Four spindles on the trackball have a tiny circular magnet the end; each of these are paired with an SMD hall effect sensor, which are used to measure up, down, left and right movements of the trackball.
You have a data phone? Blackberry / Googlephone? Something with a physical input device, like a tiny trackball? Neat device, eh? Well, SparkFun found some, and built a breakout board it.
These are cool little devices. The four spindles on the trackball have a tiny circular magnet the end which are each paired with an SMD hall effect sensor, which measure up, down, left and right movements of the trackball. An SMD momentary switch is placed under the trackball to give you a select switch (pulled low when the switch is pressed).
Particularly cool are the 4 LEDs installed under the Trackballer :Red, blue, green and white. These can be powered to light the clear trackball up any color you can imagine. Disco-scroller, here we come!
All features are broken out to a 0.1" pitch header. Regulated, 2.5-5.25VDC power must be provided to power the Hall sensors. The trackball is attached with strong CA glue. Board comes as shown, with all components populated.
The hall-effect sensors and trackball combo are surprisingly sensitive. A slight roll of the trackball creates multiple high/low transitions on the four axis pins, easily picked up by any microcontroller. A 360° rotation of the trackball, along a single axis, will result in about 9 high/low transitions.