urgent plz....

i have to design an anti theft device which would cling to an object and when the object is moved , the buzzer gets on.However , when the circuit receives a tapping sound in a particular code ( Fibonacci ) using a micro phone the buzzer shoild be turned off so that object can be moved without any noise .


Plz give me ideas as quickly as possible


thank you

hi jaravind, i've been thinking about making just about the same exact circuit. Theres a couple things that you could do for the alarm. A vibration sensor would work (although its sensitivity would have to be low so that it wouldnt pick put people walking n stuff). Also, you could make something like in the picture. The big black thing is a ball bearingon top of a little platform. They are both negative. The thing around them is a plate that is positive. When this contraption is moved, the two thigns will make a connection n set off an alarm. Or you could make a little IR sensor that sees if it is getting farther away from a tabletop or something.

My idea for the tapping thing was actually to use tones, because you could easily make 3 filters (3 tones). If you do the tapping thing, thats probably getting into IC's, which is not my specialty, but I'm sure it can be done!!

BTW, what is it that you want to put the alarm on?

Jaravind,

How about using a pizo sounder element, it is sensitive to vibrations and might be attached to an amplifier and a decoder. Just a thought!

Ante :roll: