Cat detector

Archiver · 2001-02-06 12:44

I am building an intelligent Cat flap that lets the family cat in an out
at certain times using a BS2. I want a way to be able to tag the cat so
that all the neighbours cats don't get in. I don't want to use magnets as
they are clumsy but a system similar to in-store security tags. Does
anyone have any info on this technology?

Thanks
jim

Archiver · 2001-02-06 14:53

Try http://www.microchip.com/10/lit/pline/security/index.htm for the
Microchip Keyloq technology.

Tim
[noparse][[/noparse]Denver, CO]

> I am building an intelligent Cat flap that lets the family cat in an out
> at certain times using a BS2. I want a way to be able to tag the cat so
> that all the neighbours cats don't get in. I don't want to use magnets as
> they are clumsy but a system similar to in-store security tags. Does
> anyone have any info on this technology?
>
> Thanks
> jim
>
>
>
>

Archiver · 2001-02-06 15:56

Jim Wilkins wrote:
>
> I am building an intelligent Cat flap that lets the family cat in an out
> at certain times using a BS2. I want a way to be able to tag the cat so
> that all the neighbours cats don't get in. I don't want to use magnets as
> they are clumsy but a system similar to in-store security tags. Does
> anyone have any info on this technology?

The tags are resonant circuits. The detector generates an
electromagnetic field. A nearby tag loads the detector's
tuned circuit, which trips the alarm.

Jack

Archiver · 2001-02-06 17:08

goflo@p... wrote

>The tags are resonant circuits. The detector generates an
>electromagnetic field. A nearby tag loads the detector's
>tuned circuit, which trips the alarm.

That sounds like what I need. Has anyone any idea where I can get the kit?

J.

Archiver · 2001-02-07 05:06

>>>I am building an intelligent Cat flap that lets the family cat in an out
>>>at certain times using a BS2. I want a way to be able to tag the cat so
>>>that all the neighbours cats don't get in. I don't want to use magnets as
>>>they are clumsy but a system similar to in-store security tags. Does
>>>anyone have any info on this technology?
>>

goflo@p... wrote

>> >The tags are resonant circuits. The detector generates an
>> >electromagnetic field. A nearby tag loads the detector's
>> >tuned circuit, which trips the alarm.
>
>That sounds like what I need. Has anyone any idea where I can get the kit?

I doubt if you will find it as an experimenters' kit. I have seen
systems that purport to do all you ask advertised from outfits like
"Sharper Image".

The kind of circuit mentioned is called a "grid dip meter", ref: the
ARRL handbook. The dip (in oscillation amplitude) occurs when the
resonant frequency of the tag matches that tuned in on the dip meter.
Another approach is to use two coils of wire as the detector, placed
at an angle to one another so that the coupling between them is
normally zero. One coil is driven with a constant or swept
frequency. When an animal wearing a tag comes along, it couples
energy from one coil to the other at its resonant frequency. Another
approach uses microwaves, and the resonant tag has a nonlinear
element (a diode) that causes the tag to emit microwaves at twice the
frequency received.

I was involved in a project for monitoring the movements of animals
in and out of their nest in a lab setting, where we had to
distinguish different animals. The tags were simply self-resonant
coils of wire, sorted by frequency. That was a while ago; the uP we
used was a Heathkit H8.

-- Tracy Allen
electronically monitored ecosystems
http://www.emesystems.com

Archiver · 2001-02-07 10:37

tracy@e... wrote

>The kind of circuit mentioned is called a "grid dip meter", ref: the
>ARRL handbook. The dip (in oscillation amplitude) occurs when the
>resonant frequency of the tag matches that tuned in on the dip meter.
>Another approach is to use two coils of wire as the detector, placed
>at an angle to one another so that the coupling between them is
>normally zero. One coil is driven with a constant or swept
>frequency. When an animal wearing a tag comes along, it couples
>energy from one coil to the other at its resonant frequency. Another
>approach uses microwaves, and the resonant tag has a nonlinear
>element (a diode) that causes the tag to emit microwaves at twice the
>frequency received.

This is a little beyond my skills. I was hoping to get my hands on a
circuit diagram and a list of parts.

Thanks for you help.

J.

Archiver · 2001-02-07 14:35

Tracy I like the Idea of using microwaves after your done monitoring
there movements you can eat them!

Tracy Allen wrote:
>
> >>>I am building an intelligent Cat flap that lets the family cat in an out
> >>>at certain times using a BS2. I want a way to be able to tag the cat so
> >>>that all the neighbours cats don't get in. I don't want to use magnets as
> >>>they are clumsy but a system similar to in-store security tags. Does
> >>>anyone have any info on this technology?
> >>

goflo@p... wrote

> >> >The tags are resonant circuits. The detector generates an
> >> >electromagnetic field. A nearby tag loads the detector's
> >> >tuned circuit, which trips the alarm.
> >
> >That sounds like what I need. Has anyone any idea where I can get the kit?
>
> I doubt if you will find it as an experimenters' kit. I have seen
> systems that purport to do all you ask advertised from outfits like
> "Sharper Image".
>
> The kind of circuit mentioned is called a "grid dip meter", ref: the
> ARRL handbook. The dip (in oscillation amplitude) occurs when the
> resonant frequency of the tag matches that tuned in on the dip meter.
> Another approach is to use two coils of wire as the detector, placed
> at an angle to one another so that the coupling between them is
> normally zero. One coil is driven with a constant or swept
> frequency. When an animal wearing a tag comes along, it couples
> energy from one coil to the other at its resonant frequency. Another
> approach uses microwaves, and the resonant tag has a nonlinear
> element (a diode) that causes the tag to emit microwaves at twice the
> frequency received.
>
> I was involved in a project for monitoring the movements of animals
> in and out of their nest in a lab setting, where we had to
> distinguish different animals. The tags were simply self-resonant
> coils of wire, sorted by frequency. That was a while ago; the uP we
> used was a Heathkit H8.
>
> -- Tracy Allen
> electronically monitored ecosystems
> http://www.emesystems.com

Archiver · 2001-02-07 16:27

You might want to try an ibutton by Dallas Semiconductor.

Dave Martin

Archiver · 2001-02-08 05:13

Jim,

Did not read all of the replies but I did find an interesting item ay
http://www.goldmine-elec.com. Om page 17 of the catalog, there is a
laptop alarm or kiddie finder. This has a settable range of 30 or 60
feet.

Good luck.

Dick, N2TOY

--- In basicstamps@y..., Jim Wilkins <jimslists@o...> wrote:
> I am building an intelligent Cat flap that lets the family cat in
an out
> at certain times using a BS2. I want a way to be able to tag the
cat so
> that all the neighbours cats don't get in. I don't want to use
magnets as
> they are clumsy but a system similar to in-store security tags.
Does
> anyone have any info on this technology?
>
> Thanks
> jim

Archiver · 2001-02-09 00:04

Thanks to all of you for your suggestions for my cat detecting cat flap.
I need to go off and read up all about coils and resonant frequencies.

Cheers,
Jim

Cat detector

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