Introduction: Automatic Pet Feeder
I needed a reliable fish feeder for my pond for when I'm away. This instructable gives details on the feeder that I just finished building and testing. The same idea could be used for feeding other pets or for an indoor aquarium. I made a number of internet inquiries to find out details on the microwave carousel motor that I planned on using to drive the auger. The problem with the motor is that it will often reverse rotational direction when it is turned ON and OFF and ON again. I learned from internet contacts that a ratchet would solve the reversing problem so that is what I ended up using here. A short demo near the end of the video (below) shows me stalling the motor to reverse direction. Some microwave carousel motors work directly from the line voltage in which case you wouldn't need a transformer. However I feel comfortable with the lower voltage setup for this application as it gives an extra level of safety when the feeder is operated outdoors. The electronic timer allows programmable ON and OFF times for the motor. (Better still if you have or can find a gear head dc motor the rotation direction is controlled just by reversing the polarity of the connections.)
I decided to change the name of this instructable to Automatic Pet Feeder from Automatic fish feeder as viewers are using the idea to feed other things...
In any application like this it is important to plug the timer into a ground fault circuit interrupter (GFCI) electrical outlet.
I had an old 7/8 inch diameter auger-type wood drilling bit on hand and figured it would work fine for the size of food pellets that I normally feed the trout. I needed a plastic container that would let the drill bit stick out from both sides of the container. The two auger holes should be made as close to the bottom of the container as possible so that most of the feed will be pushed out by the auger as the supply nears the end. I drilled the large hole with a Forstner bit but the auger bit would probably work as well as long as you feed it very slowly through the soft plastic. Before going on with the assembly I decided to check out the auger operation using the portable drill.
I replaced the set screw in the drill bit stop collar with a longer screw that extends from the collar far enough to work as a ratchet tooth. Holding one of the toggle bolt wings with locking pliers made for a safe way to drill the two holes for the ratchet mounting screws. I assembled the auger, collars, washers, and ratcheting parts in place to do a quick test of the ratcheting action.
All of the collars are drill bit stop collars. I got some of these in a set and they cost only a dollar or so each. The collar used in the ratcheting system is also a drill bit stop collar, but it was selected for the ratchet because of the way the screw extends (tangent like) from the collar.
Here I temporarily screwed the motor mounting brackets to the pressure treated wooden base and I then temporarily clamped the motor on the brackets to do an alignment and operational test. After a successful test, I marked, punched, and drilled the bracket holes to accept the motor. After that I did the final assembly of the feeder.
I moved the feeder to the shed next to my fish pond to do the final wiring and testing. I found that I needed an additional (resistive) load on the electronic timer to give me reliable and consistent timing action. I plugged a lamp with an incandescent bulb into the second socket of the timer (if you have only one outlet you could use a power bar to do the same thing). I like the electronic timer because you can very precisely set the ON and OFF times - also, the battery backup keeps the programs in place should there be a power failure. I'm still experimenting to find a most suitable ON time but right now it looks like 5 or 6 mins will do it. The timer is set to repeat every day of the week.
I've conducted multiple indoor tests running the motor for long periods to see how it would react with the 16 volt doorbell transformer. The temperature rise was barely noticeable and the motor torque was more than sufficient in all of the tests.
Every thing is working fine so far but I want to continue testing to be sure the feeder will function reliably over 10 plus days. My concern is primarily with the electronic timer. I want to be sure that the program holds in place with multiple ON-OFF cycles.
The pond testing went well and the fish quickly adapted to the new feeding method. I used a larger plastic bin to protect the feeder from the weather and critters (mainly crows and cats). But I can't knock the crows as they have been cleaning up food pellets that the fish didn't eat .