Simple and reliable pet feeder

Discussion in 'The Projects Forum' started by HBB, Nov 15, 2013.

  1. HBB

    Thread Starter New Member

    Mar 3, 2012
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    I have a commercial pet feeder but is nor reliable. Its rotary drum gets stuck very often, and after 3 factory repairs I gave up.

    I want to build one based on a gravity discharge tube about 3 inch diameter closed by a metallic door held up by a spring.

    A solenoid triggered once a day will open the door for some 6 to 8 seconds and let the food drop.

    Accuracy is not a main issue. Reliability is.

    I have 48 VDC source, since it is for feeding a defense dog that lives in a cabin in a no line area. Of course also 12 VDC is available.

    Question 1: I feel that a simple 555 circuitry will do this, but where to get the "starting up inspiration"

    Question 2: Accuracy of the cloch will need an external quartz or not ?

    Thanks a lot,
    Horacio
     
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Asking a 555 to time for 24 hours is quite a stretch; that's not to say it can't be done, but the accuracy will be poor, and it will be hard to test and regulate due to the long times between operation.

    I would use a real time clock circuit. You can buy one already assembled, or you can build one. The complication there is that most require a micro-controller to interface to them.

    Simplest way is with a commercial timer if you had mains power available.

    Can you post a link to the commercial feeder that doesn't work (just for my curiosity)?
     
  3. MrChips

    Moderator

    Oct 2, 2009
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    Yes, to maintain time-of-day accuracy you will need a quartz crystal.
    Even the best of clocks can be expected to drift by 1 sec per month.
    You can reduce the drift by carefully adjusting the crystal frequency with an adjustable trimmer capacitor.

    Overall this is a fairly straight forward project especially if you have some knowledge programming a microcontroller. 12VDC would work fine but I would choose a DC motor instead of a solenoid.
     
  4. crutschow

    Expert

    Mar 14, 2008
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    It doesn't seem that a timed opening of a door would give a repeatable amount of food. Wouldn't it depend upon the amount of food in the hopper and the consistency of the food? Also, how you going to insure that it doesn't stick or jam?

    For the primary timer how about this? You could use that to trigger a 555 one-shot to operate the solenoid.
     
  5. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    Ditto ready made timer on ebay...
     
  6. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I have always thought that a mechanism similar to a grain auger, and driven by a small motor for a controlled amount of time would work. But I have never tried it.
     
    Last edited: Nov 16, 2013
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I second the augur method.
     
  8. helijoc

    New Member

    Nov 16, 2013
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    I made a feeder that feeds my 2 outside dogs twice a day. It holds enough food for 3 weeks. It is auger based driven by a windshield wiper gear motor. The timer is a pre-made unit I found new on ebay for $25, it is designed for feeding deer. Basically it has 4 program times per day with the amount of on time programmable. One problem I have is that it gains about 50 minutes per year, the dogs don't care but I do. I contacted the seller and got some crystals but they didn't make much difference.

    I am interested in how I could change "crystal frequency with an adjustable trimmer capacitor".
     
  9. tracecom

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    Apr 16, 2010
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    I would like to know more about the mechanical construction, especially what you used for the auger.
     
  10. helijoc

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    Nov 16, 2013
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    SgtWookie and tracecom like this.
  11. HBB

    Thread Starter New Member

    Mar 3, 2012
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    Thanks very much to all of you.
    I will follow the auger method with plastic tubes.
    Cheers !
    Horacio
     
  12. HBB

    Thread Starter New Member

    Mar 3, 2012
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    tracecom likes this.
  13. tracecom

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  14. HBB

    Thread Starter New Member

    Mar 3, 2012
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    Hello

    What kind of PIC circuit are you going to use?
    I will follow the idea of a commercial timer to trigger a 555 Time Machine.
    Is simple.
    Pls let me know what you think about.

    Kind regards,
    Horacio
     
  15. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I will start with a very simple routine for a PIC12F683. It will have nested counter loops that will time 24 hours. Every 24 hours, the PIC will go high for a pre-determined time period. The high pin will drive a MOSFET, which will turn a DC motor. The motor will turn the auger and dispense the feed.

    The challenge will be making the mechanical dispenser, but I have a scheme in mind using PVC pipe and fittings.

    Once that works, I may connect a real time clock and set alarm(s) on the clock to dispense the feed.

    A 555 one-shot connected to a commercial timer should work very well.
     
  16. iONic

    AAC Fanatic!

    Nov 16, 2007
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    I hope you don't leave you dogs alone for 3 weeks at a time!
     
  17. helijoc

    New Member

    Nov 16, 2013
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    Not at all. My daughter used to feed them but would over feed them and we had bird and mice problems because of the uneaten food. The feeder solved that. When we are on vacation we have a CCTV system that monitors the complete property I access the cameras from any internet connection and my cell phone. Additionally I have good neighbors that watch and check in on them even if we are gone for 1 day.
     
  18. helijoc

    New Member

    Nov 16, 2013
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    I went that route even welding up a 1.75" diameter auger only to find out that it was only good for VERY small kibbled food, like hamster food. The spacing anywhere inside the auger, shaft to walls, between blades, etc has to be more than 3 kibbles side by side. Three kibbles can and will lodge together and block all passage. Since the system is gravity fed there is no helping force to break through. The one I recommended was not by guess, I learned by trial and error.

    [​IMG]
     
    Last edited: Nov 25, 2013
  19. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    That's interesting. I would have thought that close fits would be the way to go, i.e., make any gaps too small for the kibbles to lodge in. What size is your motor driving the auger? Would a bigger motor help to break the jams?

    Anyway, my dispenser is intended for bird feed (chickens and/or quail), so maybe the auger I bought (which hasn't arrived yet) will suffice. As you say, it will be a learning experience.
     
  20. helijoc

    New Member

    Nov 16, 2013
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    My drive motor is a windshield wiper motor, Dodge I think. It is running on 12 volts supplied by a lithium battery, at full stall it pulls 5-6 amps. If a kibble gets half way into the feed tube on the entry end it will break it. The jam up I speak of doesn't stop the auger from moving it just blocks the path for the food to continuously travel.

    In any case if you are only working with bird feed then the small auger will work fine. That feed will almost "flow" like a liquid through the auger so it may be necessary to angle the auger / tube upward on a slight incline.

    I started developing a feeder for my Macaw using my smaller auger but ran into the problem of getting rid of the empty shells he leaves in the bowl. I considered many ways to empty the bowl before each feeding but then went simple and put a trough in that holds 1 week of food, that has been working for over a year, simple wins again.
     
    Last edited: Nov 27, 2013
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