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Sound excitation switch circuit

2015-03-20 14:48  
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Sound excitation switch circuit
This circuit can be used as the sensor of the anti-theft alarm, and it can be used to open the monitor recorder to record the conversation. You can get the required sensitivity by adjusting R8. LM229 is the quad comparator, the first part A1 can be used in the amplification and the wave detection, the gain is 100; A2 compares the DC output of A1 with the selected reference level of R8, the output can trigger the Q1 to produce the 200mA load current and turns on the light-emitting diode.