LED Matrix Earrings Show Off SMD Skills

February 21, 2024 by 12 Comments

We’ll be honest with you: we’re not sure if the use of “LED stud” in [mitxela]’s new project refers to the incomprehensibly tiny LED matrix earrings he made, or to himself for attempting the build. We’re leaning toward the latter, but both seem equally likely.

This build is sort of a mash-up of two recent [mitxela] projects — his LED industrial piercing, which contributes the concept of light-up jewelry in general as well as the power supply and enclosure, and his tiny volumetric persistence-of-vision display, which inspired the (greatly downsized) LED matrix. The matrix is the star of the show, coming in at only 9 mm in diameter and adorned with 0201 LEDs, 52 in total on a 1 mm pitch. Rather than incur the budget-busting expense of a high-density PCB with many layers and lots of blind vias, [mitexla] came up with a clever workaround: two separate boards, one for the LEDs and one for everything else. The boards were soldered together first and then populated with the LEDs (via a pick-and-place machine, mercifully) and the CH32V003 microcontroller before being wired to the power source and set in the stud.

Even though most of us will probably never attempt a build on this scale, there are still quite a few clever hacks on display here. Our favorite is the micro-soldering iron [mitxela] whipped up to repair one LED that went missing from the array. He simply wrapped a length of 21-gauge solid copper wire around his iron’s tip and shaped a tiny chisel point into it with a file. We’ll be keeping that one in mind for the future.

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Dot Matrix Printer Gets An Epson Ribbon Transplant

October 31, 2023 by 19 Comments

What do you do when your dot matrix printer’s ribbon is torn to shreds after decades of use, and no new cartridges are available? You might like to attempt a ribbon transplant from another printer’s cartridge, and that’s just what [Chris Jones] did.

[Chris] was hoping to find a new ribbon for his Canon PW-1080A after the 33-year-old ribbon had been hammered to bits. With replacements unavailable, he instead turned to the more popular Epson FX80, for which new ribbons can still be found. Thankfully, the FX80’s ribbon is the same width as the one used in the Canon printer, even if the cartridge is of a completely different design.

The first step was to crack open the Canon cartridge to dump out the old ribbon. With that done, the Epson ribbon could be looped into the Canon cartridge and wound in using the built-in winder. With this done, [Chris] attempted a test print, but found results to be poor. The ribbon wasn’t advancing properly and there was a rather horrible noise.

The problem was that the Epson ribbon was significantly longer than the Canon part, and thus was getting jammed inside the cartridge housing. [Chris] was able to fix this by cutting out a slice of the Epson ribbon and sticking the two ends back together with superglue. With that done, the printer was happily up and running once more.

If you’ve got a dot matrix printer ribbon that’s dried up but not yet falling apart, you can always try reinking it. Video after the break.

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Giant LED Matrix Fills Blank Space In The Kitchen

October 9, 2023 by 8 Comments

We’ve all got one: a blank space somewhere in our home that we don’t know what to do with. [James Miller] had one above his kitchen cabinets, so he filled it with a giant LED matrix. The result is a large but surprisingly attractive LED screen that can send messages, provide illumination, or while away the idle hours of the night playing Conway’s Game of Life.

[James] built the matrix using the usual suspect for these builds: several strings of WS2812 lights . He initially ran this from a Raspberry Pi, but realized that there was no need for such a dizzying amount of computing power, so he switched to an ESP32 instead. The frame is built from wood and foam board.

The first version he built used a fabric diffuser, but after a close encounter with a flaming steak, he switched over to commercial ceiling light diffusers cut down to size. We might have been tempted to keep going and try an “egg crate” style ceiling light panel for a the smaller pixel size, but [James] thinks he has reached the “good enough” point of this project. It’s certainly a fun build, and it looks very cool with minimal materials.

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Is This The World’s Largest Dot Matrix Printer?

June 22, 2023 by 27 Comments

[RyderCalmDown] was watching a road painting vehicle lay down fresh stripes on the road one day and started thinking about the mechanism that lets it paint stripes in such a precise way. Effectively the system that paints the interspersed lines acts as a dot matrix printer that can only print at a single frequency. With enough of these systems on the same vehicle, and a little bit more fine control of when the solenoids activate and deactivate, [RyderCalmDown] decided to build this device on the back of his truck which can paint words on a roadway as he drives by. (Video, embedded below.)

Of course, he’s not using actual paint for this one; that might be prohibitively expensive and likely violate a few laws. Instead he’s using a water-based system which only leaves temporary lettering on the pavement. To accomplish this he’s rigged up a series of solenoids attached to a hitch-mounted cargo rack. A pump delivers water to each of the solenoids, and a series of relays wired to a Raspberry Pi controls the precise timing needed to make sure the device can print readable letters in much the same way a dot matrix printer works. There’s an algorithm running that converts the inputted text to the pattern needed for the dot matrix, and after a little bit of troubleshooting it’s ready for print.

Even though the printer works fairly well, [RyderCalmDown] had a problem thinking of things to write out on the roadways using this system, but it’s an impressive build based around a unique idea nonetheless. Dot matrix printers, despite being mostly obsolete, have a somewhat vintage aesthetic that plenty of people still find desirable and recreate them in plenty of other ways as well, like this 3D printer that was modified to produce dot matrix artwork.

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Restoring Dot Matrix Printer Cartridges For 2023

May 27, 2023 by 17 Comments

The noise of a dot matrix printer is probably as synonymous with 1980s computing as the modem handshake would become with the desktop experience a decade or more later. But unlike the computers that would have driven it, a dot matrix printer can still be a very useful device here in 2023. And why not? They’re cheap to operate and can produce surprisingly good quality when paired with suitable drivers. There is a snag though; while cartridges for popular models can still be found, there are plenty whose consumables are long gone. [Drygol] had an Apple ImageWriter II with exactly that problem, and after finding all his cartridges were non-functional, took a look at how to bring them back.

Inside a dot matrix cartridge is a fabric ribbon similar to the one that might once have been found on a typewriter. It’s not on a roll but folded into the space, and it’s drawn through by a pair of rollers. Not only had the ink on the fabric dried out, but the foam on the rollers had also disintegrated. Some careful dismantling, and a solution presented itself in the form of O-rings to replace the rollers. Those and a bit of mineral oil to soften the ink had the vintage Apple printing again as though it was the ’80s once more.

It’s a subject we’ve looked at before, as it turns out WD-40 makes a good ink solvent.

Barcodes Enter The Matrix In 2027

May 3, 2023 by 80 Comments

Beep. We’ve come a long way since June 26, 1974 when the first bar code was scanned at a grocery store in Troy, Ohio. That legendary pack of Juicy Fruit proved that even the smallest of items could now carry numbers associated with inventory and price.

By now, we’re all too familiar with this sound as self-checkouts have become the norm. Whereas you yourself could at one time literally check out during the transaction, you must now be on your toes and play find the bar code on every item.

What does the consumer gain from the bar code today? Practically nothing, except the chance to purchase, and potentially return, the item without too much hassle. Well, the non-profit outfit that runs the bar code world — GS1 US — wants to change all that. By 2027, they are confident that all 1D bar codes will be replaced with 2D bar codes similar to QR codes. Why?

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LED Matrix Displays Get New Look Thanks To SMD Stencils

April 28, 2023 by 26 Comments

Even if surface-mount skills aren’t in your repertoire, chances are pretty good that most of us are at least familiar with SMD stencils. These paper-thin laser-cut steel sheets are a handy way to apply a schmear of solder paste to the pads of a PCB before component placement and reflowing. But are stencils good for anything else?

It turns out they are, if you’ve got some plain old 8×8 LED matrix displays you want to jazz up a bit. In this case, [upir]’s displays were of the square pixel type, but this trick would work just as well for a matrix with circular elements. Most of the video below is a master class in Adobe Illustrator, which [upir] used to generate the artwork for his stencils. There are a lot of great tips here that make creating one simple shape and copying it over the whole array with the proper spacing a lot easier. He also details panelizing multiple stencils, as well as the workflow from Illustrator to manufacturing.

When lined up properly over the face of the LED matrix, the stencils have quite an effect. We really liked the narrow vertical bars, which make the LED display look a bit like a VFD. And just because [upir] chose to use the same simple shape over all the LEDs in a matrix doesn’t mean that there aren’t other options. We can see how you might use the same technique to create different icons or even alphanumeric characters to create custom LED displays. The possibilities are pretty much limited to your imagination.

This isn’t the first time we’ve seen [upir] teaching old displays new tricks.

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