Pi Fan

I build "embedded" systems based on the Raspberry Pi. For heat dissipation, these systems have a fan. This little program checks the temperature of the Raspberry Pi and turns on a fan connected on a GPIO port.

Here is an example of such a system: AllStar Node I am also using this program for the ParachuteMobile APRS iGate. You can also check that my blog on this little project.

Dependencies

The program fan does not require any dependencies besides the RPi.GPIO library to access the GPIO pins on your board. If you are using an image made for the Raspberry Pi it comes pre-installed. In case you still need to install it here are the instructions.

Installing the GPIO library on any Debian based distro

First, you need to update the available package versions:

 $ sudo apt-get update

Then install the RPi.GPIO package:

 $ sudo apt-get install rpi.gpio

If it is already installed it will be upgraded if a newer version is available. If it is not already installed it will be installed.

GPIO Library installation on Allstar distro from hamvoip

The Allstar distribution built by hamvoip doesn't provide the GPIO library. Also, at the time I am writing these lines hamvoip uses an older ArchLinux distro with an old GPIO library. Therefore the best way to have GPIO library in good working condition is to install it from the sources. Don't worry, it is not that hard.

The version of the GPIO library used in the following lines is the version 0.7.0. In your installation, you should use the latest version.

From your shell, prompt here are the command to use

 # cd /tmp

 # wget https://pypi.python.org/packages/source/R/RPi.GPIO/RPi.GPIO-0.7.0.tar.gz

 # tar xzvf RPi.GPIO-0.7.0.tar.gz

 # cd RPi.GPIO-0.7.0/

 # python ./setup.py install

Installation

To install the program fan and the service just run the install script.

 $ sudo install.sh

This will install and run the service. The next time you boot your the system, the fan service will be automatically started.

Typical installation's output

$ sudo install.sh
Installing fan.py
Installing the fan service
Starting the service
* fan.service - Fan Service
   Loaded: loaded (/usr/lib/systemd/system/fan.service; static; vendor preset: disabled)
   Active: active (running) since Sun 2019-07-28 10:38:16 PDT; 2s ago
 Main PID: 9771 (fan)
    Tasks: 1 (limit: 512)
   CGroup: /system.slice/fan.service
           `-9771 /usr/bin/python /usr/local/bin/fan

Jul 28 10:38:16 echostar systemd[1]: Started Fan Service.
Jul 28 10:38:16 echostar fan[9771]: 10:38:16 INFO: GPIO pin(26) configured

Manual installation

To install the program fan just copy the file fan.py from this directory to /usr/local/bin/fan. Then make sure that file is executable.

$ sudo cp fan.py /usr/local/bin/fan
$ sudo chmod a+x /usr/local/bin/fan

Running

To start fan at boot time. You need to install the fan service. Copy the file fan.service into the directory /lib/systemd/system, then inform systemd that it needs to run that service.

$ systemctl enable fan.service

Configuration.

By default, pifan will use the GPIO pin 26 and the temperature threshold for turning on and off the fan is 42 degC (107 degF). You can change these values by creating a pifan configuration file in /etc/fan.conf

Here is an example of this configuration file:

[FAN]
thermal_file: /sys/class/thermal/thermal_zone0/temp
pin: 26
sleep: 31
threshold: 42.0

Example

Debug output of the program fan running.

11:29:46 INFO: GPIO pin(26) configured
11:29:46 WARNING: Temperature: 41.86
11:29:46 INFO: Fan(26) -> OFF
11:30:17 WARNING: Temperature: 41.86
11:30:48 WARNING: Temperature: 42.93
11:30:48 INFO: Fan(26) -> ON
11:31:19 WARNING: Temperature: 42.93
11:31:50 WARNING: Temperature: 42.39
11:32:21 WARNING: Temperature: 41.86
11:32:21 INFO: Fan(26) -> OFF
11:32:52 WARNING: Temperature: 41.86
11:33:23 WARNING: Temperature: 42.39
11:33:23 INFO: Fan(26) -> ON
11:33:54 WARNING: Temperature: 41.86
11:33:54 INFO: Fan(26) -> OFF
11:34:25 WARNING: Temperature: 42.93
11:34:25 INFO: Fan(26) -> ON
11:34:56 WARNING: Temperature: 41.86
11:34:56 INFO: Fan(26) -> OFF
11:35:28 WARNING: Temperature: 42.39
11:35:28 INFO: Fan(26) -> ON
11:35:59 WARNING: Temperature: 42.93
11:36:30 WARNING: Temperature: 41.86
11:36:30 INFO: Fan(26) -> OFF

0x9900 / pifan