A Performance Analysis System for the Sport of Bowling

2.3 SENSING REQUIREMENTS
The module must be able to sense when the ball is released, when it hits the lane, when it
hits the pins, and the ball's angular velocity as it rolls down the lane. The module must
be able to accurately sense the passage of time, and to record time-stamped samples of
the light waveform and of the impacts the ball experiences. It also must be able to sense
the presence of the communication device and contain a transceiver of some type so that
the module can transfer information to/from the MASTER application.
The ease-of-use, size, cost, and power consumption criteria, combined with locating the
module underneath a finger insert, limit the types of sensors that the module can employ.
2.3.1 Sensing Rotation of the Ball (Angular Velocity)
Several methods have been considered to directly sense the rotation (angular velocity) of
the ball using passive techniques (measuring some response to ambient conditions):
• Sensing the changing orientation of the ball in the earth's magnetic field.
• Sensing the changing orientation of the ball in the earth's gravitational field.
• Measuring the angular acceleration directly with an accelerometer.
• Measuring the ambient light falling on a fixed point on the ball.
Honeywell makes an integrated two-axis magnetometer (HMC1052) that physically fits
the application, but the cost ($18) and peak current draw (~400 mAmps) are both
prohibitive [17]. Analog Devices makes a dual-axis tilt sensor/accelerometer
(ADXL202E) that also fits the application, both in size and power requirement, but its
cost (~$15 in 1000 piece quantities) makes it too expensive for this application, although
it could be used for a later upscale version of the module [15].
The main thrust of the research for this project centers on the fourth, albeit less obvious,
alternative. Besides presenting the feasibility of the in-situ sensor module, this paper
demonstrates that a photometric sensor placed at the bottom of a finger hole, underneath
a finger insert, can be used to accurately sense the angular velocity of the ball.
TAOS (Texas Advanced Optical Systems) makes a series of small, inexpensive, lowpower,
integrated visible light detectors (TSL25x) that suit the application [23]. In
addition, the same light sensor can also be used to detect the moment of release (indicated
by a sudden transition from dark-to-light), and serve as the receiver for an IR-based
wireless communications scheme. Refer to Figure 2-1 for the orientation of the light
sensor in relation to the finger insert.
An increasing light level is seen as the finger hole revolves up to face the ceiling, while a
decreasing light level is sensed as the finger hole revolves toward the lane. Peaks in the
light waveform occur at the top of each revolution (defined as the orientation of the ball
when the finger holes are facing toward the ceiling), and valleys occur at the bottom of
each revolution (defined as the orientation of the ball when the finger holes are closest to
the lane). In developing the light-sensor based module, it was the author's belief that the
ambient light level the sensor "sees" as the ball rotates would roughly transcribe a
sinusoidal shape, and that the sampled and digitized light waveform could be stored,
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