How to automatically control the Raspberry Pi fan with Home Assistant

I've set up a Raspberry Pi 4 with Home Assistant in my van. To manage its cooling, I want to programmatically control the fan through Home Assistant, triggering it only when the CPU temperature exceeds a specific threshold.

• Hardware Setup
• Software Requirements
• Configuration
• Result

# Hardware Setup

I used a 5V fan connected to the Raspberry Pi's GPIO pins.

The little fan has three cables:

• Red: Power (5V)
• Black: Ground (GND)
• Blue: Control signal

I connected the blue cable to GPIO 14, which is not a PWM-capable pin on the Raspberry Pi, but it works fine for simple on/off control.

# Software Requirements

To control the GPIOs from Home Assistant, you need to install the following component in this order:

1. HACS - the Home Assistant Community Store
2. HA RPi GPIO - a plugin to control the GPIO pins of the Raspberry Pi

I let you read the documentation of these components to install them correctly.

Once you installed HACS, you can install the RPi GPIO plugin from the HACS dashboard on your Home Assistant instance.

# Configuration

In your configuration.yaml file, add the following lines to configure the GPIO pin for the fan:

switch:
  - platform: rpi_gpio
    switches:
      - port: 14
        name: "RPI Cooling Fan"
        unique_id: "rpi_cooling_fan"
 
climate:
  - platform: generic_thermostat
    name: RPI Cooling Fan Controller
    unique_id: rpi_cooling_fan_controller
    heater: switch.rpi_cooling_fan
    target_sensor: sensor.system_monitor_processor_temperature
    min_temp: 45
    max_temp: 80
    ac_mode: true
    target_temp: 55
    cold_tolerance: 0.5
    hot_tolerance: 0.5
    min_cycle_duration:
      seconds: 60 # Minimum time the fan should run before turning off
    keep_alive:
      minutes: 5
    initial_hvac_mode: "cool"

This configuration does the following:

• Defines a switch for the fan connected to GPIO 14.
• Sets up a generic thermostat that uses the fan as a heater.
• Monitors the CPU temperature using the sensor.system_monitor_processor_temperature sensor.
• Sets the target temperature to 55°C, with a minimum and maximum temperature range of 45°C and 80°C, respectively.
• Configures the thermostat to run the fan for at least 60 seconds before turning it off, and keeps it alive for 5 minutes after the last activation.

# Result