Patent ID: 7009387

Claim:
The combination of a motor driven bicycle gear changer and a transducer for detecting rotation of a shaft associated with the gear changer, the combination comprising: a shell positioned within the bottom bracket of a bicycle frame; an electric motor which includes an output shaft associated with a drive means of the bottom bracket; a rotor that is associated with the motor and is rotated by the motor about an axis; a stator connected to the shell; a magnetized element connected to the rotor; an integrated microcontroller; and, a transducer comprising at least one pair of linear, ratiometric and temperature compensated Hall-effect sensors that are connected to the stator in proximity to the magnetized element, set angularly staggered with respect to one another, and produce at least first and second analog, sinusoidal output signals corresponding to a relative position of the magnetized element; whereby the output signals are communicated to the integrated microcontroller to indicate a rotational position of the shaft, and for determining the direction of rotation of the shaft.