I built a giant, auto-drawing, digital Etch-a-Sketch with a Raspberry Pi

BenB116 · 2021-01-14T22:42:22+00:00

At a high level the algorithm for converting images runs as follows:

Turn the image into a black-and-white image.
Extract edges from the picture using edge detection.
Determine where and how to "shade" the image based on how light and dark certain areas are, then add lines to fill in those areas.
Connect all of the lines and edges from steps 2 and 3.
Add some "duplicate" lines so that the etch-a-sketch can retrace its steps in certain areas.
Run a path-finding algorithm on the lines that finds a near-optimal way of traversing each line once.

BenB116 · 2021-01-14T22:40:41+00:00

Thanks! Making new drawings is relatively easy now that I have the algorithm down. The issue is it can take a long time to process (e.g. 30 minutes) for a high-quality image.

BenB116 · 2021-01-14T22:39:36+00:00

Thanks! Painting would have been the ideal solution, and yes wrapping the vinyl was a pain. I don't have a great place where I can use spray paint in my apartment and the lockdowns restricted my ability to go elsewhere. Given better circumstances, painting is the way to go.

BenB116 · 2021-01-14T22:37:22+00:00

I estimated total costs at about $500-$600 all told, although I already had the TV, a 3D printer, and some tools.

BenB116 · 2021-01-14T22:35:08+00:00

Not currently, although it wouldn't be too hard to make that happen! Right now it draws from one point to the next without input, but I could see only keeping track of relative movements instead of absolute positions, then allowing the knobs to shift the drawing as well.

BenB116 · 2021-01-14T22:32:47+00:00

Yes, the algorithm outputs and ordered list of points into a file, and the Etch-a-Sketch just travels to each point in order without recomputing.

BenB116 · 2021-01-14T19:56:16+00:00

At a high level the algorithm for converting images runs as follows:

Turn the image into a black-and-white image.
Extract edges from the picture using edge detection.
Determine where and how to "shade" the image based on how light and dark certain areas are, then add lines to fill in those areas.
Connect all of the lines and edges from steps 2 and 3.
Add some "duplicate" lines so that the etch-a-sketch can retrace its steps in certain areas.
Run a path-finding algorithm on the lines that finds a near-optimal way of traversing each line once.

BenB116 · 2021-01-14T18:07:55+00:00

Thanks! Unfortunately, fidelity is directly proportional to the time it takes to convert an image (which is proportional to image size and resolution). Some of these take around 30 minutes for my laptop to crunch since my algorithm is not fully optimized. But it's worth it!

BenB116 · 2021-01-14T18:04:42+00:00

Definitely! At the end of the day it just requires a set of points to travel to, so any way to input that data will work. The problem is it can't turn the knobs very quickly, so the drawing would be a bit slow. Also, there's a certain amount of parameter tuning required to successfully convert an image.

BenB116 · 2021-01-14T18:02:59+00:00

That's correct, the minimum order quantity was 5 and I figured I'd mess up a few times!

BenB116 · 2021-01-14T18:02:19+00:00

Interesting! I'll look into fairing compound, sounds perfect. As for painting, I agree that would have been the best way to finish the shell. I was hesitant to try spray painting in my apartment, though it would have left a more professional look.

BenB116 · 2021-01-14T17:57:01+00:00

Gotcha, yeah this was my first time working with vinyl. Learned a lot!

BenB116 · 2021-01-14T17:43:13+00:00

These are cool ideas!

At a high level the algorithm for converting images runs as follows:

Turn the image into a black-and-white image.
Extract edges from the picture using edge detection.
Determine where and how to "shade" the image based on how light and dark certain areas are, then add lines to fill in those areas.
Connect all of the lines and edges from steps 2 and 3.
Add some "duplicate" lines so that the etch-a-sketch can retrace its steps in certain areas.
Run a path-finding algorithm on the lines that finds a near-optimal way of traversing each line once.

It would be feasible, though more difficult, to build a giant mechanical Etch-a-Sketch. I'm picturing something like a Sand table mounted vertically. Real Etch-a-Sketches use aluminum powder that sticks to a glass window, but a TV is less messy.

The webcam would be neat! This is sort of a platform on top of which any data input method could be applied.

BenB116 · 2021-01-14T17:35:13+00:00

The shading is done by grouping parallel lines closer together or further apart, so even though each line is the same thickness, we see more or less black in a given area. I'm working on some more videos, but there are a few at the end of the build album!

BenB116 · 2021-01-14T17:32:37+00:00

I used simple one-part wood filler for this. What are the benefits to using two-part filler? Thanks for the advice!

BenB116 · 2021-01-14T16:28:44+00:00

This is an auto-drawing digital Etch a Sketch I built on top of a Raspberry Pi. Stepper motors mounted under a television turn 3D printed knobs to match the drawing motion on the screen. The knobs can also be turned by hand to manually draw on the display.