rpi-pwm-fan-control

Motivation

This Python script was created for the purpose to control a PWM FAN Noctua NF-A4x20 5V, using Raspberry Pi 4B hardware features.

While the original script uses WiringPi this script rebuilds everything on top of gpiozero.

• To read the FAN speed a DigitalInputDevice is used that counts the falling flanks.
• Depending on the pin that is used for fan PWM control gpiozero uses hardware or software PWM (Hardware PWM is available on pins GPIO12, GPIO13, GPIO18, GPIO19)
• The temperature is directly read from the linux file system
• The input values are then used to update an PID controller
• The output of the PID controller is mapped to the PWM range of the Noctua Fan (20% - 100%)

Wiring

• Set PWM pin to control the FAN (e.g. GPIO12)
• Set TACHO pin to read FAN speed (e.g. GPIO6)
• The other 2 fan pins can be directly connected to 5V & GND pins
• CPU usage stays between 1% and 3% (if a higher pwm frequency is used it requires more processing power although it shouldn't)

Dependencies

• Python 3 - The script interpreter
• GPIO Zero - Control Hardware features of Rasbberry Pi

Documentations

• Noctua white paper - Noctua PWM specifications white paper

How to use

git clone https://github.com/katringoogoo/rpi-pwm-fan-control.git
cd rpi-pwm-fan-control
pip3 install -r requirements.txt
./rpi-pwmfan.py

Most of the variables from the script can be overridden via commandline arguments. Have a look at

./rpi-pwmfan.py -h

Hardware PWM

In order be able to use Hardware PWM make sure that you connected the PWM pin of the fan to a hardware capable pin on the Raspberry Pi.

Next install the pigpio library & daemon:

sudo apt-get install pigpio
sudo systemctl start pigpiod    # start the daemon
sudo systemctl enable pigpiod   # optional: autostart on startup

and start the script with the following arguments

./rpi-pwmfan.py --use-pigpio

Note: if you want to disable pigpiod again you have to stop the daemon with sudo systemctl stop pigpiod

More information is available on the pigpio website