Following this you’ll be able to using a transistor to draw 5V current into the fan’s motor. Then you’ll write a Python script to . Finally, you’ll be able to . tutorial assemble a fan activate the fan when the CPU reaches a certain temperature run the script automatically at boot time Scope I use the latest 3 for a lot of things. Plex is one one of them. The RPI3 is very fast in indexing all my media files but it struggles in transcoding .mkv files: it works well but the movie has frequent interruptions, which is not a great user experience. Fortunately, Plex has the built-in converter that enables free .mp4 to browser streaming. To do that in the background, the CPU reaches 380% and the temperature increases greatly over 80C. So I thought: time to add some cooling. RaspBerryPi Hardware setup First things first: I have bought on Amazon. All the fans that I’ve seen are DC 5V with a maximum of 200mA: therefore the active power is 1W. However, the GPIO pins on the pi can only deliver 3.3V with a maximum of 16mA each: we cannot — and should not — feed the motor with the pin’s power. Huston, we have a problem (?). this fan What we need is some sort of that can be activated by a standard pin to draw current at full throttle to our fan. Meet the . More specifically, an (S8050). The final setup is the following (the , this is a real DC motor): relay transistor NPN Transistor fan is represented as a DC motor NOT The Breadboard The Schematic Do not, EVER, connect a real DC motor to your board: you’ll definitely damage it. My finalhacky solution Once everything is setup, it’s time for the software part. Software setup Create a file called “run-fan.py” in a custom location (mine is in ~/Development/run-fan.py) and copy-paste the following code: #!/usr/bin/env python3# Author: Edoardo Paolo Scalafiotti edoardo849@gmail.com import osfrom time import sleepimport signalimport sysimport RPi.GPIO as GPIO pin = 18 # The pin ID, edit here to change itmaxTMP = 40 # The maximum temperature in Celsius after which we trigger the fan def setup():GPIO.setmode(GPIO.BCM)GPIO.setup(pin, GPIO.OUT)GPIO.setwarnings(False)return() def getCPUtemperature():res = os.popen(‘vcgencmd measure_temp’).readline()temp =(res.replace(“temp=”,””).replace(“’C\n”,””))#print(“temp is {0}”.format(temp)) #Uncomment here for testingreturn tempdef fanON():setPin(True)return()def fanOFF():setPin(False)return()def getTEMP():CPU_temp = float(getCPUtemperature())if CPU_temp>maxTMP:fanON()else:fanOFF()return()def setPin(mode): # A little redundant function but useful if you want to add loggingGPIO.output(pin, mode)return() try:setup()while True:getTEMP()sleep(5) # Read the temperature every 5 sec, increase or decrease this limit if you wantexcept KeyboardInterrupt: # trap a CTRL+C keyboard interruptGPIO.cleanup() # resets all GPIO ports used by this program Ok, now let’s test it from the console: python run-fan.py If everything was setup correctly you should see your fan spinning and stopping accordingly to the CPU temp. Cool. One more thing… Obviously we don’t want to manually run the program each time we reboot the pi, won’t we? We want everything to be loaded at startup, right? Then let’s create a boot script in /etc/init.d simply called “fan”: nano /etc/init.d/fan …and copy-paste in it the following code: #!/bin/sh### BEGIN INIT INFO# Provides: dnscheck# Required-Start: $remote_fs $syslog# Required-Stop: $remote_fs $syslog# Short-Description: Start fan script at boot time# Description: Enable service provided by daemon.### END INIT INFO python /home/pi/Development/run-fan.py …then create the symbolic links by running: update-rc.d /etc/init.d/dnscheck defaults …and next time you’ll reboot your pi, your fan script will run automatically.
