Browse Prior Art Database

Method to Advance the Paper Half a Dot With a Stepper Motor

IP.com Disclosure Number: IPCOM000060197D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Bolash, J: AUTHOR [+2]

Abstract

Printing techniques such as Near Letter Quality, Double Strike and Subscript, for example, require two-pass printing with the paper being advanced half a dot between passes. A stepper motor is used to advance the paper half a dot for each motor step. The stepper motor is driven by a pedestal driver, as shown in Fig. 1. When the transistor Q1 is turned ON, current flows through the motor. The transistors Q2, Q3, Q4 and Q5 select the coils or phases. The microprocessor (MPU) controls the rate that the phases A and B are changed, as well as the interval that current is passed through the phases, as shown in Fig. 2. The stepper motor, in operation, is subjected to a variable load when the printer is loaded with multi-part forms and when the motor is experiencing frictional variations.

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Method to Advance the Paper Half a Dot With a Stepper Motor

Printing techniques such as Near Letter Quality, Double Strike and Subscript, for example, require two-pass printing with the paper being advanced half a dot between passes. A stepper motor is used to advance the paper half a dot for each motor step. The stepper motor is driven by a pedestal driver, as shown in Fig. 1. When the transistor Q1 is turned ON, current flows through the motor. The transistors Q2, Q3, Q4 and Q5 select the coils or phases. The microprocessor (MPU) controls the rate that the phases A and B are changed, as well as the interval that current is passed through the phases, as shown in Fig. 2. The stepper motor, in operation, is subjected to a variable load when the printer is loaded with multi-part forms and when the motor is experiencing frictional variations. Thus, advancing the paper a single step presents a problem. When the motor is supplied enough current to overcome the worst-case load, the motor over-shoots and the paper is moved further than one step. If less current is passed through the motor, then the paper is moved less than one step in the presence of a high load. There are known techniques for controlling the motor over-shooting such as back phase damping and deceleration ramps, for example, but they do not perform satisfactorily. A technique for over-coming the shortcomings of known techniques consists of passing current through the motor at a lower level but for a lon...