Touch-type anti-theft alarm circuit

Published:2011/4/24 9:38:00 Author:Christina | Keyword: Touch-type, anti-theft alarm | From:SeekIC

The touch-type anti-theft alarm can be used in wide range of applications such as the burglar alarm and the alarm of dangerous touch.etc. This alarm can automatic alarm and can automatic stop at the scheduled time. As the figure showns. IC1 is the time-base integrated circuit NE555, the monostable trigger is composed of the IC1 and Ｒ１、Ｃ１、Ｃ２、Ｃ３. When no one touch the metal M1 to Mn, the circuit is stable, pin-3 of IC1 outputs the low-level signal, alarm circuit does not work. If anyone touch any piece of metal M1 to Mn, EMF of human body gives a negative pulse to pin-2 of IC1, the monostable circuit gets into the temporary-steady-state, pin-3 of IC1 become the high-level signal. This high-level signal makes the transistor V1 connect, so V2 also connect too, audio integrated circuits IC2 enters the working state.



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