SAFE - Safe Air For Everybody

This is the code repository for the SAFE project. This project was funded by the OpenPlant Biomaker Challenge 2019.

More information in our hackster webpage.

The code used to read values from the PM SDS011 sensor was originally based in this repository.

Configuration Instructions for Raspberry Pi (before first use)

1. Flashing the microSD

We followed the official instructions from Raspberry Pi. Specifically, we used balenaEtcher to flash Raspbian Buster with desktop and recommended software into a microSD card of 16GB.

2. Setting up Wifi

After being flashed, you should have a boot directory in the microSD, which you should be able to edit in your computer. Create a file named wpa_supplicant.confwith the network information for your raspberry pi to connect. Most of your networks should have this configuration (we were not able to connect to eduroam):

country=GB # Your 2-digit country code
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
network={
    ssid="NETWORK_NAME"
    psk="NETWORK_PASSWORD"
    key_mgmt=WPA-PSK
}

3. Enabling ssh

Instead of having a keyboard and monitor to work directly with your raspberry pi, you can enable ssh. That is achieved simply by creating an empty file in the boot directory named ssh

4. (Optional) Changing raspberry pi hostname

In order to connect multiple units to the same network, it's necessary to change their identification for network access.

You should also have a root directory (or a directory with a similar name) in the microSD. You should edit the files /etc/hostname and /etc/hosts, by changing raspberry to whatever name you wish.

Configuration instructions for the raspberry pi

1. SSHing into the unit

In Linux that's easily achieved in a terminal:

$ ssh pi@raspberrypi

The username/password is pi / raspberry by default, which you should change after.

2. Updating the unit

Just run the following commands after ssh'ing there:

$ sudo apt-get update
$ sudo apt-get upgrade

3. Downloading/configuring the actual code

This code will download/install the necessary packages and code.

$ sudo apt install git-core python-serial python-enum lighttpd
$ sudo apt-get install screen
$ sudo chown pi:pi /var/www/html/ 
$ cd /var/www/html/
$ git clone https://github.com/tjiagoM/safe-biomaker-challenge.git
$ cd safe-biomaker-challenge/
$ chmod +x run_sensor.py
$ chmod +x sleep_sensor.py
$ mkdir /var/www/html/logs

4. Defining configuration variables

From the previous terminal, you will be in the folder where the main python script (run_sensor.py) will be executed. Two important variables which you might consider changing are:

• LOGS_LOCATION: Where the reading logs will be stored
• RASPBERRY_NAME: The identification/name of the raspberry pi unit where the code will be run. This is important because when the file is created to save the sensor's readings, it will use this name
• TIMESTEP: How many seconds for each reading. By default the script will read every 30 seconds

Running it!

We recommend running screen in the unit's terminal before executing any code so you can leave the code running without the need of always being connected to it. To leave the screen just do CTRL+D and to open the screen again run screen -r in the terminal next time you ssh.

Reading from the sensor

You just need to execute the run_sensor.py script. You can specify the name of the experiment so the file name with the logs will be easier to identify:

$ ./run_sensor.py EXPERIMENT_NAME

Stopping the sensor

When the sensor is connected to raspberry pi, its fan will be working. You can completely stop the sensor by running:

$ ./sleep_sensor.py

Webviewer

If you followed the previous instructions, you can check the sensor readings with a simple webviewer (also originally based from this repository). If your computer/laptop is connected to the same network as your raspberry pi, you just need to open a browser and go to http://raspberrypi_location/safe-biomaker-challenge. There, you will be able to see the values being read from the sensor, as well as the respective AQI value for each.

There are a few files which you should be aware of in order to understand how this done.

• run_sensor.py: The script will have a variable named JSON_FILE_LOCATION which is the location of a json object in disk. New readings will be dumped to this object, and the script will keep the size to 10.
• index.html: You have a call to setInterval(), in which the second argument should be smaller then the rate of readings in run_sensor.py in order to keep up with new readings.
• aqi.js: In this Javascript file the Json object is read from disk, then the AQI values are calculated and updated in the HTML page.