The original case fan is pretty loud and this is annoying. This script allows adjusting the fan speed dynamically depending on the CPU temperature. As a result, the average fan speed with no significant load is around 40-50% and the fan noise level is almost silent. Also, it should increase the fan life.
The Hardware PWM is used in this script, which allows using all the built-in PWM possibilities e.g. precise frequency control and no CPU usage for PWM generation.
See rpi-hardware-pwm library installation here https://pypi.org/project/rpi-hardware-pwm (currently tested with v0.1.3).
MIN_TEMP (default: 40) - if the CPU temperature is below MIN_TEMP the fan will be completely off. At MIN_TEMP the fan speed will be set to FAN_LOW
MAX_TEMP (default: 70) - if the CPU temperature is above MAX_TEMP the fan will be set to the maximum speed. At MAX_TEMP the fan speed will be set to FAN_HIGH
FAN_LOW (default: 0) - fan low speed limit for mapping from MIN_TEMP to MAX_TEMP
FAN_HIGH (default: 100) - fan high speed limit for mapping from MIN_TEMP to MAX_TEMP
WAIT_TIME (default: 1) - read CPU temperature and adjust fan speed every WAIT_TIME seconds
PWM_FREQ (default: 10000) - PWM frequency to control the fan in Hertz
JSON (default: True) - write fan metrics to JSON file for monitoring
VERBOSE (default: False) - print fan metrics to console
systemd service unit is created for convenient autostart and management. Copy pwm-fan-control.service file to /etc/systemd/system directory and reload daemon with systemctl daemon-reload command. Then you will be able to do:
# systemctl enable/disable pwm-fan-control
# systemctl start/stop/restart pwm-fan-control
With the recommended default settings I got the following results (all numbers are average)
- Idle: CPU temperature is 53-54℃, fan speed is 42-45% with CPU utilization of 9-10% and Load Average of 0.55
- Stress test: CPU temperature is 64-65℃, fan speed is 80-83% under the max load (
stress --cpu 4 --timeout 300)
