The script turns a fan on and off when temperature exceeds thresholds.

the temperature is aquired by a MCP3008 ADC connected on the raspberry SPI Interface (MCP3008 Adafruit library needed); the sensor configured in the script is a 10KOhm NTC with Beta=3950 and pull-up resistor of 12K, but can be changed; the fan is controlled by one of the Raspberry GPIO pin (pin 25 by default);

If a 12V fan is used, it should be driven by a NPN transistor (eg: 2N2222) connected as follows:

• emitter: connects to Raspberry GND and power supply GND
• base: connects to 110 Ohm Resistor. The other pin of resistor to GPIO pin 25
• collector: connects to fan GND
• fan red (+): connects to external 12V power supply

If other type of fan are used, the BJT can drive a 12V relè

The scripts write on/off and exception events on a log file

The original script is from: Source: https://github.com/dumbo25/rpi-fan/blob/master/run-fan.py

You can start automatically the script using systemd

Create a systemd service file using:

$ sudo nano /lib/systemd/system/run-fan.service

with the contents as shown below (remove # and leading spaces):

[Unit]

Description=run fan when hot

After=meadiacenter.service

[Service]

User=root

Group=root

Type=simple

ExecStart=/usr/bin/python /home/pi/run-fan.py #Insert real path of the script!!

Restart=Always

[Install]

WantedBy=multi-user.target

ctrl-o, ENTER, ctrl-x to save and exit the nano editor After any changes to /lib/systemd/system/run-fan.service:

sudo systemctl daemon-reload

sudo systemctl enable run-fan.service

sudo reboot

Ensure the run-fan.service in systemd is enabled and running:

systemctl list-unit-files | grep enabled

systemctl | grep running | grep fan

systemctl status run-fan.service -l

If there are any issues with starting the script using systemd, then examine the journal using:

sudo journalctl -u run-fan.service