Abstract: There is provided a method for monitoring paper or other jams of a carriage in a printer by monitoring the current waveshape in a first winding of a stepper motor at or near the time when a second winding of the stepper motor commutates. The current waveshape is received from a low-value sensing resistor, typically within an integrated circuit stepper motor driver device. Changes in the current waveshape during this time window may be interpreted and accurate deductions may be made concerning the loading of the stepper motor. In the case where the stepper motor is the drive motor for a printer carriage, the loading information may be used to detect a paper jam or similar problem in the printer carriage.

Abstract: The present invention features a check-reading and check-validation machine having a programmed microprocessor, a photo-sensor, a magnetizing unit, a magnetic head reader, feed rollers and a stepper motor drive for rotatively driving the feed rollers. The machine may be a sub-unit of a printer. A check is introduced to the nip of the feed rollers. The photo-sensor detects the presence of the check and activates the stepper motor drive. The stepper motor drive then causes the feed rollers to rotate, drawing the check into the reading and validating machine. The microprocessor instructs the stepper motor to feed and discharge the check into and out of the machine, according to a specialized program. The microprocessor program initially instructs the stepper motor to rotate the feed rollers for forward drive, utilizing half-step pulsing.

Abstract: The present invention features a photosensing mechanism for a receipt-printing machine which senses a low condition of a paper supply roll housed within a bucket of the receipt-printing machine. The paper-supply roll has a "floating" characteristic; that is, no fixed rotational mounts align the roll within its feed bucket. The photosensing mechanism adjusts to different supply-roll positions within the feed bucket, the different positions of which result from different mounting orientations of the receipt-printing machine.

Abstract: A printer has a bi-directional stepper motor that drives an endless toothed belt which is secured to a print head carriage for driving the carriage back and forth across the printer along a line of printing. A timing strip is molded integral with the frame of the printer and positioned under the print head carriage. An optical sensor of the light emitting diode and phototransistor type is secured to the underside of the carriage and positioned to straddle the timing strip as the carriage is driven back and forth across the printer. The printer controller uses timing strip/sensor signals to place the print head in a home position when the printer is turned on and also when the print head has been moved from an operating position, e.g. in the case of changing a ribbon. The timing strip/sensor signals are also used to detect a carriage jam condition.