high-sensitive alarm

Published:2011/8/14 19:56:00 Author:chopper | Keyword: high-sensitive, alarm | From:SeekIC

The picture shows the simplified circuit of high-sensitive alarm,and its photoresistor resistor are connected with three LDR ordinary resistors. Thus, when light varies from dark to full light,the potential range of point X is about 1/4 to 3/4 as large as power supply voltage. This potential is also added to input ends of two double contact switches.A self-excited oscillator and a grouping circuit of inverter control the switches to transform alternately,and the switching frequency is usual a few Hertz, making two capacitors charge alternately.



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