Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1992-12-04
1994-02-15
Messinger, Michael
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
250214B, 250221, 340556, G01J 132, H01J 4014, G01V 904
Patent
active
052869679
ABSTRACT:
A modulated light beam obstacle detector for use as a safety mechanism in an automatic closure operator which must operate in varying ambient light conditions. If the obstacle detector senses the interruption of the light beam, the motion of the door is arrested or reversed. The obstacle detector uses an auxiliary light source connected in a feedback circuit to maintain a constant background illumination on the light detector and thereby hold the light detector in conduction at all times. In this manner, the presence of the light beam can be sensed regardless of the ambient light conditions.
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Messinger Michael
Stanley Home Automation
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