simple-fan.py

#!/susr/bin/python

# >>> THIS SCRIPT ONLY WORKS with a 5v 1.2Amp Fan <<<

# connect red lead to a 3.3v pin (e.g., physical pin 1 or 17)
# connect black lead to GPIOfan (e.g., physical pin 7, GPIO 4)

# on NEMS run
# $ sudo apt-get install python-rpi.gpio python3-rpi.gpio -y

#########################
#
# simple-fan turns a fan on and off when temperature exceeds temperature
# thresholds.
#
# The fan comes with a MiuZei case, and can run on 3.3V (low speed) or
# 5V (high speed). The fan can be plugged into either 3.3V or 5.5v GPIO
# pin and to a ground GPIO pin, but that means the fan will always run
# and that isn't very much fun. Any fan can be used as long it can operate
# at 3.3V
#
# run-fan was tested on a raspberry pi 3b+ running nems linux and kodi on OSMC
#
#########################

#########################
#
# simple-fan.py is based on:
#    https://stackoverflow.com/questions/41819683/how-can-i-control-a-fan-with-gpio-on-a-raspberry-pi-3-using-python
#
#########################

#########################
#
# simple-fan starts automatically using systemd
#
# Create a systemd service file using:
#   $ sudo nano /lib/systemd/system/simple-fan.service
#
# with the contents as shown below
# remove # and leading spaces:
#   [Unit]
#   Description=run fan when hot
#   After=meadiacenter.service
#
#   [Service]
#   # If User and Group are not specified as root, then it won't work
#   User=root
#   Group=root
#   Type=simple
#   ExecStart=/usr/bin/python /home/pi/simple-fan.py
# >>> Replace the following line: on OSMC or Raspberry Pi OS with Restart=on-failure instead of Restart=Always
#   Restart=Always
#
#   [Install]
#   WantedBy=multi-user.target
#
# end of the simple-fan.service
# ctrl-o, ENTER, ctrl-x to save and exit the nano editor
#
# After any changes to /lib/systemd/system/simple-fan.service:
#    sudo systemctl daemon-reload
#    sudo systemctl enable simple-fan.service
#    sudo reboot
#
# Ensure the run-fan.service in systemd is enabled and running:
#    systemctl list-unit-files | grep enabled | grep simple
#    systemctl | grep running | grep fan
#    systemctl status simple-fan.service -l
#
# If there are any issues with starting the script using systemd,
# then examine the journal using:
#    sudo journalctl -u simple-fan.service
#
#########################

import os
from time import sleep
import signal
import sys
import RPi.GPIO as GPIO

GPIOfan = 26
TurnOnTemp = 65.0

GPIO.setmode(GPIO.BCM)
GPIO.setup(GPIOfan, GPIO.OUT)

while True:     # Loop forever

    # Read the current temperature
    # osmc requires path
    res = os.popen('/opt/vc/bin/vcgencmd measure_temp').readline()
    # other OS's do not require path or may use different path
    # use $ which vcgencmd to find path
    # res = os.popen('vcgencmd measure_temp').readline()

    temp = float((res.replace("temp=","").replace("'C\n","")))

    # print 'Temperature from vcgencmd: {}'.format(temp)

    # Control the fan
    if temp > TurnOnTemp:
        # print 'Turning on fan = ' + str(GPIOfan)
        # The red fan pin is connected to 3.3V and the GPIOfan pin is the black pin on the fan
        # this doesn't seem to make any sense, but it works
        GPIO.output(GPIOfan, False)
    else:
        # print 'Turning off fan = ' + str(GPIOfan)
        GPIO.output(GPIOfan, True)

    # Wait before the next iteration

    sleep(10)