Raspberry 4/4B Fan Hat Manual

1. Use of script
First, you need to install his GPIO access library on the Raspberry Pi by accessing the system with SSH or opening a terminal:

cd /tmp

wget https://project-downloads.drogon.net/wiringpi-latest.deb sudo dpkg -i wiringpi-latest.deb

Waiting to download and install WireingPi:

sudo dpkg -i wiringpi-latest.deb

Check out Gpio:

gpio -v

2. Create a text document
Then create a text document in your home directory and copy the contents of fan.sh:

#!/bin/bash
#Define GPIO pin 18 as PWM
gpio -g mode 18 pwm
num=true
while [ $num ];
do
# Print CPU temp
temp=$(cat /sys/class/thermal/thermal_zone0/temp)
temp=$(($temp/1000))
clear
printf "Temperature: $tempºC\nTurning on fan."
# Variable temperature control
if [ $temp -gt 40 ] && [ $temp -lt 69 ];
then
vartemp=$(echo $[ temp * 13 ])
gpio -g pwm 18 $vartemp
# Maximum fan RPM
elif [ $temp -ge 69 ];
then
gpio -g pwm 18 1024
# Switch off the fan
else
gpio -g pwm 18 0
clear
printf "Temperature: $tempºC\nFan off."
sleep 60
fi
#Pause 1 second
sleep 1
done
exit 0

cd ~

nano fan.sh

Paste the script and save it with CTRL+X. When we exit the editor, we'll give the script execution permissions with:

sudo chmod +x fan.sh

Now the script is ready to be used. But we'll need run it manually every time the computer is started. To solve this we'll use a Linux daemon called Cron:

crontab -e

Paste the next line at the end of the file where there is no #:

@reboot /bin/bash /home/pi/fan.sh > /dev/null 2>&1

Save it with CTRL+X and exit.
Now the script is scheduled. To execute it we need to restart and it'll start running in the background.

sudo reboot

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