RaspberryPi

Fan control

Script run a system service to control GPIO-connected active cooler (Fan PIN is 18):

/usr/local/bin/fan_control.py

#!/usr/bin/env python3
import os
import time
 
# GPIO setup
FAN_PIN = 18
 
def setup_gpio():
    # Export GPIO if not already exported
    if not os.path.exists(f'/sys/class/gpio/gpio{FAN_PIN}'):
        with open('/sys/class/gpio/export', 'w') as f:
            f.write(str(FAN_PIN))
    # Set direction
    with open(f'/sys/class/gpio/gpio{FAN_PIN}/direction', 'w') as f:
        f.write('out')
 
def get_cpu_temp():
    with open('/sys/class/thermal/thermal_zone0/temp', 'r') as f:
        return float(f.read()) / 1000.0 # temp is in milli Celsius
 
def set_fan_level(level):
    with open(f'/sys/class/gpio/gpio{FAN_PIN}/value', 'w') as f:
        f.write(str(level))
 
def main():
    setup_gpio()
    
    while True:
        temp = get_cpu_temp()
        
        if temp > 70:
            set_fan_level(4)
        elif temp > 50:
            set_fan_level(3)
        elif temp > 40:
            set_fan_level(2)
        else:
            set_fan_level(1)  
            
        time.sleep(5)
 
if __name__ == "__main__":
    try:
        main()
    except KeyboardInterrupt:
        set_fan_level(0)

[Unit]
Description=RPi Fan Control
After=multi-user.target
 
[Service]
Type=simple
ExecStart=/usr/local/bin/fan_control.py
Restart=always
User=root
 
[Install]
WantedBy=multi-user.target

sudo systemctl enable fan_control
sudo systemctl start fan_control

• Always keep the fan running at 25% (Level 1)
• Increase to 50% when temperature is 40-50°C (Level 2)
• Increase to 75% when temperature is 50-70°C (Level 3)
• Run at 100% when temperature is above 70°C (Level 4)

To stop:

sudo systemctl stop fan_control
echo "0" > /sys/class/gpio/gpio18/value