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Stepping Motor Control Circuit

IP.com Disclosure Number: IPCOM000091787D
Original Publication Date: 1968-May-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Holloway, JT: AUTHOR

Abstract

The control circuit energizes a stepping motor used to incrementally drive a tape transport mechanism. The stepping motor comprises windings 10...13, each having one of the control transistors 14...17 connected in series relation with it. When one transistor 14...17 is energized, current flows from power source V through control circuit 18, the corresponding motor winding and the energized transistor to ground. The current is switched between the motor windings by sequentially energizing transistors 14...17 with the control signals indicated by waveforms 18. During the initial portion of the time interval each transistor 14...17 is conducting, a control pulse is supplied to the base of transistor 19 as in waveform 20. Transistor 21 also conducts to provide a shunt path about resistors 22 and 23.

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Stepping Motor Control Circuit

The control circuit energizes a stepping motor used to incrementally drive a tape transport mechanism. The stepping motor comprises windings 10...13, each having one of the control transistors 14...17 connected in series relation with it. When one transistor 14...17 is energized, current flows from power source V through control circuit 18, the corresponding motor winding and the energized transistor to ground. The current is switched between the motor windings by sequentially energizing transistors 14...17 with the control signals indicated by waveforms 18. During the initial portion of the time interval each transistor 14...17 is conducting, a control pulse is supplied to the base of transistor 19 as in waveform 20. Transistor 21 also conducts to provide a shunt path about resistors 22 and 23. During the time interval the control pulse is applied to transistor 19, a high current flows to the energized motor winding. After the control pulse is removed, the current in the energized motor winding is reduced to a value dependent on the size of current limiting resistor 22 or 23. The high starting currents reduce the time required to increment transport mechanism 24 by counteracting the effect of friction forces during initial movement of such transport. Transport mechanism 24 is moving at high speed due to the large starting current when the recorded bits pass magnetic transducer 25 during a step of the tape. This produces high-level...