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.

# Example configuration entry
  - platform: adc
    pin: A0
    name: "Living Room Brightness"
    update_interval: 60s

Configuration variables:

  • pin (Required, Pin): The pin to measure the voltage on. Or on the ESP8266 alternatively also VCC, see ESP8266 Measuring VCC.

  • name (Required, string): The name of the voltage sensor.

  • attenuation (Optional): Only on ESP32. Specify the ADC attenuation to use. See ESP32 Attenuation.

  • update_interval (Optional, Time): The interval to check the sensor. Defaults to 60s.

  • id (Optional, ID): Manually specify the ID used for code generation.

  • All other options from Sensor.


This component prints the voltage as seen by the chip pin. On the ESP8266, this is always 0.0V to 1.0V Some development boards like the Wemos D1 mini include external voltage divider circuitry to scale down a 3.3V input signal to the chip-internal 1.0V. If your board has this circuitry, add a multiply filter to get correct values:

  - platform: adc
    # ...
      - multiply: 3.3

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:

  • 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

ESP8266 Measuring VCC

On the ESP8266 you can even measure the voltage the chip is getting. This can be useful in situations where you want to shut down the chip if the voltage is low when using a battery.

To measure the VCC voltage, set pin: to VCC and make sure nothing is connected to the A0 pin.


To avoid confusion: It measures the voltage at the chip, and not at the VCC pin of the board. It should usually be around 3.3V.

  - platform: adc
    pin: VCC
    name: "VCC Voltage"

Multiple ADC Sensors

You can only use as many ADC sensors as your device can support. The ESP8266 only has one ADC and can only handle one sensor at a time. For example, on the ESP8266, you can measure the value of an analog pin (A0 on ESP8266) or VCC (see above) but NOT both simultaneously. Using both at the same time will result in incorrect sensor values.

See Also