This is a PWM driven fan based on the core temperature. It was originally designed for my MediaCenter that ran on my overclocked RPi Model B (the very first model)
I recently needed something like this for my RPi Model 3 B+, so I looked it up again.
Here is the original post : https://www.raspberrypi.org/forums/viewtopic.php?f=35&t=62438&p=463458
Even after all the changes with Raspbian, 6 years later it still works.
The code posted in the forum works, but there is a more clever way to get the temperature reading without having to put it in a file, and then read it out again for processing. I now also use Python 3.5.
I'm using a small 5V fan. I like the Noctua NF-A4x10 5V, it is very quiet does not consume a lot of power and I'm using it for all my RPi Model 3's.
If you like what you see, please support me by buying me a coffee: https://www.buymeacoffee.com/M9ouLVXBdw
Here is the latest version that I'm using at the moment:
#!/usr/bin/python3
#-------------------------------------------------------------------------------
# Name: run_fan.py
# Purpose: use PWM to run a fan to keep the core temperature in check
#
# Author: Paul Versteeg
#
# Created: 01-12-2013, modified june 2019
# Copyright: (c) Paul 2013, 2019
# Licence: <your licence>
#-------------------------------------------------------------------------------
import RPi.GPIO as GPIO
from time import sleep
import subprocess
import shlex
import string
import sys, os
import traceback
DEBUG = True
FAN_PIN = 4 # GPIO 4
GPIO.setwarnings(False) # when everything is working you could turn warnings off
GPIO.setmode(GPIO.BCM) # choose BCM numbering scheme.
GPIO.setup(FAN_PIN, GPIO.OUT)# set GPIO port as output driver for the Fan
Fan = GPIO.PWM(FAN_PIN, 100) # create object Fan for PWM on port 22 at 100 Hertz
Fan.start(0) # start Fan on 0 percent duty cycle (off)
delay = 30 # seconds of delay, testing the core every 30 seconds is OK
cool_baseline = 60 # start cooling from this temp in Celcius onwards
pwm_baseline = 40 # lowest PWM to keep the fan running
factor = 3 # multiplication factor
max_pwm = 100 # maximum PWM value
fan_running = False # helps to kick-start the fan
def main():
global fan_running
'''
This program controls a Fan by using PWM.
The Fan will probably not work below 40% dutycycle, so that is the
fan PWM baseline. The maximum PWM cannot be more than 100%.
When the cpu temperature is above 50 'C, we will start to cool.
When the cpu reaches 70 degrees, we would like to run the fan at max speed.
To make the PWM related to the temperature, strip the actual temp from the
cool baseline, multiply the delta with 3 and add that to the the baseline
PWM to get 100% at 70 degrees.
I have selected a PWM frequency of 100Hz to avoid high frequency noise, but
you can change that.
'''
try:
while True:
# get the core temperature
# need to use the full path otherwise root cannot find it
cmd = "/opt/vc/bin/vcgencmd measure_temp"
args = shlex.split(cmd)
output, error = subprocess.Popen(args, stdout = subprocess.PIPE, \
stderr= subprocess.PIPE).communicate()
# strip the temperature out of the returned string
# the returned string is in the form : b"temp=43.9'C\n"
# if your localization is set to US, you get the temp in Fahrenheit,
# so you need to adapt the stripping somewhat
#
core_temp = float(output[5:9]) # for Celcius
if DEBUG : print (core_temp)
if core_temp < cool_baseline :
Fan.ChangeDutyCycle(0) # turn Fan off
fan_running = False
if core_temp > cool_baseline :
if fan_running :
duty_cycle = ((core_temp - cool_baseline)*factor)+pwm_baseline
if duty_cycle > max_pwm : duty_cycle = max_pwm # max = 100%
else:
# kick-start the fan for one cycle
duty_cycle = 70
fan_running = True
Fan.ChangeDutyCycle(duty_cycle) # output the pwm
if DEBUG : ("pwm {:.2f}".format(duty_cycle))
sleep(delay)
# the following will allow you to kill the program
except KeyboardInterrupt:
Fan.stop() # stop the PWM output
GPIO.cleanup() # clean up GPIO on CTRL+C exit()
except Exception as e:
sys.stderr.write("Got exception: %s" % e)
if DEBUG :
print(traceback.format_exc())
print("GPIO.cleanup")
GPIO.output(FAN_PIN, GPIO.LOW)
GPIO.cleanup(FAN_PIN) # leave the other pins alone
os._exit(1)
if __name__ == '__main__':
main()
Enjoy!
