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infrared beacon for pet door

I have a cat door and now I have way more cats than I used to. I want
to block all cats except for my cat, so I figure I will make a little
lock on the cat door that only unlocks when my cat walks up to it. I
will fit my cat with a collar that has infrared LED's which emit a
short pulse a few times a second. There will be a infrared receiver on
the door which looks straight down at the cat door, and when it sees
this short pulse, will unlock the door.

I know this can be done with RFID, radio, magnets, etc... fill in the
blank. I want to do it with infrared. I haven't played with any opto
circuits for a long time and I miss them.

I know there are already devices for sale which do this.

SO.

I am thinking 1 to 3 button cell 1.5V batteries to power the collar.
These are 150mAh each. I want the batteries to last at least 3 months.
The receiver on the door will be powered by wall power so there is no
problem there.

I dont want to make a transponder collar, I want it to simply emit a
short infrared pulse at a fixed interval.

So basically its a game of reducing the infrared pulse to meet the
battery life requirements, but still be able to detect said pulse.

The cat should not have to wait more than half a second after walking
up to the door before it unlocks.

Lets say somehow the pulse is 10uS long, twice a second, and the total
current used by 3 led's is 30mA.

So assuming a square wave driving the LED's, its 15mA average current.
And for 10 us, its 150nA per pulse, and at two pulses per second its
300nA.

Per hour its 300nA x 3600 = 1.08mA.

Per day its 1.08mA x 24 = 25.92mA

So a single 150mAh battery would last about 6 days.

Thats not gunna do it!

What can I do?

Use sub microsecond pulses? Can those be detected at 6 feet?

Remember, no transponder! (not yet anyway)
 
G

GregS

Jan 1, 1970
0
I have a cat door and now I have way more cats than I used to. I want
to block all cats except for my cat, so I figure I will make a little
lock on the cat door that only unlocks when my cat walks up to it. I
will fit my cat with a collar that has infrared LED's which emit a
short pulse a few times a second. There will be a infrared receiver on
the door which looks straight down at the cat door, and when it sees
this short pulse, will unlock the door.

I know this can be done with RFID, radio, magnets, etc... fill in the
blank. I want to do it with infrared. I haven't played with any opto
circuits for a long time and I miss them.

I know there are already devices for sale which do this.

SO.

I am thinking 1 to 3 button cell 1.5V batteries to power the collar.
These are 150mAh each. I want the batteries to last at least 3 months.
The receiver on the door will be powered by wall power so there is no
problem there.

I dont want to make a transponder collar, I want it to simply emit a
short infrared pulse at a fixed interval.

So basically its a game of reducing the infrared pulse to meet the
battery life requirements, but still be able to detect said pulse.

The cat should not have to wait more than half a second after walking
up to the door before it unlocks.

Lets say somehow the pulse is 10uS long, twice a second, and the total
current used by 3 led's is 30mA.

So assuming a square wave driving the LED's, its 15mA average current.
And for 10 us, its 150nA per pulse, and at two pulses per second its
300nA.

Per hour its 300nA x 3600 = 1.08mA.

Per day its 1.08mA x 24 = 25.92mA

So a single 150mAh battery would last about 6 days.

Thats not gunna do it!

What can I do?

Use sub microsecond pulses? Can those be detected at 6 feet?

Remember, no transponder! (not yet anyway)

Going to have to attach a solar panel to the back.

How about a infra red reflector, so the cat has no juice at all ??
Bounce pulses off it. Its got to be special so other collars
will not trip it.

How much do you charge for a nights sleep at the cat motel.

greg
 
J

Jim Yanik

Jan 1, 1970
0
[email protected] (GregS) wrote in
Going to have to attach a solar panel to the back.

How about a infra red reflector, so the cat has no juice at all ??
Bounce pulses off it. Its got to be special so other collars
will not trip it.

How much do you charge for a nights sleep at the cat motel.

greg

first problem is getting the IR pulse aimed towards the detector.

Beer companies hand out bottle caps with blinky LEDs in them,that run on
tiny button cells for a long time;no problem switching the red LED for an
IR LED. Use a 123 cell and it'd run for years.

At least RFID doesn't have to be aimed.
 
[email protected] (GregS) wrote in









first problem is getting the IR pulse aimed towards the detector.

Beer companies hand out bottle caps with blinky LEDs in them,that run on
tiny button cells for a long time;no problem switching the red LED for an
IR LED. Use a 123 cell and it'd run for years.

At least RFID doesn't have to be aimed.

--
Jim Yanik
jyanik
at
kua.net- Hide quoted text -

- Show quoted text -

I'm thinking that if I use three or four IR leds spaced evenly on the
collar, it wont have to be aimed. Plus the IR light should be bright
enough to reflect off the ground, and the detector should be very
sensitive.

Lots of 'shoulds' I know but I think its reasonable.

Are you sure those blinky caps last for YEARS?
 
T

TTman

Jan 1, 1970
0
SNIP
What can I do?

Use sub microsecond pulses? Can those be detected at 6 feet?

Remember, no transponder! (not yet anyway)
You only need one wide angle IR led... and 1 pulse per 2-3 seconds is
enough... average latency will be 1.5 seconds. Cats are quite patient....
 
S

shortT

Jan 1, 1970
0
I have a cat door and now I have way more cats than I used to. I want
to block all cats except for my cat, so I figure I will make a little
lock on the cat door that only unlocks when my cat walks up to it. I
will fit my cat with a collar that has infrared LED's which emit a
short pulse a few times a second. There will be a infrared receiver on
the door which looks straight down at the cat door, and when it sees
this short pulse, will unlock the door.

I know this can be done with RFID, radio, magnets, etc... fill in the
blank. I want to do it with infrared. I haven't played with any opto
circuits for a long time and I miss them.

I know there are already devices for sale which do this.

SO.

I am thinking 1 to 3 button cell 1.5V batteries to power the collar.
These are 150mAh each. I want the batteries to last at least 3 months.
The receiver on the door will be powered by wall power so there is no
problem there.

I dont want to make a transponder collar, I want it to simply emit a
short infrared pulse at a fixed interval.

So basically its a game of reducing the infrared pulse to meet the
battery life requirements, but still be able to detect said pulse.

The cat should not have to wait more than half a second after walking
up to the door before it unlocks.

Lets say somehow the pulse is 10uS long, twice a second, and the total
current used by 3 led's is 30mA.

So assuming a square wave driving the LED's, its 15mA average current.
And for 10 us, its 150nA per pulse, and at two pulses per second its
300nA.

Per hour its 300nA x 3600 = 1.08mA.

Per day its 1.08mA x 24 = 25.92mA

So a single 150mAh battery would last about 6 days.

Thats not gunna do it!

What can I do?

Use sub microsecond pulses? Can those be detected at 6 feet?

Remember, no transponder! (not yet anyway)

Have you considered a strong magnet and a hall effect sensor?

shortT
 
If I really had to do it, I'd use 32 khz watch crystals. They "sing"
rather loudly, and have a high enough Q that just bringing one within
a few feet of a oscillating one will cause it to resonate. So 4000
series cmos oscillator on the collar and another cystal on the door,
loaded only by a preamp with no capacitance and maybe 10 megohms or
more input impedance. You could also use a 40 khz piezo ultrasound
transducer, and listen for the 40 khz version of the watch crystal.

When I worked at the university, we used all sorts of watch crystals
with the can removed as various sensors, including sensing for the
tips of atomic force microscopes.

or cheat and use a 4040 clocked by the 32 khz to get you a half
second pulse and use it to gate a led.

Steve Roberts
 
If I really  had to do it, I'd use 32 khz watch crystals. They "sing"
rather loudly, and have a high enough Q that just bringing one within
a few feet of a oscillating one will cause it to resonate. So 4000
series cmos oscillator on the collar and another cystal on the door,
loaded only by a preamp with no capacitance and maybe 10 megohms or
more input impedance.  You could also use a 40 khz piezo ultrasound
transducer, and listen for the 40 khz version of the watch crystal.

When I worked at the university, we used all sorts of watch crystals
with the can removed as various sensors, including sensing for the
tips of atomic force microscopes.

 or cheat and use a 4040 clocked by the 32 khz to get you a half
second pulse and use it to gate a led.

Steve Roberts

Steve,

Is this for real or an interesting idea? Can I really get two watch
crystals to vibrate sympathetically like that? Do I have to take them
out of their cases?
 
J

Jasen Betts

Jan 1, 1970
0
I have a cat door and now I have way more cats than I used to. I want
to block all cats except for my cat, so I figure I will make a little
lock on the cat door that only unlocks when my cat walks up to it. I
will fit my cat with a collar that has infrared LED's which emit a
short pulse a few times a second. There will be a infrared receiver on
the door which looks straight down at the cat door, and when it sees
this short pulse, will unlock the door.

I know this can be done with RFID, radio, magnets, etc... fill in the
blank. I want to do it with infrared. I haven't played with any opto
circuits for a long time and I miss them.

I know there are already devices for sale which do this.

SO.

I am thinking 1 to 3 button cell 1.5V batteries to power the collar.
These are 150mAh each. I want the batteries to last at least 3 months.
The receiver on the door will be powered by wall power so there is no
problem there.

I dont want to make a transponder collar, I want it to simply emit a
short infrared pulse at a fixed interval.
Per day its 1.08mA x 24 = 25.92mA

So a single 150mAh battery would last about 6 days.

Thats not gunna do it!

What can I do?

to prolong battery life you could consider installing a reed swith in the pendant
and putting a strong magnet near the door, you could up the signal
rate then too.
Use sub microsecond pulses? Can those be detected at 6 feet?

that's a big cat! why do you need such range?

single pulses will be hard to detect bursts are much easier
(repeat 1us 3us off 10 times instead of 10 us on)
Remember, no transponder! (not yet anyway)

I saw one cat door with an enlarged sill with a magnetic balance in it,
any small piece of ferromagnetic material (I used a coin) would trip
the balance and unlock the door
 
J

Jasen Betts

Jan 1, 1970
0
I bet there's a market for automated dog/cat doors that just make use of the
passive RFID tags that "chipped" pets already have. (Although I believe
there's a handful of "popular" pet chips out there, and preferably you'd want
it be be universal...)

most of them work at 125 Khz and it's just the encoding that differs,
it's may be possible to get a unique signature even if the makers
serial number can't be decoded from the signal.
 
Nope, you can do it with the cases on. The crystals are under vacuum.
Dont rigidly mount the sense crystal with short leads.

bench experiment.

Use two crystals from the same production lot.

One goes right into high impedance input on a oscilloscope set to a
10=100 mV scale.

Unit two gets a mW of drive in a cmos gate oscillator. It works
better if the launch crystal is in a sine wave oscillator, but for
your app, you dont care.

At 6" or of of being near each other, you'll start to see big
sympathetic oscillations in the sense crystal.

It was a problem for me, as I needed to have several 32 khz crystals
free running next to each other.

It can work better if the sense crystal is open cased, and our first
ones were cut open by hand with a dremel tool, then we made a lathe
like jig to do it.

Steve Roberts
 
parallax has a RFID reader for 35$ Sparkfun is selling tags for $1.25

Don't know what the range is, I suspect its the diameter of the search
coil. The cat will quickly learn to twist his head around to hear a
click and gain entry.

I hate feral cats, so I strongly support not feeding the strays.
I had a neighbor who fed the strays, and soon there were 2, then 6,
then 13 , then mega breeding.
We'll see if the songbirds recover around here.

Akron, Ohio's city council are my heros. They require licensing of
cats and offer free havaheart traps on loan.

Remember the kids movie about the dogs having to save the world
from the evil cats at Christmas...........

This may sound cruel, but put on leather gloves, dunk the stray in
very cold water for 5-10 seconds , toss them out in the cold ohio
night air, they don't come back. You'll see them about 300 feet out,
but they don't come near you again! It however, requires a level of
body armor , planning, and nerves of steel that most people don't
have. You will be holding onto a 4 legged buzzsaw that can do things
never imagined in Alien Vs Predator. The neighbor kids thought it
would be fun to feed their cat in my dog's house. Poor 15 year old Max
didn't have a chance of clearing out the squatter. Hated to do that,
but my dog has his house back.

Steve
 
 This may sound cruel, but put on leather gloves, '

One minor detail, leather welders jacket,faceplate, heavy leather
reinforced welders gloves, watch for the rear paw coming in to get you
at the juncture of the glove to the jacket. Perhaps best to have glove
duck taped to jacket radiological warfare style. DONT ASK!

Steve Roberts
 
U

Usual Suspect

Jan 1, 1970
0
Thoughts:
The 32KHz oscillators... might the cat develop a ringing in his/her ears from
hearing this all the time? Might make their life hell...

Re. aiming: all animal collars I've seen always rotate to one position: with
the buckle down. The heaviest part of the collar always ends up at the
bottom. If you make sure batteries (if you use them) are near the buckle,
you're assured to control the orientation at all times.

If you're still worried about aiming, place highly reflective material, ie:

<http://www.lylesigns.com/rollgoods/rollgoods.asp>

around the door (parallel to the cat's path). This would help direct the IR
energy to the sensor.

Good luck.
 
D

David Lesher

Jan 1, 1970
0
Where's the video clip of the guys with the imaging processing system? It
was deployed to let the cat in, but NOT if she had a "present" in her
mouth....
 
R

Rich Grise

Jan 1, 1970
0
I have a cat door and now I have way more cats than I used to.

You're supposed to sterilize your pets.

Good Luck!
Rich
 
J

James Arthur

Jan 1, 1970
0
I will fit my cat with a collar that has infrared LED's which emit a
short pulse a few times a second. There will be a infrared receiver on
the door which looks straight down at the cat door,
....

I am thinking 1 to 3 button cell 1.5V batteries to power the collar.
These are 150mAh each. I want the batteries to last at least 3 months.
The receiver on the door will be powered by wall power so there is no
problem there.

I dont want to make a transponder collar, I want it to simply emit a
short infrared pulse at a fixed interval.

So basically its a game of reducing the infrared pulse to meet the
battery life requirements, but still be able to detect said pulse.

The cat should not have to wait more than half a second after walking
up to the door before it unlocks.

Lets say somehow the pulse is 10uS long, twice a second, and the total
current used by 3 led's is 30mA.

So assuming a square wave driving the LED's, its 15mA average current.
And for 10 us, its 150nA per pulse, and at two pulses per second its
300nA.

Per hour its 300nA x 3600 = 1.08mA.

Per day its 1.08mA x 24 = 25.92mA

So a single 150mAh battery would last about 6 days.

Thats not gunna do it!

What can I do?

Use sub microsecond pulses? Can those be detected at 6 feet?

Remember, no transponder! (not yet anyway)

Or just drive a pulse into a small coil & pick it up with
another door-mounted coil. Those make for simple Tx and Rx,
omnidirectional, etc.


If you're stuck on IR...

Cut the range: you don't need 6 feet, more like 6 inches.
cut the LED pulse to 1mA,
trim the pulsewidth.


That should get you pretty close.

And for a receiver you might ignore the IR and just
pick up the RFI...

(I test IR remote controls by holding them close
to an AM-band radio--you can hear the pulses.)

Cheers,
James Arthur
 
J

JosephKK

Jan 1, 1970
0
One minor detail, leather welders jacket,faceplate, heavy leather
reinforced welders gloves, watch for the rear paw coming in to get you
at the juncture of the glove to the jacket. Perhaps best to have glove
duck taped to jacket radiological warfare style. DONT ASK!

Steve Roberts

For forcibly handling unhappy cats i prefer the gauntlets that
concertina wire installers use. Otherwise OK.
 
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