Automated Cat door

Discussion in 'The Projects Forum' started by Meesen, Mar 19, 2014.

  1. Meesen

    Thread Starter New Member

    Dec 9, 2012
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    0
    Hi guys was wondering if i could get someone too help me design a circuit for my automated cat door i am currently building :)

    What i want too do is have a motor driven system too close and open the door for me in the mornings and at night,

    It would consist of a 2 button momentary switch mounted in my house, ideally being powered off a universal 12v power supply as i have an old one in the shed,

    I guess there would be a controller of some sort involved too take the button press and send power too a relay in either direction until it either opened or closed or had an obstruction

    Ive got a little motor out of a old drill I'm using with a gear attached running on a geared rack on the door

    So think it would need some sort of sensing circuit too know when too stop the motor, I have good soldering skills and can understand basic circuits but as for designing them i wouldn't know where too start so any help would be appreciated :)
     
  2. wayneh

    Expert

    Sep 9, 2010
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    I've thought about this quite a lot over the years but haven't built one. If I do, I won't move the door (the cats can do that) but rather only the latch. This simplifies the system quite a lot. The latch can be 2 rotating discs on a shaft, with 4 settings; door locked in both directions, open in both, or in-only or out-only. The shaft is parallel to the cat's path. The discs are on either side of the door and have quadrants cut out that allow the door to open corresponding to the 4 settings. Where the quadrant is not cut out, the door is blocked.

    For me, daytime is open in both directions and nighttime is closed in both. At dusk I want them to come in but not be allowed back out. I don't have much use for the 4th setting where they can get out but not back in, but it could be useful I suppose to reduce the chance of an unwelcome cat from visiting.
     
  3. Meesen

    Thread Starter New Member

    Dec 9, 2012
    6
    0
    Thats another great way to do it, but sadly i have already made my door and fitted it all into the wall, i am currently manually opening and closing it though until i get something made up :) im sure some guys on here would know how to make a circuit as mentioned... i hope!
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,153
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    So basically you need a mini garage door opener?

    There have been several chicken coop projects in this forum that might be worth looking at.
     
    #12 likes this.
  5. magnet18

    Senior Member

    Dec 22, 2010
    1,232
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    from the simplest beginners standpoint-
    arduino or other microcontroller of the likes of timing and/or control
    relay shield for taking arduino pin to 12V motor controlling
    mechanical sensor (reed switch or magnetic?) to detect when door is fully open or shut, feed that back to the arduino

    looking up those should get you a good start
     
  6. GRNDPNDR

    Member

    Mar 1, 2012
    435
    7
    This could be done all mechanically I think.

    You could use a relay and a 3-wire control with 2 limit switches.

    When you press the button it latches the relay closed until the door opens and hits the limit switch stopping power.

    Press the close button and it would do the same only in reverse.

    Much like a garage door system.

    An Arduino would be a much neater/smaller solution, but if you don't have the programming skills (and I'm sure others would be there to help) or if you don't mind your cat door looking like something from Doc. Browns house then the mechanical way would be an option.
     
  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    I'm with GRNDPNDR on this one, very garage-door-ish, no silicon expressed or implied. A uC seems like massive overkill for something that was worked out in the 1890's. A 3PDT relay has two sets of contacts for the motor and one to make it self-latching. Two of these, one for each direction, and two limit switches, one to open each relay as the door hits the endpoint.

    The only complication is if power goes out while the door is in motion. A third "power-on-reset" relay will force the logic to a known state, such as always move to close the door after a power outage.

    Is everything (motor, relays, etc.) going to be 12 VDC powered?

    ak
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    OK, time has passed.

    1. The relays can be 3PST.

    2. The system does not need a power on reset relay. I rethrought the limit switches, and now if power is lost during a cycle, the system just sits when power comes back on. The door sits half-open until one of the control switches is pushed, then it goes in that direction.

    3. Prelim sch is attached.

    4. The two control switches can be combined into a single SPDT momentary. This makes it impossible to have both closed at the same time.

    5. If you want to stick with two separate control switches, then for added protection make each of them DPDT. The second NC pole of each switch is in series with the limit switch of the other side. When you push either control switch it kills power to the other direction relay, eliminating a possible momentary dead short on the supply.

    ak
     
  9. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,805
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    To avoid guillotining your cat you may wish to add an obstruction-sensor :).
     
  10. inwo

    Well-Known Member

    Nov 7, 2013
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    +1

    A string "pull" with gravity close. Maybe?

    Here are some diagrams from similar projects.

    They all have limitations from AnalogKid's design.

    One needs four power wires to switch, but needs no relays.
    One needs maintained switch, and relay remains powered in one position.
    One uses PB switches, but also keeps relay powered. Returns "home" after power failure.
     
  11. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    inwo - I had a thought about using diodes to steer the motor, then lost it when I was editing the sch. Nice, makes things much simpler.

    Your third sch gets the minimalist award. Winner.

    ak
     
  12. inwo

    Well-Known Member

    Nov 7, 2013
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    I was going to draw one with two relays, but you beat me to it.

    The concern being; a single relay would have to remain energized, in one position of the door..
     
  13. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    True, and that is why I jumped to two. But one DPDT, non momentary, dumb-as dirt toggle switch can't be beat - it comes with free zero-power, non-volitile memory, and uses a bio-fuel source for actuation. Very green.

    ak
     
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  14. burger2227

    Member

    Feb 3, 2014
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    WARNING: Allowing your cat outside turns it into a hunter. Unfortunately it will only bring back about 10% of its kills.
     
  15. GRNDPNDR

    Member

    Mar 1, 2012
    435
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    and drop the entire 10% at your feet.....as half kills, with guts spilling out, to say "I love you human, have this"....
     
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  16. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    My wife (dog person) discovered this when we got married and moved into our house. My cat (pure hunter) brought her breakfast...
     
  17. wayneh

    Expert

    Sep 9, 2010
    12,153
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    Mine just barfed up some poor rodent onto my carpeted stairs. Grrr.... :mad:
     
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