Pi Cooldown

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Adapted from Tim Etherington's guide.

Bash scripts for automatic & manual control of USB-powered fan on Raspberry Pi. Supported Raspberry Pi models:

• B+
• 2B
• 3B
• 3B+
• 4B

Table of Contents

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• Install
• Usage
  • Automatic Control
  • Manual Control
    • Turn ON
    • Turn OFF
  • Logs

Install

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The libusb-1.0 library is required for uhubctl (>=1.0.16 recommended)

sudo apt-get install libusb-1.0-0-dev

Install the uhubctl system package

sudo apt install uhubctl

Clone this repository & provide the scripts read and write privileges

git clone https://github.com/feram18/pi-cooldown.git
cd pi-cooldown
sudo chmod 755 cooldown.sh power.sh

Usage

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Firstly, you will need to figure out the hub you want to control according to the Raspberry Pi model you have. From uhubctl's documentation:

Raspberry Pi B+, 2B, 3B

• Single hub 1-1, ports 2-5 ganged, all controlled by port 2:

  uhubctl -l 1-1 -p 2 -a 0
  

  Trying to control ports 3,4,5 will not do anything. Port 1 controls power for Ethernet + WiFi.

Raspberry Pi 3B+

• Main hub 1-1, all 4 ports ganged, all controlled by port 2 (turns off secondary hub ports as well). Port 1 connects hub 1-1.1 below, ports 2 and 3 are wired outside, port 4 not wired.

  uhubctl -l 1-1 -p 2 -a 0
  

• Secondary hub 1-1.1 (daisy-chained to main): 3 ports, port 1 is used for Ethernet + WiFi, and ports 2 and 3 are wired outside.

Raspberry Pi 4B

⚠️ If your VL805 firmware is older than 00137ad (check with sudo rpi-eeprom-update), you have to update firmware to make power switching work on RPi 4B.

• USB2 hub 1, 1 port, only connects hub 1-1 below.

• USB2 hub 1-1, 4 ports ganged, dual to USB3 hub 2 below:

  uhubctl -l 1-1 -a 0
  

• USB3 hub 2, 4 ports ganged, dual to USB2 hub 1-1 above:

  uhubctl -l 2 -a 0
  

• USB2 hub 3, 1 port, OTG controller. Power switching is not supported.

Once you have figured out the hub you want to control. Edit the PORT variable on both the cooldown.sh and power.sh scripts. By default, it is set to 1-1. If you had to edit the default value, make sure to give the script privileges once again as previously demonstrated.

Automatic Control

The cooldown.sh script handles the automatic control. By creating a cron job, you can set the script to run automatically at a given rate.

sudo crontab -e

Get the path to your pi-cooldown directory and add the following line at the bottom of the file, so that the script runs every 5 minutes and determines if the fan should be turned on:

*/5 * * * * <path to your pi-cooldown directory>/cooldown.sh

Your line will look something like */5 * * * * /home/pi/pi-cooldown/cooldown.sh. You can also edit how frequent the script gets executed as you desire:

┌───────────── minute (0 - 59)
│ ┌───────────── hour (0 - 23)
│ │ ┌───────────── day of the month (1 - 31)
│ │ │ ┌───────────── month (1 - 12)
│ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday;
│ │ │ │ │                                      7 is also Sunday on some systems)
│ │ │ │ │
│ │ │ │ │
* * * * * <command to execute>

Manual Control

The power.sh script allows you to manually control the power state of the Raspberry Pi's hub, by providing the on or off argument accordingly.

Turn ON

~/pi-cooldown/power.sh on

Turn OFF

~/pi-cooldown/power.sh off

Logs

Both the cooldown.sh and power.sh write logs to the pi-cooldown.log file so you can keep track of the power state changes.