Sunday, March 23, 2014

Automated Pet Food Dispenser -- 2

Tim and I started working on a different version of the automated pet food dispenser.  Originally, I was trying to duplicate a design I saw on Instructables.  Long-story-short, I could not get the 3D printed pieces to mate with the PVC T.  I tried grinding off some surface area of the various pieces but they just got ruined.

So, we switched gears and are going to make a more traditional project based on something I saw on YouTube.  This is actually better because Tim and I can work on it together.  The former project was something I was mostly doing alone at the Milwaukee Makerspace.  We can work on this project together at home.

The first step was to get a new motor.  I found a small 17 volt DC motor on the hack rack at the Makerspace. It seems to be a good choice for this project. I wanted a motor that would not spin too fast but also had enough torque to push the food through if it got stuck.  I can get both torque and slow speed by putting only 5 or 7 volts DC into the motor.

I'm not exactly sure how we will power the motor. One idea would be to use a common AC to DC power supply. I  have one that provides 5v and one that provides 12v. The 5v PSU spins the auger at the right speed.  Not sure if it has enough torque. The PSU would plug in to a timer that would turn it on for a enough time to fill the bowl once a day or so.

The other idea is to connect the motor to an Arduino or Raspberry Pi. The advantage of this is that the device can provide power for a specific time on a specific schedule. It could change the direction of the motor if needed. Plus, we could have it detect when more food is needed in the future. The disadvantage of this idea is the cost of the device as well as the fact that the device can provide, at most, 5v of power.  If more power is needed, the microcontroller have to control another source of power.

Another main piece of the pet feeder is the Auger that will move food along the pipe to the bowl. I bought a 8 inch long, 1 inch diameter Auger drill bit for wood at the local hardware store. One problem is that the auger has a sharp tip.  We'll try to keep the tip inside the tube so the dog does not stick himself trying to get more food.

Someone suggested that I find an old refrigerator with an ice maker.  That would have a motor and auger powerful enough to move the dog food.  I'll keep my eyes out for one but for now, these parts will have to do.

Delivery Tube
We are thinking about using a PVC tube to deliver the food into the bowl.  I had some extra PVC pipe with a 1.5" inside diameter.  We cut it to a length of 8" with a pipe cutter.  Then, we used a reciprocating saw to cut a 2" long hole in the middle of the pipe.  When the whole feeder is done, dog food will drop through the hole and on top of the auger.  The auger, powered by the motor, will move the food through the tube and into the bowl.

The final thing to report for this blog post was the adapter we made to connect the auger to the motor. The shaft of the motor is much smaller than the shaft of the auger.  Also, the shaft on the auger is a hexagon while the shaft on the motor is D shaped.  To make a connector, I needed help from Tom G. and Charles at the Makerspace.

We found a round aluminum rod on the hack rack and cut a small piece off using the horizontal bandsaw.  

Next, Tom helped drill a small hole through the entire piece and then a slightly bigger hold about 1.25" into one end.  We used the lathe to make sure the hold was perfectly centered and straight.

Finally, we drilled small holes on each end of the connector, and threaded each hole.  Inserting small taps into the holes when the shafts are inserted into the connector will secure the shafts in the connector.  Here is a picture of the connector.

The next step is to put the auger and motor into the tube and see if the motor has enough power with 5 volts of electricity to push dog food through.

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