Tim and I worked on the automated pet feeder yesternight. We tested the motor to see if it could push dog food through the pipe. In all the tests, we used the 8" long, 1" diameter auger that I bought at the hardware store and a 17 volt DC motor that I found on the hack rack at the Milwaukee Makerspace.
We started out using a pipe with a 1.5" inside diameter. First, we hooked up a 5v power supply to the motor. It did not have enough power to push the food through the tube. Pieces would get stuck on the lip of the hole. We tried reversing the power so the auger went backwards, then had it turn forward. This did not help.
Next, we hooked up a 9v power supply. Pieces still got stuck on the lip. The motor could not push the pieces through.
For the next test we used a T shaped pipe with a 2" inside diameter. This was the pipe and wood stand that we were going to use for the other pet feeder project. The 5v power supply did a bit better in this pipe, but the food still got stuck. The motor was not able to push it through.
The 9v power supply faired much better. It was able to push the food through most of the time but it still got stuck. Again, we reversed the spin on the motor and it seemed to work better. One downside to using a 9v power supply with this motor is that it spins so fast it will fill up the bowl in about five seconds.
We think the final solution should use the 2" ID T PVC with the 9v power supply. In order to make sure the food is always pushed through the pipe, a raspberry pi will be used to spin the auger forwards and backwards. The RPi will also control how long the motor operates.
One other problem is getting the RPi to control the power flow from the 9v PSU. The current idea is to use a DC to DC relay. The 9v PSU will plug in to the relay. The RPi would turn the relay on and off allowing the PSU to power the motor.
The next step is to test the RPi with a relay and a motor. A python program is needed to make the motor spin both directions for a specific amount of time.