Electronics Design¶
Goals¶
Group assignment:
- Use the test equipment in your lab to observe the operation of a microcontroller circuit board (as a minimum, you should demonstrate the use of a multimeter and oscilloscope)
- Document your work on the group work page and reflect what you learned on your individual page
Individual assignment:
- Use an EDA tool to design a development board that uses parts from the inventory to interact and communicate with an embedded microcontroller
Prior Knowledge¶
I’ve used KiCad in Electrical Engineering, although I haven’t made many boards without guidance from a video or teacher.
Note that I designed and produced this board in the same week, but the milling is in Electronics Production.
Projected Timeline¶
- Wednesday
- Start group assignment
- Start individual assignment
- Thursday
- Finish group assignment
- Friday
- Work on individual assignment
- Saturday
- Document
- Sunday
- Document
- Monday
- Finish individual assignment
- Tuesday
- Plan for next week
Actual Timeline¶
- Wednesday
- Start group assignment
- Finish group assignment
- Start individual assignment
- Thursday
- Work on individual assignment
- Friday
- Work on individual assignment
- Start and finish group
- Saturday
- Work on individual assignment
- Sunday
- Work on individual assignment
- Document
- Monday
- Work on individual assignment
- Tuesday
- Finish(?) individual assignment
Group Assignment¶
I was in a group with Tyler Russell and Wilson Zheng. I was assigned the multimeter and oscilloscope.
You can see our documentation on our group site.
Individual Assignment¶
Preparation¶
Initial Attempts¶
I installed KiCad 9.0 - while there are less informational resources due to its recency, I figure I would do so eventually and there was no use in waiting.
I then downloaded the fab library, which Zaina Gibrine walked me through as I was not used to importing libraries into EDA software. I would use all my component symbols and footprints from this library.
Tutorial¶
My first attempt at this assignment was to follow a tutorial on creating a light-up LED activated through USB plugin. While slightly ambitious, I found the tutorial simple to grasp. I decided to adapt to an ESP32-S3 for practice, doing so by converting the pinouts and tweaking the organisation.
I created a schematic using components mostly from the Fab library.
The tutorial guided me through customizing symbols and footprints for the USB connector. In hindsight, a connector from the Fab library would have most likely worked, although the process would help me with more complex circuits in the future.
I updated the PCB when the schematic was complete. The software displayed no errors, although I never ran the design or electrical check as I trusted the tutorial. I neglected to consider that, regardless of the circuit violating rules, KiCad can only take so many measures to fix a circuit that does not work.
Still, I saw no issues with the general design.
I created an edge cut and reorganized the PCB to conserve space before routing the wires.
While routing the wires, I found that very few connected properly. I reconsidered my initial impression that adapting to more inputs would pose no difficulties. The microcontroller rotation and placement, as well as the resistor logistics, did not fit the circuit. The design was made for the ATTINY-412, and I lack the experience to change this. I deleted the very little routing I had and abandoned the design.
Book¶
I dropped in on the Saturday Help Session and learned about []”Getting Started in Electronics”](https://www.amazon.com/Getting-Started-Electronics-Forrest-Mims/dp/0945053282), an extremely helpful book on electronics. While I was unable to review the contents in depth with my work, I found the circuits quite helpful. I decided to experiment with NAND gates, and learned that while this logic gate has 14 pins, there are 5 units. Each symbol represents a unit, however, I assign one 14-pin footprint to any symbol and KiCad updates the PCB accordingly.
As usual, I decided to hop over to Nueval and reflect on my progress. I re-read the requirements.
I reviewed the components of my board, realizing that something was off. The key word here was “microcontroller”. As it turns out, my components were not, by definition, microcontrollers. This KiCad work was, albeit helpful practice, not ideal for the assignment.
Find Wokwi Reference¶
I decided to use my circuit from embedded programming. I found the Wokwi simulation and tweaked it to include pull-up resistors.
Note that I plan to use the S3 as opposed to the C3 this week, I just never re-made the simulation since they have the same pinout. I make this distinction because I researched the difference and found an article explaining the higher level of power and complexity in the S3. Since both microcontrollers are provided in our lab, I would not need to consider the cost-effectiveness of the C3. The pros of the S3 led me to work with it as I will likely use it in my final project.
Below is the Wokwi simulation I modeled the circuit off of.
Schematic Editor¶
- Add symbols
- Add footprints
- Add wiring
PCB Editor¶
Update PCB from Schematic¶
I navigated to PCB view and found no errors in this process as all the footprints were assigned.
Add Edge Cut¶
I made a rectangle and fit it to the dimensions of the board. I conserved as much space as possible.
Add Image¶
I decided to add a small image of a lightbulb to the board. I figured that since my final project would need to seem realistic, I should accustom myself to decoration now. I found a generic lightbulb clipart image and referenced David Vaughn’s documentation since he added an image as well. I downloaded the image as an svg from the image provider and used an image converter to generate a bitmap image. From here, I returned to the PCB editor and imported the image file.
I made two modifications: scaling and layers. I scaled to a 2% ratio because the circuit board is substantially smaller. I also placed the image on the front silkscreen layer which mills it on the front side of the board. I went back and changed the resistor values before returning to this screen, which is why the values show up differently.
Run ERC¶
Although I should have done this while editing the schematic, I just realized this after using the Design Rules Checker. I navigated back to the schematic and ran the check. No warnings!
Troubleshooting¶
Oh, all right, I’ll show the whole screenshot.
The main issue was unconnected pins. I searched this up on the KiCad website and found that this is in fact normal, I simply needed to add No Connection flags to stop receiving the error message. I found out that I can press Q and place the blue X on floating pins.
Although this reduced my number of errors, I was not finished. I re-ran the checker and found that there were issues with input-output connections. I looked into this, connecting the 3.3V net to the microcontroller pin solved it. I still received a persistent message about the input power pin and it turned out that I need a power flag.
I initially used a power symbol, hence the remaining errors. KiCad did not register the power supply. After searching up power flags specifically in the symbols section, the error stopped.
While there were no more errors or warnings, the ignored tests confused me. I took a look and found issues with mainly the SPICE model and global labels. The former error seemed quite unlikely since there were no obvious design issues, I was unfamiliar with the latter error.
I right-clicked and found a checkbox with the option to ignore checked. I realized, fortunately, that these are just tests and not actual errors. After checking the error checkbox, which runs these tests and marks any issues as errors, I found that the only issue was with global labels.
I needed two or more global labels, typically for 3.3V, so I added them to the main wires with voltage supply and pull-up resistors. I re-ran the check with the two global labels.
It worked!
Run DRC¶
I first updated to the PCB. My schematic had additional labels and information after the changes I made.
I also viewed the 3D model.
I ran the DRC and found several errors, however, this was similar to the ERC performed earlier. I had mostly the same type of error, which was the text height being out of range. The test also mentioned the silkscreen being clipped by the solder mask.
Group Assignment¶
I was in a group with Tyler Russell and Wilson Zheng. I was assigned the multimeter and oscilloscope test.
You can see our documentation on our [group site]
Reflection¶
Group Work¶
Both the multimeter and oscillscope took no more than an hour combined. Understanding voltage-time graphs were quite helpful. I found that I prefer oscilloscopes to multimeters - while they measure different things, I find the information an oscilloscope provides more immediately informative than the detail of multimeters.
Positives¶
I am glad that I familiarized myself with KiCad. I need to program synchronized servos for an automated drawbridge with a PCB. After that, a golf cart with a predefined path using steppers. Electronics is the foundation for several parts of my final project.
Negatives¶
The learning curve here is steep. All I wanted to do was program two LEDs that blink with a little button. Why did it take me a total of nearly twelve hours - not an exaggeration - to plan, design, mill, and document two blinking lights? Still, I’ll keep working since the process can only get faster from here.
Takeaways¶
I should add more specific tasks to my timelines. Not specifying beyond the individual and group distinction worked when the assignments had less steps. With the new complexity of each assignment, I will be breaking down tasks in my projections to better understand the rate at which I am meeting my goals.
Advice¶
- Install the Fab library for your chosen design software.
- Whichever EDA software you use should be based on experience, research, and design considerations. No software is a superior PCB designer. Except KiCad.
- Run the ERC in the schematic editor before using the PCB editor. Run the DRC only when that is finished.
- Flags and global labels are key for labeling your schematic. Add power flags to power symbols and no connection flags to unconnected pins.
- For those unfamiliar with KiCad, keep running DRCs and ERCs until no errors show up! As tempting as it is to ignore errors that you do not need to solve, I would not recommend doing so. You miss out on opportunities to further understand KiCad. More concerningly, though, you run the risk of ignoring other errors that must be solved for a working board. I imagine gaining experience in EDA troubleshooting would eventually remove this need.
- Use bitmaps to import graphics, converting the file is easier than it looks. Clipart is the most intuitive style to mill, although I’ve seen more complex images render quite well.
- If you are designing a surface-mount board, use surface-mount for every component. There was no need for me to add holes, which Mr. Budzichowski explained to me. However, I neglected to change the through-hole microcontroller footprint, hence me designing some sort of hybrid layout. I would not recommend it, one ought to change the actual footprint and directly solder a microcontroller without headers.