Three Computers, One Keyboard With USB Triplexer

November 4, 2022 by 25 Comments

Many of us will have the problem of several computers on the same desk, and to avoid clutter we’ll use a KVM switch to share the peripherals. [The Turbanned Engineer] has an interesting solution to this problem in the form of a USB triplexer. It’s a device that routes USB data lines depending upon which of its connections is powered up.

The circuit is simple enough: a CMOS analogue multiplexer does the routing, and a set of opto-couplers do the selecting based on the power inputs. A set of USB A sockets connect to the computer, and a USB B socket connects to the peripheral.

We’re not entirely sure whether an analogue multiplexer chip would be good for the higher-speed USB data rates, but since keyboards and mice talk at the slowest data rates, we think he’ll get away with it. Either way making a USB switch however basic with such mundane components has something of the hack about it. What he does with the display we’re not so sure about, but at least his keyboard and mouse woes are dealt with.

Other similar switches we’ve featured have been somewhat more basic.

3D Printed Newtonian Telescope Has Stunning Looks, Hadley Breaks The Bank

November 4, 2022 by 49 Comments

Have you ever considered building your own telescope? Such a project can be daunting, especially if you grind your own mirrors. But with a 3D printer, hardware store bits and bobs, and some inexpensive pre-made mirrors, you too can be the proud owner of your very own own Hadley — a 114/900mm Newtonian Telescope that can cost less than $150 USD to build! Check out the video below the break to get a good scope on the project.

Astrophotography is possible with the Hadley

The creator’s stated goal is to “make an attractive alternative to the shoddy, hard to use “hobby-killer” scopes in the $100-200 range“, and we have to say that it appears to have met its goal admirably. The optics — the most complex part of any build — can be easily purchased online, and the rest of the parts are available at your local hardware store.

While the original build was provided in Imperial measures, a metric version is now available. Various contributors have created a rich ecosystem of accessories and alternative versions of various parts, all in the interest of making the telescope more useful. Things like tripod mounts, phone mounts (for use with your favorite star chart app) and more are only a click away. The only real question to answer is “What color filament will I use?”

Of course, sometimes light waves can get a bit long in the tooth, and for those cases you’ll want a radio telescope, which can also be DIY’d thanks to the availability of satellite dishes and SDR dongles!

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3D Printer Tuning: An Engineering Approach

November 4, 2022 by 14 Comments

[MirageC] is a bit of a contrarian. Instead of taking pictures of 3D printed objects that show them in their best light, he takes pictures that show them at their worst. The reason? He wanted to figure out why he was seeing a strange artifact in his printer when using a direct extruder. Just at a quick glance, you might think the problem was Z wobble, but, in this case, it was something else. You can see the fine detective work in the video below.

There were a few odd things about the problem. First, it scaled with the part size. Secondly, the problem got better when he switched to a Bowden tube setup. We don’t want to give away the ending, but you can guess from that clue that the problem had something to do with the extrusion system.

The resulting analysis led [MirageC] to work with BMG to create a special gear which — surprisingly, didn’t help as much as he thought it would. However, it did help point the way to the correct solution.

Along the way, you can learn a lot from following along, and maybe you’ll even improve the quality of your prints. We always enjoy these detailed analyses of printer issues, like the ones from [Stefan], for example. If you want to go hardcore engineering on your 3D prints, you can always do finite element analysis on your infill.

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This Week In Security: OpenSSL Fizzle, Java XML, And Nothing As It Seems

November 4, 2022 by 3 Comments

The security world held our collective breaths early this week for the big OpenSSL vulnerability announcement. Turns out it’s two separate issues, both related to punycode handling, and they’ve been downgraded to high severity instead of critical. Punycode, by the way, is the system for using non-ASCII Unicode characters in domain names. The first vulnerability, CVE-2022-3602, is a buffer overflow that writes four arbitrary bytes to the stack. Notably, the vulnerable code is only run after a certificate’s chain is verified. A malicious certificate would need to be either properly signed by a Certificate Authority, or manually trusted without a valid signature.

A couple sources have worked out the details of this vulnerability. It’s an off-by-one error in a loop, where the buffer length is checked earlier in the loop than the length variable is incremented. Because of the logic slip, the loop can potentially run one too many times. That loop processes the Unicode characters, encoded at the end of the punycode string, and injects them in the proper place, sliding the rest of the string over a byte in memory as a result. If the total output length is 513 characters, that’s a single character overflow. A Unicode character takes up four bytes, so there’s your four-byte overflow. Continue reading “This Week In Security: OpenSSL Fizzle, Java XML, And Nothing As It Seems” →

Thin Client And Smartphone Step In For 3D Printer’s Raspberry Pi And Touchscreen

November 4, 2022 by 19 Comments

It’s no secret that Raspberry Pi’s are a little hard to come by these days. Unless you had the foresight to stock up before the supply dried up — and if you did, we want to talk to you — chances are good that you’ve got a fair number of projects that use the ubiquitous SBC on indefinite hold. And maybe that’s got you thinking about alternatives to the Pi.

That’s apparently what was on [Crimson Repair]’s mind lately, the result being the discovery that an old thin client PC makes a dandy stand-in for a Raspberry Pi, at least in some cases. The video below is on the long side, true, But it’s chock full of command-by-command instructions for getting a Dell Wyse 3040, a thin client that can be found on the secondary market for $25 or so, up and running as a Klipper alternative for a 3D printer. These machines, which usually see use in point-of-sale applications and the like, sport a 1.4-GHz Intel Atom processor and a couple of gigs of RAM, and the form factor is just right for tucking into the base of an Ender 3.

Getting one up and running is a matter of getting a Debian image onto a USB key and configuring the thin client to boot from USB. After that it’s a simple matter of installing Klipper and wiring up a buck converter to power the machine. It’s not exactly rocket surgery, but why muddle through the process when someone has already been down the path ahead of you? And if you want to take it further, the second video below walks you through all the steps needed to add a touchscreen using an old Android phone. With a 3D printed bracket, the whole thing is a nicely complete printer control solution.

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A blue cabinet. Inside, along the front and back are wooden sawteeth holding a cleat. On the cleat sits the shelf itself.

Adjusting Shelves Like It’s 1899

November 4, 2022 by 39 Comments

In most modern homes, any adjustable shelves or cabinets have metal shelf pins set inside conveniently spaced holes. Before the accoutrements of modern life, like easily replicated metal parts, you may have found a sawtooth shelf doing the same job with just wood.

The system comprises three parts: a series of “sawteeth” running up and down the front and back edge of a cabinet, a cleat to sit between the teeth, and a shelf with notched corners that can then be set down on the cleats on either side.

While not as convenient as running a drill through a shelf pin jig, this method has a certain charm and sturdiness that isn’t present in more modern methods of making adjustable shelves. We can see this being particularly useful for restoration projects of homes from the 19th Century or earlier where you want some of those aforementioned accoutrements without things looking too anachronistic.

If you want some shelving that’s decidedly more 21st Century, check out this MP3 Player Shelf or this Smart Shelf with Serious Functionality.

Walnut Case Sets This Custom Arduino-Powered RPN Calculator Apart From The Crowd

November 3, 2022 by 12 Comments

How many of us have an everyday tool that’s truly unique? Likely not many of us; take a look around your desk and turn out your pockets, but more often than not, what you’ll find is that everything you have is something that pretty much everyone else on the planet could have bought too. But not so if you’ve got this beautiful custom RPN calculator in a wooden case.

This one comes to us from [Shinsaku Hiura], who generally dazzles us with unique mechanical clocks and displays. This calculator solves a more practical problem — the dearth of RPN calculators on the market with the correct keyboard feel, specifically with the large keys and light touch he desired. Appropriately, the build started with a numeric keypad, which once liberated of its USB interface was reverse-engineered to figure out how the matrix was wired. Next up, a custom PCB to connect the keypad to an Arduino and a 20×4 LCD display was milled up, while a test case was designed and printed to check fitment. The final case was milled from a block of solid walnut and fitted with an acrylic window, for a sharp look with clean lines and pleasing colors.

As for the calculator itself, the demo below shows it going through its paces. The code is clever because it leverages the minimal number of keys available by hiding all the scientific and engineering functions behind a “secret silver key” that was once the equals key and obviously not needed in RPN. Hats off to [Shinsaku] for a handsome and unique addition to his desk.

Continue reading “Walnut Case Sets This Custom Arduino-Powered RPN Calculator Apart From The Crowd” →