This is an update to my original automatic dog feeder that is here:
   • Homemade Automatic Dog Feeder Lego Mi...  

I decided to completely rebuild the dog feeder. My old one has worked great the last year, however because of the small hole the food was hard to fill and the drum was small so the food portions would only last a few days. The Lego RCX requires outdated software in order to program, so I decided to build something simpler to use.

My new design is build out of 1/2 inch plywood. The box holds the food and it it is dispensed using a 1 inch auger bit. A 12 volt DC 5rpm gearmotor is connected to the auger bit with a special coupler. The motor is connected to a 12V DC adapter which is plugged into a digital timer. The timer is programmed to feed our dog Snowball twice a day. This timer is really easy to program and is much more versitile than the Lego Mindstorms. The large food hopper makes it easy to fill, and it can store enough food for 2 weeks or more.

This motor is a Amico brand gearmotor and has 31kg-cm of torque. Originally I build the hole just as big as the auger bit, however this motor was really straining and grinding up all the food. When I enlarged the food hole by a 1/4 inch, the straining almost disappeared and whole food pieces were coming out. There is still some slight straining as you will hear in the video, however I have not had any jams yet because the motor is strong enough to push the food through. My lego motor definately would not have been strong enough. My adapter has the ability to put out different voltages, so I can adjust the amount of food coming out by giving the motor less volts, or I can increase the run time on the timer. This is good because I made need to adjust the food coming out if I have larger or smaller kibble.