RE: [TCA] [Fwd: Off topic Circuit for automatic cat door.]

[lai...@wcoil.com]

That is just about what I am thinking of. I just worry that the loud
speaker announcing please return to the store and the flashing lights
might scare the cat! Just kidding of course. Wire loop and a small cap for
the cat. Then the sweeping oscillator for the door. Now I need to find the
circuit diagram. The other simple way to do it would be to build a metal
detector and put a couple of nuts in each bowl of cat food! I think that
would work better with a dog though. Yes yes just kidding again. We were
up wrapping presents all last night so I could mail them today. It is
rought when you don't get the gift list for the grandchildren till 3 days
ago!
Tim Laing
>
> If you want to do something simpler, you could try a passive resonance
> absorber - this is how some of those anti theft things in shops work -
> have an oscillator sweeping a small frequency range - the tag on the cat
> is a resonant LC circuit. When it is near the search coil, there is a dip
> in te spectrum - basically the same idea as a grid dip meter. This might
> be more sensitive than just a shorted loop. The oscillator sweep will give
> immunity to random objects - something like a shorted loop will absorb
> across the whole range - the sweep is wide enough that thermal variations
> etc in the resonant circuit are accounted for - youare just looking for an
> absorption dip anywhere in the range. Shop sensors typically do this in
> the 6-8mhz range.
> Dan
>
>>
>> I work with RFID tags at work all the time, I hate those little buggers,
>> half the time they don't want to read on the pallets. Knowing the
>> typical
>> cat I will have to be replacing them all the time. I think if I can get
>> a
>> simple circuit to detect a shorted loop about 1.5-2 inches in diameter I
>> will be pretty well set. I just want to throw something together with
>> parts I have on hand. The RFID is a good idea though, thank you for
>> suggesting it.
>> Tim Laing
>> >
>> > get an RFID reader. some RFID dev boards can be had for pretty cheap.
>> Put
>> > the tag on the cat, door opens for the cat with the tag...
>> > Dan
>> >
>> >>
>> >> Hi, this is off topic but I know there are a lot of electronics guys
>> >> here.
>> >> I posted this on Neonixie-L first. I also thought I would post here
>> as
>> >> well. This cat door is for the black cat that was guarding my CRA
>> >> skysweeper tube! I guess a automatic cat door would be on topic if I
>> >> used
>> >> tubes. The tubes could sit under his cat bed and keep him warm. But I
>> >> think that transistors or an IC or two would be more practical.
>> Thanks
>> >> guys.
>> >> Tim Laing
>> >>
>> >> ---------------------------- Original Message
>> >> ----------------------------
>> >> Subject: Off topic Circuit for automatic cat door.
>> >> From: lai...@wcoil.com
>> >> Date: Thu, December 20, 2012 3:04 am
>> >> To: neoni...@googlegroups.com
>> >> Cc: lai...@wcoil.com
>> >> --------------------------------------------------------------------------
>> >>
>> >> There are a lot of smart people on this group so I thought I would
>> ask
>> >> for
>> >> some help. We have a stray cat that we have adopted. He is an indoor
>> >> outdoor type of cat. My personal experience is if they started
>> outdoors
>> >> they are very unhappy if you try to keep them in all the time. Well
>> the
>> >> problem is there are some other strays that beat up on him and get at
>> >> his
>> >> food. My temporary solution was to leave the window to our stair
>> landing
>> >> open and Skink could jump up about 5 feet and get in through the
>> window.
>> >> Then he could sleep on the landing if we were not home and eat as
>> well.
>> >> Well we have two problems, 1) it is now pretty cold(The stairs lead
>> to
>> >> our
>> >> front door so that area is not heated.) 2) The big problem is I came
>> in
>> >> tonight and the wild stray that has been going after Skink had him
>> >> cornered on the landing. Needless to say I wasn't too happy, the last
>> >> thing I need is a tom spraying on the landing! And no, I am not
>> going
>> >> to
>> >> shoot the other cat as I live in town and I don't shoot cats etc.
>> >> My idea was to make a automatic cat door that would open for only
>> one
>> >> cat. I was thinking that if I made a cat collar out of light gauge
>> >> copper wire with male and female spade connectors this would form a
>> >> single turn shorted loop. (The wire would be light gauge so if he got
>> >> caught the wire would break.) The cat door would be a partly formed
>> with
>> >> a square wood tube that the cat would enter with a solinoid latched
>> door
>> >> at one end. On the outside of the wood cat tunnel I would wind some
>> >> turns of copper wire that would be tied into an oscillator circuit.
>> The
>> >> shorted turn would either kill the oscillator or shift its frequency
>> >> allowing the door to open.
>> >> I can build just about anything electronic or mechanical and have
>> lots
>> >> of parts on hand but I am not very skilled on scratch designed
>> circuits
>> >> like this. Would somebody here be willing to help me with some
>> pointers.
>> >> I can work from an hand drawn schematic. I should be able to supply
>> >> power from a wall wort if needed.
>> >> Thanks
>> >> Tim Laing
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> ------------------------------------
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>> >>
>> >>
>> >>
>> >
>>
>>
>>
>>
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>>
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>>
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>

[lai...@wcoil.com]

Here is a link for a (old)patent on a vehicle in lane detector using
passive coils in the roadway. No circuit details but it sounds like what
Dan was talking about. 12 inch single turn coils in the road with a 100nF
cap in series. etc. The hard part of this project is figuring out what
the search description should be.

http://books.google.co.in/patents/US5708427

Tim Laing

> I don't think anyone has suggested a simple 'tag' which consists of just
> a coil with a diode in series. Could be a loop with detector, such as
> some of the cheapest RFID tags use. The interrogator is something
> driving a large coil [in this case just around the openint] and
> detecting the second harmonic generated by current flowing in the
> diode. I think it could be very simple but not proposing a design.
>
> Ed

[lai...@wcoil.com]

Hello, well the cat problem has escalated. I opened the door this morning
and there was a unfamiliar tom on the stairs who had our cat backed up by
the window so he couldn't get to his accustomed cat bed. I caused some
consternation on the part of the 2 cats, finally after some growling the
tom bailed out the window which I promptly closed. This is the second time
that I have seen the tom on the stairs and some things on the landing got
broken.
One of the guys on Neonixie-l pointed out some cat doors that work with
a collar. Due to the situation with our cat and me having to spray
Fabreze on the landing for the smell. I went and ordered a cat door
that was pointed out to me on E-bay, it works with a special collar. So
till that comes we will have to work out something with the cat on
going in and out. Skink the cat is going to the vets for a neutering
on the 9th of January, I will get him chipped at the same time and then
I may look to upgrade the door. Chip operated doors run well over $100
though.
So I want to thank everybody for the ideas and the links to the door. I
havn't had a cat that we let inside for well over 10 years so I havn't
kept up on any of the doors etc for cats. All your ideas were a help
and I appreciate them very much.
Happy holidays to everybody!
Tim Laing
> Simple receiver tuned to harmonic would be easy.
>
> danial stocks wrote:
>
>>
>>
>> Yep the nonlinear junction detector is another interesting approach. I
>> think the harmonic generation is possibly a less easy thing to detect
>> than an on frequency passive resonator, although the harmonic method
>> is also used in a number of systems.
>> Dan

[lai...@wcoil.com]

I just wanted to say thanks for the help with the cat door. I have decided
if I ever get a orange marmalade cat I will name it Nixie in honor of the
group! I hope everybody here has a happy holiday season.
Tim Laing

[lai...@wcoil.com]

Hi, I just wanted to give an update. I purchased the magnetic cat door as
the cat does not have a digital chip yet, he is still all analog! Although
he does have 20 digits. I have to say this quietly as Skink is sitting in
my lap, he will be visiting the vet on January 9th and will come home a
little lighter in the gonad department. I will get him chipped at the same
time, $25.00 more. In the long run I will probably get a microchip
operated door. I am not very worried at all about other cats with
magnetic collars in this area of town. We only seem to get the lowbrow
slumcats that have no collars. We mostly have businesses and old houses
divided into apartments. The typical landlord will not let a appartment
dweller cut holes for cat doors. My biggest worries are stray cats,
racoons, oppossums, and probably squirrels. Racoons I realy hate as they
have gotten into the big house and done a lot of damage. Well many thanks
for all the help with this issue. And happy holidays to everybody!
Tim laing

[Nick]

We have two dogs... (and two cats)

Any unknown cat that makes it through the cat flap in one piece deserves to be in the house...

[Raymond Weisling]

About 1977 I had two cats and a 24/7 cat flap, but a stray was coming in during the night and getting food left  for the residents. I breadboarded a cat discriminator. It used two telephone relay coils that could detect a small magnet passing between them, added to the cat collars and a light bulb plus detector (photoresistor). If the magnetic signal was triggered and a cat entered, it was a resident, if the non-resident entered, not wearing the magnet, it sounded an alarm. I added  larger flap made from cardboard and a solenoid that allowed the large flap to fall and close off the smaller flap so no exit was possible. The no-exit flap solenoid was actually manually energized by touching two wires together on the end of a cable that ran to my bedroom. Everything was rather crude. I expected that I needed it once.

After I installed it I tested it with my cats with and without collars and it seemed to work well.

That same night at around 02:00 the alarm sounded, I touched the wires together, the larger flap fell and I went out. The non-resident, hearing me stirring, made a mad dash for the door and hit the large flap covering the bidirectional flap. I tried to catch this panicking cat, and in the process the breadboard and the lamp, photoresistor and coils all came undone from their temporary mounts. It was a jumble.

The non-resident had to be chased around the house, leaping up at closed windows, and eventually I caught him, and trimmed off his whiskers with a scissors. This is a very powerful yet harmless reminder since they depend on them for feeling for passages that their body can get through. (A fellow cat lover told me that once they trimmed off their cat's whiskers and the can would be ware of going from room to room in the house especially if the door was partly closed leaving a narrow gap.) They will be disoriented for some months until new whiskers grow back. A good reminder.

I finally opened the door and released the non-resident, who seemed to traverse the back yard that was a least 15 meters (or 40-some feet) long in three or four leaps. He never again appeared. The damaged cat discriminator was summarily taken apart. I remember using LM324 and LM 339 in the circuit.

One of the cats was a great hunter, and I lived north of the San Fernando Valley in foothill areas (Newhall, CA) where some ground squirrels lived. My hunter cat, a gentle calico, would bring home slain squirrels and leave various parts somewhere in the house as a token of her skill, for me to find and clean up when I got home. This happened on a nearly daily basis one spring. Eventually it stopped and I found that the nearby colony has been totally exterminated by my calico. For a while I had wondered what it would take to build a prey discriminator that could block her entry only when she carried a victim, but even now I suspect that that is a much greater challenge.