Published January 5, 2020 © GPL3+

Temperature Controlled Fan for Raspberry Pi

Keep your Pi cool by having it turn on a fan whenever it gets hot.

IntermediateFull instructions provided2 hours11,113

Temperature Controlled Fan for Raspberry Pi

Things used in this project

Hardware components

Raspberry Pi 3 Model B

I'm using a Model 3 B+, but any Pi will do - Just adjust your case choice to the model you have

General Purpose Transistor NPN

40 mm Fan

Any 40 mm 5 volt fan will work. There are plenty of choices out there depending on the connector you want. Mine is similar to these

Software apps and online services

Fritzing App

Used for wiring diagram

Makerbot Thingiverse

Find a custom case for Raspberry Pi

puTTY SSH Client

Used to remote into the Raspberry Pi to the command line.

RPi-GPIO

Needed for your python code to interact with the RPi pins

Hand tools and fabrication machines

3D Printer (generic)

I used my trusty printrbot Simple Metal to fabricate my case. Sadly printrbot is no longer in business.

Soldering Station, Hobbyist

Story

I have a Raspberry Pi (RPi) dedicated to controlling my 3D printer using OctoPrint (https://octoprint.org/). Since printing can sometimes run for hours, I wanted some active cooling on my pi, but only when the RPi exceeds a set temp.

I found this article some time ago for inspiration:

https://hackernoon.com/how-to-control-a-fan-to-cool-the-cpu-of-your-raspberrypi-3313b6e7f92c

Recently, I finally had a few minutes to actually wire it up and deploy the code to my printer computer. One problem with waiting: the Raspbian OS of the RPi has evolved, so the code from the post I was referencing needed to be rewritten.

I also found that the original code tended to cycle the fan too often. One way to avoid this is to change the time between temperature checks from 5 seconds to something more. I chose instead to add a temperature range, so the fan would cool the computer to a lower temp and then wait for a higher temp to turn back on (in my case 38C and 42C instead of a single temp of 40C).

The other thing I had to change was the method for auto-running the script on startup. The official OS for the Raspberry Pi is Raspbian which is based on Debian Linux. Debian seems to have deprecated the method in the article, so I went with this method: https://www.dexterindustries.com/howto/run-a-program-on-your-raspberry-pi-at-startup/#systemd. I'll lay it all out below.

Hardware Setup

The Raspberry Pi has 40 pins that can be used to interface to other hardware.

Source: https://www.raspberrypi.org/documentation/usage/gpio/images/gpio-numbers-pi2.png

I've used three of these for this project:

5v power
Ground
Pin 18

The wiring is pretty simple. In the diagram below, the motor represents the fan. The fan I used has a red and black wire, so I hooked the red wire to a 5v pin of the RPi and the black wire one of the outside legs of the NPN transistor. The other outside leg is connected to the RPi ground and the center leg to the RPi control pin. I used 18, but you can use any of them—just make sure your code references the correct one.

Don't connect a real motor to your Raspberry Pi - it is shown for wiring reference only

Software

The Raspberry Pi was originally created to teach kids software development, so Raspbian comes with full Python support. In addition, there is a great python library called RPi-GPIO which allows your python program to interact with the on-board pins

There are many ways to get the code onto the RPi. You can wire up the pi to it's own keyboard and monitor, or you can, as I do, remote into it using either an SSH client to work in the command line (I use puTTY) or a VNC client to remote into the GUI. There are config settings that need to be enabled on the RPi for remote access: SSH or VNC

Pick a place to save the file. I already had a /scripts directory in my /home/pi user directory so I put it there.

Copy the run-fan.py code below
Switch to your chosen directory
Create a file on your RPi by typing nano run-fan.py This will open the nano text editor with a blank file.

Right-click to paste the code into the editor and adjust the four variables to match your setup:

pin = 18
maxTMP = 42
minTMP = 38
sleepTime = 5

Press Ctrl+X, Y, Enter to save your file.
Test the code by running

python3 ./run-fan.py

If you already have your hardware wired up, you should start seeing your fan cycle on/off. For testing purposes, if you uncomment this line, the program will print the temp readings to the screen:

# print("temp is {0}".format(temp)) # uncomment for testing

Auto-run the Script

Once your wiring and script work well together, you can configure the script to run at startup. As mentioned earlier, I chose to use the SYSTEMD method from this website

Start by creating a new file on you RPi by typing

sudo nano /lib/systemd/system/runfan.service

The system will prompt you for your password so you can make a change in the system directory.

In the file, copy and paste the runfan.service code and save the file. Make sure the ExecStart line references the location of your run-fan.py file

Once you have saved the file, change the permission on the file by typing:

sudo chmod 644 /lib/systemd/system/runfan.service

Then type:

sudo systemctl daemon-reload
sudo systemctl enable runfan.service

And finally, reboot the pi:

sudo reboot

After the RPi reboots, the script should be running and the fan is now controlled based on CPU temp

Final Assembly

I chose to keep the assembly simple. I soldered some header pin connectors on the transistor and used the pin connectors on the fan to complete the wiring. This makes it easy for me to remove the cover on the RPi without worrying about permanent connections. I then used shrink tubing to cover the solder joints.

Two quick solder connections. The third leg will take the black lead from the fan using the supplied pin connector

I modified the case from the original design. The hole above the fan is for a future shut-down switch and status led

I chose to attach the transistor to the fan with a bit of hot glue. All that was left was to connect the three wires to the correct pins on the Raspberry Pi and snap the cover in place. A quick reboot and now the RPi stays nice and cool!

Thanks for reading! Next up will be to finally wire up the shutdown switch and led indicator light,

Schematics

Code

#!/usr/bin/env python3

# adapted from Edoardo Paolo Scalafiotti <edoardo849@gmail.com>
# https://hackernoon.com/how-to-control-a-fan-to-cool-the-cpu-of-your-raspberrypi-3313b6e7f92c

from time import sleep
import subprocess
import RPi.GPIO as GPIO

# Adjust these settings for your environment
pin = 18
maxTMP = 42
minTMP = 38
sleepTime = 5

def setup():
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(pin, GPIO.OUT)
    GPIO.setwarnings(False)
    return()

def getCPUtemperature():
    res=subprocess.check_output(['vcgencmd', 'measure_temp']).decode("utf-8")
    temp = (res.replace("temp=","").replace("'C\n",""))
    # print("temp is {0}".format(temp)) - uncomment for testing
    return temp

def fanON():
    setPin(True)
    return()
def fanOFF():
    setPin(False)
    return()
def getTEMP():
    CPU_temp = float(getCPUtemperature())
    if CPU_temp>maxTMP:
        fanON()
    elif CPU_temp<minTMP:
        fanOFF()
    return()
def setPin(mode):
    GPIO.output(pin, mode)
    return()

try:
    setup() 
    while True:
        getTEMP()
        sleep(sleepTime)
except KeyboardInterrupt: # trap a CTRL+C keyboard interrupt. Not needed for autorun but good for testing 
    GPIO.cleanup() # resets all GPIO ports used by this program

Credits

Tom Kintop

2 projects • 7 followers

Too many projects, so little time.

Temperature Controlled Fan for Raspberry Pi

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Hardware Setup

Software

Auto-run the Script

Final Assembly

Custom parts and enclosures

Raspberry Pi 3 B+ Fan Enclosure

Schematics

Basic Wiring

Code

run-fan.py Code

runfan.system

Credits

Tom Kintop

Comments

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Temperature Controlled Fan for Raspberry Pi

Temperature Controlled Fan for Raspberry Pi

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Hardware Setup

Software

Auto-run the Script

Final Assembly

Custom parts and enclosures

Raspberry Pi 3 B+ Fan Enclosure

Schematics

Basic Wiring

Code

run-fan.py Code

runfan.system

Credits

Tom Kintop

Comments

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