Adding fan control buttons to the system page on a Pi5 with a GPIO controlled fan

[chvvkumar]

Wanted to document my steps to get system page buttons working to control a 12v GPIO Fan connected through a relay which is on GPIO21. Not sure if this is the right way but this is how I got it working using pinctrl.

Prerequisites

Allsky camera software installed
Raspberry Pi 5 with GPIO fan connected to pin 21
Root/sudo access to the Pi

Directory Structure

/home/pi/fan_control/
├── fan_on.sh                  # Turn fan ON script
├── fan_off.sh                 # Turn fan OFF script
├── fan_status.sh              # Manual status update script
├── cron_status_update.sh      # Automatic status updater (cron job)
├── fan_status.txt             # Status data file
└── fan_buttons.txt            # Button configuration file

File Contents

1. Fan ON Script (/home/pi/fan_control/fan_on.sh)

#!/bin/bash
# Fan ON script for Raspberry Pi 5
GPIO_PIN=21

# Set GPIO as output and set to HIGH using sudo
sudo pinctrl set $GPIO_PIN op dh

if [ $? -eq 0 ]; then
    # Update status file
    printf "data\t0\tFan Status\t<span style='color: green; font-weight: bold;'>ON</span>\n" > /home/pi/fan_control/fan_status.txt
    echo "Fan turned ON"
    exit 0
else
    echo "Error: Failed to turn fan ON"
    exit 1
fi

2. Fan OFF Script (/home/pi/fan_control/fan_off.sh)

#!/bin/bash
# Fan OFF script for Raspberry Pi 5
GPIO_PIN=21

# Set GPIO as output and set to LOW using sudo
sudo pinctrl set $GPIO_PIN op dl

if [ $? -eq 0 ]; then
    # Update status file
    printf "data\t0\tFan Status\t<span style='color: red; font-weight: bold;'>OFF</span>\n" > /home/pi/fan_control/fan_status.txt
    echo "Fan turned OFF"
    exit 0
else
    echo "Error: Failed to turn fan OFF"
    exit 1
fi

3. Manual Status Update Script (/home/pi/fan_control/fan_status.sh)

#!/bin/bash
# Fan status script for Raspberry Pi 5
GPIO_PIN=21

# Get GPIO status using sudo
STATUS_OUTPUT=$(sudo pinctrl get $GPIO_PIN 2>/dev/null)
EXIT_CODE=$?

if [ $EXIT_CODE -eq 0 ]; then
    # Check if output contains "hi" (high/on) or "lo" (low/off)
    if echo "$STATUS_OUTPUT" | grep -q "| hi"; then
        printf "data\t0\tFan Status\t<span style='color: green; font-weight: bold;'>ON</span>\n" > /home/pi/fan_control/fan_status.txt
        echo "Status updated: Fan is ON"
    elif echo "$STATUS_OUTPUT" | grep -q "| lo"; then
        printf "data\t0\tFan Status\t<span style='color: red; font-weight: bold;'>OFF</span>\n" > /home/pi/fan_control/fan_status.txt
        echo "Status updated: Fan is OFF"
    else
        printf "data\t0\tFan Status\t<span style='color: orange;'>Unknown</span>\n" > /home/pi/fan_control/fan_status.txt
        echo "Status unknown"
    fi
else
    printf "data\t0\tFan Status\t<span style='color: red;'>Error reading GPIO</span>\n" > /home/pi/fan_control/fan_status.txt
    echo "Error reading GPIO status"
fi

4. Automatic Status Updater script - Cron for job (/home/pi/fan_control/cron_status_update.sh)

#!/bin/bash
# Cron-based fan status updater
GPIO_PIN=21
STATUS_FILE="/home/pi/fan_control/fan_status.txt"

STATUS_OUTPUT=$(pinctrl get $GPIO_PIN 2>/dev/null)
EXIT_CODE=$? 
TIMESTAMP=$(date '+%H:%M:%S')

if [ $EXIT_CODE -eq 0 ]; then
    if echo "$STATUS_OUTPUT" | grep -q "| hi"; then
        printf "data\t0\tFan Status\t<span style='color: green; font-weight: bold;'>ON</span> <small>Auto: $TIMESTAMP</small>\n" > "$STATUS_FILE"
    elif echo "$STATUS_OUTPUT" | grep -q "| lo"; then
        printf "data\t0\tFan Status\t<span style='color: red; font-weight: bold;'>OFF</span> <small>Auto: $TIMESTAMP</small>\n" > "$STATUS_FILE"
    else
        printf "data\t0\tFan Status\t<span style='color: orange;'>Unknown</span> <small>Auto: $TIMESTAMP</small>\n" > "$STATUS_FILE"
    fi
else
    printf "data\t0\tFan Status\t<span style='color: red;'>GPIO Error</span> <small>Auto: $TIMESTAMP</small>\n" > "$STATUS_FILE"
fi

# Optional: Log to file for debugging
echo "$(date '+%Y-%m-%d %H:%M:%S'): Status updated automatically" >> /tmp/fan_cron.log

5. Initial Status Data File (/home/pi/fan_control/fan_status.txt)
   data 0 Fan Status <span style='color: orange;'>Unknown</span>

6. Button Configuration File (/home/pi/fan_control/fan_buttons.txt)

# Type	Message			Command					Color	FA icon	Button Label
button	Fan turned ON		/home/pi/fan_control/fan_on.sh		green	play	Fan ON
button	Fan turned OFF		/home/pi/fan_control/fan_off.sh		red	stop	Fan OFF
button	-			/home/pi/fan_control/fan_status.sh	blue	refresh	Update Status

Setup Commands

1. Create Directory and Files

mkdir -p /home/pi/fan_control
cd /home/pi/fan_control

2. Set Permissions

# Make scripts executable
chmod +x /home/pi/fan_control/*.sh

# Set proper ownership and permissions
sudo chown -R pi:www-data /home/pi/fan_control/
sudo chmod -R 755 /home/pi/fan_control/
sudo chmod 664 /home/pi/fan_control/fan_status.txt

3. Add www-data to GPIO Group
   sudo usermod -a -G gpio www-data

4. Configure Sudo Permissions
   sudo visudo -f /etc/sudoers.d/fan_control

Add these lines to the file:

www-data ALL=(ALL) NOPASSWD: /home/pi/fan_control/fan_on.sh
www-data ALL=(ALL) NOPASSWD: /home/pi/fan_control/fan_off.sh
www-data ALL=(ALL) NOPASSWD: /home/pi/fan_control/fan_status.sh
www-data ALL=(ALL) NOPASSWD: /usr/bin/pinctrl

5. Fix Sudo File Permissions
   sudo chmod 440 /etc/sudoers.d/fan_control

6. Configure Allsky System Page Additions
   In the Allsky WebUI, go to Allsky Settings
   Set System Page Additions setting to:
   /home/pi/fan_control/fan_status.txt:/home/pi/fan_control/fan_buttons.txt

Automatic Status Monitoring script Setup

1. Make the Cron Script Executable
   chmod +x /home/pi/fan_control/cron_status_update.sh
2. Test the Cron Script

# Test the script manually
/home/pi/fan_control/cron_status_update.sh
cat /home/pi/fan_control/fan_status.txt

3. Add to Crontab
   (crontab -l 2>/dev/null; echo "* * * * * /home/pi/fan_control/cron_status_update.sh") | crontab -
4. Verify Cron Job Installation
   crontab -l
5. Restart Allky (I restarted the Pi, just to be sure)

Testing

Command Line Testing

# Test as regular user
/home/pi/fan_control/fan_on.sh
/home/pi/fan_control/fan_status.sh
/home/pi/fan_control/fan_off.sh

# Test as www-data user
sudo -u www-data /home/pi/fan_control/fan_on.sh
sudo -u www-data /home/pi/fan_control/fan_status.sh
sudo -u www-data /home/pi/fan_control/fan_off.sh

# Check status file updates
cat /home/pi/fan_control/fan_status.txt

GPIO Testing

pinctrl get 21           # Check current status
pinctrl set 21 op dh     # Set high (ON)
pinctrl get 21           # Should show "hi"
pinctrl set 21 op dl     # Set low (OFF)
pinctrl get 21           # Should show "lo"

Troubleshooting

Verify Sudo Configuration, All files should show "parsed OK"
udo visudo -c

Check Group Membership

groups www-data
# Should include: www-data gpio

Debug GPIO Access

sudo -u www-data pinctrl get 21
# Should return GPIO status without errors

Check File Permissions

ls -la /home/pi/fan_control/
# Scripts should be executable, status file writable by www-data

[Astro-Stuff]

I did something similar a while ago. Starting/stopping the fan from a button as well as automatically based on the temperature.
I set up different fan speeds based on the temp.

[Alex-developer]

Nice, thanks for documenting that.

I m not sure if you are aware but there is a module that can control. fan based upon temperature. In the next release this cN LSO BE PWM Controlled

[chvvkumar]

Nice, thanks for documenting that.

I m not sure if you are aware but there is a module that can control. fan based upon temperature. In the next release this cN LSO BE PWM Controlled

I do already use that module (Control Allsky Fans)! But this is to manually over ride the state. I also plan to add buttons for manually overriding heater control, too but need to figure out the layout and formatting first. Shouldn't be too hard as most of it is almost exactly the same as the fan control with just the GPIO being a different pin.

[Michal198569]

I just wanted to ask – will this also work with the Power over Ethernet HAT (C) – PoE power supply and 802.3af/at network – for Raspberry Pi 3B+ / 4B? It seems unnecessary to me for the fan to run constantly. By the way, I didn’t even know that such a module existed. 😊

[chvvkumar]

I just wanted to ask – will this also work with the Power over Ethernet HAT (C) – PoE power supply and 802.3af/at network – for Raspberry Pi 3B+ / 4B? It seems unnecessary to me for the fan to run constantly. By the way, I didn’t even know that such a module existed. 😊

If the fan is controlled by GPIO, I don't see why it won't. But I would leave that fan on as the PoE hat does get warm. If you still want to control the speed, try this too:

raspberrypi/linux#2715 (comment)

[EricClaeys]

@chvvkumar,
In the cron job, use EXIT_CODE=$?
after your if [[ $? -ne 0 ]]
Check is looking at the "date" command's return code.

[chvvkumar]

Nice catch! Fixed it by capturing the exit code immediately after the STATUS_OUTPUT=$(pinctrl get $GPIO_PIN 2>/dev/null) command.