This guy get 0 to 5 v output with this circuit:
HALL Sensor is reused from 5" or 1.44" floppy drive.
Magnets seen like ferrite ones...
Trin pot allow easy find 2,5v center and adjust gain.
Google translation:
http://translate.google.com/translate?hl...55fcbdf2ddd393dEdit: Notice that magnet travel in this setut is ~40 degrees (+20, -20)
Sokol1