User:Merielle213/ENES-100:/Project 2: Pet Food Controller (continued)

Week 4 Narrative
This week I designed and printed the gear assembly that opens the retractable food box lid. The box lid needs to slide 5.75 inches but the box is only 3 inches high and the servo that turns the gears can only turn 180 degrees. So, any gear that fits inside the box does not have a large enough diameter to have a circumference (that moves the lid) large enough. I began designing a gear assembly to increase the turn provided.

The gear design was the most challenging aspect. Gears may be created manually, by drawing one line at a time, but the measurements and angles must be very precise, and there are a lot of them. After a lot of searching I managed to find a Sketchup plugin that allows for relatively easy gear creation. It can be downloaded here. Note that this plugin only works in Sketchup 8 or earlier versions, so I also downloaded Sketchup 8 from this site. After downloading both of these files the plugin .rbz file must be manually placed into the Google > Sketchup8 > plugins folder. The gear function is found under menu item Draw > Involute Gear. It was recommended by multiple sources that for simple gears you leave the pressure angle at 20 degrees (If the gear teeth are not perfectly square, that is, they are slightly rounded or cut off at an angle, the pressure angle is the angle between the vertical side of the tooth and the line that angles away from it to the horizontal side of the tooth).

The teeth and pitch radius determine whether the teeth of two gears fit together. Pitch radius is the distance from the center of the gear to the center of one of the teeth. This is, in effect, the radius of part of the gear that interacts with the adjoining gear(s) and is the number which may be used in mathematical calculations if needed. The teeth:gear ratio must be the same for each gear. So, if one gear has 10 teeth and a diameter of 1 inch, a 2 inch diameter gear must have 20 teeth to interlock with the first. I created a gear assembly with a 2.25 inch diameter gear (.25 in width) that will be attached by screw to the servo. It turns a 0.9 inch diameter gear linked to another 2.25 inch diameter gear. That second 2.25 turns another 0.9 inch diameter gear which slides the rack built into the box lid's underside.

Week 5 Narrative
This week I printed the rack gear and attached box lid, which came out perfectly. The gears and rack fit and turn together. I then continued the design of the box which holds the components. I included mounts for the servo and pegs that the gears will slide on, complete with stoppers so that the gears sit where they should on order for the servo to turn them. I was unable to get servo specifications for the Radio Shack servo that Rick purchased, so I used specifications from the Futaba s3004 Servo we have in the Engineering Lab and we will use that in the final product. When printed, all components should mount and line up perfectly.

After some issues getting access to the Makerbot printer, we decided to make the main housing of the feeder box out of wood. Rick is working on creating that based upon the Sketchup file's specifications. I took the interior components of the gear assembly area and will print those so that they slide down inside the main wooden housing.

I also practiced and recorded the process for creating files to be printed on the Makerbot.

Week 6 Narrative
This week I did not move forward on the project much. After working through some details with my team, we decided that Rick would use the dimensions from my 3D mockup and build the gear compartment housing (the box) out of wood, complete with the servo mounts and wooden dowels, rather than printing an insert on the Makerbot. We have also been preparing to present out project in the Engineering Seminar this week.

Because our group member Carlos has not come to class in some time, I also began repeating work that he did initially. I started creating a 3D mockup of the food housing and dispensing apparatus. This includes a cylinder with one quadrant hollow sitting below a container that holds pet food. The hollow quadrant faces upward, filling with food. Then it turns 150-180 degrees to face downward and dumps the food into a chute that passes the food to a pet bowl.

Week 7 Narrative
This week I am working to make some progress on the code to control our RFID reader, food dispenser, and bowl housing. Mike has started on the code - his code to read and RFID chip is here and his code to turn the servo for the food dispenser is here.

Rick has also written code to turn the servo that opens the bowl housing lid here.

I have some previously written code that reads and compares RFID chip to previously stored data as well. One question we encountered is whether we need to convert Hexadecimal input to ASCII code. I am working on that issue. Another consideration is that we ideally would like to have a user interface to allow pet owners to program which chips are allowable and how much food each should receive in a 24-hour period.