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Building a better CAT trap

splintergroupie | Posted in General Discussion on November 5, 2008 08:43am

I volunteer with a group that catches feral cats, spays and neuters them, then returns them to the colony. We’ve used the live traps you’re probably all familiar with, but the vet involved in this is looking for a better way since sometimes the mechanical traps don’t close fast enough to keep the cat from bolting.

He knows i wire my own houses so he asked if i had any ideas for one part of the problem that’s holding him up. I don’t have any electronics experience, so i said i’d turn the problem over to the BT Brain Trust.

The idea is to make a trap so that when the cat’s head breaks the infrared beam across the food bowl far inside the trap, a mechanism slams down the gate before the cat can turn around and escape. Mechanical models rely on the cat stepping on the pan holding the food and releasing a spring loaded gate.

Attached is the schematic the vet sent me. If more information is needed, let me know and i’ll ask him. Thanks for looking at this for us.

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Replies

  1. User avater
    BossHog | Nov 05, 2008 08:48pm | #1

    Interesting problem. Wish I could help ya.

    You should get lots of input here, since there are a lot of guys on the board. And guys are ALWAYS chasing.....................Cats.

    (-:

    If you hold a cat by the tail you learn things you cannot learn any other way. [Mark Twain]

  2. User avater
    Luka | Nov 05, 2008 08:53pm | #2

    Some automatic gates have a beam of some sort, that keeps the gate from closing, if the beam is broken.

    There is a small box on one side of the gate that transmits the beam.

    A reflector on the other side.

    I'm sure this could be used to trigger the trap, instead of keeping it from triggering.

    1. splintergroupie | Nov 05, 2008 09:23pm | #4

      Triggering the trap by breaking the beam is the idea, as the cat head interrupts it when it reaches for the food bowl. It's the part about blowing the circuit that the vet (Alan) is having trouble with...and i unfortunately don't know enough about it to re-state the problem any other way.

      1. User avater
        Luka | Nov 05, 2008 09:34pm | #6

        Hopefully Junkhound will stop in. I'd bet he'd have the answer.

        1. junkhound | Nov 07, 2008 06:44am | #37

          Did not read the rest yet, but use a FET, a generic IRF150 will easily work and is great overkill (pun intended).  With a MOSFet, you can simplify the circuit also, looks like something from the 1950's. 

          1. junkhound | Nov 07, 2008 07:10am | #38

            Can be a VERY simple circuit, forgot to add the avalanche diode voltage - anything between 7 and 18 volts is OK.

            Cat paws complete the gate circuit to the FET, FET (IRF150) turns on solenoid, gate drops. Cat wont feel the 9V battery unless feet are cut and in salt water.

            Edit clarification - drew this fast, this will not automatically reset as shown, need to add a few megohm gate to source resistor to the FET.  With that, solenoid will turnoff if the cat lays down on it's fur or is not stepping on both contat pads simultaneously-

            View Image

            Edited 11/6/2008 11:23 pm ET by junkhound

          2. splinteredux | Nov 07, 2008 10:43am | #39

            The vet's plan is that the cat's head breaks an infrared beam to trigger the solenoid. The traps are often in wet areas because we're catching ferals, so they get shoved under trailer houses and in barns...all kinds of places that could get rain or ground water, so the [wet] paw thing wouldn't work. They're very quick learners, so if we zapped a few, even by accident, i believe our trapping rate would fall way off.<G>Beyond that, i have no idea what the vet is asking to be fixed in his schematic or why his idea isn't working; i'm merely the messenger.Please, sir, may i have another...schematic? Thanks!~Splintergroupie

          3. oldbeachbum | Nov 07, 2008 10:54am | #40

            These guys?...The unspoken word is capital. We can invest it or we can squander it.  -Mark Twain...Be kind to your children....they will choose your nursing home....aim low boys, they're ridin' shetland ponies !!

          4. oldbeachbum | Nov 07, 2008 11:16am | #41

            All right.   Which one of you said cat trap?...The unspoken word is capital. We can invest it or we can squander it.  -Mark Twain...Be kind to your children....they will choose your nursing home....aim low boys, they're ridin' shetland ponies !!

          5. User avater
            IMERC | Nov 07, 2008 11:56am | #42

            so three days later this is what showed....

            a way cool cat.....

            View Image 

            Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->

            WOW!!! What a Ride!Forget the primal scream, just ROAR!!!

          6. gfretwell | Nov 07, 2008 10:13pm | #43

            This is a nasty cat. A black bobcat caught by the Florida Wildlife Servicehttp://esteroriverheights.com/wildlife/fwcblackbobcat.jpg

          7. User avater
            IMERC | Nov 07, 2008 10:24pm | #45

            that looks more like a panther...

            there's a pair here now (bobcats) that are fearless and agressive....

            we shall see...  

            Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->

            WOW!!! What a Ride!Forget the primal scream, just ROAR!!!

          8. User avater
            Luka | Nov 08, 2008 12:03am | #47

            Thank you.That's three days I don't have to sit and twiddle my thumbs.Cool cat.

          9. User avater
            IMERC | Nov 08, 2008 12:13am | #48

            somebody else did it and mailed it to me... 

            Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->

            WOW!!! What a Ride!Forget the primal scream, just ROAR!!!

          10. User avater
            Luka | Nov 08, 2008 12:42am | #49

            Well thank you to both of you, then.=0)

          11. gfretwell | Nov 07, 2008 10:16pm | #44

            The more I read of this thread the more I think you should stay with a mechanical trap and just fine tune that. I had the same issue with a rat trap I built and just increasing spring size and making them work a little harder for the bait worked fine.http://esteroriverheights.com/wildlife/rattus_rattus.jpg

  3. JMadson | Nov 05, 2008 08:58pm | #3

    Just electrify the trigger plate. Not a single cat will get away.

     
    1. splintergroupie | Nov 05, 2008 09:23pm | #5

      That'll save a lot of time and trouble in alternations, too! <G>

  4. gfretwell | Nov 05, 2008 09:34pm | #7

    You can get SCRs that are good for hundreds of amps. I dobt you need any kind of buffer transistor at all. Radio Shack has them in the 5-6a range. Put a diode across the coil to clamp the back EMF

    1. splintergroupie | Nov 05, 2008 09:37pm | #8

      Greek to me, but i'm copying the thread and passing it on. Thanks for the input.

      1. gfretwell | Nov 05, 2008 09:41pm | #10

        You should put switch in there to open the coil circuit once the trap is sprung to save your coil and your battery. That is when you need that diode across the coil.

        1. splintergroupie | Nov 05, 2008 09:46pm | #12

          Keep the ideas coming and i'll be the courier!

          1. CAGIV | Nov 05, 2008 09:53pm | #13

            I think you win the prize for most interesting/wierd request on BT this year.

            I have nothing constructive to offer other then good luck... all a bit above my head.

  5. DanH | Nov 05, 2008 09:40pm | #9

    Unfortunately, it's been about 20 years since I dabbled around in that stuff. Otherwise I'd possibly have an idea.

    But I'll take another peek and see if anything comes to mind.

    Conscience is the still, small voice which tells a candidate that what he is doing is likely to lose him votes. --Anonymous
    1. splintergroupie | Nov 05, 2008 09:44pm | #11

      Any help you can offer is most welcome.

  6. DanH | Nov 05, 2008 09:53pm | #14

    For a small solenoid wiring directly from the open SCR connection to the open solenoid connection would seem likely to work. You'd have a better opportunity of success, though, if you placed a small "DIP" relay in place of the SCR as described above, then powered the solenoid off of the relay.

    Something like this:

    Conscience is the still, small voice which tells a candidate that what he is doing is likely to lose him votes. --Anonymous
    1. DanH | Nov 05, 2008 09:57pm | #15

      Let's try that again:
      Conscience is the still, small voice which tells a candidate that what he is doing is likely to lose him votes. --Anonymous

      1. ncproperties | Nov 05, 2008 10:02pm | #19

        Run current thru trap to stun it, than the cat isn't quicker than the door.

        Mmmm, 480v should do it.   

        1. Toolsguy | Nov 07, 2008 11:51pm | #46

          200 lb Rottie

    2. splintergroupie | Nov 05, 2008 09:58pm | #16

      Edit: OK, it wasn't just me being blonde! Got it on the second try.

      Edited 11/5/2008 2:00 pm by splintergroupie

  7. john7g | Nov 05, 2008 09:59pm | #17

    can a cat see infrared?  I thought that some animals do and if so will this be a detractor?  something to do with the tapetum?

    1. splintergroupie | Nov 05, 2008 10:02pm | #18

      I guess we'll find out if they can see it, and if they can, whether it matters to them. Good question, for sure.

  8. DanH | Nov 05, 2008 10:06pm | #20

    PS: If this works out I have some cats to try it on.

    Conscience is the still, small voice which tells a candidate that what he is doing is likely to lose him votes. --Anonymous
  9. User avater
    PeterJ | Nov 06, 2008 02:32am | #21

    Electronics aside, would a faster-stronger spring on the door release work? Maybe gently punt the kitty back in.

    I wonder if there's some other trap with a greater distance from door to bait?

    So what's it like to transport one of these things when you get one? Does the cat go nuts or do you knock it out first?

     

    Everything will be okay in the end.  If it's not okay, it's not the end. 

  10. User avater
    IMERC | Nov 06, 2008 02:52am | #22

    use the reader from an overhead door and a selinoid...

     

    Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming

    WOW!!! What a Ride!
    Forget the primal scream, just ROAR!!!

  11. woodway | Nov 06, 2008 03:01am | #23

    How about some sort of capacitive discharge device, sorta like a "cat stun gun," that would freeze em in place for a short while to allow the trap doors to close?

  12. frenchy | Nov 06, 2008 03:06am | #24

    way too complex.. sort of like NASA spending a fortune making a pen that would write in zero gravity and the Russians simply used a pencil.

      Door not fast enough? Simple, make the cage bigger! So the cat takes more time getting back to the door and gets trapped.. that way you don't have to lpug in things and deal with electical failures etc..

      KISS (keep it simple stupid)

  13. Huntertn | Nov 06, 2008 06:32pm | #25

    I have had pretty good luck catching feral cats using a HavaHart mechanical trap. I don't remember the exact model but I think it is a model 1092. If you are putting the food on the trigger plate that might be the problem. I tried that at first but I had much better luck placing the food on the back side of the trigger plate so that the animal (cat) will need to step on the plate to reach the food on the other side. Placing the food that far back will get the cat further into the trap and prevent them from being able to get to the food without setting it off. Assuming that your trap is only open at one end.

    Your cats may be smarter than the ones we have around here so it may not work... but it may be worth a shot.

    Steve

  14. JohnT8 | Nov 06, 2008 06:54pm | #26

    I suppose it wouldn't be easier to find some feral dogs to keep the feral cat population down?

     

    jt8

    The creative individual has the capacity to free himself from the web of social pressures in which the rest of us are caught. He is capable of questioning the assumptions that the rest of us accept. -- John Gardner

    1. DanH | Nov 06, 2008 07:35pm | #27

      Then you'd need feral tigers for the feral dogs. It just never ends.
      Conscience is the still, small voice which tells a candidate that what he is doing is likely to lose him votes. --Anonymous

      1. User avater
        Luka | Nov 06, 2008 07:42pm | #28

        Let me guess.All this started with a feral fly...

        1. DanH | Nov 06, 2008 07:47pm | #29

          Then I guess we need to work a goat in there somewhere.
          Conscience is the still, small voice which tells a candidate that what he is doing is likely to lose him votes. --Anonymous

          1. User avater
            Luka | Nov 06, 2008 07:52pm | #30

            Can't.Dovetail hid it too well.

    2. Norman | Nov 06, 2008 11:26pm | #31

      Ever see a dog / cat fight? Dog leads with its mouth, directly below the nose and eyes. Cat claw in either one really dilutes the dogs agenda.

      1. cm59870 | Nov 06, 2008 11:34pm | #32

        Howdy, boys and girls. I just wanted to say thanks for the effort and the emails helping me with this. Don't you just love technology? <VBG>

        1. frenchy | Nov 07, 2008 02:42am | #33

          I hope that's splintergroupie who's figured out the trick to avoid the whiners..

        2. mhole | Nov 07, 2008 02:50am | #34

          Translating screennames to their real persona is like learning a second language...;)

  15. gstringe | Nov 07, 2008 03:25am | #35

    The circuit you have as drawn is incorrect. The 10k resistor from the emitter of the 2n2222 transistor should go to ground. The trigger of the SCR then should be connected to the emitter of the 2n2222 transistor. The output of the SCR should be connected to the bottom lead of the solenoid. The circuit works thusly: The Infrared beam shines on the photo transistor and turns it on. The conducting photo transistor then has a very low resistance in the on state and that means that the voltage at the bottom of the 100k adjustable resistor will be very low and not high enough to turn on the 2n2222 transistor. When the IR beam is broken and the photo transistor shuts off, voltage at the bottom of the 100k resistor will rise and turn on the 2n2222. The 2n2222 in the on state will have a low resistance and hence the voltage at the emitter and top of the 10k resistor will rise to towards the 9 volt supply. This positive voltage will trigger the SCR to turn on and conduct thru the solenoid. This circuit will not reset until the power is removed and reapplied, so the solenoid will continue to be pulled in.

    Nobody gets in to see the wizard...not nobody...not no how!
    1. splinteredux | Nov 07, 2008 04:07am | #36

      It's Greek to me, but that sounds very authoritative and i'll pass on the info to the vet so he can modify his set-up. Merci!~Splinter

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