10. Input devices¶
My Input Device¶
This week, my input device was a Greyhound single-pole, five-throw rotary key switch. I’m very grateful to Mr. Dubick for giving this to me for free, as it’s an expensive component on its own.
Breadboard Prototype¶
Before designing my PCB, I wanted to fully understand how the switch worked. Mr Dubick helped me trace a copy of the datasheet for the switch, which was pretty usefull to see. I also used a schematic I found on an Arduino forum to wire it onto the breadboard. The schematic used a pull-up resistor configuration for each switch position, with all of them connected to ground. I followed this setup and connected the necessary pins to the ESP. Everything worked fine.
During this process, I discovered that all pins, except for the selected one, are set to high by default. I made a mental note to account for this in my code later to ensure proper functionality.
Designing the PCB¶
Since this week was shortened due to spring break—and the lab would be closed—I had to design my PCB within just a few hours. This time constraint led to a few issues, which I’ll discuss later.
The PCB design itself was straightforward. I chose 1206-sized SMD components since I was already familiar with them from Design Week. The schematic was relatively simple, but transferring it to the PCB layout proved more challenging. Fitting all the traces onto a single layer required some careful routing, but I eventually got everything to work. Once finalized, I sent the design for milling.
Milling the PCB¶
Milling the PCB went smoothly. Since the lab was closing in 15 minutes, I had to work quickly and didn’t have time to document the process in detail. However, it was very similar to what I had done during Electronics Design Week—straightforward and without issues.
Soldering¶
For soldering, I didn’t have access to the lab, so I relied on the Accent MD book provided for Fab. I used five 10K resistors, five LEDs, my soldering iron, a solder fan, and a modeling mat to protect my wooden desk. The soldering process took about 45 minutes, but it was relatively simple.
The biggest challenge was the lack of a multimeter—we lost the one we usually have at home. To solve this, I came up with a clever workaround. I took a spare chip, placed it on a breadboard, and connected the 3.3V pin through a 220Ω resistor to a jumper cable, which I left hanging. Then, I connected another jumper cable to ground. Using this setup, I was able to test the polarity of the LEDs and ensure they were oriented correctly. This method worked even better than I expected, and I felt pretty proud of my improvisation.