Making Headway on the PCB

We're finally making headway on this project! We are very close to finishing the PCB (thanks to a few extra weekend work days) and could most likely finish the PCB layout tomorrow. After passing around several versions of pieces of the PCB board, using the gschem software, Dr. Phillips, Prof. Battat and I have redrawn electrical connections, replaced components with others, implemented PCB footprints in all the components, checked for back termination and proper voltage levels, and, overall, used the "divide and conquer" method.

I started with a tutorial on gEDA schematic drawings, and, now, I am drawing complicated, detailed schematics on my own. Most first-year Engineering majors wouldn't have half as much exposure to such professional techniques as Dr. Phillips and Prof. Battat have allowed me. They're absolutely challenging me, but I wouldn't take back one minute of this experience. Over the last two days, I've received constant feedback from my advisors on the drawings and with each comment, I revise the system and become a more critical editor. I, myself, can see the evolution clearly. Based on the hand-drawn schematic that I sent during the weekend, we have drawn and modified the layout for the PCB.

First Pass at Glue Logic and MUXs
Utilizing the "divide and conquer" methodology, Battat started me on three tasks (glue logic, multiplexers, and the oscillator). As I finished those rather quickly, I took more responsibility by handling the input circuit and mounting holes as well. Battat focused on the power regulations and connectors. The first round was very messy with a considerable lack of "tags" or inputs/outputs and tangled electrical lines. By the third round, the drawings were much more reasonable and understandable.

After cleaning up the schematic itself, we went through multiple conversations regarding:
  • the addition of resistors and their values (for back termination);
  • the distinction between Digital GND and Analog GND (and their respective symbols);
  • the use of an inverting buffer rather than a general octal buffer;
  • the proper values for dividing the 5V input voltage for the input design to limit it to a range of 0-2V with a 160 Ohm load (16 "10 Ohm" resistors);
  • the need for capacitors along the input lines and simply using them as placeholders in the case of manual soldering;
  • and, most importantly, PCB footprints.
Footprints are placed under the attributes of each gschem symbol used in the file, so that, when the schematic drawings are translated into a PCB editor (which determines on the layout of the board itself), the proper shapes and sizes are respectively. These shapes are indicators of the shape and size of the components that are to be soldered later on. Incorrect shape and/or size will distort the ability to solder pins to a pad without error (i.e. bridges, crookedness, weak connections). Finding the most accurate footprint determines the board's success. For example, if the BNC connector is right-angled, meaning half of its body hangs over the board, a footprint for an vertical BNC connector won't help us adequately determine the size of the PCB board itself or spacing between components. Some footprints were in the default library while others, particularly the hardware components, had to be found in online community posts and imported. Fortunately, I found all that I need for my three designs today and, hopefully, by tomorrow, we'll have a layout finished!

Comments

Post a Comment

Popular posts from this blog

Hackathon: TechTogether Boston

Image
iOS app Last weekend, I had the wonderful opportunity to participate in Boston's largest all-female and non-binary hackathon! A group of friends and I wanted to digest as much tech and nerd information as possible, and we basically made it our mission to go to nearly every workshop session offered for two days straight. I don't know how we managed this but we did. From 5p on Friday and all day on Saturday, it seemed I bounced from one room to the next with a nap here and there. There was a workshop on rapid prototyping with AdobeXD -- which I am in love with. Then, I was able to create my first phone application during a workshop on iOS app development with Swift  (it's much easier than I had imagined), followed by a workshop at 2am on Android app developmen t. For my very first hackathon-conference, I wanted to focus on skill development and learning, rather than the competition. However, seeing everyone so wrapped up in their individual designs and programming ...
Read more

Women of Color in Graduate School

Image
Recently, I've been asked (by a few people) how it feels to go through graduate school as a woman of color. And, to be completely honest, it's incredibly exciting and exhausting all at the same time. Being a woman of color -- specifically a black woman, particularly in STEM -- has a lot of challenges. If you simply search the phrase "black in graduate school," you will get statistics that are very humbling; articles and think-pieces on how different the Black or person-of-color experience is from students who are not minorities; and other outlets detailing how little support many Black and non-Black students of color feel that they have. In fact, the Council on Graduate Schools recently reported that, in 2017, Black students made up just 11.9% of all first-time graduate students in the United States. (That said, 68% of them were women! So, we are making p r o g r e s s.) I'm not sure what the numbers are at Boston University, but it doesn't seem that far o...
Read more

Truss Design (Final)

Image
We finally made it to the end! After the preliminary design report, it was time to finalize our actual design (since we were given enough materials to make one truss to test). After doing a few more draft sketches and analysis, I was able to pick up on patterns on which types of designs produced the maximum strength (all within the parameters we were given). Finally, I came up with the sketch at the bottom-right, and the MATLAB analysis produced the highest load we were able to reach. We theorized that: two members would buckle first instead of just one (Members 3 and 4); the maximum load is 11.62 ± 0.063N; and the total cost of the truss is $290 (under the budget limit). From there, we moved to prototyping: we cut the straws as close as possible to the lengths specified in our final design. To create uniform gusset plates, our "joints," we used the circular cap of an individual Tropicana Orange Juice bottle. It met the area requirements and acted as a stamp...
Read more