Digital Electronics Lecture 2018 – Assignment for Week 11: Final Project Writeup (for Lecture, Week 1)

As Mark suggested, I’ve spend most of my focus this week on the actual hardware for my project.

This past Friday afternoon, I travelled with Jack to pick up a 1/8″X18″X24″ sheet of clear acrylic at Canal Plastics.  (They have quite an interesting selection of different plastics there, who would have figured.)

In addition, my potentiometers (knurled shafts) and knobs arrived in the mail. It turns out that the knobs were poorly labelled – they are meant for pots with smooth shafts, but the description mislead me by saying “knurled.” That was annoying, so I then ordered 20 different knobs, which turned out to be correctly labelled. Also, as Mark suggested, I bought a pair of digital calipers. These would prove very useful in the coming days.

The latter shipment arrived on Monday. I booked a time to use the prototyping lab (in the basement of the Leslie eLab) for Tuesday during the weekend, indicating that I would need someone to stop by and assist me in the design of the Adobe Illustrator file.

IMG_7201Franklin, a guardian at the eLab, read my request, and set aside his time to help. I read out the measurements I acquired with my digital calipers of various important dimensions, including the diameter of the potentiometer shafts, the length and width of the stabilizing metallic protrusion on the sides of the pots, and the distance between these two items. I then determined how far apart I wanted the pots to be placed in relation to one another. Here is a list of the important measurements we found:

  1. Diameter of shaft: 0.27″ (radius = 0.135″)
  2. Distance between edge of shaft and stabilizing protrusion: 0.155″
  3. Width of protrusion: 0.05″
  4. Height of protrusion: 0.083″
  5. Distance (in both x and y-axes) between adjacent pot shaft centers (decided upon by me): 0.65″
  6. Sheet width (decided upon by me): 5.255″
  7. Sheet height (decided upon by me): 6.17″

We first cut a test piece to ensure the measurements were right before we went ahead and duplicated the holes for the other pots.

Carefully inputting these measurements one at a time into Illustrator, we came up with the following file:


Franklin doubled the pass of the laser, just to ensure that all the unwanted pieces would separate. The result was impressive: very clean and even. Thank you Franklin!


Popping out some of the small pieces proved difficult, but I eventually managed to wiggle them free with a very small box cutter:


The whole boxcutter process was reminiscent of wiggling out my baby teeth as a kid: some fell out easily, while others were rather stubborn.

To remove residue, I used cleaning pads containing isopropyl alcohol. This actually took a long time to do thoroughly.


When I arrived home in the evening, I began placing the 20 potentiometers in their spots. Strangely, it was easier to mount them on one face than the other. I suspect this is due to the fact that the laser may have done a slightly better job on one – the one that was directly facing the beam. Like before, some went in with an audible snap, while others required quite a bit of force on my part. (I just had to be careful not to break the acrylic.)


Finally, I placed on the knobs — the ones that had the knurled insides. However, they ended up being really long, and I’m afraid that they may fall off too easily. Therefore, I might try to use a hand power tool (like a Dremel) to shorten them.

So, here’s what I’m left with as of now! I’m quite happy and excited with how it’s turning out.



Time Spent: 3.5 hours.

What I have left to do

  • Solder the power and grounding wires.
  • solder wires to a board onto which the Teensy will be mounted.
  • Create a serial communication protocol
    • testing this protocol
  • Interfacing with Arduino and Processing
  • Building outwards: making commit functions and adding functionality
    • [simply dependent on time]

What left to buy:

  • Perhaps mounts or a box? Not essential at the moment.

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