Assignments:

  -  propose a final project that integrates the range of units covered, answering:
      what will it do?
      who's done what beforehand?
      what materials and components will be required?
      where will they come from?
      how much will it cost?
      what parts and systems will be made?
      what processes will be used?
      what tasks need to be completed?
      what questions need to be answered?
      what is the schedule?
      how will it be evaluated?
   projects can be separate or joint, but need to show individual mastery
      of the range of skills covered
   where possible, you should make rather than buy the parts of your project
          

- It rotates the solar panel towards the brightest direction using its own power generated by the sun, and also charge a LIPO battery which can be redirected to USB charging board.

There are a lot of 2 axis solar trackers, so this is not a unique one although mine is 100% from my idea.

Most components are from the lab. I bought only some components such as LT1302 from Digikey.
Solar panel (138x160mm, 3W, approximately $12 at seeedstudio)
+ 3D Printer filament($4)
+ 3mm,5mm acryl (just small leftover pieces, totally less than $5)
+ 18mm Plywood piece for pot (not indispensable. Small leftover pieces. Less than $5)
+ wax (I recycled chips. New wax is worth about $25.)
+ 2 servo motor (Hobby Electronics HES-288. less than $4 at aliexpress)
+ Lipo IC controller MCP73831 (less than $1 at digikey)
+ LIPO battery (3.7v, 1100mAh, about $5 at aliexpress)
+ Mold max 10t silicone (used less than 1/3 lb, so about $5)
+ 3D printer filament stool(free)
+ Boost switching regulator: LT1302($6.5 bought from digikey)
+ All the other components on PCB + copper plate (totally less than $10)

=Totally worth $82.5 (although we spent only about $10 for real).

- This is two axis model, so need to have at least three separated parts: panel back-(servo)-panel stand-(servo)-bottom. For the servos to turn the panel towards the light source, I need a board that collects light strength from four directions (up-down, right-left), and rotate each servo so that the light strength between up and down, or between right and left becomes the same. I also need a solar power charging system+usb charging system.

- laser cutting, 3D printing, CNC machining, molding and casting, electronic design/production.

- I want to make the same system with higher voltage, probably 12V. It requires different panel and (probably quite) different charging system. I want to keep working on it.

- End of May: 1.decided what to make. 2. Began working on two phototransistors + one servo model. 3. Completed most of programming with two phototransistors.
- The very beginning of June: 1. tested with laser cut mechanic parts for servo rotation. 2. Designed a wax mold, and recycled wax chips to make a wax box. 3. Made the mold and cast. (To do so, I designed panel back first and 3D printed since I need to use it for the casting.) 4. Designed and printed out panel stand, and also finalized the laser cut mechanical parts. 5. Tried one axis model with tilted bottom, but discarded the idea, and began modifying to two axis model.
- The late beginning of June: 1. designed PCB (with four phototransistors and two servos) small enough so that I can put it behind the panel back. 2. Wiring, locating servo motors. 3. Making lipo charging + USB charging system. (At first I used solarbag model from here to understand how it works.)
- Mid June: 1. made a wooden pot and acrylic cover, organize the wires. 2. Made my own charging system. 3. Made a presentation video.

- Hmm.. maybe by its function? For now it is working fine: it turns its face towards the source of light, and also it provides electricity.