raspberry pi fan control

readme.md

place fan_control.service in /etc/systemd/system and then:

$ sudo systemctl enable fan_control
$ sudo systemctl start fan_control

fan_control.py

import wiringpi  
import time
from subprocess import PIPE, Popen

def init_fan():
    wiringpi.pwmSetMode(0) # PWM_MODE_MS = 0

    wiringpi.wiringPiSetupGpio()  

    wiringpi.pinMode(18, 2)      # pwm only works on GPIO port 18  

    wiringpi.pwmSetClock(6)  # this parameters correspond to 25kHz
    wiringpi.pwmSetRange(128)

def fan_set(percent):
    wiringpi.pwmWrite(18, int((percent/100.0)*128))


def get_cpu_temperature():
    """get cpu temperature using vcgencmd"""
    process = Popen(['vcgencmd', 'measure_temp'], stdout=PIPE)
    output, _error = process.communicate()
    return float(output[output.index(b'=') + 1:output.rindex(b"'")])

desired_temperature = 52.0

fan_speed = 100
sum = 0
p_temp = 15
i_temp = 0.4

def get_fan_speed(actual_temperature):
    global fan_speed,sum
    diff = actual_temperature - desired_temperature
    sum = sum + diff
    pDiff = diff * p_temp
    iDiff = sum * i_temp
    fan_speed = pDiff + iDiff
    if fan_speed > 100:
        fan_speed = 100
    if fan_speed < 10:
        fan_speed = 0
    if sum > 100:
        sum = 100
    if sum < -100:
        sum = -100
    return fan_speed

init_fan()

control = 0
while True:
    temp = get_cpu_temperature()
    control = get_fan_speed(temp)
    fan_set(control)

    # print(control, temp)
    time.sleep(1)

fan_control.service

[Unit]
Description=PWM fan control
After=network.target

[Service]
ExecStart=/usr/bin/python3 fan_control.py
WorkingDirectory=/home/pi/bin
StandardOutput=inherit
StandardError=inherit
Restart=always
User=root

[Install]
WantedBy=multi-user.target