Print paper detecting circuits with gain reduction

Details Print paper detecting circuits with gain reduction Print paper detecting circuits with gain reduction

1992-10-28

1993-10-05

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250214B, H01J 4014, G01N 2186

Patent

active

052508137

ABSTRACT:
A print paper detecting circuit for installation on a printer, to detect whether a print paper is supplied at a predetermined position along a paper path by using an optical sensor composed of a light emitting diode and phototransistor. The circuit detects the existence of the print paper according to the detection of light which is emitted from the light emitting diode, which is reflected from the print paper, and which arrives at the phototransistor. According to one embodiment, circuit has a current amplifier and a gain reducing circuit. The current amplifier feeds a pulse current which is greater than the normal constant current to the light emitting diode while the gain reducing circuit reduces the output of the output voltage. From the phototransistor during the time that the pulse current is supplied with this circuit arrangement any external light entering the printer does not affect the detection of the presence of the printer paper since the quantity of the light from the light emitting diode is greater than the quantity of the external light.

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patent: 5084627 (1992-01-01), Ueki et al.
patent: 5117119 (1992-05-01), Schubert et al.
J. C. McKenney et al, "Printer Paper Top of Form and End of Form Sensor", IBM Technical Disclosure Bulletin, vol. 27, No. 28, Sep. 1984, pp. 2535-2538.
"Mechanism on a Serial Printer", IBM Technical Bulletin, vol. 30, No. 4, Sep. 1987, pp. 1894-1895.

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