Homemade photo-couplers Circuit

Published:2011/5/5 2:06:00 Author:chopper | Keyword: photo-couplers | From:SeekIC

Combine the Φ55mm, red LED with photoresistance by transparent tape and put them in a pigmented penholder(black for good),and then seal both end,which has made a photo-coupler.Photo-coupler can applies to low frequency switch circuits ,just as shown in picture a.And picture b shows an outage alarm circuit adopting photo-couplers that can make an alarm if the electricity is not available.As usual,the red LED is ashine and the photo-coupler reduce the resistance of photoresistance through coupling.So,VT1 stops working,and the oscillator comprised by VT1、VT2 stops as well.When meet a commercial power cut, the resistance increases and makes VT1 connected,so that the oscillator starts to run,giving out a warning signal.



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