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Copyright © Parallax Inc. Trackball Module (#27908) v1.0 4/8/2010 Page 1 of 3
Trackball Module (#27908)
Add a fun human interface component to your Propeller microcontroller projects with the Trackball
Module from Parallax! Similar to the trackball found on many smart phones, this sensor is easily portable
and can be used to replace a mouse in many applications. The Trackball Module comes with a built-in
center select switch and a red LED, which can be programmed to light up the trackball when desired.
Features
y
Built-in center select switch and red LED
y Detects movement in the up, down, left, right, and
diagonal directions
y 8-pin DIP module is ready for breadboard or
through-hole projects
y Built-in 1 kΩ series resistors for compatibility with
the Propeller microcontroller and other 3.3 V devices
Key Specifications
y
Power requirements: 5 VDC
y Communication: Four-pin variable-frequency binary
signaling output (for trackball)
y Operating temperature: 32 to 158 °F (0 to +70 °C)
y Dimensions: 1.0 x 1.0 x 0.67 in
(25.4 x 25.4 x 17.08 mm)
Application Ideas
y
Mouse replacement
y Video game input
Device Information
Theory of Operation
The Trackball Module has four tiny rotatable magnets attached to each corner of the component.
Rotating the Trackball Module in the up, down, left, or right directions will result in the rotation of one
magnet, while any diagonal movement will result in the rotation of two magnets.
Whenever any of the magnets rotate, a tiny magnetic field is created, which can be detected by a Hall
Effect sensor paired with each magnet. The Hall Effect sensor will then output a series of high/low signals
which can be monitored by the Propeller microcontroller to determine the direction of movement of the
trackball. The speed of rotation is then proportional to the period of the pulse, where slow rotation will
result in a longer period and faster rotation will result in a shorter period.
Note: The Trackball Module does require a small break-in period before the ball will rotate smoothly.
