Drehzustandssensor und Gleichstrommotoren unter Verwendung eines solchen

摘要

For sensing the rotation of a DC motor and controlling the operation thereof, for example in a window-lift application in an automobile, a magnetic search coil (1) is used to provide a signal as the magnetic field around the motor varies with motor operation. The output of the search coil is subjected to noise discrimination by use of filter circuits combining low-pass and high-pass characteristics so as to provide signal conditioning in the range of about 500Hz to 1000Hz. The filter circuits are constituted by a high-pass filter (C3, R3, R4) coupled to the search coil output, and by first and second resistor capacitor networks (R1, C1 and R2, C2) in the feedback loop of an operational amplifier (A1). A second operational amplifier (A2) is configured as a Schmitt trigger with hysteresis at its switching points. The output of the Schmitt trigger can be applied to a micro-controller for controlling the motor operation.