Control method for stepper motor - using magnetic field detector allowing compensation for ambient magnetic field by adjusting drive pulses

摘要

The stepping motor for control of an analogue type display uses a series of pulses whose form may vary according to external conditions. The ambient magnetic field is detected, and its value is compared with a number of threshold values. If the value is between the first two threshold levels, the rate at which pulses are cut may be modified. When the value lies between a second pair of thresdhold values the pulses may become full pulses. Above the third threshold, the duration of the pulses may be augmented, and above a fourth threshold, the motor may be momentarily stopped, and recovery pulses transmitted. USE - Controlled stepping motor e.g. for watch. Compensates for external magnetic fields, and minimise need for magnetic screening.