----- Original Message ----- 
From: "Brad Stockdale" <brad_lists@greenepa.net>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Monday, October 15, 2007 1:38 PM
Subject: Re: [EE] Magnetic driveway monitor


> Hello all,
>
>   I am working on a little project to help secure my home... I have a long
> driveway and would like to know when someone is approaching my house. I 
> used
> to use a driveway monitor that had an IR motion detection sensor. This
> worked, but produced more false alarms than true alarms. Not that it was
> malfunctioning, but since I live in a rural area, it would detect every 
> deer,
> groundhog, dog, whatever...
>
>   I would like to design something similar to:
>
> http://www.smarthome.com/790908.html
>
>   It uses magnetic probes to detect vehicles approaching.
>
>   Unfortunately, I know nothing about metal detection. I've never even 
> used a
> metal detector, let alone know how one works well enough to design one.
>
>   Can anyone give me some pointers on how to go about making magnetic 
> probes
> such as the ones used in the above system? Maybe a website explaining the
> basics of ferrous material detection and some simple schematics for a 
> basic
> metal detection probe? Basically I just want to find a circuit that upon
> detection of the metal, it sends out a digital pulse. From there I'll use
> that to activate the alarm be it over wireless, wired, whatever...
>
>   I'd appreciate any advice.
>
> Thanks,
> Brad
> -- 

Brad,

A search for magnetic vehicle detector produced many results. Maybe 
something like these?

http://www.sensourceinc.com/PDF/SS-MS30%20Vehicle%20Sensor.pdf
http://www.ssec.honeywell.com/magnetic/mark_det.html

Good luck,
Richard


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