Method to Advance the Paper Half a Dot With a Stepper Motor
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
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.