Cubic-Western Data

Charles L Hayman

John B Roes

Royal C Moore

A digital input signal is fed through an interface to a logic phase control which decodes the signal to provide a plurality of phase signals in a predetermined relationship for driving a sychronous DC stepper motor. The phase signals are fed to corresponding phase drivers which amplify the pulses of the phase signals before they are applied to the corresponding phase windings of the stepper motor. Each phase driver includes an operational amplifier and a power transistor connected in a closed loop to provide a current pulse having a constant predetermined peak amplitude to the corresponding phase winding during acceleration of the motor. The inductive time constant of the motor phase windings is thus overcome so that an applied mechanical load can be rapidly accelerated without stalling and the absence of dropping resistors minimizes power dissipation and heat generation. A pulse detector turns off the phase drivers after a predetermined time interval following the last pulse of the digital input signal to provide a time brake holding torque and near zero standby power comsumption. Components in the circuit are provided for protecting the power transistors from breakdown due to back emf signals generated in the phase windings.

Stepper motor control circuit

A ticket transport which is capable of rapidly reciprocating a ticket to permit a single transducer to read, write and/or verify information on the ticket. Upper and lower ticket guide plates define a ticket channel through which a ticket is propelled past an adjacent transducer by a plurality of rollers driven by a stepper motor. The upper ticket guide plate is hingedly mounted to permit access to the ticket channel. The stepper motor is controlled by special circuitry adapted to overcome the inductive time constant of the stepper motor to permit rapid acceleration, for example 0 to 50 inches per second in 30 milliseconds, of the ticket with minimum power dissipation. Sensors in the transport provide ticket position information. A combined magnetic head and pressure shoe assembly is provided for adjusting the thickness of the ticket channel.

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Riverside, CA, United States of America

Charles L Hayman