Re: Doggie doors

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"AZ Woody" <reply@here> wrote in message news:457cb2d2$0$10298

<stuff snipped>

> It wasn't that it didn't work, it was the magnet was a hassle!  I'd find
> all kinds of stuff stuck to the magnets that the cats had found in their
> "adventures", like paper clips, metal filings, etc!  Also, I found that
> the metal food bowls I had presented a "challenge" and couldn't be
> used...  The cat would stick to the food bowl, and knock it over!

That's a hoot!  The Law Of Unintended Consequences operating at full force!

There's a thread in CHA that's got to be three or four years old, maybe
more, about a guy who designed a visual ID system to monitor his cat door.
He examined a silhouette of the animal seeking entry via his PC and if it
matched a cat, he let it in.  The best part about the images he captured
were all the non-cat creatures that sought entry.  There was a bird
silhouette, a shadow of a racoon and some bulbous nosed creature I think
might have been a possum or a badger.

If I were going to design a pet door, I'd look at something akin to the
passive tags they use to prevent shoplifting.  Might even be possible to buy
a used commericial assembly off Ebay.

You might be able to do it with a reflective collar and some IR emitters and
detectors.  A reflective collar would send back a very "hot" signal not
likely to be detected with anything but such a collar.  You might even be
able to make the emitter out of one of those laser levels that shoots out a
broad line.  That would be easily reflected back to a photodiode and
positively detected if the animal had a reflective collar.  The big payoff
is that there's nothing more expensive than an off-the-shelf collar to lose
if that cat somehow ditches his collar.

--
Bobby G.