DIY Cat Feeder and Water Dispenser

Video: DIY Automatic Cat Feeder [2.3 mb]


I have two wonderful cats, and many wonderful neighbours.  Naturally, for my vacation, I combined the best of both worlds and had one of the neighbours watching my cats. 


Despite this, I didn’t want to force my neighbours to come over twice a day to feed the cats.  So I sought out to make an automated cat feeder and water dispenser out of parts lying around the house.  As for the cat litter?  That’s fine – that can be left to stupid humans  :)


 


The Automatic Cat Feeder



Naturally, I looked around the internet first for ideas and plans.  I knew that the ‘Maker’ attitude could do better than the expensive pre-made contraptions you can find in stores.  I stumbled on the nifty hack in Make Magazine that repurposed an old VCR, but it portions out soft cat food – and requires some pretty complex mechanical pieces.


At first, I tried playing around with some little stepper motors and gears I had laying around in my electronics toolbox.  After applying some electricity, I realized that the motors had nowhere near enough power to move anything significant.  So I went down to my computer junk box in the garage in search of inspiration.


As I dug around this box, I found an old CD Rom drive and power supply.  The thought struck me that I could use the ejecting tray of the CD Rom as a solenoid to push the trigger mechanism of some sort of physical contraption.  But then I had a bootstrapping problem – what can I use to push the eject button of the CD Rom on schedule?


After some more thought, I realized that I could just use my spare (working) computer as the basis of the cat feeder.  It’s also my home’s Subversion source control server – a rare mix of server workloads indeed!  It has a CD Rom drive, so I could just use software to open and close it. 


The computer runs Ubuntu Linux, so a crontab entry controls the scheduling.  The script calls eject /mnt/cdrom to open the CD Rom, delays, and eject –t /mnt/cdrom to close it again.  It actually does this twice, as I found it made the portions more consistent.


Automatic Cat Feeder CD Rom in Action


Since it’s a full fledged Ubuntu system on my wireless network, it allowed for an obscene show of technology.  I was able to use my JasJar PDA phone to SSH into the box, and feed the cats on demand just by running the script.


JasJar Controls Cat Feeder


With that as the basis, the only thing left was to design the physical contraption to actually feed the cats.  My first thought was some sort of rotating mechanism at the bottom of a container to dispense portions from pie-shaped wedges.  However, my primary concern (aside from killing the cats if the idea fails) was that the oddly shaped food pieces might jam the mechanism. 


From there, my second idea was to fill a box with cat food, and have a little trap door at the bottom.  And that’s the plan I went with.  An elastic holds the trap door closed, and the CD Rom tray pushes the door open.  When the CD Rom closes, the elastic shuts the trap door again.  Binding is no problem, as the food just binds in the trap door.


Automatic Cat Feeder and Computer


Finally, a cardboard chute directs all of the food into the bowl, and a big cardboard box encloses everything to prevent the cats from getting curious.


Automatic Cat Feeder Chute and Arm



 


The Automatic Water Dispenser


This idea is extremely simple, and is based on the same physical concept that governs most other automatic water dispensers.  Punch a pencil-sized hole about 1 inch from the bottom of a large jug.  Fill with water, seal, then place in a dish greater than one inch high.


Automatic Cat Water Dispenser


Water flows out of the jug as long as the water level is below the hole at the bottom.  When water flows out, the air pressure in jug decreases until it sucks in some air to equalize.  When the water level covers the hole, though, the air pressure can no longer equalize, so the water flow stops.


When the cats drink the water level down a bit, the jug can once again equalize its air pressure, and lets more water out.


Both contraptions worked extremely well for over a month (including testing time and vacation time.)  I’ve now taken apart the cat feeder, though, as it’s not the most aesthetic addition to my kitchen.


[Edit: Some kind soul put the video on YouTube for me.]
[Edit2: More detailed build instructions and meta-blogging here.]

22 Responses to “DIY Cat Feeder and Water Dispenser”

  1. Ted Holmes writes:

    Using the CD ROM drive as a programmable solenoid to start a chain reaction was a great idea. There are so many possibilities. I can imagine triggering an avalanche of bowling balls at the top of the stairs in a new version of "Home Alone".

    Also, with a little work, you could put everything inside a small appliance skin so that it matches the kitchen.

    Thanks for posting in my native language of English today Lee :)

  2. Travis Pettijohn writes:

    That’s awesome. I especially like SSH from the JasJar…just because you can.

  3. Matt writes:

    Just like Doc’s!! :O

  4. Kristian writes:

    Doesn’t your cat try to take the food directly from the box then?

  5. Lee writes:

    Hah :) It first they pawed around the box which moved it. That’s why there are 2 heavy phone books on top now.

  6. malejko writes:

    So – how much food does the cat get, and how are you controlling the portions? Or do you? My girlfriend and I have been looking for a ‘better’ cat feeder for when we go away for a few days, but just can’t find anything good enough to give one of our cats his 1/2 or 1/4 cup portion twice daily. We’ve been thinking of building something, but the ideas haven’t managed to figure out how to portion properly without binding, and without being too bulky or too flimsy.

  7. Lee writes:

    The entire purpose of this thing was to control the portions :) Both cats were previously stray, so self restraint isn’t exactly their forte.

    There are two aspects that control the portioning. The first aspect is the distance between the computer and feeding arm. That controls how much the trap door opens, which controls the flow.

    The second aspect is how long the CD Rom stays open. It doesn’t actually just open and close — the script keeps it open for 0.4s, twice. That doses properly for my two cats, which is about 1 cup (twice daily) in total.

    Can’t help you with the bulky thing, though :) This is absolutely a bulky contraption. If it’s something you do often, you might just opt for buying a feeder from the store.

  8. FunkSpray writes:

    So…automatic water and food dispenser. Now all you need is an automated toilet cleaner and you are set for holliers.

  9. Lemmons writes:

    Theoretically, you’d be able to program that script with a scheduler to autoexecute at a certain time each day (say, 5 am and 5 pm) and skip the whole feeding thing altogether. All you’d need to do is buy food and make sure it stays full. In the words of those annoying Guinness mascots, "BRILLIANT!"

  10. Lee writes:

    Actually, I had it feeding automatically at 7 AM and 7 PM :) It’s fun to log into the machine and all, but it was primarily operated by schedule.

  11. Nixnooi writes:

    Dude you rock! My problem is my cat sitter is 15 and some times not so reliable. I would love to be able to log in and throw some dry food out, when at 10pm I find she has not shown up for the whole day… I "do" linux but I’ve never built anything like this though .. but the need is there man! I used zoneminder.com (linux live cd) to monitor the house and know the cat sitter missed .. if I could only push a button …..

  12. Leigh writes:

    Hi..just wanted to thank you for this great idea* the water feeder..how simple and yet effective..I am thrilled..bought a electric ‘fountain’ one and after a few months it just stopped working..’motors’ etc…this is safer and easier too* Great invention** thanks again..keep up the great work..good for you! Leigh

  13. Miss writes:

    Great concept. Not the prettiest looking contraption, but it sure is ingenious.

  14. Dave writes:

    The water dispenser works great for the bird bath as well

  15. ivan writes:

    There is an idea. An automatic cage for release of mice with a sound signal.

  16. Mathew Newton writes:

    Excellent stuff Lee – your feeder inspired me to give it a go myself but the requirements soon crept out of control… Before I knew it I had the lid off a Cisco switch modifying it to act as a network-enabled motor controller… The user interface similarly didn’t stop creeping and I moved from SSH access to a full-blown web frontend with live video streaming! You can see the end result at http://www.newtonnet.co.uk/catfeeder

  17. Robin writes:

    We who are non-techies, without electronic toolboxes, garages, stepper motors, etc., … salute you.

  18. Jean writes:

    I was told that the cat needed fresh water all the time. Wouldn’t your water dispenser collect cat hair and food particles and grow bacteria over some time? Did you have to have the container cleaned from time to time? I really want to try it for my long vacation. Please reply and thanks for the great post!

  19. Lee Holmes writes:

    Hi Jean… the water stays pretty fresh just by coming out when they drink the other stuff. As for the dispenser collecting random stuff – it does over time, but you can just wash it like you do a regular water bowl. After using that makeshift one during my vacation, I went and bought a regular one gravity-fed one (not pump-driven) from the pet store and it’s been doing great for years. (kind of like this one: http://www.amazon.com/Pureness-X-Small-Auto-Waterer-Liter/dp/B0002DK6HM/ref=zg_bs_2975260011_16)

  20. Mar writes:

    Absolutely brilliant – ur a genius! Totally McGyver:)

  21. rob writes:

    Dude thats an awsome project

  22. Yeun writes:

    You sound like a real character! LOL! What’s your next project?

Leave a Reply