We want to setp up an automatic, GPIO and temp controlled fan using a Raspberry Pi without additinal software. After the CPU Core temperature exceeds a specific temperature, the fan starts spinning. Needed: Raspberry Pi (Model B+) ( ) Buy Fan (4-Pin, 12V) in this case from an old NVIDIA Graphicscard Pinboard GPIO Connector wires (3x) ( ) Buy Transistor BC337–40 800mA ( ) Buy Resistor 1 kΩ 0.5W ( ) Buy These hyperlinks are just recommended. You can use similar parts. Helpful Links: GPIO Pinout 4-Pin Fan Wireing (pcbheaven.com) 4-Pin Fan Wireing (allpinouts.org) Plan We connect directly to the fan. will be connected over the Transistor with the 2nd fan wire. Pin 4 (5V out) Pin 6 (Ground) To activate the Transistor, we need a low volatage, which we gain by . The GPIO Pins have a standard voltage of 3.3V. We reduce this by inserting the Resistor. Pin 3 (GPIO2) Result If we now switch on Pin 3 (GPIO2), the fan should start to spinn. Enable GPIO2: (root) echo ”2”>/sys/class/gpio/exportecho ”out”>/sys/class/gpio/gpio2/direction Switch on GPIO Pin / Fan (root) echo ”1”>/sys/class/gpio/gpio2/value Switch off GPIO Pin / Fan (root) echo “0”>/sys/class/gpio/gpio2/value Set up autmoatic temp control In the following, we will set up the fan so that it starts after reaching a special temperature. We log into the Raspberry Pi as root. Prinzip: The Raspberry Pi autmoaticly checks the core temperature throught the built-in control panel. If the temperature exceeds a certain value, the fan will start. As long as the temp doesn’t fall below our value, the fan will not stop. apt-get update && apt-get upgradeapt-get install nano Now we locate our directory of the script… mkdir /home/fancd /home/fan …and create our script. nano fan.sh Copy the following content into the script: (Use right mouse button to paste) #!/bin/shtimestamp() {date +”%Y-%m-%d %T”}LOGDIR=”/var/log/fan.log” VALUE=42 TEMP=`vcgencmd measure_temp | cut -c6,7`STATUS=`cat /sys/class/gpio/gpio2/value`echo `timestamp` ” Info: Temperature: $TEMP”>>$LOGDIRif [ $TEMP -ge $VALUE ] && [ $STATUS -eq 0 ]thenecho `timestamp` ” Warning: Fan started.”>>$LOGDIRecho ”1”>/sys/class/gpio/gpio2/valueelif [ $TEMP -le $VALUE ] && [ $STATUS -eq 1 ]thenecho `timestamp` ” Warning: Fan stopped.”>>$LOGDIRecho ”0”>/sys/class/gpio/gpio2/valuefi To change the value, you have to edit line 6. To let the script run in background, we need `cronjob`. crontab -e and paste the following content: * * * * * /home/fan/./fan.sh (repalce with your path) The script ist now automaticly executed at every minute.
