LIGHT_CHANGE_DETECTOR

Published:2009/7/6 6:10:00 Author:May | From:SeekIC

Combination amplifier and detector using 3140 opamp responds only to sudden changes in light on photocell while ignoring slow changes in ambient light. When beam is suddenly broken, opamp output swings positive and stays positive for delay time set by recharging of 0.05-μF capacitor on positive input. Delay locks out spurious signals until photocell resets itself to normal illumination. Values shown give time-out delay of about 1 s, with clean conditioned rectangular output pulse.-D. Lancaster, CMOS Cookbook, Howard W. Sams, Indianapolis, IN, 1977, p 346-347.



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