When I started solar car, one of the first things I was taught was how to design PCB's using Altium
Designer. I was then placed on my first project, buttonboard. The job of this board was to take
inputs from latching and nonlatching buttons on the steering wheel and have them read by our
microcontroller to turn on different lights and our horn. The circuit itself was pretty
straightforward, consisting of pull-down resistors that would be connected to each of the buttons
and read by the compute. We also later down the line included some filtering with an RC circuit to
denoise the lines. I was able to get our first rev of the board ordered around winter break and test
it. Testing the board mostly consisted of checking the power circuit and seeing how much voltage
drop was on it to adjust it with the trim up resistor on the 5V switching regulator. We have talked
about stepping the voltage down to 3.3V in the future since the microcontroller can still handle
that and since it would also save us a little bit of power. This board was implemented in the front
of the car behind the steering wheel. It was really fun to see my first board get tested and
implemented over the course of my first year.
In the Spring, I also helped to redesign and layout another one of our boards, Headnode. This board
is in charge of turning on three large relays that are in our battery pack box to start the battery
pack. This works by using logic IC's with AND gates to check to make sure different pins are
connected and what we expect. For example, we have a button on the outside of the car called
external kill, and if that is pressed then Headnode shuts out the relays and makes sure the battery
pack relays are not closed. This then cuts off power from the battery pack in a "safe state". We
moved these relays to Headnode on the rev I worked on and also added a third one, the charge relay,
to help meet regulations for our car for rayce. The board got much “busier”, since we had to keep it
the same size as a previous rev while also packing in more parts. Headnode was the first 4 layer
board that I helped design too. This board was much more complicated than my first board but it was
very fun to learn about it throughout the Spring and Summer.
I also began work on a new project for solar car in the Spring for a power supply board. This board
was designed by two alumni of the team for a senior design project, intended to be used for solar
car. After the fall semester was over, they handed the board off to us with one of the project
members to help ease us into it. We tested the first rev of the board while identifying a few key
issues. The board takes in AC power and turns it to 34V DC through 4 transformers. This is then
stepped down by various power regulators to 12V and 5V. One issue was that the enable pin for the
linear regulator was taking 34V instead of the maximum of around 12V. To fix this, we added a
voltage divider to the next rev to ensure we wouldn't fry the IC again. We also had lots of issues
with software connections to multiple pins on our microcontroller. I helped lead redesigning the
4-layer board to help clean it up too at the start of the Summer. We made 1-layer horizontal traces
and another vertical for the in-between layers. The top layer had many different planes spanning
different voltages, depending on which section of parts were close. The bottom layer was ground
which contained mostly vias to help ground parts on our top layer. I am now going into my second
year of solar car as the manager of this board which I am very excited for. We will start with
testing the newest rev that we had designed over the Summer.
Throughout my first year, I spent more and more time working on solar car since I joined it. This
was mostly obvious during the Summer, where after work at my internship ended, I would go to help
work on the car. During my time over the Summer, I was able to learn about the overall electrical
system of our solar car. I worked to meet with different managers during this time so they could
help explain boards I was unfamiliar with to understand how our battery pack fully turned on. This
in turn helped me understand more what I was doing on Headnode from the Spring before. On weekends
we would take our car out to the Jack Trice Stadium on campus to drive it around parking lots. This
helped us see what did and didn't currently work on the car. We were also able to give drivers the
chance to practice driving more in figure eights like we would for dynamics testing on rayce. The
summer was also a great time to learn better how to debug a full electrical system. When something
didn't work, we would pull out multimeters and probe around to check for continuity or different
voltages of lines on test points. This was great, because I was able to watch other people test this
at the start of the Summer and ease in to doing my own debugging as I got more confident with our
system as a whole. I came to realize how much I learned over the Summer after I was teaching other
members who hadn't been around the whole Summer about different aspects of the car as we led up to
rayce.
As for the actual rayce, there are two. The first is FSGP, which is a track event including many
different cars from teams around the United States. The track event includes both the single
occupant and multi occupant cars, where we had a multi occupant. I was slated to go on the second
rayce, ASC, that would be a cross state rayce to compete who could drive the most miles on their
car. Due to some technical problems, we were not able to get on the track until the third and last
day of the first rayce. So, our team failed to qualify but we still did learn a lot about the whole
process of scrutineering and what it takes to rayce. There will be a rayce coming up next year so
the team is working hard currently to get our car in a reliable driving state before then. We have
also been working hard on outreach as the next school year starts to bring on new members to the
team.
In the spring of my first year, I had got picked to be the librarian for our electrical team. This
meant I would be in charge of organizing parts, helping transition to Altium 365, and building parts
libraries. My main focus of the Summer was to organize and catalogue all of our parts. This meant
that I had logged and labeled over 500 parts in our parts system, EPCOS, that some of our software
team had designed the year prior. This was something that I heard was very helpful on rayce, and I'm
hoping it will be nice as we get new board orders coming in this year too. Going forward, I have
started the process of building a parts library containing all of our currently used parts. After we
have filled in all of our current parts, I plan to buff out the library with other common resistors,
capacitors, and MOSFETs. This should help make board orders much easier in the future, but the
initial switch will be the hardest part. Hopefully in a year this is all done so it makes future
revs much easier to manage and order!