system-scripts/fanctl.py

#!/usr/bin/python3

import os

servo = 18

if true: # set to false to skip using dotenv
    from dotenv import load_dotenv
    load_dotenv()
    servo = int(os.getenv('FANCTL_SERVO_PIN'))

import RPi.GPIO as IO
import time
import subprocess


IO.setwarnings(False)
IO.setmode (IO.BCM)
IO.setup(servo,IO.OUT)
fan = IO.PWM(servo,2000)
fan.start(0)

def get_temp():
    output = subprocess.run(['/opt/vc/bin/vcgencmd', 'measure_temp'], capture_output=True)
    temp_str = output.stdout.decode()
    try:
        return float(temp_str.split('=')[1].split('\'')[0])
    except (IndexError, ValueError):
        raise RuntimeError('Could not get temperature')

def set_speed(fan, speed):
    fan.ChangeDutyCycle(speed)

while 1:
    temp = get_temp()                   # Get the current CPU temperature
    if temp > 60:                       # Check temperature threshhold, in degrees celcius
        set_speed(fan, 100)             # Set fan duty based on temperature, 100 is max speed and 0 is min speed or off.
    elif temp > 50:
        set_speed(fan, 85)
    elif temp > 40:
        set_speed(fan, 60)
    elif temp > 35:
        set_speed(fan, 50)
    elif temp > 32:
        set_speed(fan, 45)
    elif temp > 25:
        set_speed(fan, 40)
    else:
        set_speed(fan, 0)
    time.sleep(5)                       # Sleep for 5 seconds