Sprucing Up A Bell & Howell Model 34 Oscilloscope

July 4, 2019 by 20 Comments

We’ll admit it, in an era when you can get a four channel digital storage oscilloscope with protocol decoding for a few hundred bucks, it can be hard not to see the appeal of analog CRT scopes from decades past. Sure they’re heavy, harder to use, and less capable, but they just look so cool. Who could say no to having one of these classic pieces of gear on their bench?

[Cody Nybo] certainly couldn’t. Despite the fact that he already has a digital scope, he couldn’t pass up the chance to add a Bell & Howell Schools Model 34 from circa 1973 to his collection. It needed a bit of TLC before it could be brought back into service, but now it’s all fixed up and ready to put in some work. Not bad for a piece of gear with nearly a half-century on the clock.

The restoration of the Model 34 was aided by the fact that [Cody] got the original manual and schematics for the scope in the deal, which he was kind enough to scan and upload for the rest of the class to enjoy. Those of you who have worked on older electronics can already guess where the scope needed the most love: all the capacitors needed to be swapped out for fresh ones. He also found a few resistors that were out of spec, and the occasional bad solder joint here and there.

Even if you’re not looking to repair your own middle-aged oscilloscope, his pictures of the inside of Model 34 are fascinating. The scope was sold as a kit, so the construction is surprisingly simple and almost entirely point-to-point. Of course, there’s something of a trade-off at work: [Cody] says it won’t display much more than 2.5 MHz before things start getting wonky. But then again, that’s a more than reasonable frequency ceiling for audio work and most hobbyist projects.

Oscilloscopes have come a long way since the days when they had to draw out their readings on a piece of paper. While newer devices have all but buried the classic analog scope, a beauty like this would still have a place of honor in our lab.

MIDI-Gurdy, MIDI-Gurdy, MIDI-Gurdy Man

July 4, 2019 by 19 Comments

The hurdy gurdy is the perfect musical instrument. It’s an instrument with a crank, and a mechanical wonderment of drone strings and weird chromatic keyboards. No other musical instrument combines the sweet drone of bagpipes with the aural experience of an eight-year-old attempting to play Hot Cross Buns on a poorly tuned violin.

Now, the hurdy gurdy is going digital. The Digi-Gurdy is [XenonJohn]’s entry into this year’s Hackaday Prize, and it’s exactly what it says on the tin: it’s a musical instrument that drones on and on, with keys plunking out a melody.

If you’re not familiar with a hurdy gurdy, this video is a varily good introduction. It’s a box with somewhere between four and six strings mounted on the outside. The strings vibrate by means of a wooden wheel powered by a crank. There’s a keyboard of sorts along the body of the instrument that ‘fret’ a single string providing the melody; all the other strings are drone strings that sound continuously. I think it was in, like, a Led Zeppelin video, man.

While it’s a slightly complicated build to make an analog hurdy gurdy, delving into the digital domain is easy: [XenonJohn] is building a hurdy gurdy that simply outputs MIDI commands with some buttons and a Teensy 3.6 microcontroller. The parts are 3D printed, and since this hurdy gurdy is completely digital, you can change the tuning of the drone strings without actually tuning them. Awesome.

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Hacked Calipers Make Automated Measurements A Breeze

July 4, 2019 by 22 Comments

Now, digital calipers with wired interfaces to capture the current reading are nothing new. But the good ones are expensive, and really, where’s the fun in plugging a $75 cable into a computer? So when [Max Holliday] was asked to trick out some calipers for automating data capture, he had to get creative.

[Max] found that cheap Harbor Freight digital calipers have the telltale door that covers a serial connector, making them a perfect target for hacking. A little Internet sleuthing revealed the pinout for the connector as well as some details on the serial protocol used by most digital calipers: 24-bit packets is six four-bit words. [Max] used his SAM32, a neat open-source board with both a SAMD51 and an ESP32 that can run CircuitPython. An inverting buffer interfaces the serial lines to the board, which is just the right size to mount on the back of the caliper head. It’s hard to tell how [Max] is triggering readings, but the SAM32 is mounted as a USB device and sends keystrokes directly to a spreadsheet – yes, with the ESP32 it could have been wireless, but his client specifically requested a wired setup. Taking multiple readings is easy now that the user never has to swap calipers for a pen.

Cheap calipers like these are pretty hackable – you can add Bluetooth, turn them into DROs for a milling machine, or even make them talk.

Project Egress: [Fran] Makes A Latch

July 4, 2019 by 11 Comments

[Fran Blanche] is on the team of elite hackers that has been offered a chance to contribute to [Adam Savage]’s Project Egress, a celebration of the engineering that got humanity to the Moon 50 years ago this month. By the luck of the draw, she landed a great assignment: building a replica of one of the fifteen latches that kept the Apollo Command Module hatch dogged down against the vacuum of space, and she’s doing a great job documenting her build with some interesting videos.

The first video below is mostly her talking through her design process, materials choices, and ideas about fabricating the somewhat intricate pieces of the latch. All 44 makers involved in the project get to choose what materials and methods they’ll use to make their parts, and [Fran] decided to use wood. Her first inclination was to use oak and brass, a nice combination with an 80s vibe, but in the second video, which covers more of the initial fabrication, she explains her switch to walnut. Unfortunately, the only CNC option she has is a Shaper Origin, which presents some difficulties; the handheld tool requires some complicated fixturing to safely machine the small parts needed, and its inability to read STL files means that [Fran] is stuck with a complicated software toolchain to drive the tool.

There are more videos to come as [Fran] gets further into the build, and we’re looking forward to seeing how her part and the rest of the makers’ builds come out.

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E3D’s Love Letter To Toolchanging 3D Printers

July 4, 2019 by 20 Comments

It’s been just over a year since E3D whetted our appetites for toolchanging printers. Now, with the impending release of their first toolchanging system, they’ve taken the best parts of their design and released them into the wild as open source. Head on over to Github for a complete solution to exchanging, locating, and parking tools on a 3D printer.

For anyone interested in fabricating the design, the files are in a format that you can almost re-zip and email to a manufacturer for quotes. As is, the repository offers STP-style CAD files, a complete set of dimensioned drawings, exploded views, and even a bill of materials. Taken as a whole, the system elegantly solves the classic problems that we’d encounter in toolchanging. Locking tools is done with a spring-based T-bar that swivels onto an wedge-shaped groove on the back of each tool plate. Locating tools is done so with a 3-groove kinematic coupling fabriacted from dowel pins. With these problems solved and presented so cleanly, these files become a path by which we can establish a common means for exchanging tools on 3D printer systems.

It’s worth asking: why develop an exceptional design and then release it for free? I’ll speculate that E3D has done an excellent job over the years establishing a well-recognized standard set of stock parts. Nearly every 3D printer builder is bound to have at least one spare V6 hotend sitting idle in a disassembled pool of former-3D-printers. With tool-changing positioned to become another step forward in the space of possibilities with 3D printing, setting the standard for tools early encourages the community to continue developing applications that lean on E3D’s ecosystem of parts.

In the last 30 years, 3D printing has transformed away from a patent-trolling duopoly to a community-friendly group of contributors that lean on each other’s shoulders with shared findings. It’s a kind gesture to the open-source community of machine builders to receive such a feature-complete mechanism. With that said, let’s start rolling the toolchanger hacks.

E-Book Reader Gets Page Turn Buttons, Is None The Wiser

July 4, 2019 by 13 Comments

Most e-book readers don’t have physical page turn buttons. Why? They just don’t. Virtual page turns are accomplished with a tap at a screen edge. Determined to reduce the awkwardness of one-handed use, [Sagar Vaze] modified a Kobo e-reader with two physical page turn buttons as a weekend project.

[Sagar] points out that since the underlying OS of the Kobo device is Linux, it is possible to fake touches to the screen (and therefore trigger page turns) by recording then replaying the appropriate input event. However, there was a more direct solution available to those willing to tamper slightly with the hardware. Touch sensing on the screen is done via an infrared break-beam system. Along two edges of the screen are IR emitters, and opposite the emitters are receivers. Broadly speaking, when a fingertip touches the display a minimum of two IR beams are broken, and the physical location of the fingertip can therefore be determined by analyzing exactly how the IR pattern has been changed.

To spoof page turns, [Sagar] briefly shorts two IR emitters: one on each axis. The sudden winking out of the IR is interpreted by the device as a crisp tap, and the device obediently turns the page. The only hitch is that both IR emitters must be shorted at the same time. If one is shorted before the other, the device ignores it. Double-pole switches would probably do the trick, but with the part bin coming up empty in that respect, [Sagar] instead used a few transistors to accomplish the same thing. A 3D printed enclosure rounds out the whole mod, and a brief video is embedded below.

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The Power Of Directional Antennas

July 3, 2019 by 32 Comments

AM broadcasting had a big problem, but usually only at night. During the day the AM signals had limited range, but at night they could travel across the country. With simple wire antennas, any two stations on the same frequency would interfere with each other. Because of this, the FCC required most radio stations to shut down or reduce power at night leaving just a handful of “clear channel” stations for nighttime programming. However, creating directional antennas allowed more stations to share channels and that’s the subject of a recent post by [John Schneider].

When it comes to antennas, ham radio operators often think bigger is better. After all, hams typically want to work stations far away, not some specific location. That’s not true in the commercial world, though. The big breakthrough that led to, for example, cell phones was the realization that making smaller antennas with lower power at higher frequencies would allow for reuse of channels. In those areas the focus is on making cells smaller and smaller to accommodate more people. You can think of AM broadcasting as using the same idea, except with relatively large cells.

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