pi-temperature-logger is a collection of scripts used to turn a raspberry pi into a LAN accessible temperature logger. This is a very hacked-together proof-of-concept and should not be confused with a "proper" project.
You will need:
- Raspberry pi (any recent model)
- 8GB or larger Micro SD card burned with the OS of your choice (Raspbian recommended)
- Adafruit MCP9808 I2C module. Product page
- Wires to connect the two
- (optional) Headers for both the pi and the module to make connecting easier
The following guide is for the Raspberry Pi Zero-W, but should be more or less the same for other models.
First write the operating system image of your choice on the micro SD card to be used with the raspberry pi.
Before putting that card into the slot and booting it you will need to do 2 things:
Connect the SD card to another computer, a boot drive should be mounted.
In the root of this drive, create a blank file called ssh.
touch /volumes/boot ssh
This simply tells the Raspberry Pi operating system to allow incoming SSH connections
On the same boot partition you will need to create a file called wpa_supplicant.conf
touch /volumes/boot wpa_supplicant.conf
The content of this file will tell the raspberry pi which network(s) to connect to. There are a number of different options to include in this file, but it is recommended that you use the one included in this repo as it can be very finicky to get working correctly.
You should now be able to connect to the pi with SSH over WiFi, but first you will have to find it! Either log in to your router, look at the connected devices or use the handy Fing app for android phones to scan your network for connected devices.
Once you know the IP address, write it/save it/commit it to memory then SSH in with the usual command:
ssh pi@xxx.xxx.xx.xx
If you are using a mac, or have the
bonjour serviceinstalled on your computer, you should be able to useHOSTNAME.localinstead of the IP (where HOSTNAME is the actual name assigned to your pi).
The password will be raspberry. You should change this using the passwd command.
Run the update and upgrade commands to...update and upgrade everything:
sudo apt update
then:
sudo apt full-upgrade
Using full-upgrade ensures that apt will bring in all dependencies.
Before we install the necessary libraries, connect the following togther either by soldering or by using headers and jumper wire:
| Sensor Pin Name | Pi Pin Name | Pi Pin Number |
|---|---|---|
| Vdd | 3v3 | 1 |
| Gnd | Gnd | 9 (or 6) |
| SCL | SCL | 5 |
| SDA | SDA | 3 |
This project relies on libraries from the ever-helpful Adafruit company — specifically the circuitpython and circuitpython-mcp9808 libraries.
It's probably easiest to follow their guides:
circuitpython installation guide
To make the information accessible in-browser from any device on the same network as the pi, we're going to turn it into a webserver.
All we need to do is install Apache and PHP 7:
sudo apt install apache2
sudo apt install php libapache2-mod-php
Test this by putting a php file in /var/www/html and using a browser on another device to go to your pi's IP address.
Assuming everything has installed properly, (and you haven't already tested everything as in the guides above) it's time to test everything.
First, place all python files in a folder called python your home directory, then:
python3 ~/Documents/python/blinkatest.py
You should get some positive stuff in the terminal.
python3 ~/Documents/python/mcp9808-test.py
The terminal will print the temperature once a second.
Now it's time to actually "install" the code and get it working.
Get all the files from the html directory and put them in /var/www/html.
In html/raw you will see two files: temp_current.txt and temp_log_1.csv. these are used to store data generated by the temperature sensor before it's read by the web interface. They should both be blank, unless you are migrating over old data.
This project uses the open source dygraphs.js library to display a graph of the data. Please visit the Dygraphs homepage for more information about this great project.
Simply place the temp-log-single.py file in the ~/Documents/python directory.
Run this file once using
python3 ~/Documents/python/temp-log-single.py
You will not get any visual feedback but if you navigate to /var/www/html/raw and open the temp_log_1.csv file you should see a (new) line with the current temperature and a timestamp of the time that you ran the command above.
This is what actually ensures that the pi will log the temperature at a regular interval. We need to set a cron job.
In the terminal type:
crontab -e
The window will now show a lot of lines of commented instructions. At then end of these instructions add a new line:
*/5 * * * * /home/pi/Documents/python/temp-log-single.py
Check the path used. If you've changed the hostname of your pi, you will need to reflect that change here.
The line above tells the OS to run the python file once every 5 minutes, you can of course edit this to be more or less frequent.
Everything should now be installed and running. Even if the pi reboots, the cron task will ensure that the pi still logs the temperature.
To view the current temperature, ensure your device is connected to the same network and simply point your browser to the pi. You will see the current temperature and a graph of previous measurements.
Please be aware that if you have literally just installed everything there may be no data yet to display.