When it comes to air quality monitoring, there are many different gases and parameters that are useful to monitor, and many different grades of sensors. However, all-in-one solutions can be very costly and are not typically portable. One of the strengths of IoT devices comes from the fact that lots of separate devices can work together to provide the data for a larger system. There are projects such as the World Air Quality Index project that democratizes air quality data on a global scale, but it is a coarse, city-to-city view of air quality. This project aims to provide a solution that can help provide people with a detailed picture of outdoor air quality in their area.

The solution we’re proposing is to create a small, low-cost, low-power IoT device that gives a user the flexibility to tailor their device to their area’s needs. The device will consist of a controller module and a sensor module. The controller module can be attached with various sensor modules, allowing a wide range of parameters to be monitored. It is equipped with a BLE transceiver for communicating the sensor information to the cloud, and it is equipped with a GPS receiver to allow the portable device to cover a large area. A strong magnet on the device lets it be placed on cars, buses, bikes, or buildings for collecting air quality data passively. The device collects data periodically, keeping track of the relative timestamp, its GPS location, and the data parameters from the connected sensor module. The user must use an Android application to harvest the data from the device via Bluetooth, which sends the data to a cloud database. The Android application can fetch the data from the database and present it as heatmaps and graphs, making the data available to everyone.

The system is powered by a 2000 mAh LiPo battery, giving the system an expected battery life of 24 hours. A BMS chip monitors and maintains the power levels of the circuit, and has a USB OTG connector to charge the primary battery and power the circuit. Any 5 V source can be connected to the device this way, allowing it to run indefinitely off of constant source (e.g. a wall adapter). A diagnostic LED is used to indicate battery life, and the BLE payload will contain a characteristic for tracking the battery charge. The module will be designed such that it is protected from overvoltage and undervoltage conditions.

Data from the sensor is collected periodically (every 5 minutes) by the controller, and stored to the onboard flash. The relative timestamp and the location are stored with this data acquisition. Once the Android application establishes a connection with the device, UART over BLE is used to transfer all the readings to the Android application. Once the data has been verified and successfully transfered to the database, the app will indicate to the device that all prior readings can now be deleted.

The novelty of this device is in its configurability; this would be the first device of its kind where the module is portable, but the sensors are configurable. By making the sensors modular, users can choose sensors based on cost and utility. The controller module is equipped with I2C, SPI and analog banks which allows it to interact with different sensor modules. The sensor modules can be for air-quality, water-quality and any future sensor clusters that can be added. The user has the ability use a controller module to monitor the parameters of their choosing.

Although the core functionality of the device is common, we have added some unique features to the design. Monitoring air quality in a big city would often imply having multiple devices. However, this portable design can be carried by everyone on their daily commutes and each module can cover a large area for data collection. This will allow fewer modules to cover a large section of the city. These modules added to city vehicles and public transit vehicles will allow a very reliable mapping for the air quality parameters using minimal units. In addition, by attaching a power bank or a wall adapter, the device could be fixed to a building or window and monitor data from a single area. In areas of the city where Wifi/LTE connections are not reliable due to low network connectivity or overcrowded channels, this device can store the collected data and transmit it to the database once the user’s phone has internet connectivity.

The main controller module consists of a 2-layer PCB with connectors to allow the sensor module to interface with the main controller module. The controller and sensor modules will be each enclosed in a small casing which will be 3D printed making it a small, portable and durable product. The overall cost of a unit is expected to be between 30 to 40 dollars. The sensor modules cost vary depending on which modules the user decide to add on. 

 

Inspiration

As a team we are very passionate about the technologies which can help protect the environment. Over the recent years we have come across several documentaries and research papers that highlighted the increasing levels of air pollution especially in cities like Beijing and Delhi. This competition inspired us to use our technical background to help overcome this problem. We have applied our passion for hardware and software development to come up with a configurable and interesting way to help control this problem.

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