When last we discussed rotary encoding, it was all experimental. Since the project (which will eventually be revealed) is complete, I figured I should share a bit more about the exploration and final solution.

Encoding Disk

I moved from printed paper disks to laser-cut disks. I cut some 3mm Baltic Birch plywood at Milwaukee Makerspace. They worked well, but since I was hoping to get more steps/resolution I continued with the paper prototypes as well.

Encoding Disk

The one in the photo above was a bit too fine… too many steps. The more steps the more precise the alignment has to be, and the more chance of errors.


We had some concerns about a disk spinning between a U-shaped sensor with just a few millimeters on each side, so rather than just go with the GP1A57HRJ00F Photo Interrupter, I started experimenting with the QRD1114 Optical Detector / Phototransistor as an alternative.


The idea would be to use a wider disk and instead of it spinning between two pieces, it would have the encoding stripe on the edge, and the sensors would be on the outside of the disk. Back to the breadboard! The QRD1114s require a pair of resistors to work properly, so I wired it up and did a few tests and things seemed to work.

Encoding Strips

My first tests just involved sliding a piece of striped paper across the sensors, but I needed a real disk. I used the laser cutter at Brown Dog Gadgets to cut some disks from 1″ pink foam, and also from 1/4″ foamcore board. The pink foam actually ended up with concave sides due to the melting power of the laser, so I used the foamcore board pieces stacked up.


Math time! How long of a strip do we need to wrap around the disk? Well, you can determine the circumference of a circle if you know the radius or diameter. Hooray for math! Above is a letter size file that I could print on a laser printer to produce the stripes I needed. The thin line on the right side was used for alignment since I had to use multiple stripes to wrap around the disk.


Here’s a sneak peek of what the final disk looks like. There’s a few more steps before we got this far though, so I’ll continue the story next time.


Graduate reviews are done, and I got feedback from faculty on my current work. I was a great opportunity to gain insight into how others view the work I do. Typically these sort of things help reveal ideas that you don’t think about while making the work, or bring up new questions in regards to why you make specific choices.

One of the interesting takeaways from today was when a few of my pieces were called “sketches”. If you think about a sketch, it’s defined as “a rough or unfinished drawing or painting, often made to assist in making a more finished picture.” Many of the pieces I created are experiments, or explorations of ideas. They’re often not highly crafted pieces. I appreciate craft and people who are skilled at creating beautiful objects, but I often think I don’t have it in me to do that sort of thing.

I thought more about sketches, and the fact that in the Processing and Arduino worlds, the programs are called “sketches”. As I understand it, this was done specifically to appeal to artists and creative people who didn’t have a background in computers. Tell an artist they are going to write a computer program, and that’s a frightening proposition, but tell the same artist they are going to create a sketch and that’s an achievable goal.

I sketch with physical things…

That’s today’s revelation. Many of the things I make are real-world sketches. The physical manifestation of an idea. Often there’s an immediacy to the creating of the thing, but not always. I tend to work in two ways. The first is a reactionary mode, where I have an idea and act on it immediately. I start building without too much thought, and see what the process and the piece reveal. The second method involves thinking, designing, and prototyping as an iterative process. The pieces created from the second method are often more polished, but both methods produce valid work, and the reaction to each kind of work may be equal (meaning, people don’t always gravitate to the work that had more initial thought or took more time.)

Oh, I also want to drop the other definition of sketch here, “a short humorous play or performance, consisting typically of one scene in a comedy program.” This also relates to some of my work, but I’m going to leave that exploration to a future post.

Machine Drawing

I stumbled upon this project titled Machine Drawing Drawing Machines by Pablo Garcia a while ago, and then I found this great video of a talk he did at MIT about the history of drawing machines.

Pablo Garcia

Technology and art have always come together in some way…

It is a long video, and it was an hour into it before I realized Pablo was the guy behind the NeoLucida Kickstarter. I’m not as much a fan of drawing aids as I am machines, but there’s a ton of great info in the video.

There’s also a DrawingMachines twitter account worth checking out, as well as Pablo’s account, and his web site at pablogarcia.org

The video revealed a lot about machines and drawing that I’ll be thinking about for a while, especially in relation to my own work and views on these things. Good stuff!

I’ve been designing a new drawing machine that is inspired by turntables. You know, those old-fashioned devices that old people used to listen to music…

I’ve made some progress on the electronics so far, and the controls will most likely consist of two potentiometers to control two stepper motors, and there may or may not be a servo involved for the pen lifting. (And yes, two steppers and a servo are sort of the common elements of many drawing machines.)

While many of my drawing machines are cobbled together with bits of wood and hot glue, I’m going to attempt to actually design this one. I’ve been looking at a number of turntables for design ideas, and wow, some of those things are just beautiful! Some examples below…





Wood Turntable

Belt Drive

I’ve started to collect other images/links over on a Pinterest board. Some are just interesting machines or mechanisms, but a lot of them are turntables or drawing machine related.

Motor Mounts

I needed a few motor mounts for a project and since I was at Milwaukee Makerspace it seemed quicker/faster to just laser cut a few since I had files on my laptop. (I could have 3D printed them as well.)


I assembled a quick and dirty polargraph, and while I attempted to use an Adafruit Motor Shield I had on hand, it did not work. The steppers were not moving, just humming and stuttering.

I then grabbed the CNC Shield I’ve been testing and put that in place. The steppers worked fine with a test sketch, but the firmware I wanted to load (Dan’s Makelangelo code) expects either an Adafruit Motor Shield or a RUMBA board. I thought about trying to rewrite things to work with the Pololu motor drivers, but it was also after 11pm.

(I later realized that I should have looked at the RUMBA firmware, as that supposedly works with RAMPS. And yes, while I do have a spare RAMPS board, it’s across town at my studio. I decided to punt and see what I could do with what was in my workshop.)


I figured I’d throw Grbl on it and see what happened. I used Grbl Controller to connect to the board and loaded some G-code to run. I knew it would not work (as expected) but I tried anyway.


Grbl supports machines that use Cartesian coordinates, but not those that use polar coordinates, like a polargraph. Still, I was surprised at what I got. It basically worked, except for flipping the image and running it diagonally up to the left.

Grbl Controller

I then took my original vector file and flipped it, and skewed it up and to the left, to match (somewhat) how it was drawn by the machine.

Shapes skewed

It actually sort of worked! I think it was after midnight by now so I gave up on it. My lack of math skills prevent me from converting between coordinate systems, but I think there’s a few things to explore here, and if I get time (uhhh) it may be something I play with a bit in the future. Also, if anyone wants to add polar coordinate support to Grbl that would be lovely. :)

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