# This script is to control a fan via PWM signal on GPIO14. I have a MOSFET acting as a low side switch connected to this pin It measures the temperature, and if it corosses a set limit turns on the fan. The fan speed will be relative to temperature Once the temperature goes down fan will be turned off, it also logs it to a local influx DB

cpuFanControl.py

#!/usr/bin/env python
#~/.local/bin/cpuFanControl.py

#################################################################################
# This script is to control a fan via PWM signal on GPIO14
# I have a MOSFET acting as a low side switch connected to this pin
# It measures the temperature, and if it corosses a set limit turns on the fan
# The fan speed will be relative to temperature
# Once the temperature goes down fan will be turned off
# it also logs it to a local influx DB
#################################################################################


import RPi.GPIO as GPIO
from gpiozero import CPUTemperature
from time import sleep, time
import requests
import psutil



fanControlPin = 14
tempThreshold = 75
maxFanTemp = tempThreshold * 0.9
minFanTemp = 50
minDutyCycle = 50
maxDutyCycle = 100

GPIO.setmode(GPIO.BCM)
GPIO.setup(fanControlPin, GPIO.OUT)
GPIO.output(fanControlPin, 0)
#setup 100Hz PWM
pwmHandle = GPIO.PWM(fanControlPin, 100)
cpu = CPUTemperature()
fanRunning = False

while True:
    temp = cpu.temperature
    if temp >= maxFanTemp : delta = maxDutyCycle
    elif temp < minFanTemp : delta = 0
    else:
        delta = (temp-minFanTemp) / (maxFanTemp - minFanTemp) * 100
        #map 0-100 to min to max duty cycle
        delta = delta * (maxDutyCycle- minDutyCycle) / 100 + minDutyCycle
    if delta >= minDutyCycle:
        if not(fanRunning):
            pwmHandle.start(1)
            fanRunning = True
        pwmHandle.ChangeDutyCycle(delta)
    elif fanRunning:
        pwmHandle.stop()
        fanRunning = False
    sleep(60)
    requests.post('http://localhost:8086/write?db=raspi_data&rp=one_month',  "raspi_cpu,host=raspberrypi4 cpu_temp={0},fan_dc={1},cpu_load={2}".format(temp,delta,psutil.cpu_percent()).encode())
pwmHandle.stop()
GPIO.cleanup()