I started by buying an SK450 from Hobbyking and disassembling it. If I were to do it again, I would probably buy each part individually but as this was my first time, I wanted to make sure that I got all the right parts. What better way than to use an existing aircraft? After disassembling it, I put together an SK450 Dead Cat frame and put the parts on it. If you are interested in learning why it is called a "Dead Cat" please take some time to watch this video:
I will not be making the same design decisions as the makers of the quadcopter shown in the video but the frame is the same.
After some assembly, I worked on mounting the Raspberry PI to the frame. I used one plate from the old quadcopter and drilled holes for screws.
There was an experimentation period where I thought I could just use pulse-width modulation (PWM) on any old pin on the Raspberry PI. During this phase, I quickly discovered that this was not something I could realistically do. I eventually decided to buy the Adafruit 16 channel PWM hat for Raspberry PI. I chose this part to handle PWM because it used I2C to send messages from PI to PWM controller and if I ever (for whatever reason) decided to change to an Arduino or another micro-controller, all I would need is an I2C interface on that controller and I have an easy way to connect to the speed controllers with minimal physical reconfiguration. I also chose this device because it was a "hat" for the Raspberry PI and that ability to be stacked really helps the design. After zip-tying everything together, and tightening the last few screws, I pretty much completed the physical assembly.
