The building-block (Lego) sensor is a hands-on teaching module that illustrates how light scattering can be used to detect particle pollution. It cannot detect atmospherically relevant levels of pollution.
The AirU package will be distributed to Salt Lake County schools, beginning in the Fall of 2017. AirU can measure relevant levels of particle and carbon monoxide pollution. It contains sensors for:
- Temperature and relative humidity with a DHT22 sensor from Aosong Electronics (DHT22). This is a digital-output relative humidity and temperature sensor.
- Pressure with a Bosch BMP180 (Datasheet). This is a digital pressure sensor that is based on piezo-resistive technology.
- CO and NO2 with a SGX Sensor Tech MiCS-4514 (Datasheet). This is a metal-oxide based sensor.
- GPS location with the Adafruit Ultimate GPS Module, based on the FGPMMOPA6H chip from GlobalTop Technology (Datasheet).
- Particulate matter (PM) with a Plantower PMS 3003 laser particle counter (Datasheet). It uses a fan to draw air through a chamber where it is exposed to a laser-induced light, and 90o scattered light is detected by a photo-diode detector. According to the manufacturer, it detects PM in the range of 0.3 um to 10 μm, and it has a 10-second response time. The sensor converts light scattering to PM1, PM2.5 and PM10 concentrations. We estimate the laser wavelength at approximately 650. See our paper evaluating the performance of this sensor.
The sensors listed above are integrated onto a custom printed-circuit board (PCB), which acts as a supplementary shield/cape for a BeagleBone Black, a low-cost, community-supported and Linux-based development platform for developers and hobbyists. Each AirU station currently supports two modes of operation, lab and field mode. The mode of the station can be set by toggling an operation mode switch between these two modes. Field mode automatically uploads data over the internet to our AirU web service. Lab mode can be used when an internet connection is unnecessary or difficult to acquire. In this mode of operation, air quality samples are written to a CSV file with a file name of the form "m-d-Y.csv". These files are stored on a microSD card inserted into the station.