used for reported values. Particularly useful when "auto_mode" is selected.
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- **actual_integration_time** (*Optional*): Integration time used for reported values, ms. Particularly useful when "auto_mode" is selected.
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See Also
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--------
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- :ref:`sensor-filters`
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- `VEML 7700 datasheet <https://github.com/latonita/datasheets-storage/blob/main/sensors/VEML7700.pdf>`__
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- Application note `Designing the VEML7700 Into an Application <https://github.com/latonita/datasheets-storage/blob/main/sensors/VEML7700-designing.pdf>`__
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- `VEML 6030 datasheet <https://github.com/latonita/datasheets-storage/blob/main/sensors/VEML6030.pdf>`__
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- Application note `Designing the VEML6030 Into an Application <https://github.com/latonita/datasheets-storage/blob/main/sensors/VEML6030-designing.pdf>`__
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- `Radiometric vs. Photometric Units <https://www.thorlabs.de/catalogPages/506.pdf>`__
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- :apiref:`veml7700/veml7700.h`
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- :ghedit:`Edit`
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