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Locking cat door, really need some help...

Discussion in 'General Electronics Discussion' started by DarrenF, Aug 23, 2016.

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  1. DarrenF

    DarrenF

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    Aug 23, 2016
    Here is the situation. I have in a closet, a CatGenie automated litter box. The cats have access to the closet through a standard cat door. What I want to do, is have the door prevent entry while the litter box is running for it's 45 minute cleaning cycle. The reason for this, is if the cats enter the closet during the cycle, they'll just do their business on the closet floor instead of waiting. I suspect that they will only go on the closet floor, and not somewhere else if they find the door locked temporarily. I already have a surge strip with triggered outlets that provide AC power when the litter box is cycling, so I can use that to trigger the door. I cannot use off the shelf magnetic locks because they only work with a door that only swings one direction, and a cat door swings both directions.

    Any thoughts?
     
  2. AnalogKid

    AnalogKid

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    Without photos or information on the door and the off the shelf locks, it's kinda hard to say. But. The door swings in both directions, but the cats *enter* from one direction only ...

    ak
     
  3. DarrenF

    DarrenF

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    Aug 23, 2016
    Correct. They then "exit" going the other direction.
     
  4. AnalogKid

    AnalogKid

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    Not my point. If the off the shelf lock can lock in one direction only, that isn't a problem because you don't care about locking them in, just out. If you mean it permits door movement in one direction only, that's something different.

    ak
     
  5. DarrenF

    DarrenF

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    Aug 23, 2016
    It is a problem because an of the shelf magnetic lock is in the way if the door wants to swing toward the lock. The magnetic lock prevents a door from pulling away from it when engaged, but as I said, it is designed for a door that only swings one way ( which would be away from the magnet). In the case of a cat door, the magnetic lock when engaged would prevent the door from swinging both directions, and when not engaged would prevent it from swinging in one direction, thus making the door always a one way door for the cats.
     
  6. AnalogKid

    AnalogKid

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    Easy part: A small DC solenoid with a spring built-in to keep the plunger extended when off. Power comes from a wall wart plugged into the switched outlet strip.

    Not so easy: To the end of the plunger attach a metal strip (or, if it has a hole through it as many do, a long bolt secured by a nut) that sticks out to the side maybe an inch past the solenoid body. Position the solenoid on the inside of the cat door frame, oriented vertically, down low and against the edge of the door opening. At this point the strip is parallel to the bottom edge of the movable door panel. Down low enough that when the solenoid is off the strip is below the bottom edge of the door, and when the solenoid is on it pulls the strip up until it blocks door movement inward.

    ak
     
  7. 73's de Edd

    73's de Edd

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    .


    Sir DarrenF . . . . .


    From the aspect of its mechanical construction and particularly the door aspect . . . .is this being your
    PORT-A- KITTY ?


    GENIE DOOR.png



    73's de Edd

    .
     
  8. DarrenF

    DarrenF

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    Aug 23, 2016
    I have tried exactly this, problem is the solenoid gets extremely HOT during the 45 minutes it's engaged. I tried knocking the DC voltage way down, but if there is enough voltage to move the plunger, there is enough to generate a LOT of heat. Maybe you have a parts suggestion? Thanks in advance.
     
  9. DarrenF

    DarrenF

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    Aug 23, 2016
    That is the Cat Genie, but I do not have the dome attached.

    As for the door, it goes through the wall separating the closet from a hallway..

    This is it....
    [​IMG]
     
  10. AnalogKid

    AnalogKid

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    Surplus market car door lock mechanism. These are based on a reversible DC motor that moves a plunger in or out with a gear mechanism. The motor sits there unpowered no matter which location the plunger is in. If you find one of those and again put a tab or bolt on the armature to block the door, then we can discuss how to control it automatically. Since this is an EE forum, the controls are the easy part to us.

    http://www.allelectronics.com/make-a-store/item/dla-1/door-lock-actuator/1.html

    With a regulated +12 V power supply or wall wart, measure the time it takes for the plunger to fully extend, measure the time it takes to fully retract, and measure the current while running. Driving the motor in both directions will take either two SPDT relays or a transistor circuit (or IC) called an H-bridge, plus a CMOS logic chip to control things.

    The basic plan could go like this. When AC power is applied to the 12 V wall wart, the control circuit wakes up and pulses the motor in one direction. The wall wart also charges up a storage capacitor. When AC power goes away, the control circuit detects this and uses the energy in the storage capacitor to pulse the motor in the opposite direction.

    There is another way that involves a large capacitor in series with the motor, but that depends on how much current the motor needs. Lotsa options.

    ak
     
    Last edited: Aug 24, 2016
  11. hevans1944

    hevans1944 Hop - AC8NS

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    Cats are smart. Teach your cats how to read and then put a little electronic display panel on the door. Display a message during the cleaning cycle: OUT OF SERVICE USE KITCHEN FLOOR. Or, if you do modify the cat door to lock during the cleaning cycle, perhaps the cats will figure that out for themselves. Mine always did if I forgot to empty their litter box, although most of the time they thought the bedroom had better ambiance (and a warm waterbed blanket cover to poop on).

    Perhaps you could rig up two solenoids that slide a locking bolt back and forth. One solenoid to lock, the other to un-lock, momentary operation for both. Get the mechanics of that worked out and the 'lectronics should be simple, as the @AnalogKid said in his post #10.
     
  12. BobK

    BobK

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    Or you could power an electric fence from the switched outlet.

    Bob
     
    hevans1944 likes this.
  13. DarrenF

    DarrenF

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    Aug 23, 2016

    OK, Door lock ordered. Once it comes in and I have the info you need I'll resurrect this thread. Thanks so much. Can't wait to get to building the circuit, that is not something I've done before.
     
    hevans1944 likes this.
  14. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    As for the door, it goes through the wall separating the closet from a hallway..

    Totally missed that . . . . in concentrating so heavily on the cat Genie proper.

    Hope that you zeroed in on this economical unit or a variant of it.


    Application:





    It only has 2 leads and probably will be using minimal 12 VDC power in cycling open and closed .
    It should have a mechanical cycling and switching such that power application causes it to then cycle to the end of its function and automatically stop. then the reverse direction on the opposite action.

    So overall, it just needs external " brains" to sent 12 VDC power on the activation of the cleaning mechanism and a like situation, sent at the end of the units cycle.

    Two 12 VDC relays and a couple of electrolytic capacitors could accomplish that.


    73's de Edd


    .
     
  15. AnalogKid

    AnalogKid

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    See the link in post #10. It has no internal protection or switches of any kind, so you have to drive it with a timed power pulse that lets the motor stall for only a short time.

    ak
     
  16. DarrenF

    DarrenF

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    Aug 23, 2016
    Thanks everyone for the ideas. Once the activator arrives, I'll gather the data AK asked for and post that here. :)
     
  17. hevans1944

    hevans1944 Hop - AC8NS

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    You could, of course, sense the sudden increase in current that occurs when the motor stalls, and use that event to turn off the motor. A few turns of wire around a Hall sensor will do that. Timing the lock-time required, and using energy storage in a capacitor to un-lock seems simpler. Could also use micro-switch limit switches with some increase in cost and complexity. With hardly any effort at all you could also add microprocessor control, but the cats might not be able to cope with that. Mine went bananas whenever I used a red-laser pointer to annoy them, so who knows how they would respond to microprocessor control of the hallway door to their litter box... might want to add a cat's paw sensor somewhere to justify the added complexity.
     
  18. david gordon

    david gordon

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    Nov 14, 2012
    use twin plunger solenoids to lock from both sides &use the really cheap ones they sell as after market automobile
    door solenoids
     
  19. AnalogKid

    AnalogKid

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    Jun 10, 2015
    Posts 10, 13, 14.

    ak
     
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