User:Merielle213/ENES-100:/Project 1: Pet Food Controller

Week 1 Narrative
This week my group began planning for our Pet Feeder Project.

We began by identifying what the feeder should do, including the following: Read a pet's implanted (or worn on the collar) microchip when the pet comes close; provide access to that pet's food once microchip has been read; restrict access to that pet's food by other pets; restrict quantity of food each pet receives in a set period.

Next we identified systems that we might utilize and their components. The first system considered was a [probably transparent] box with a door that is unlocked after a pet's microchip is read by an RFID reader at the entrance. There was concern that this setup may allow a second pet to bully its way in through the door, so we considered adding a second RFID reader at the back of the box and adding a food dispenser that would only dispense after the pet had entered the box and it was verified that this pet was entitled to food. We also discussed the possibility that the pet may leave behind some food that another pet might hen eat, or that another pet may still run into the box after the first and the food could be dispensed while both pets were in the box.

After presenting our idea to the class, it was suggested that we use a "turntable" like setup to rotate the food out of view/access when another pet is in the vicinity (inside the box). If this device is to provide food to multiple pets, a turntable seemed like a good idea.

So, we had a number of components and considerations in mind at the end of week 1:
 * Turntable: consider material; mechanism for turning or swiveling; size of the food dish; mechanism for hiding dish; whether the owner fills or food is dispensed from a separate bin (see below); consider bowl material as some pets have allergies.
 * Box: material to preserve transparency or ease of production at this point?; size - consider convenience for user; design - l;ift-top for full user access?
 * Power: battery vs. corded; placement of RFID readers informs wire and power component placement.
 * Dispenser: Use a "hopper"?; material - transparent to view food levels?; design of dispenser - screw mechanism?

We also hoped to be able to build separate feed dispensing units that could be linked based upon the number of pets being fed (up to 4). It was decided that Mike would begin work on the door locking mechanism, Carlos would look into food dispensing designs, and Rick and I would work together to look at options for a bowl rotator.

Week 2 Narrative
This week Carlos brought some great "hopper/food dispenser" ideas to the table. The one that was decided upon was a vertical container whose bottom opening narrows to feed food into a wedge shaped cut out of a horizontal cylinder divided into quarters. Picture a hockey puck turned so that it rests on its curved edge. Divide it into quarters, and make one of those hollow. That hollow quarter faces the food dispenser and fills with food, then rotates to the side until the food is dumped out (See Mike's sketches here). That food is fed through a tube to the bowl.

One issue with this type of feeder is monitoring the amount of food dispensed. We talked about measuring in ounces, but decided upon measuring in 1/4 cup increments as that is how many pet owners measure and how many veterinarians instruct owners to measure. (Because I love math) I took some time to calculate how large the "hockey puck-like" cylinder needed to be in order for one quadrant of it to hold 1/4 cup of food. The resulting formula is as follows: Let r be the radius of the circular "base" of the cylinder and let x be the cylinder's height (or the hockey puck's width). X = (57.75/(pi * r^2)) or r = sqrt[57.75/(pi * x)]. Carlos and Mike used this formula to create the specifications of the rotator piece in the food dispenser/hopper.

It was also brought to our attention this week that if we attempt to build all these pieces we may run out of time and that perhaps we should focus on some and if we complete them, begin the others. So, Mike and Carlos began work on the pet food dispenser and Rick and I continued work on the bowl rotator.

A servo seemed to be the best method of rotating up to 4 bowls around a central axis so that only one bowl is accessible at a time. It was decided that a thin plastic sheet would be the most lightweight material from which to build the bowl holder, with holes for the bowls to be dropped in from above. We discovered that the affordable servos and those available in the engineering lab could not offer enough torque to rotate the platform and bowls with food. The next option was using a DC motor to power the rotational motion, but that would require a rotational sensor as the servo had one built in that we could use and we needed a way to control how far the servo/rotator turned. Professor Dolge suggested that we make a rotational sensor.

The simplest rotational tracker design I found was an incremental rotary encoder, which uses a pattern displayed around the item whose rotation is to be tracked and a visual sensor picking up the pattern and relaying the current position. I had concerns about the stopping time of the rotating piece, but I was not completely sure how the tracker would work. I also felt certain there must be a simpler way, rather than having so may additional components under the rotating dish holder, which lead to more opportunity to malfunction. I spent time looking for an affordable self-contained potentiometer but found none that seemed easily implementable.

After all this I talked with Rick about potential alternatives and he suggested a garage-bay type door for a one-dish container, rather than the rotator. From there we decided to move away from the rotator and instead to a shallow box whose top/lip retracts to reveal food.

Week 3 Narrative
This week I worked on the design of the box which will hold the pet food bowl and the retractable lid and its components. I used Sketchup to design a 3x6x12 inch box with a groove 1/8 inch from the top edge for the lid to slide in. The right side is slightly larger to allow for a piece of rack gear to protrude into the compartment and link with the gear assembly and still be able to retract completely to open. I also added mounts for the servo (see the below image). The servo specs were in mm and my sketch in inches, so I converted the measurements and used those illustrated in the following image: