Self-checking light curtain system and method of operation

Details Self-checking light curtain system and method of operation Self-checking light curtain system and method of operation

1990-01-09

1991-05-14

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

2502083, 2502221, 340556, G01V 904

Patent

active

050158406

ABSTRACT:
A light curtain system and method of operation which detects the intrusion of objects into a protected zone. The system is characterized in having an inherent self-checking mode of operation by logic circuits which analyze data signals from both the LED light transmitters and phototransistor receiver circuits. A shutdown signal is generated if the logic circuit determines that light is not received in a selected channel at the time that the LED is strobing light exclusively for that channel. The system further provides a relatively simple and inexpensive method of selecting and amplifying the LED transmitters and PT receivers. In the circuit each PT acts as a switch which selects itself, and a single amplifier is employed for a plurality of the channels. The circuit further provides for the concatenation of groups of amplifier/PT circuits into a longer chain using a single diode.

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