EMC2101 Fan Controller and Temperature sensor

The emc2101 component allows you to control a cooling fan from ESPHome (datasheet). It also provides temperature sensors and a tachometer. The fan can be controlled either by a PWM signal or by outputing a DC voltage using its DAC.

The I²C Bus is required to be set up in your configuration for this sensor to work.


EMC2101 Fan Controller and Temperature sensor


Original image at https://learn.adafruit.com/assets/97827 created by by user Bryan Siepert under Creative Commons BY-SA 3.0 and modified for this documentation.

EMC2101 Component

# Example configuration entry
    resolution: 8

Configuration variables:

  • address (Optional, int): Manually specify the I²C address of the sensor. Defaults to 0x4C.

  • inverted (Optional, boolean): Inverts the output so 0 means 100% duty cycle and 1 means 0%. Defaults to false.

  • pwm (Optional): Enable PWM output.

    • resolution (Optional, int): Determines effective resolution and the frequency of the PWM signal. Defaults to 23.

    • divider (Optional, int): Value for the frequency divider. Defaults to 1.

  • dac (Optional): Enable DAC output.

    • conversion_rate (Optional, string): The number of digital to analog conversions perfomed per second. One of 1/16, 1/8, 1/4, 1/2, 1, 2, 4, 8, 16, 32. Defaults to 16.

The PWM signal frequency is determined by the following formula:

\[\text{PWM Frequency} = \frac{360KHz}{2 \times resolution \times divider}\]

And the PWM resolution, the steps in the duty cycle, is calculated by the following formula:

\[\text{PWM resolution} = \frac{100\%}{2 \times resolution}\]

So, with the default values the PWM signal will have a frequency of 7.83KHz and a resolution of 2.17%. The maximum resolution value is 31 which will configure a frequency of 5.81KHz with a resolution of 1.61%.

EMC2101 Output

  - platform: emc2101
    id: fan_duty_cycle

Configuration variables:

  • id (Required, ID): The ID to use for code generation, and for reference by dependent components.


When using the emc2101 output with a Speed Fan it is advised to configure the speed_count as twice the resolution so the number of speeds in the fan matches the number of steps in the fan controller.

EMC2101 Sensors

  - platform: emc2101
      id: internal_temperature_sensor
      name: "Internal Temperature Sensor"
      id: speed_sensor
      name: "Speed Sensor"
      id: duty_cycle_sensor
      name: "Duty Cycle Sensor"
    update_interval: 5s

Configuration variables:

  • internal_temperature (Optional): The internal temperature sensor. All options from Sensor.

  • external_temperature (Optional): The external temperature sensor. More accurate but it needs an additional transistor to be installed. All options from Sensor.

  • speed (Optional): The fan speed sensor in RPMs. All options from Sensor.

  • duty_cycle (Optional): Duty cycle sensor. All options from Sensor.

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

See Also