Analog To Digital Sensor
========================

The Analog To Digital (``adc``) Sensor allows you to use the built-in
ADC in your device to measure a voltage on certain pins. On the ESP8266
only pin A0 (GPIO17) supports this. On the ESP32 pins GPIO32 through
GPIO39 can be used.

.. figure:: images/adc-ui.png
    :align: center
    :width: 80.0%

.. code:: yaml

    # Example configuration entry
    sensor:
      - platform: adc
        pin: A0
        name: "Living Room Brightness"
        update_interval: 15s

Configuration variables:
~~~~~~~~~~~~~~~~~~~~~~~~

- **pin** (**Required**, :ref:`config-pin`): The pin to measure the voltage on.
- **name** (**Required**, string): The name of the voltage sensor.
- **attenuation** (*Optional*): Only on ESP32. Specify the ADC
  attenuation to use. See :ref:`adc-esp32_attenuation`.
- **update_interval** (*Optional*, :ref:`config-time`): The interval
  to check the sensor. Defaults to ``15s``. See :ref:`sensor-default_filter`.
- **id** (*Optional*, :ref:`config-id`): Manually specify the ID used for code generation.
- All other options from :ref:`Sensor <config-sensor>` and :ref:`MQTT Component <config-mqtt-component>`.

.. note::

    On the ESP8266, the voltage range is 0 to 1.0V - so to measure any higher voltage you need to scale the voltage
    down using, for example, a voltage divider circuit.

.. _adc-esp32_attenuation:

ESP32 Attenuation
~~~~~~~~~~~~~~~~~

On the ESP32, the voltage measured with the ADC caps out at 1.1V by default as the sensing range
or the attenuation of the ADC is set to ``0db`` by default.

To measure voltages higher than 1.1V, set ``attenuation`` to one of the `following values
<http://esp-idf.readthedocs.io/en/latest/api-reference/peripherals/adc.html#_CPPv225adc1_config_channel_atten14adc1_channel_t11adc_atten_t>`__:

- ``0db`` for a full-scale voltage of 1.1V (default)
- ``2.5db`` for a full-scale voltage of 1.5V
- ``6db`` for a full-scale voltage of 2.2V
- ``11db`` for a full-scale voltage of 3.9V

See Also
^^^^^^^^

- :ref:`sensor-filters`
- :doc:`ads1115`
- :doc:`max6675`
- :doc:`API Reference </api/sensor/adc-sensor>`