Off topic Circuit for automatic cat door.

[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

[Ray Fenwick]

Hi Tim

Just in case you didn't know, exactly this device has been built already and
is commercially available. It uses the subcutaneously implanted RFID
'microchip' that is used worldwide for identifying animals, and will let in
your cat(s) and only yours (you program which cat's to allow).

They're great because they're fool proof, and do not rely on a collar that
could be lost or pose a strangulation hazard to for the cat.

I understand you may rather build than buy an off-the-shelf product, but
maybe it can give you a few pointers? Here's a sample listing (not
affiliated etc.)

http://tinyurl.com/ct6abq5

HTH

Ray

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[John Rehwinkel]

> 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.

To get started, look for circuits for grid dip meters, theremins, or (best of all) metal detectors.
You should be able to get a reliable frequency shift with a shorted-turn sort of collar at
pretty much any reasonable frequency. I'm imagining about a 30-turn coil as the sense
coil (that the cat walks through) resonating with a couple of capacitors in a Colpitts
configuration (that avoids having to make a tapped coil).

Actually, thinking about it, I'd hang a resistor in the power supply to the oscillator to
measure the current draw - when a shorted turn shows up, the oscillator should draw
more power, creating a larger voltage drop across the sense resistor. A simple RC
filter and or peak detector after that would let you use a simple comparator to detect
the change (detecting a change in a DC level seems easier than detecting a change
in frequency).

As Ray pointed out, RFID would work too, with a tag in the collar or the in-the-body kind.
There are commercial versions of this, as well as RFID sensors available from adafruit
and the like.

There was also a project that used a video camera and profile recognition to let in a specific
cat - and only if the cat wasn't carrying an animal in its mouth! It's a little over the top, but does
refer to a ready-made cat door ("Cat Mate") with a solenoid to unlock it, which might be useful
if you don't want to build your own door mechanism.

http://www.quantumpicture.com/Flo_Control/flo_control.htm

- John

[Terry S]

There are plenty of magnetic or RF collar products available designed
for this purpose -- coupled with an actuated door flap. Do a little
googling, you'll find something you can buy cheaply enough.

[Mich...@aol.com]

http://www.ebay.com/itm/160942129905

$50 shipped

 

That is the exact unit I use.   2 cats.

 

Replace battery about once every 6 months.

 

My cats in - all others out.

 

Took the cats about a day to figure it out.

 

Michail

 

 

 

In a message dated 12/20/2012 12:04:14 A.M. Pacific Standard Time, lai...@wcoil.com writes:

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.

[Terry Kennedy]

On Dec 20, 3:37 am, Ray Fenwick <rayfenw...@me.com> wrote:
> Just in case you didn't know, exactly this device has been built already and
> is commercially available.  It uses the subcutaneously implanted RFID
> 'microchip' that is used worldwide for identifying animals, and will let in
> your cat(s) and only yours (you program which cat's to allow).
>
> They're great because they're fool proof, and do not rely on a collar that
> could be lost or pose a strangulation hazard to for the cat.

They're also handy for cats that have never worn a collar and might
object to it.

The only thing to watch out for is that there were several competing
microchip solutions not too long ago, and in the past someone reported
installing one of these cat flaps, being unable to get it to recognize
their cat's microchip, and the cat flap support people told them they
needed to take their cat in to be upgraded from a 16-digit to a 20-
digit chip!

[Ray Fenwick]

Can't you just set the cat to download and install updates automatically? ;)

Ray

[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.

[Lucky]

Ermm and you find the mutilation of an animal ok?
You find terrorising another animal ok?
You think the extermination of a group by unnatural means (a 'domestic' cat is not natural) is ok?
"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." this is what 'cat lovers' do??

I'm sorry but I have got to say this, personally I do not particularly like cats (yet they always seem to find me as a 'friend'. I will always pet them if they desire etc) but find this post so offensive. It borders, no IS cruelty to trim a cats whiskers, it is cruel to allow, worse encourage your domesticated cat to 'exterminate' a complete colony of a different species!
I have not spoken on this thread before becuase of my bias of not being a 'cat lover' but gotta say just close your windows peoples, stop worrying whether they can get in or out that's what DOORS are for! If you can't mange that don't have a cat period!
When you start thinking/saying "My hunter cat, a GENTLE calico, would bring home SLAIN squirrels" you have lost the plot somewhere along the line, exterminating an entire colony via a 'domesticated' animal is WRONG!

[JohnK]

Yes Lucky I agree. [And I have several cats].

Years ago I supported this Weisling when I thought 'down on his luck', but subsequent events have shown me to be wrong in that.

I found the original/initial recent fishing expedition re the FLW clock in bad taste in this venue.

This Weisling is trying to Weisle its way back and I vote NO !

 

Sometimes you just gotta let go.

 

John Kaesehagen

Australia.

[I applied the Christmas Spirit and considerably toned-down my thoughts !]

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[glasslinger]

I had the same problem and used an induction coil on the cat food bowl. Doesn't hurt the cat but they never go back to that bowl again! I wouldn't cut the cat's whiskers (or claws) off. That is really harming them.

[Shane Ellis]

Dont get so self righteous about animals.  Do you drive a car?  look at all the poor little animals splattered on your windshield.  Get over it.

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