Temperature-Controlled-USB-Fan

A BME280 temperature sensor triggers a relay that turns on a fan and also sends temperature, pressure and humidity data to an Influx DB server. The data is then available through Grafana.

Requirements

Software

• Python 3 (Should be installed by default on Raspbian - How to install)
• Python 3 smbus2 package sudo pip install smbus2
• Python 3 bme280 package sudo pip install RPi.bme280
• Python 3 RPi.GPIO package sudo pip install RPi.GPIO
• InfluxDB - Instructions
• Grafana - Grafana download website (follow the Ubuntu and Debian instructions depending on your OS architecture)
• Tested on Raspbian/Raspberry Pi OS Stretch/Buster/Bullseye (Debian 9/10/11)

Hardware

• Raspberry Pi
• BME280 Sensor
• 1 Channel 5V Relay (Something like this)
• 5V fan
• If you plan on using a 5V USB fan you also need a USB female to motherboard header (something like this)
• Breadboard

Wiring scheme

Wiring is fairly straight-forward.

General

1. Connect PIN 2 (5V) and PIN 6 (GND) to two of the breadboard's power rails
2. Connect USB VDC to 5V power rail
3. Connect USB GND to opposite GND power rail (not the one you connected the wires in the first step)

BME280

1. 3.3V - PIN 1
2. GND - you can use the main one on the breadboard (not the one that goes to the USB plug)
3. SDA - PIN 3
4. SCL - PIN 5

Relay

1. Connect PIN7 to any wiring rail and from there to the SIGNAL PIN on the relay (you can also use a direct connection)
2. Connect + PIN on the relay to 5V power rail
3. Connect - PIN on the relay to GND power rail
4. Connect NO to the power rail you used for USB GND
5. Connect COM to the GND power rail
6. Connect NC to any unused wiring rail

LEDs

Red

1. Connect the anode of the LED to the wire coming out of NC
2. Use a 220Ω resistor (150Ω or 100Ω are fine too) to avoid frying the LED. Connect one side to the cathode and the other on the 5V power rail

Green

1. Connect the anode of the LED to the secondary GND power rail (the one used for USB GND)
2. Use a 220Ω resistor (150Ω or 100Ω are fine too) to avoid frying the LED. Connect one side to the cathode and the other on the 5V power rail

Usage

You simply need to create a new InfluxDB database, run the python script and configure Grafana.

Check your sensor's address

1. Enable I2C via sudo raspi-config - Interfacing options > I2C > Yes > Reboot if needed
2. Use the command i2cdetect -y 1 - You should see a number, usually 77 or 76 for this sensor
3. If you don't have i2cdetect install i2c-tools sudo apt update && sudo apt install i2c-tools
4. If your sensor doesn't show up check your connections. If it still doesn't show up you might have a dead sensor

Configuring InfluxDB

1. Open the InfluxDB CLI influx
2. Create a new database CREATE DATABASE “choose-a-db-name"

Configuring the script

1. Create a directory and CD into it
2. Download sensor.py in this folder
3. Edit it using nano or any other text editor nano sensor.py
4. Change your sensor address in line 9
5. Change your database parameters in line 19
6. Save and exit

Running the script manually

1. Execute the script python3 sensor.py
2. The script should print temperature, pressure and humidity values
3. Use CTRL+C to terminate it
4. OPTIONAL: you can run it to save a log file python3 -u sensor.py > ./SomeFile.txt or ignore all output python3 sensor.py &> /dev/null - You can also use screen to hide the output (sudo apt update && sudo apt install screen && screen press enter and write your command. You can use CTRL+A+D to detach from your screen session and screen -r to resume it)

Using the autostart with logging

1. Download the sensorLog.sh script in the same directory of the python file
2. Make it executable chmod +x sensorLog.sh
3. Execute it

Please note that the log file is erased every time you start this script.

Using the silent autostart

1. Download the sensor.sh script in the same directory of the python file
2. Make it executable chmod +x sensor.sh
3. Execute it

Using crontab to automatically start this script at boot time

1. Edit your user's crontab (don't forget to edit the path to match your system settings - also if you want to save a log file make sure that the user you're editing the crontab is allowed to write to the script folder): crontab -e
2. Add one of the following, depending on your setup:

• If using the logging start script sensorLog.sh:
  @reboot /path/to/your/sensorLog.sh
• If using the silent start script sensor.sh:
  @reboot /path/to/your/sensor.sh
• Or you can execute the python script directly (not tested but should work fine - not logging version):
  @reboot python3 path/to/your/sensor.py >& /dev/null
• Or you can execute the python script directly (not tested but should work fine - logging version):
  @reboot python3 path/to/your/sensor.py > /path/to/log.txt 2>&1

Creating a Grafana dashboard

1. Point your browser to http://<your-raspberrypi-ip>:3000 - default user admin/admin - you will be asked to set a new password
2. Click on "Add Data Source", then on "Influx DB" and finally write your database name, database URL and make sure that the query language is InfluxQL
3. Click on "Save and Test" to test your configuration and save it
4. On the left sidebar, click on Dashboard, then New Dashboard
5. You can add a graph or any other element by using the "Add a New Panel" button in the top right corner of the web page
6. Hover your mouse on the ghrap's title and choose "Edit":

• In the "General" tab you can change the title
• In the "Metrics" tab you can change the data shown by the graph:
  • Select Influx DB as Data Source
  • Click on the "select measurement" field in the query and choose sensors_data
  • Click on the "field(value)" field in the query and choose the data you want to show - You can choose between temperature, pessure and humidity
• In the "Axes" tab you can change the measurement unit - data will be converted automatically
• In the "Legend" tab you can hide or show the legend
• In the "Display" tab you can define how data will be shown

7. Repeat from 5 for every measurement
8. To change dashboard name go to Settings -> Name, specify the name you want, then click on Save Dashboard -> Save
9. Profit!

Thank you

I originally made this project to cool down my ADSB fan but some of my friends were interested so I uploaded all needed stuff here and wrote this how-to guide. I don't know much about electronics so I tried making this circuit as easy as possible. Suggestions are welcome.