555 shock vibration alarm circuit

Published:2011/5/30 9:48:00 Author:TaoXi | Keyword: 555, shock vibration, alarm | From:SeekIC

This alarm circuit uses the double time base circuit 556 as the core, it has some points of features: small size, pure report sound, and it can be used in wide range of applications such as the knocking door alarm, the breaking door alarm, the vibration or shock warning. The circuit is as shown in figure 15-44. The IC1 uses the double time base circuit 556, the monostable trigger timing circuit is composed of it's left part IC1-a(1/2 556) and R3, C1. In peacetime, the partial pressure effect makes the trigger port pin-6's electric potential higher than 1/3VDD, and this trigger circuit is in the reset state. When HTD is impacted or oscillated, the exchange piezoelectric signal which is produced by the deformation will make the trigger to flip and set, pin-3 has the high electrical level.



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