Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1989-08-15
1991-04-16
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250214AG, 250221, 330284, 330144, 307360, G01V 904, H03G 310
Patent
active
050085328
ABSTRACT:
The light reception signal circuit for photoelectric switch includes a photoelectric conversion circuit for receiving light from a light emitting part controlled for periodic emission. The photoelectric conversion circuit generates an electrical signal corresponding to the quantity of the received light. A programmable attenuator receives the output electrical signal, and attenuates it in even step in response to a digital control signal. A first comparator compares the output voltage with a predetermined upper bound threshold. The first comparator generates a clock signal when the output voltage exceeds the upper bound threshold. A peak holding circuit for receives an output voltage of the programmable attenuator, and holds the peak value of the output voltage on a time constant that is much longer than an emission period of the light emitting part. A second comparator compares the output voltage of the peak holding circuit with a predetermined lower bound threshold and generates an outgoing signal when the output voltage decreases below the lower bound threshold. A counter counts the clock pulses thereby generating a digital control signal for increasing the attenuation of the programmable attenuator. The counter is reset outgoing signal of the second comparator. A third comparator compares the output voltage of the programmable attenuator with a predetermined decision level to produce the detection output of the photoelectric switch.
REFERENCES:
patent: 4064509 (1977-12-01), Stockdale
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patent: 4097732 (1978-06-01), Krause et al.
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patent: 4301445 (1981-11-01), Robinson
patent: 4459475 (1984-07-01), Flint et al.
patent: 4517526 (1985-05-01), Di Cicco
patent: 4807167 (1989-02-01), Green, Jr.
Kobayashi Atsuhito
Ono Shoichi
Chinon Kabushiki Kaisha
Messinger Michael
Morrison Thomas R.
Nelms David C.
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