DreamMachineFan

A python script to control the fan of a Unifi Dream Machine SE depending on system temperature.

Disclaimer

Use on your own risk. This script will modify your Dream Machine's fan configuration. It will not set speeds not seen for existing firmware versions, but there are several assumptions which are not necessarily correct.

Introduction

Unifi's Dream Machine SE doesn't adjust fan speeds dynamically depending on board and other system temperatures. This results in high values being applied to cover worst case temperature scenarios.

This script will constantly monitor system temperature and adjust the speeds for fans 2-4 so a setpoint / target temperature is kept. The script uses a state of the art algorithm to adjust this speed - a PID controller. For more information see the Wikipedia article on https://en.wikipedia.org/wiki/PID_controller.

Instead of re-implementing a PID controller, this script uses simple-pid as published by Martin Lundberg https://github.com/m-lundberg/simple-pid - thanks a lot!

Installation

• Enable ssh for your Dream Machine and log in as root.
• To allow a full restore, memorize your Dream Machine's default fan value by entering cat /sys/class/hwmon/hwmon0/device/pwm2 on the command line; memorize the number shown (I will refer to this number as DEFAULTSPEEDMEMORIZED)
• Check if python3 is preinstalled by entering python3
• In case it isn't, install it using apt-get install python3
• Install Python dist utilities using apt-get install python3-distutils
• Install pip: curl "https://bootstrap.pypa.io/get-pip.py" > get-pip.py; python3 get-pip.py
• Install simple-pid: pip install simple-pid
• Finally, load the script dream_machine_fan.py as provided in this repository

Running the Script

Before running the script, open dream_machine_fan.py with your favorite editor and check the global definitions marked with # configure here. They allow you to adjust a number of values I have selected for my own system. As most of these follow assumptions (see Disclaimer), I want to comment on them here:

• target_temperature is the set point temperature the script will try to meet; I have entered 45 (degree Centigrade) although this value looks ridiculous low for a electronic system; values documentated as 'critical' by Unifi are by far higher
• sensors_temperature_tag select the temperature used to compare the current state against the set point; I use temp1: without any knowledge where it is measure and what its meaning is; alternatives are listed; according to what I have seen, all temperatures reported by Unifi's sensors tool are related and change in parallel; a safer approach would be to read all temps reported and use the max
• loop_seconds is part of the PID controller tuning which is made up from the number of iterations done for a certain time period (this value) and the three factors Kp, Ki, Kd set in the script using pid = PID(-1.0, -0.1, 0, setpoint=target_temperature); I haven't played a lot with these - someone with better knowledge of PID controllers and electronic hardware may find better tunings (thanks for feedback) for fans / temperatures; for me, these parameters stabilize fan speed after a few minutes
• min_pwm2 and max_pwm2 are the boundaries of fan (pwm2) values actually set; the script will never set fan speeds outside this range - so it is your insurance to keep this in a range you have seen in official firmware

O.k. so we are ready to test operation by entering

> python3 dream_machine_fan.py

This will start to spit out log entries that show the temperature and fan speed developement.

controlling DreamMachineSE fans 2-4 to keep temperature at 45.0°C
temperature is 45.8°C, setting fan to 89
temperature is 45.8°C, setting fan to 90
temperature is 46.0°C, keeping fan at 90
temperature is 45.8°C, setting fan to 91
temperature is 45.8°C, keeping fan at 91
temperature is 45.8°C, keeping fan at 91
temperature is 45.8°C, setting fan to 92
temperature is 46.0°C, keeping fan at 92
temperature is 46.0°C, setting fan to 93
temperature is 45.8°C, keeping fan at 93
temperature is 45.8°C, setting fan to 94
temperature is 46.0°C, keeping fan at 94
temperature is 45.8°C, setting fan to 95
...
temperature is 45.2°C, keeping fan at 118
temperature is 45.0°C, setting fan to 119
temperature is 45.0°C, setting fan to 118
temperature is 45.2°C, keeping fan at 118
temperature is 45.0°C, setting fan to 119
temperature is 45.0°C, setting fan to 118
temperature is 45.0°C, keeping fan at 118
temperature is 45.0°C, keeping fan at 118
temperature is 45.0°C, keeping fan at 118
temperature is 45.0°C, keeping fan at 118
temperature is 45.0°C, keeping fan at 118
temperature is 45.0°C, keeping fan at 118
temperature is 45.0°C, keeping fan at 118
temperature is 45.0°C, keeping fan at 118
temperature is 45.0°C, keeping fan at 118
temperature is 45.0°C, keeping fan at 118
...

I suggest to monitor what is happening for an hour. Once you see it is fine in your environment and converges towards the set point temperature, you can make the script a permanent background process.

To run the script permanenty, kill the test process and start a new one in background:

> python3 /root/dream_machine_fan.py >> /root/dream_machine_fan.log 2>&1 &
> disown

This will make the script run in background independent from our ssh session.

Next, we prepare the system to be restarted automatically when the Dream Machine is rebooted:

> crontab -e

Now, enter

@reboot python3 /root/dream_machine_fan.py >> /root/dream_machine_fan.log 2>&1 &

as a separate line, save and leave the editor.

The above commands will write to a log file all day. To limit storage space used, we use logrotate to create a daily backup for the last 7 days but purge everything beyond that:

> vim /etc/logrotate.d/dream_machine_fan 

Add the text

/root/dream_machine_fan.log {
  rotate 7
  daily
  compress
  missingok
  notifempty
}

and save / leave the editor.

NB: During firmware updates, crontab is wiped and needs to be re-edited. The script in root folder will not be touched, neither is /etc/logrotate.d/dream_machine_fan.

Uninstalling / Return to Factory Settings

That's straight forward:

• return to the default fan speed by entering echo DEFAULTSPEEDMEMORIZED > /sys/class/hwmon/hwmon0/device/pwm2 (see Installation section)
• stop the process and delete dream_machine_fan.py
• remove the crontab line added by after entering crontab -e again
• remove /etc/logrotate.d/dream_machine_fan