It's time to think about how we'll assemble the components.
We decided to use polysterene because it's a really light material. We dug holes for each components to fit. You can see a photo above.
We are thinking about covering all this with fabric to hide the wires, and add a scratch to make it an armband.
We decided not to sold the arduino with the breadboard, so it won't be complicated if the card needs to be change. It happened to us, our computer didn't recognize the arduino pro micro anymore so we had to find a new one.
During this session, we tried both sensors (CO and O3) on a same circuit.
As the first test with the Arduino Leonardo went well last time, we decided to try on an Arduino pro micro. To connect both sensors we used a breadboard. You can see the circuit below:
For the code, we added some lines. We created a second variable for the O3 sensor. In the EEPROM memory, values from both sensors are alternating line by line.
The website above gives a worldwide air pollution map. You can compare the air quality index in different countries quickly. Our project is based on the same idea but on a smaller scale: people will be able to compare the air quality during their daily routine.
To have the pourcentage, you divide the level in ppm by 104 .
Below 200 ppm, there is no real danger but normally in a non polluted area, the CO level is around 0.2 ppm. As we can see, our air is already quite polluted.
We used the information in the previous log to understand the connections. We decided to try first on an Arduino Leonardo card, because on a nano it will be the same principle.
Here is a photo of the circuit we made:
Then, we wrote a code in the Arduino software. We put the code below:
This code give the quantity of CO in the air in ppm(parts per million) multiply by 100, every 100ms.
You need then to verify and compile the code on the Arduino. Take care to check if you are connected to the right type of board and in the right COM port. This is what we get:
We wanted to try then to take the measure every 30s, means every 30000ms.
We just had to chage the delay value (in ms).
There is about 1,35 ppm of CO in the air, in our classroom.
It worked really well!! We need now to choose at which frequency we want to have the measures.
First, we thought about using the wifi to obtain the position. It’s called wifi positioning system (WPS). After some researches we found out that it may be really complicated as we are totally novice in coding. Also, this solution is more adapted to indoor positioning. WPS is well explained on the website below:
So then, we had to think about a second solution. We thought about putting a gps on the Arduino card but that kind of device is relatively big. It wouldn’t be very convenient, because we still want to make a wristband and our components are already quite large. A GPS is also expensive, it’s not the best solution in our case.
Finally, we found out a Google function, that can be use in our case: the timeline in Google Maps. All you need is a google account. Google can track your mobile device during the day, and then give you all your positions at any time. By combining this timeline to the data collected with our device, people will have access to their personal daily air pollution exposure, simply and without any supplementary cost :).