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Small loop alarm circuit

2016-02-19 04:44  
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The article describes a small loop alarm circuit. The circuit is very simple, very helpful. If you understand this principle is not very thorough, it is recommended to understand an important component of the circuit: 1n4148 . Circuit is completely original and consists of two identical transistor switches. Each has its own alarm LED and they are coupled to a neat 82 db buzzer. Two 1 n4148 diode is used to prevent the signal from a sensor triggers two light-emitting diodes. Sensors use either wire loops or normally closed reed switch or even a combination of both. You can, for example, wire loop your suitcase and place a reed switch to the door of your hotel room. Because this small alarm clock in order to maintain the reach of time, there is no requirement automatically turn off after a period of time. The buzzer will sound until you turn the whole circuit off or connecting wire loop-back jumper. Similarly, the two light emitting diodes, each indication own area. Two 100 n capacitors is not really necessary, I also included them in order to ensure that no noise from the long-term cycle. Pair of transistors, you can use any NPN general-purpose audio amplifiers / switches (BC BC 107/108/109, 237/238, 2 n2222, 2 n3904 ...). Perforated circuit board assembly. Together with the buzzer and 9 v battery. 


 


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