-> NO2: NO2-B43F, Alphasense
-> Particulate Matter (pm10, pm2.5): PPD42NS, Shiney
-> Temperature and Humidity: AM2303 (aka DHT22).
Out of Shelf Boards
-> Main board: Arduino Uno R3
-> Wireless communication: nodeMCU1.0 (12E Module)
-> Arduino shield: it's the interface between the main board and the wifi module. It has the debugging leds. It's the physical support for the power and sensors data lines.
-> Sensor board: it includes an ADS1115 (adc 16bit...the resolution anyhow it's 15bit) to read the NO2 sensor and it's used to bring the data of the Dust sensor.
-> Power board: it generates the 5V, main domain of the whole system.
Why did we use out-of-shelf boards?
Because the kit need to be as much simple as possible. These products perfectly fit the modular solution we adapted and it was a matter of time....we produced 16 kits. A further reason is the possibility to take apart the different parts and re-use it. The kits are only in a prototype phase so their future is not certain.
Why do you need the wall adapter and it's not portable?
Current consumption! the wifi module can reach peak of 350mA in transmission mode, we are sending data every minute, a battery would last few hours....
the code has been written in Arduino IDE v1.6.9
The sketches are two:
1- for Arduino Uno: it's the data logger, it collects the data from the sensors. The loop is so divided: 30seconds are dedicated to the NO2 measurement and the 30seconds are dedicated to the dust sensor. Every minute the package with all the information is sent to the wifi module.
2- for the NodeMCU: it receives the package data from the main board, it creates the payload and it send it to the server. the code also manage the network configuration set-up of the kit. To connect the kit to the internet network, indeed, it's not necessary to change and upload the code, this process is based on the possibility of the esp8266 chip to become a local server and by the WifiManager arduino library.
The messaging protocol is MQTT, publish-subscribe-based.
The boards needed to be enclosed in a Dutch weather proof case, it means that need to survive under stressful conditions of strong wind and rain. The case is completely done using parts supplied by an hardware local store.
The Bora Kit has been developed for Making Sense project (http://making-sense.eu/), European Union’s Horizon 2020 research and innovation program. In details the kit was employed during the first pilot study in Amsterdam, Urban AirQ project.
During the pilot the sensor kit was provided to a community of interest, a group of citizens who lives around an high traffic congested area of Amsterdam. The citizens could measure NO2 and Dust concentration.
The data could be real time visualized on a temporary online page, but the final results will be released during the next weeks. This is due to the fact that the data need to be analysed and interpolate with other parameters and factors that, in this case, were provided by the professional and official measurement station that are around the city and managed by local government.
The data and the calibration process will be also made open and shared with the final results.
What is the next?
We would like to get rid of the wifi limitation and improve the portability of the kit. For the second pilot, indeed, we are developing the comunication using the new and emerging LoraWAN technology. We also want to use the smartcitizen.me platform for a friendly-adaptable and charming visualization of the data.