GB1400995A - Circuit arrangements including an electric stepping motor - Google Patents

Abstract

1400995 Control of stepping motors SANGAMO WESTON Ltd 13 Sept 1972 [13 Sept 1971] 42584/71 Heading H2J [Also in Divisions G4 and H3-H5] An electric circuit supplying pulses of alternate polarity to the winding 10 of a stepping motor, comprises a battery 14, a capacitor C1 in series with winding 10, and two switch means. The first switch means conducts upon the arrival of an input pulse on line L, Fig. 3, or at an input T, R or E, Fig. 4; capacitor C1 charges up through a diode D1 and winding 10 and the rotor of the stepping motor rotates through 180 degrees. In the absence of an input pulse the second switch means conducts to discharge capacitor C1 through winding 10 thus rotating the rotor through a further 180 degrees. The rotor may operate the cyclometer register 12 of a pulse counter. In the embodiment of Fig. 3, the first switch means comprises an NPN transistor T2, across the base and emitter electrodes of which are applied the filtered, rectified and smoothed input pulses, and a Zener diode. When an input pulse ceases T2 stops conducting and C1 discharges through the second switch means which comprises a transistor T1. In the embodiment of Fig. 4, the input pulses are fed to a resonant filter transformer TR, the resulting A.C. pulses being applied across the base and emitter of an NPN transistor T4 which constitutes the first switch means and which, with a PNP transistor T3, constitutes a trigger circuit. In this embodiment a pulse will be applied to winding 10 even if the duration of the input pulse to TR is shorter than the charging time of C1. A positive-going pulse from TR in excess of the threshold voltage of Zener diode ZD switches on T4 and C1 charges through a resistor R4. As the voltage drop across R4 rises T3 begins to conduct until C1 is charged up. In the absence of a signal from TR the trigger circuit ceases to conduct and C1 discharges as in the previous embodiment. The arrangements may be connected with a telephone line to monitor call charges.