# Tag type anti-theft alarm



## tomtn (Mar 28, 2010)

I would like help to construct an anti-theft alarm, like the one used in shops.
I mean some kind of oscillator-based alarm that is capable of sense the passing of a passive small antenna-type tag.


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## octaneman (May 13, 2009)

Hi tomtn


The simplest oscillator circuit is using a 555 timer, you can adjust the time base by using the equation:



t1 = (Ra+Rb)C
t2 = (Rb)C


It all depends on the configuration that you decided on for building your system. 


Good Luck!


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## Basementgeek (Feb 7, 2005)

Hi and welcome to TSF :wave:

Well octaneman gave you basic information on at least were to start, but I am going to close this post. We feel it is not wise for us to advise you any further.

If you need a security system, your best bet is to invest in one that is already on the market. It will be tested as to accuracy, carry a guarantee of that accuracy, something we can't offer.

BG


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