Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1995-10-25
1997-06-03
Le, Que
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
2505591, 83370, G01J 132
Patent
active
056357044
ABSTRACT:
This invention features a sensing system and a method for dispensing financial and retail receipts from a receipt-printing machine. The sensing system of this invention can use any one of a myriad of typical supply rolls having a media strip (usually paper) that has black marks periodically located at given intervals along its edge. The sensing system usually has a light-emitting diode (LED) and a photo-transistor. The light from the LED is directed on the supply roll, where, as the paper is advanced, it is reflected to the photo-transistor. When a black mark comes into the range of the LED, the light from the LED is absorbed and not reflected to the photo-transistor. The printing machine then stops advancing the paper, and cuts it to form a receipt of adequate length. The invention utilizes a microprocessor that has a pulse width modulator (PWM) for providing a square wave output to a digital-to-analog (D/A) converter. A program of the microprocessor controls the frequency and the duty cycle of the PWM. The D/A converter changes the square wave to a direct current (DC) voltage, and an exact relationship between the PWM duty cycle and the current level flowing in the LED is thus established. The system is a self-adjusting one, due to an analog-to-digital (A/D) converter in the microprocessor. This allows for the automatic calibration of the system.
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Del Signore, II James R.
Nye, III Andrew B.
Le Que
Levy Mark
NCR Corporation
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