Yep, you can usually see where the coil is, fairly big loop.

Tend not to work for motorcycles though, which is a pain if you're riding
one.

Parking garages use them too, you usually see them on the 'in' entrance.
Years ago, a friend of mine determined that there was enough metal in the
average toolbox to trigger them.  He'd send the apprentice off to trigger
the gate, then drive out the in entrance, thus saving the parking fee.

Tony


> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
> Of Jake Brownson
> Sent: Wednesday, 18 May 2005 1:21 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: Detecting vehicles by magnetism
>
>
> I'm pretty sure most of the traffic light sensors do this, no?
>
> On 5/18/05, Jinx <joecolquitt@clear.net.nz> wrote:
> > This detects vehicles magnetically with a coil
> >
> > http://www.siliconchip.com.au/cms/A_102998/article.html
> >
> > There are other options, depends on the actual application
> >
> > Could use broken beam/reflected beam, pressure sensor/air
> > pipe, shadow etc
> >
> > --
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> > http://mailman.mit.edu/mailman/listinfo/piclist
> >
>
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