Date Added: Aug 2010
This paper researches the potential of a novel ball switch as a wearable vibration sensor for activity recognition. The ball switch is available as a commercial, off-the-shelf sensor and is unique among such sensors due to its miniaturized design and the low mass of the ball. The authors present a detailed analysis of the physical properties of the sensor as well as a recommendation for circuit design, sampling method and a feature generation algorithm for activity recognition. The analysis reveals that it is sensitive to vibrations between 1.5 kHz and 8 kHz, where the acceleration sensor is responsive below 1.6 kHz. Furthermore, the ball switch is substantially cheaper (3x), smaller (2x) and uses less power (50x) than an accelerometer based system, but delivers less information.