Wednesday, February 13, 2013

Mobile Device Sensors

I've been evaluating the sensors available for the various mobile devices and thought I'd document some of the highlights. Sensors are an interesting aspect of mobile devices because your mobile device, whether Android or iOS,  tablet or phone, solve the last mile communication problem of many sensors. Many sensors are very local in their communication distance capabilities, either tethered with a cable, or short range like the 50 meter Bluetooth Low Energy range. However, your mobile device can link a sensor to the Internet via your wireless cell phone carrier, or via your phones WiFi connection. Furthermore mobile devices provide the computing platform and user IO functionality for sensors. So with mobile devices you have the computational, communication and user IO covered, which allows for cost effective development of sensors and sensor applications. I'm interested in sensors for both end-user capabilities as well as APIs so I'll be sure to note any APIs.

For starters, similar to the my business model and technology idea list, here is a high-level overview of some of the sensors I've been finding. 

External Sensors

HiJack: More of a sensor development platform than a sensor itself, Hijack is a University of Michigan project that provides a general purpose hardware and software platform to build sensors using power and IO from the iPhone's 3.5mm iPhone audio jack. The hardware, pictured below, is a small board with an integrated headphone jack. The software API allows the creation of general purpose sensors. The hardware is available at Seeed Studio. Some demo project built on the platform include an EKG monitor and soil moisture sensor.

Node: A multipurpose sensor platform, which includes a hardware device, pictured, and an API. The hardware device is Bluetooth ( (BLE) enabled so sensor apps can be readily developed. The built in sensors include a gyroscope, magnetometer, and accelerometer. Additional sensors can be attached to the device. Current sensors include the Clima (Sensing barometric pressure, temperature, and humidity), Choma (a color scanner, paint matcher), Therma (temperature) and OXA (Carbon Monoxide gas sensor, with optional capabilities for NO, NO2, Cl2, SO2, and H2S). Presumably more sensors will be added to the platform.

Oscium Spectrum Analyzer: This is an enterprise-grade mobile RF analysis tool for iPhone and iPad which uses the 30-pin or Lightening connector. This is a $200 multi-purpose tool. While more of an end-user product than raw data sensor or development platform this is an impressive effort that shows the extent mobile devices will be leverage as generic computing platforms used for various in-field, sensor and Internet of Things projects. Thanks to Larry Gust, electrical engineer and leader in environmental sensitivity research for pointing this out to me.

EMF Sensor: Mr. Ghost, which successfully funded some production on Kickstarter last year, is a hardware antenna attachment and iOS app which measures elector magnetic radiation. It's not clear to what extent this is for fun or serious use, but it's an example of a new wave of sensors (ala Square credit card reader/scanner) that uses the 3.5mm iPhone audio jack for IO.

Built-in Sensors

And for the sake of a reference point, here are some of typical the built in sensors built into iOS and Android mobile devcies.
  • Proximity sensor: this is what de-activates the touchscreen when you move your phone up to your ear for a call. on iOS Apple provides limited API access to the proximity sensor, basically a true/false value if the device is close to the face.
  • Ambient light sensor: Apple uses this to adjust screen brightness depending on current environment. No API access on iOS.
  • Accelerometer: Measures acceleration changes in three dimensions and can be used to determine current orientation relative to the ground (i.e. portrait or landscape mode) and changes to orientation. API access is available in both Android and iOS.
  • Magnetometer: Used to measure compass direction. API available for Android and iOS.
  • Gyroscope: Measures rate of rotation around 3-axes. API available for iOS.

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