I built it last year and took a bunch of pictures to document the build. Then life happened and I didn’t. Someone noticed I had an undocumented v2 and asked about it, so it was time to fix this.
X,Y Coordinates Tradition
I just did my yearly X,Y Coordinates stint with local 5th graders. It’s the 5th time I do it and this year is notable in that I didn’t write anything I wanted to fix for next year. Every time previous I came out thinking I needed to fix a bug, prevent a confusion, or improve something or other. This time it looks like the formula has been refined to its optimum.
Kids will definitely push the limits, and I love that relentless will to push, it’s identical in nature to IT security curiosity. 1 kid wrote some code and then copy/pasted it a bunch of time, no problem there’s an upper limit on instructions. Another tried to hog all the squares by having them draw just a single dot, no problem there’s a cool-off timer that prevents you from blasting through squares. I haven’t had to use it but I also have a censorship mechanism :), I can scribble over any square and the machines will prioritize it.
So this year went really well, I think I can say with confidence now that the magic operates every time, this isn’t just luck with a good batch of kids or other. Every time we launch into “coding”, there’s a moment of sheer teeth grinding where I think it’s going to be a disaster. And every time they are all extremely motivated by the idea of controlling the machines when they hit “submit”, and so they all pull through and help each other out. Once one of them has gotten the machines moving, there’s a real frenzy to figure things out, and then their next drawings get more and more sophisticated. 5th grade might have a few blasé pre-teens who are hard to motivate, and they will inevitably get sucked in. Now they might “whatever” out of the activity after a bit, but even they will want to have done it at least a couple of times :). I particularly like when kids realize they can coordinate action on neighboring squares to do something greater, I purposefully don’t suggest that to them. I’ve gotten good at fending off “learned-helplessness”, not that I was doing it for them before, I’m just quicker to disengage. “You want to control the laser kid? Well you better figure it out”.
The “coding” interface
One of the snag we always hit is kids not able to discern the difference between typing in a URL or doing a search with Google. And a giant middle finger please for all the corpos purposefully blurring lines so kids form the habit early of running anything they might want to do on a computer through Big Corp Inc.
At the end of the day I send the wall plotter on an overnight portrait of a well liked central figure in the school. The next morning when I pick up the machine, the kids get one last wow effect. I’ll make a note of how many “go_to” statements went into the picture, usually several hundred thousands to get them thinking about scale and how curves can really be just a few tiny straight lines. They submit an average of 30 such statements for their cool drawings.
Dragon of Recursion / Light Show / Post-it Portraits
7 days, 47438 pen strokes :\. Lara’s work and a recurring dragon on this blog :). I sped up the machine to make it 7 days instead of 10, so it’s slightly more inaccurate, but more importantly I failed to anticipate that ink would run out faster. I used to have about 1.5 days between pen swaps, here it’s barely above 1 day. No harm done I got there in time, but I should have thought about it when I adjusted speed.
I lined it up with a big public event and tons of people got to see it.
No sure if there’s anything more to say about lasers & post-it portraits, it was the now usual formula. I’ve enhanced the pipeline some to do auto-face-cropping as it is a step we usually waste lots of time on. Esther & I rehearsed over the week end. She runs the operation during the event.
Some recurring questions I get asked at these events:
“What are the machines for normally?” Nothing, their sole purpose is to drag pens and shine cat lasers.
“Is this your job?” Nope, just a side quest.
“So how does this work?” I try to see what part they’re interested in before I launch into a 3 hour tirade :).
“Did you build this?” yes.
It’s very gratifying to see people stare at your work for a while. You can see the gears turning in their heads. I’ll sit by the big machine sometimes to watch people’s reaction to it. When I swap its pen people will come up and tell me how much they like it. I’m just glad for having the opportunity to do something cool in the world.
Refining the Formula
I was invited back to the science museum to do something cool with my machines. Any time I do a public event it’s an opportunity to figure out what’s engaging and do better the next time around.
I was maybe a little too motivated and brought several machines, almost my whole apparatus, and deployed them in various modes. 1 PewtyBot, 1 Mirror PewtyBot, 1 PlottyBot & 1 SkecthyBot doing portraits, and 1 PewtyBot people could control with their phones. The laser portraits worked wonders again, but the original PlottyBot drawing post-it portraits worked even better.
People were clearly keen on getting a tangible souvenir from the evening. Having a robot draw their portraits on a Post-it note struck a chord hard. I think what I’ve learned from this event is that while the lasers throw a lot of pazzazz at you, they are more complex machines that most people don’t try to engage with beyond taking in the light show. While a pen based machine is doing the same thing you’d do with your hand so it’s more approachable to be curious about. As usual a small fraction of them were fixated beyond reason on watching the machine at work. There has to be a “drawing automaton obsession” gene present in ~10% of the population.
Unfortunately, I only had one PlottyBot doing the Post-it portraits, and they take much longer than the lasers so I spent much of the evening trying to keep track of a queue of people who wanted one.
I built 2 4’x4′ photoluminescent paper holders so I could deploy this easier. In the past, finding a decent spot on a wall for the rolls and unrolling them was difficult and time consuming. I also have plans for doing random outside events at dusk in random places this Summer, which is why having something deployable was worth the construction effort. I tried it some already at home last Summer and it’s kind of cool to have the lasers go on a warm Summer night.
I had several people ask me if this was AI :), this seems to have become the go-to explanation for anything tech based that can’t be explained easily. Much like Clarke’s law that “Any sufficiently advanced technology is indistinguishable from magic”, only now it’s AI instead of magic. I’d respond that it was just good old organic grain-raised free-range “I”.
As usual, it was very hard to capture the coolness while manning it so I don’t have much visuals to represent what went on. Ultimately it’s just me running 5 machines, a software stack and talking a lot. Suffice it to say people were into it and I’m emboldened to keep trying public events. Fun times!
Overcoming Inertia
The design of PewtyBot 1.0 left something to be desired: the whole top section (stepper motor, assembly & laser) is moving, and that is a decent amount of mass that needs to be accelerated rapidly many times over.
As I was tuning parameters, it became obvious that I needed to slow things down to avoid inaccuracies from the vibrations of a fast accelerating mass. I found happy parameters which led to several public deployments, but deep inside I knew I wanted to try the mirror approach. Instead of moving the laser, it remains static and only a couple of light mirrors are doing all the moving.
Introducing PewtyBot 1.1!
There’s a funny story in there about losing code, reimplementing, and a core issue I was struggling with being solved without knowing why. As always, a few unforeseen challenges got in the way, but ultimately the math is exactly the same as PewtyBot 1.0 so that was a relief. It’s just the motion code that needs to be adjusted some to deal with mirrors.
And well the results are cool, but somewhat mitigated. Definitely not “rocks your socks off” levels of cool. I can definitely move the laser a lot faster. Although through the exercise, I’ve realized that the “slow” speed of PewtyBot 1.0 may have been in the perfect sweet spot for laser light retention on a photoluminescent medium. And so maybe I got lucky there. Of course I could get a beefier laser that emits more light to compensate for the reduced time it spends on any particular area. I’m pretty convinced though that I want to remain in the “cat laser” realm for risk & safety. And so the other variable I get to play with is mirror quality, and I shouldn’t be surprised that there exist a whole world of mirrors of various specs. I got some very cheap craft type acrylic mirrors at first to test concepts. But you can tell the pointer hits the medium diffused and discolored. And so ultimately I’ll want to spend the money on a few square centimeters of first surface mirrors rated for blue light wavelengths. But first I’d like to convince myself that the mirror approach actually brings something extra to the table.
That’s a Wrap
Robotics 2025 concluded with 2 kids having built the small Etch-a-Sketch plotter after 5 sessions, and an extra one to just consolidate and draw. There isn’t much to say other than it went like a charm. I’ve added onto the Inherently Programmable Pi so they could have a basic HTML interface to their machine, I have yet to publish the update. This solution I feel is a bit of a game changer for engaging with robotics. At best it lowers the bar significantly for uninitiated learners; at worst it’s just darn convenient to get to work on your Pi project anywhere. A few years ago I’d promote it on a few online communities, these days I just don’t have the will to do much of anything online, but I really should.
Playing with the RPi Etch-a-Sketch
I’m recreating the small SketchyBot for an electronics/robotics curriculum. It’s a perfect opportunity to let kids play with it.
Bis Repetita
Second deployment of Laser Portraits at a public event. It was a lot busier this time around, and totally fun as previously. Also very stressful until a few portraits are behind me. It doesn’t matter how much I test and check, something always goes wrong but I got it all figured out just in time. I’m also refining the formula for how to present and interact with people. The PewtyBots performed all evening without missing a beat.
Esther’s Plotter
I love it very much.
Built Me Another
I can make them pretty fast now, I bought top notch stepper drivers and servos for it. It’s so much quieter than the previous one. I’m learning that it makes no sense to buy cheap hardware when you’re not doing volume. The few bucks saved will be paid for many times over in wasted time. I took pictures for documentation but I’m not sure if I’ll have the time to sink into it.
A lot of refinements went into this one, from the thousands of hours that the previous model was in use.
This was the very first model, built long before I got into tabletop plotters:
It’s pretty pathetic to look at 🙂 but it was a good stepping stone. I built another other one for teaching based on cheap 28BYJ-48 steppers. All this to say Gondola PlottyBot v2 is very much the result of a journey.
SketchyBot 1.0
I finally built a standard sized one. I ran into a few unexpected challenges given how smooth the small one went.
It really isn’t the most accurate machine, the belts inside aren’t timed, but it does pretty ok with some rendering algorithm and is fun.
X,Y Coordinates Redux
As is now tradition, I taught my session on X,Y coordinates to local 5th graders.
As before, the collaborative drawing website I made worked wonder for getting them to time-share on the drawing machines. Each of them picks a square and works on it, I disable actual drawing for the class and they can only “code” with go_to(x,y) type commands. When they submit their drawing, the machines get to work. Kids absolutely love the idea of controlling the machines, and having that bit of time to shine as their drawing is being rendered. They are all extremely motivated to figure out the minutia of the code to these effects.
It looks like I bring a new machine every other year, we started with the tabletop plotter, then I added the gondola one, and of course this year it was lasers!
The kids really loved it as I suspected they would. I have learned that light management is a bit of an issue in the classroom when it needs to be dark but not too dark. Something to improve for next year.
It was a good crowd this year and I’ve been tempted to see if I could do something extra having some of them build the etch-a-sketch plotter.
Laser Portraits
I had a chance to run 2 Pewtybots at a public event where people could have their picture taken to be turned into line art to be rendered by lasers. I should have taken better pictures and videos, but I was too busy manning the station and talking to people. It’s unfortunate because it’s hard to convey the experience with words.
Ever since the first successful prototype, I kind of knew I wanted to do something for this event. And so I built 2 machines, refined the software, the math… well maybe that’ll be another post… I’m not sure I have it right just yet, I might. I have it right enough at least, let’s just say I refined the math. Finally, I spent time developing and practicing a pipeline where I can take someone’s picture and send it to either Pewtybot happens to be idle.
Esther helped man the station so we practiced at home with all her toys pretending to be the various personalities she’d encounter at such an event. From the overly curious bear to the llama in a hurry. And so the pipeline is as such: first we take your picture. A monitor is facing you to see what it is.
Then we turn that into lines to be drawn (or lasered in this case). This is supposed to be a first taste of eye candy as these algorithms are cool to see at work.
Then you go in a dark room, and see it all get zapped on the wall (I don’t have a picture of the lasered dog plush).
Because this was a first on many fronts, I was pretty anxious some things would go wrong (they did). I also didn’t know how to present it, or how people would react. So the first couple of “customers” helped me figure out how to guide them through the pipeline. And when the time comes to go in the dark room, I purposefully kind of dump people in there and vaguely tell them to wait for the wall to light up. I have the laser write their name and count down from 3 to 1, and then the laser moves much faster through their portrait.
Nicole quickly realized adding chairs in the dark room would invite people to take in the experience more. And I realized I was silly to tune my setting for single portraits, I almost exclusively had families and groups of friends in the same picture. The reactions were great, although I didn’t get any from inside the room, people coming out were full of questions and kids were smiling. As always with my silly projects, there’s also a smaller fraction of people with whom they resonate more deeply.
Overall it was a big success and pretty smooth for a first. I want to do more for sure. There’s something fireworksy about when the laser really starts moving and light shows up everywhere.
Eink, Plots & Luxembourg
I’ve been revamping and refactoring the software stack for plotty… pewty… gondola plotty… etchy? bot. Everytime a new riff on drawing machines came up, I’d grab the last code I worked on and tailored it for the new endeavor, often adding generalizable improvements along the way, but never taking the time to refactor previous work.
I always try to be helpful when people reach out on this blog about something they need/want/would like, but I have limited time and I’ve learned to filter a bit and not let other people’s projects take too much of my time. Last December though, the folks from Code Club Luxembourg got in touch with a few questions, and I gave them the usual “helpful but not too much” filter. Except they went on to build 5 PlottyBots, a whole integration with Scratch, and now use it to teach coding. Music to my ears, and clearly they meant business. And so we hopped on a call to exchange ideas.
Clearly the software could use consistency and so I started thinking holistically with the laser code. Each machine has slightly different motor control, but it’s now evident which software pieces are consistent across implementations. Ideally, I’d like the same software stack no matter which machine you happen to be running on. So I refactored back to the gondola plotter, and finally the tabletop one. It’s still not finished but it’s definitely better and more consistent.
To test new software on the original PlottyBot, I ran it on my reMarkable tablet.
I’m not going to do a whole post dedicated to its merits, I’m allergic to promotional content, but I will say a quick few things on this unrelated post. I’ve been interested in Eink for the longest time but never found a compelling device I felt was more than a temporary gimmick. Even getting a pricy reMarkable was a bit of an experiment that could land in a closet gathering dust. But I did want to experiment with quieter and purpose targeted devices so I went on with it after more than a decade of seeing various Eink devices go by. I haven’t adopted it for everything I want to yet, it takes time to change long established work habits, but I will say that it absolutely NAILS writing. It nails it so hard it changed the way I problem solve to an earlier saner process. It might be a generational thing, but writing is key to information absorption and processing for me. The problem with paper is that I have pieces flying everywhere, and mistakes make for an unclean train of thought committed to paper which is frustrating to engage with further. With Eink writing, you get an infinite canvas, and the ability to massage thoughts into a perfect form, one ripe for implementation. I have found that I will pick this device with a sense of relief as it means I’m about to engage in uninterrupted deep thinking. I find many signs that it was carefully designed to be such a device and not your next fancy tech gizmo, and I absolutely love it for this. Hopping on a computer on the other hand does not yield a sense of relief, but rather stressed anticipation at the onslaught of mechanisms devised to get in the way of what I was trying to do. Of course, I can’t do as much on the reMarkable, but I’m curious more than ever to shift to it whatever I can.
Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.
Antoine de Saint-Exupéry
PewtyBot 1.0 x2
I built another one, it’s always been useful to have 2 of my drawing machines.
PewtyBot 1.0
I’ve used this project as a stepping stone and modified it some. I can’t say enough good things about it, it propelled development forward significantly and I found it to be expertly designed. Too bad the project it now defunct. I had to find assembly documentation on archive.org.
I’m not sure I’ll document it as well as I have the tabletop plotter or the gondola one. At least not yet, maybe that’ll be a Christmas project like the other 2. I did port the same software stack, it would be a shame not to given the years of feature development that went into it. Of course we should use these features with lasers. It might also change drastically, I want to investigate what rotating mirrors could do for speed. Currently some of the moving parts of the machine have enough mass that their inertia causes inaccuracies when moving at high speed.
It’s nice to have things tidied up, the development machine was a mess.
Laser Pew Pew
I have yet to crack the math, I’ve been banging my head against the wall with various implementations but this is a lot worse than the Gondola’s double polar system. I’d like the laser to be able to project a cartesian system in any position relative to the surface it’s drawing on. Alas, I’ve only been able to get decent results in ideal positions.
For Posterity
The first successful prototype of PewtyBot.
Philip from Germany got in touch to tell me about a cool project he had seen that involved photoluminescent paper. He thought maybe PlottyBot could so something with it, and maybe it could, but not fast enough I thought. I knew exactly what I wanted to do with it though, with the PlottyBot software stack, but a different machine. I love that people get in touch to show me cool things. I’ve been working on plotters for years now, and in some sense it felt like I had turned every stone. Out of nowhere Philip got in touch and steered me toward a whole new area of exploration. Of course one can buy glow-in-the-dark paper, of course I can shoot lasers at it, of course all the algorithms I’ve been working on these past years lend themselves to this new endeavor. Well, with some tweaking :).
It was a real struggle to get Trinamic drivers working on a Pi, but I wanted to step up my motor stepping game. Once I figured it out, holy shit do they work! There’s much else to talk about here, but this isn’t the point of this post, I just want to capture the miletone that is shooting lasers super fast at photoluminescent paper. I still haven’t wrapped my mind around what this all means.
No Pen up/down, No Precision
Still totally fun and I want a big one.
As is Tradition
Thanksgiving handwriting capture.
It’s pretty cool that Esther learned writing just as this project came online so I could capture her progress from the beginning. For comparison purposes, this doesn’t show lowercase letters, special characters, or cursive that she recently acquired.
PlottyBot Port
I stumbled upon electronically actuated Etch-a-Sketches, and I pretty much had to see if I could port the PlottyBot stack to the toy. It was pretty straightforward. I got the parts from someone else on Thingiverse for a smaller Etch-a-Sketch and the fit isn’t great, but it’s enough of a proof of concept to know I want to make a nice big one, and really the work is all mechanical at this point. How about a web enabled Etch-a-Sketch that can write in your handwriting?
Experimenting with Larger Ink Reservoirs
When I plot stuff that goes beyond a pen’s ink capacity, it’s a pain to swap pens. It’s a constant worry and the operation has the potential for ruining a plot. So I’m experimenting with ways to have enough ink on board, or maybe refill. Of course I’m learning that pens are designed within tight tolerances of pressure & viscosity.
I think this one is going to work. I made the reservoir’s volume 5 times that of an unaltered Precise v5 pen.
I always make an ink mess with each experimentation. I’ve learned that PLA printing is not liquid tight. And so thank you Nathan for the resin printing :). One other silly lesson I’ve learned is that various paper can suck up ink at different rates.
X,Y Coordinates
Some of the tools I’ve accumulated over the years lend themselves particularly well for teaching. I’ve gotten better at swooping in a classroom with some plotters and talking about math or machine drawing topics. I can make it very interactive.
One tool in particular is https://draw.mandalagaba.com.
It started not so much for teaching, but rather for collaborative art. Very much inspired by r/Place, I created a tool with real estate scarcity, but with my usual focus on drawing. The kicker would be that the art is rendered live on a plotter somewhere in the world, maybe in front of you in a public place, maybe a video stream and you know your pen strokes are executed by a machine thousands of miles away. You claim a square, coordinate with others to make bigger pieces, and a collaborative art piece is born. That was the idea at least. I’ve tried several permutations of this experiment, in public, on a stream, with various rules and online communities, and it simply never generated the enthusiasm I thought it would. I have 95% given up on the idea of a collaborative art piece of the sort. The big plotter still has me wondering hence the remaining 5%, but it is tedious and expensive to deploy for an experiment that has shown no promise at every iteration.
What this website became great for however is teaching as it allows for time sharing a drawing machine across several students. We can explore one concept or other, and then apply it and have the great motivator that we’ll get to control the machine by doing so. 3 years ago I taught a module on X,Y coordinates with the local 5th graders, I didn’t have this site then and it went fine. But the following year I figured I might as well use this dumb collaborative art website I made for something so I integrated it into the coursework. Now that second year The machine’s made an enormous difference in how students engage. Recently I ran this course for the 3rd year with the website and the magic happened again. Both times, kids were very much willing to go through teeth grinding (light X,Y coordinate based coding), and help each other out to see their work realized in the world by a cool machine. The first student that submits a drawing on the site inevitably has everyone jumping off their seat to see the machine move up close. Then they’re even more motivated to do it themselves. I help them with the mistakes they make at first, and once they get it I have a good half an hour of walking around and seeing the cool stuff they draw. During this time I might send one drawing machine on a more intricate plot that can finish quick. Having that plotter wield a pen expertly inevitably draws 2 or 3 kids who just sit and stare at the machine non-stop. I know what they’re going through. The whole experience has them asking so many questions, and I love interacting with the different ways in which they see the world. I also love the opportunity to get to know every kid in town a little better when they go through 5th grade.
I’m quite glad that these tools found a place in education. Sometimes I think of pushing further, there’s definitely something to this formula, and I know teachers often purchase various curricula or interventions that meet a standard or other. But I can’t push all the projects, and so far I’ve refused to let money taint anything plotter related.
Funnily enough, I even had an opportunity to guest lecture in the same way with college art students. Of course we don’t talk about 5th grade X,Y coordinates, and I’m not there to talk about art either. Rather we learn and employ tools and techniques for line art and single instrument machines. It’s only funny because I’m ashamed to admit I’ve been very dismissive of art (except music) my whole life. I never understood it and wasn’t a fan of the carefree personalities gravitating to it. I’ve seen the light now, and I do feel apologetic for the times someone showed me a something they had made and it went completely above my head. But I can’t say I was particularly impressed by the students. I’m definitely curious to try again and see if I can bridge more understanding. In the meantime, I have no issues resonating with 5th graders so I’ve got that going for me :). Except for keeping them focused, that is insanely hard.