Microprocessor controlled d.c. motor for controlling a postage meter

Abstract

In combination with a postage meter which includes a plurality of loads, a source of supply of motive power for driving the respective loads and instrumentalities for selectively coupling the source of motive power to the respective loads, there is provided an improvement which comprises: the motive power source including a d.c. motor having an output shaft adapted to be selectively coupled to the respective loads; means for sensing angular displacement of the motor output shaft; a microprocessor comprising a clock for generating successive sampling time periods, means for providing first counts respectively representative of successive desired angular displacements of the motor output shaft during successive sampling time periods, means responsive to the sensing means for providing second counts respectively representative of actual angular displacements of the motor output shaft during successive sampling time periods, and means for compensating for the difference between the first and second counts during each successive sampling time period and generating a pulse width modulated control signal for controlling the d.c. motor, the motor control signal causing the actual angular displacement of the motor output shaft to substantially match the desired angular displacement of the motor output shaft during successive sampling time periods; and a signal amplifier circuit for operably coupling the motor control signal to the d.c. motor.