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Motor Control Circuit

IP.com Disclosure Number: IPCOM000093190D
Original Publication Date: 1967-Jun-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

West, LE: AUTHOR

Abstract

This frequency sensitive feedback circuit for regulating the speed of a direct current motor is described. Motor 10 has a rotor which carries special commutator 11. The latter cooperates with brush 12 to provide an alternating signal to the base of transistor Q1. This signal has a frequency which is directly proportional to the speed of motor 10. Q1 is connected so it is alternately rendered conductive and nonconductive at the frequency of the signal supplied to its base from brush 12.

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Motor Control Circuit

This frequency sensitive feedback circuit for regulating the speed of a direct current motor is described. Motor 10 has a rotor which carries special commutator 11. The latter cooperates with brush 12 to provide an alternating signal to the base of transistor Q1. This signal has a frequency which is directly proportional to the speed of motor 10. Q1 is connected so it is alternately rendered conductive and nonconductive at the frequency of the signal supplied to its base from brush 12.

Capacitor CT is connected in a charging circuit comprising resistors R6 and R7. Charge accumulates on CT at a predetermined rate when Q1 is not conducting. Conduction of Q1 completes a discharge circuit for CT through a path comprising diode D1, capacitor CB, resistor R5, and Q1.

Transistors Q2 and Q3 are connected in emitter-follower relation. Q3 is connected in series with the energizing windings of motor 10. At low speeds, the frequency of opening and closing of the discharge path for CT relative to the rate of charging of this capacitor through R6 and R7 is such that the current in the base circuit of Q2 maintains this transistor conductive. Q3 also conducts at this time and the windings of motor 10 are energized.

The speed of motor 10 increases until the frequency of the input signal from brush 12 reaches a point where the voltage on CT never exceeds a predetermined threshold during its charging cycles. At this time the current supplied to the base of Q2...