Low Energy Air Quality Sensor Continued

In ITP, Networked Sensors for Development

Hub, Manxue and I decided to stick with our low energy air quality sensor we presented in Week 5 (please refer to this link for an outline of the problem, how to put together a breadboard arduino and the results of our energy efficiency tests). We saw an opportunity to go beyond an excersize on conserving battery life and to think about how this device could potentially aid organizations in combatting illnesses associated with breathing in solid fuels. That meant adding a data piece for organizations, in addition to the visual feedback provided directly to the people in their homes, as well as wireless data transferring and local storage for each node and hub. In short, each node in peoples’ homes would notify them when there was poor air quality but would also send that home’s air quality data to a central hub at regular intervals for the interested organizations to catalog. As a plan B, if radio communication were to fail, we would add SD card storage to both the nodes and all hubs. This system is described by Manxue’s illustration below.


system diagram


In the additional two weeks we had to work on the circuit after we presented, we were able to improve the logic of the circuit, add a voltage divider to detect low battery levels, add and SD card to store data locally and an RFM radio to transmit the data at a given interval. We were able to get the SD card and the RFM radio to work at different times, and had them working together for a short moment, however, I believe there was an issue with the soldering on the RFM breakout which resulted in very unreliable behavior. I also think that the extra noise associated to having two devices sharing the SPI pins (Mosi, Miso, Clk, Cs) contributed to the problem. As a result, we never got the system running as reliably as we wanted but I ordered new RFM Moteino breakouts from Low Power Labs to provide more stability on that front. Here is the circuit below along with a fritzing diagram.




circuit v2_bb


Lastly, here is the code below for reference.




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