It's been a while! We have been hard at work for the past several months. As we keep progressing with the development of our HealthCity project, we thought it would be a good idea to look back at what we've achieved until now. Our focus is designing an Internet of Things (IoT) platform for the city. However, designing and developing IoT-based services require a more human-centric approach to prevent it from being purely technology driven evolution and hence succumbing to inflated expectations and impractical concepts.
For the HealthCity project, We aim for transparency and sustainability, allowing citizens to interpret their everyday environment and react to changes in air quality - information and understanding is a key parameter in changing behaviours. But we have much more planned, more on that later!
Since January, we have been steadily pushing out new prototypes of increasing fidelity and complexity. Our first focus was on the solar-charging circuit and the GSM communication. We quickly prototyped mount and circuit for a 3.5W solar panel and ABS enclosure.
This was in January - the month with the least hours of sun per day in Denmark. However, it worked well and we started expanding to a series of acrylic prototypes, each with a different setup and sensors, e.g. particle matter sensor, NO2, CO, temperature, humidity, pressure, rain etc.
Since then, the first acrylic prototype has hit over 20.000 measurements, averaging a little less than 10 minutes between each measurement 24/7 using solar power solely!
Meanwhile, we have developed an RESTful API with WebSockets on AWS, which scales based on the number of probes currently active, backend traffic, visitors on the website and the amount of incoming data from the probes. To help visualise the historical data, we set out to mockup a live, singlepage website that visualised data as it arrived from our prototype sensorprobes. This creates a nice correlation between number of probes active, the time of the year and the scale of our backend. In order to retrieve data quick from a ever-increasing dataset, we have implemented a Redis-based cache for popular queries and recent sensor data.
Iterative Product Development
Since we developed the initial prototypes, which have been out in the field for almost half a year, we have started to focus our development efforts on the design of our probes. Our initial prototypes has been built using ABS enclosures and later, custom-made acrylic enclosures, but we wanted to develop something different, an beautifully designed enclosure that did not need to be hidden away, but were also designed to fit the hardware footprint and not be an overly sized ABS box. In parallel development sprints, we developed the initial hardware and designed the initial probe, which can be seen below. A main enclosure for communication technology, the microcontroller, charging circuit and battery. A connector for the solar panel is located in the bottom. The acrylic cylindrical shape is a modular sensor encasing.
However, the design itself presented some challenges, as it still took up a fair amount of space and the rectangular shape did present visual obstacles, when mounted on a lamp post. It also required a more complex injection mold for the concave curve. We began a new iteration, still focused on the modularity and inspired by simplistic, geometric shapes.
We will reveal more details on this in our upcoming post!