Vintage Hacks For Dot Matrix Printers In China

In an excerpt from his book The Chinese Computer: A Global History of the Information Age, [Thomas Mullaney] explains how 1980s computer tech — at least the stuff that was developed in the West — was stubbornly rooted in the Latin alphabet. After all, ASCII was king, and with 60,000 symbols, Chinese was decidedly difficult to shoehorn into 8 bits. Unicode was years in the future so, of course, ingenious hackers did what they do best: hack!

The subject of the post is the dot matrix printer. Early printers had nine pins, which was sufficient to make Latin characters in one pass. To print Chinese, each character required at least two passes of the print head. This was slow, of course, but it was also subject to confusing variations due to ink inconsistency and registration problems. It also made the Chinese characters twice as big as English text.

Initial attempts were made to use finer pins to pack twice as many dots in the same space. But this made the pins too thin and subject to bending and breaking. Instead, some engineers would retain the two passes but move the print head just slightly lower so the second pass left dots in the gaps between the first pass dots. Obviously, the first pass would print even-numbered dots (0, 2, 4,…), and the second pass would catch the odd-numbered dots. This wasn’t faster, of course, but it did produce better-looking characters.

While international languages still sometimes pose challenges, we’ve come a long way, as you can tell from this story. Of course, Chinese isn’t the only non-Latin language computers have to worry about.

FLOSS Weekly Episode 788: Matrix, It’s Git, For Communications

This week Jonathan Bennett and Simon Phipps chat with Matthew Hodgson and Josh Simmons about Matrix, the open source decentralized communications platform. How is Matrix a Git for Communications? Are the new EU and UK laws going to be a problem? And how is the Matrix project connected with the Element company?

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What If The Matrix Was Made In The 1950s?

We’ve noticed a recent YouTube trend of producing trailers for shows and movies as if they were produced in the 1950s, even when they weren’t. The results are impressive and, as you might expect, leverage AI generation tools. While we enjoy watching them, we were especially interested in [Patrick Gibney’s] peek behind the curtain of how he makes them, as you can see below. If you want to see an example of the result first, check out the second video, showing a 1950s-era The Matrix.

Of course, you could do some of it yourself, but if you want the full AI experience, [Patrick] suggests using ChatGPT to produce a script, though he admits that if he did that, he would tweak the results. Other AI tools create the pictures used and the announcer-style narration. Another tool produces cinematographic shots that include the motion of the “actors” and other things in the scene. More tools create the background music.

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Old Dot-Matrix Displays Give Up Their Serial Secrets

If there’s one thing we like better around here than old, obscure displays, it’s old, obscure displays with no documentation that need a healthy dose of reverse engineering before they can be put to use. These Plessey dot-matrix displays are a perfect example of that.

We’re not sure where [Michael] scored these displays, but they look fantastic. Each 8-pin DIP has two 5×7-matrix, high-visibility LED displays. They bear date codes from the late 80s under the part number, GPD340, but sadly, precious little data about them could be dredged up from the Interwebz. With 70 pixels and only six pins after accounting for power and ground, [Michael] figured there would be a serial protocol involved, but which pins?

He decided to brute-force the process of locating them, using a Pico to sequentially drive every combination while monitoring the current used with a current sensor. This paid off after only a few minutes, revealing that each character of the display has its own clock and data pins. The protocol is simple: pull the clock and data pins high then send 35 bits, which the display sorts out and lights the corresponding pixels. The video below shows a 12-character scrolling display in action.

Plessey made a lot of displays for military hardware, and these chunky little modules certainly have a martial air about them. Given that and the date code, these might have come from a Cold War-era bit of military hardware, like this Howitzer data display which sports another Plessey-made display.

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LED Matrix Earrings Show Off SMD Skills

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

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

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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