| 摘要 |
The present invention features a method and an apparatus for sensing the speed and the direction of rotation of a motor. The apparatus of the invention has a timing wheel disk that is attached to the rotational shaft of a motor and has a number of slots. Opposite the timing wheel are mounted two spaced-together proximity sensors that are a given or a fixed distance apart. The sensors are spaced to read within each slot of the disk at any given point during in the rotation of the timing wheel. When the sensors detect the edges of each slot of the rotating wheel, signals are generated. The sensors respectively define sensing channels A and B. A microcontroller contains a logic program that calculates the motor's speed and direction. Speed is determined by measuring the time that it takes for a point (the edge of a rotating disk's slot) to travel across both sensors. Direction is determined by storing the logic level of the first sensor (channel A) while a generated exclusive OR signal is high, and then analyzing the level of channel A when the exclusive OR is low. Channel A changes logic states over the exclusive OR period when the motor is rotating clockwise; it remains at the same logic state over the exclusive OR period when the motor is rotating counterclockwise. The invention requires no coupling or interface between the sensors. No moving parts are required by this invention, since the timing wheel is mounted directly upon the motor shaft, and the sensors are fixedly mounted adjacent the timing wheel on the brake drum, which requires no special bracketing.
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