Author: Al Williams

4352 Articles

In Future, Printer Documents You

June 22, 2024 by 76 Comments

[Jason Dookeran] reminded us of something we don’t like to think about. Your printer probably adds barely noticeable dots to everything you print. It does it on purpose, so that if you print something naughty, the good guys can figure out what printer it came from. This is the machine identification code and it has been around since the days that the US government feared that color copiers would allow wholesale counterfiting.

The technology dates back to Xerox and Canon devices from the mid-80s, but it was only publicly acknowledged in 2004. With color printers, the MIC — machine identification code — is a series of tiny yellow dots. Typically, each dot is about 10 microns across and spaced about a millimeter from each other. The pattern prints all over the page so that even a fragment of, say, a ransom note can be identified.

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Vintage Hacks For Dot Matrix Printers In China

June 21, 2024 by 12 Comments

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.

Build Your Own Tape Recorder/Player

June 21, 2024 by 14 Comments

If you want to read something from magnetic tape, you need a tape head, right? Or you could do like [Igor Brichkov] and make your own. It looks surprisingly simple. He used a washer with a small slot cut in it and a coil of wire.

The first experiment, in the first video below, is using a commercial tape head connected to a preamp. Music playing “through” the homemade head is readable by the commercial tape reader. This is a prelude to creating an entire tape deck using the head, which you can see in the second video below.

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Is That A Large Smartwatch? Or A Tiny Cray?

June 21, 2024 by 7 Comments

While we aren’t typically put off by a large wristwatch, we were taken a bit aback by [Chris Fenton]’s latest timepiece — if you can call it that. It’s actually a 1/25th-scale Cray C90 worn as a wristwatch. The whole thing started with [Chris] trying to build a Cray in Verilog. He started with a Cray-1 but then moved to a Cray X-MP, which is essentially a Cray-1 with two extra address bits. Then he expanded it to 32 bits, which makes it a Cray Y-MP/C90/J90 core. As he puts it, “If you wanted something practical, go read someone else’s blog.”

The watch emulates a Cray C916 and uses a round OLED display on the top. While the move from 22 to 32 address bits sounds outdated, keep in mind the Cray addresses 64-bit words exclusively, so we’re talking access to 32 gigabytes of memory. The hardware consists of an off-the-shelf FPGA board and a Teensy microcontroller to handle mundane tasks like driving the OLED display and booting the main CPU. Interestingly, the actual Cray 1A used Data General computers for a similar task.

Of course, any supercomputer needs a super program, so [Chris] uses the screen to display a full simulation of Jupiter and 63 of its moons. The Cray excels at programs like this because of its vector processing abilities. The whole program is 127 words long and sustains 40 MFLOPs. Of course, that means to read the current time, you need to know where Jupiter’s moons are at all times so you can match it with the display. He did warn us this would not be practical.

While the Cray wouldn’t qualify as a supercomputer today, we love learning about what was state-of-the-art not that long ago. Cray was named, of course, after [Seymour Cray] who had earlier designed the Univac 1103, several iconic CDC computers, and the Cray computers, of course.

Adding Texture To 3D Prints

June 20, 2024 by 20 Comments

[3DJake] likes putting textures on 3D prints using things like patterned build plates and fuzzy skin. However, both of those techniques have limitations. The build plate only lets you texture the bottom, and the fuzzy skin texture isn’t easy to control. So he shows how to use Blender to create specific textures to produce things like wood-like or leather-like surfaces, for example. You can see how it works in the video below.

As [Jake] points out, you might be able to use other artistic programs to do this, but the kind of things we use like FreeCAD of Fusion360 aren’t going to cut it.

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Arduino + TFT = Micro Star Chart

June 20, 2024 by 9 Comments

We always look at the round LCDs and wonder what to do with them other than, of course, a clock. Well, [shabaz] had a great idea: use it as a star map display. The project combines the Arduino, a round TFT, a GPS receiver, and some external flash memory to store data. You can get by without the GPS receiver or flash memory, but you’ll lose features if you do.

We like how he approached the problem. The project contains four major parts and he developed each part independently before integrating them into a whole. The four parts are: reading the GPS, driving the LCD, providing storage for star data, and determining the position of stars. The heavy lifting is done using some public domain code ported over. This code derives from a book called Astronomical Algorithms and uses the Yale Bright Star Catalog database.

The post mentions that the screen might well be a larger rectangular screen and we agree that would make this more usable. Now if you could cram it all into a watch, that might be different. If you want to play with the code, you can actually run the core on Linux. You’ll have to settle for a PNG output of the night sky, but that would be handy for debugging.

We have seen a star chart in a watch before. While this is more a star chart than a planetarium, we have no doubt the early planetarium builders would be suitably impressed.

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Ask Hackaday: How Do You Make Front Panels?

June 20, 2024 by 49 Comments

We’ll admit it. The closer a project is to completion, the less enthusiasm we have for it. Once the main design is clearly going to work on a breadboard, we’re ready to move on to the next one. We don’t mind the PCB layout, especially with modern tools. However, once the board is done, you have to do the case. Paradoxically, this was easier in the old days because you just picked some stock box, drilled some holes, and while it looked terrible, it was relatively easy.

Today, the bar is much higher. You’ll probably 3D print or laser cut an enclosure. If it looks no better than what you did in the 1970s, you won’t win many admirers. We routinely cover projects that could easily pass for commercial products. So how do you do it?

The Parts

The enclosure may even be the easy part. There are plenty of scripts and generators that will make you a nice box that meets your specifications. You can probably even get the holes made as you build. Back in the day, it was a challenge to cut odd-shaped holes for things like serial port connectors. Now, no problem. The printer or laser will just make a hole with any shape you like. You may even want to try a new angle on 3D printing.

Mounting the PCB isn’t that hard, either. With 3D printing, you can create standoffs, but even if you laser cut, you can easily use conventional standoffs. In a pinch, we’ve used long bolts with nuts.

The real problem, it seems to us, is the front panel. Only Star Trek can get away with front panels containing a bunch of knobs and dials with no markings. And although we call them “front” panels, sometimes you need markings on the back or even the sides, too. Continue reading “Ask Hackaday: How Do You Make Front Panels?” →