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Show HN: Strange Attractor on an Etch a Sketch with Raspberry Pi Pico (youtube.com)
47 points by vha3 8 days ago | hide | past | favorite | 9 comments

If you are interested in both CNC and Etch-a-Sketches, Youtuber This Old Tony has a great introduction to CNC hardware and software where he build a computer controlled E-a-S with pro-grade hardware and software (Mach 4). It is very entry level, 60 minutes in two parts.

https://www.youtube.com/watch?v=K0XfRPi_h2M (part 1)

https://www.youtube.com/watch?v=eLdlV3-JaH8 (part 2)

Beware all: This Old Tony is an absolute RABBITHOLE of machine-shop silliness.

Some additional documentation here: https://vha3.github.io/Pico/Steppers/Lorenz.html

I've been experimenting with the PIO (Programmable I/O) system on the new microcontroller from Raspberry Pi. These are coprocessors for which the user can write code in a bespoke assembly language (PIOassm) to drive the GPIO ports. You can do really interesting stuff with these, like implement high-speed communication protocols (e.g. VGA) or offload tasks like driving stepper motors.

I've also been really interested in fractals and chaotic systems. For me, they're a nice bridge between interests in engineering and art. That's why this is drawing the Lorenz system in particular.

Here's the source for my relatively recent ESP32-based Etch-a-Sketch build: https://github.com/derekenos/iome/tree/master/appliances/ske...

More pics/vids: https://derekenos.com/project-sketchy

Looks like a bit of slack in the belts, is there a way to tighten it up or account for it in software?

They're definitely a bit loose! There's some slack in the etch-a-sketch mechanism too, which is why the tops and bottoms of the curve look a bit flattened. When the motors change direction, the dials must move through a nonzero angle before the mechanism catches and starts moving the plotter. Software can help a little by moving the motor quickly through the dead region.

i built a much nicer version once and it is QUITE difficult to drive the etch-a-sketch rigidly, as there isn't much mechanical support inside the machine. i ended up removing the knobs, adding steppers directly opposite to the shafts, and using a homemade bronze coupler. it worked very nicely but was ugly.

Thanks for sharing this, this is really cool! I saw you posted a lot of details on the software, but could you expand on the hardware? Do you have any reference on the stepper motor setup/components used to control the two dials?

This makes me curious about the possibilities of using an Etch-a-Sketch screen as a low-end sort of e-ink display. How well could one of those screens be utilized? Sounds like a fun weekend project.

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