Restoring A Vintage Computer And Its Plotter

Repairing vintage computers is bread-and-butter for many of us around here. The machines themselves tend to be fairly fixable, assuming spare parts are available and there hasn’t been too much physical damage. Peripherals can be another matter, though. Since they interface with the real world they can have more esoteric problems that aren’t always solvable. [joekutz] was handed just such a device in the form of a CE-150 docking station for a Sharp PC1500 Pocket Computer, which has a plotter built in. Here’s his “tip” for getting plotters like these working again.

The first step here is to disassemble the original, dried out pens to scavenge a few of the parts. The outer case needs to be kept so that it can be put back into the plotter, and a small O-ring is saved as well. To replace the dried-out tips [joekutz] discards the original tips and replaces them with tips from a common ink pen, using shrink wrap tubing to help fit the pen’s tip into the original plotter cylinder. He also takes the ink from the pen to fill the plotter’s cartridge, completing the surgery on the multi-colored plotter and bringing it back to life.

Of course this build goes well beyond the plotter, including bringing the PC1500 back to life as well. There are a few other videos about this project covering that original restoration as well as demonstrating some of the quirks of how this computer is meant to be programmed. But we mostly focused on the plotter here since that is a little bit out of the ordinary, and we’re also sure that refilling ink cartridges of any sort gets under the skin of everyone at HP.

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The Incrediplotter: Voice Controlled Plotter From Repurposed Printer

There’s something uniquely satisfying about a pen plotter. Though less speedy or precise than a modern printer, watching a pen glide across the page, mimicking human drawing, is mesmerizing. This project, submitted by [Jacob C], showcases the Incrediplotter, a brilliant repurposing of a 3D printer built by him and his brother.

Starting with a broken 3D printer, [Jacob C] and his brother repurposed its parts to create a voice-controlled pen plotter. They 3D-printed custom components to adapt the printer’s framework for plotting. An STM32 Blue Pill running Klipper controls two TMC2208 motor drivers for the x- and y-axes, while a small standalone servo manages the pen’s height.

The unique twist lies in the software: you can speak to the plotter, and it generates a drawing based on your prompt without needing to select an image. The process involves sending the user’s voice prompt to Google Gemini, which generates an image. The software then converts this image into an SVG compatible with the plotter. Finally, the SVG is translated into G-Code and sent to the plotter to start drawing.

Thanks to [Jacob C] for sharing this impressive project. It’s a fantastic example of repurposing a broken machine, and the voice-to-image feature adds a creative twist, enabling anyone to create unique artwork. Be sure to check out our other featured plotter hacks for more inspiration.

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Capture And Plot Serial Data In The Browser

If you’re working with a microcontroller that reads a sensor, the chances are that at some point you’re faced with a serial port passing out continuous readings. The workflow of visualizing this data can be tedious, involving a cut-and-paste from a terminal to a CSV file. What if there were a handy all-in-one serial data visualization tool, a serial data oscilloscope, if you will? [Atomic14] has you covered, with the web serial plotter.

It’s a browser-based tool that uses the WebSerial API, so sadly if you’re a Firefox user you’re not invited to the party. Serial data can be plotted and exported, and there are a range of options for viewing. Behind the scenes there’s some Node and React magic happening, but should you wish to avoid getting your hands dirty there’s an online demo you can try.

Looking at it we’re ashamed to have been labouring under a complex workflow, particularly as we find this isn’t the first to appear on these pages.

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Contagious Ideas

We ran a story about a wall-mounted plotter bot this week, Mural. It’s a simple, but very well implemented, take on a theme that we’ve seen over and over again in various forms. Two lines, or in this case timing belts, hang the bot on a wall, and two motors drive it around. Maybe a servo pulls the pen in and out, but that’s about it. The rest is motor driving and code.

We were thinking about the first such bot we’ve ever seen, and couldn’t come up with anything earlier than Hektor, a spray-painting version of this idea by [Juerg Lehni]. And since then, it’s reappeared in numerous variations.

Some implementations mount the motors on the wall, some on the bot. There are various geometries and refinements to try to make the system behave more like a simple Cartesian one, but in the end, you always have to deal with a little bit of geometry, or just relish the not-quite-straight lines. (We have yet to see an implementation that maps out the nonlinearities using a webcam, for instance, but that would be cool.) If you’re feeling particularly reductionist, you can even do away with the pen-lifter entirely and simply draw everything as a connected line, Etch-a-Sketch style. Maslow CNC swaps out the pen for a router, and cuts wood.

What I love about this family of wall-plotter bots is that none of them are identical, but they all clearly share the same fundamental idea. You certainly wouldn’t call any one of them a “copy” of another, but they’re all related, like riffing off of the same piece of music, or painting the same haystack in different lighting conditions: robot jazz, or a study in various mechanical implementations of the same core concept. The collection of all wall bots is more than the sum of its parts, and you can learn something from each one. Have you made yours yet?

(Fantastic plotter-bot art by [Sarah Petkus] from her write-up ten years ago!)

Mural: The Plotter That Draws On Walls

Let’s say you’ve got a big bare wall in your home, and you want some art  on it. You could hang a poster or a framed artwork, or you could learn to paint a mural yourself. Or, like [Nik Ivanov], you could build a plotter called Mural, and get it to draw something on the wall for you. 

The build is straightforward enough. It uses a moving carriage suspended from toothed belts attached to two points up high on the wall. Stepper motors built into the carriage reel the belts in and out to move it up and down the wall, and from side to side. In this case, [Nik] selected a pair of NEMA 17 steppers to do the job. They’re commanded by a NodeMCU ESP32, paired with TMC2209 stepper motor drivers. The carriage also includes a pen lifter, which relies on a MG90s servo to lift the drawing implement away from the wall.

The build is quite capable, able to recreate SVG vector graphics quite accurately, without obvious skew or distortion. [Nik] has been using the plotter with washable Crayola markers, so he can print on the wall time and again without leaving permanent marks. It’s a great way to decorate—over and over again—on a budget. Total estimated cost is under $100, according to [Nik].

We’ve featured some neat projects along these lines before, too. Video after the break.

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Automating The Process Of Drawing With Chalk

Chalk is fun to draw with, and some people even get really good at using it to make art on the sidewalk. If you don’t like tediously developing such skills, though, you could go another route. [MrDadVs] built a robot to scrawl chalk pictures for him, and the results speak for themselves.

The robot is known as AP for reasons you’ll have to watch the video to understand. You might be imagining a little rover that crawls around on wheels dotting at the pavement with a stick of chalk, but the actual design is quite different. Instead, [MrDadVs] effectively built a polar-coordinate plotter to make chalk pictures on the ground. AP has a arm loaded with a custom liquid chalk delivery system for marking the pavement. It’s rotated by a stepper motor with the aid of a 3D-printed geartrain that helps give it enough torque. It’s controlled by an ESP32 running the FluidNC software which is a flexible open-source CNC firmware. [MrDadVs] does a great job of explaining how everything works together, from converting cartesian coordinates into a polar format, to getting the machine to work wirelessly.

Building a capable sidewalk chalk robot seems like a great way to spend six months. Particularly when it can draw this well. Video after the break.

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