Resistance Sensor ================= .. seo:: :description: Instructions for setting up resistance sensors in ESPHome :image: omega.svg The ``resistance`` platform is a helper sensor that allows you to convert readings from a voltage sensor (such as the :doc:`ADC Sensor `) into resistance readings in Ω (ohm). In order to calculate the resistance, the circuit needs to be set up in a `voltage divider circuit `__. This consists of three parts: - A voltage reference, usually this is connected to 3.3V (VCC). For example in the image below it is 5V (though on ESPs you should not use that voltage) - A reference resistor with constant resistance. For example below it is R₁ with a value of 5.6kOhm. - The variable resistor we wish the read the resistance of. Here R₂. There are two kinds of configurations for this circuit: Either the variable resistor is close to GND (DOWNSTREAM) or it is closer to VCC (UPSTREAM). .. figure:: images/resistance-downstream.png :align: center :width: 25.0% Example voltage divider configuration of type "DOWNSTREAM" and a voltage reference of 5V. .. code-block:: yaml # Example configuration entry sensor: - platform: resistance sensor: source_sensor configuration: DOWNSTREAM resistor: 5.6kOhm name: Resistance Sensor # Example source sensor: - platform: adc id: source_sensor pin: A0 Note: ------------------------ Some boards like NodeMCUv2 needs to multiply ADC reading by 3.3 to provide accurate result because they have built-in voltage divider on ADC pin (https://arduino.stackexchange.com/a/71952) .. code-block:: yaml # Example source sensor: - platform: adc id: source_sensor pin: A0 filters: - multiply: 3.3 Configuration variables: ------------------------ - **name** (**Required**, string): The name for the sensor. - **sensor** (**Required**, :ref:`config-id`): The sensor to read the voltage values from to convert to resistance readings. - **configuration** (**Required**, string): The type of circuit, one of ``DOWNSTREAM`` or ``UPSTREAM``. - **resistor** (**Required**, float): The value of the resistor with a constant value. - **reference_voltage** (*Optional*, float): The reference voltage. Defaults to ``3.3V``. - **id** (*Optional*, :ref:`config-id`): Set the ID of this sensor for use in lambdas. - All other options from :ref:`Sensor `. See Also -------- - :doc:`adc` - :doc:`ntc` - :ref:`sensor-filters` - :apiref:`resistance/resistance_sensor.h` - :ghedit:`Edit`