Piezo Pickup Makes Wax Records Easy To Digitize

Sound recording and playback have come a long way in the last century or so, but it’s fair to say there’s still a lot of interesting stuff locked away on old recordings. Not having a way to play it back is partly to blame; finding an antique phonograph that plays old-timey cylinder recordings is pretty hard. But even then, how do you digitize the output of these fragile, scratchy old recordings?

As it happens, [Jan Derogee] is in a position to answer these questions, with an antique phonograph and a bunch of Edison-style wax cylinders with voices and music from a bygone era locked away on them. It would be easy enough to just use the “reproducer” he previously built and set up a microphone to record the sound directly from the phonograph’s trumpet, but [Jan] decided to engineer a better solution. By adding the piezo element from an electronic greeting card to his reproducer, potted with liberal quantities of epoxy and padded with cotton, the piezo pickup was attached to the phonograph arm in place of the original stylus and trumpet. The signal from the piezo element was strong enough to require a shunt resistor, allowing it to be plugged directly into the audio input jack on a computer. From there it’s just an Audacity exercise, plus dealing with the occasional skipped groove.

We appreciate [Jan]’s effort to preserve these recordings, as well as the chance to hear some voices from the past. We’re actually surprised the recording sound as good as they do after all this time — they must have been well cared for.

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Hackaday Links: June 6, 2021

There are a bunch of newly minted millionaires this week, after it was announced that Stack OverFlow would be acquired for $1.8 billion by European tech investment firm Prosus. While not exactly a household name, Prosus is a big player in the Chinese tech scene, where it has about a 30% stake in Chinese internet company Tencent. They trimmed their holdings in the company a bit recently, raising $15 billion in cash, which we assume will be used to fund the SO purchase. As with all such changes, there’s considerable angst out in the community about how this could impact everyone’s favorite coding help site. The SO leadership are all adamant that nothing will change, but only time will tell.

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Counter-Strike Gets The RGB LED Treatment

Inspired by the over-the-top stage lighting and pyrotechnics used during e-sport events, [Hans Peter] set out to develop a scaled-down version (minus the flames) for his personal Counter-Strike: Global Offensive sessions. It might seem like pulling something like this off would involve hacking the game engine, but as it turns out, Valve was kind enough to implement a game state API that made it relatively easy.

According to the documentation, the CS:GO client can be configured to send out state information to a HTTP server at regular intervals. It even provided example code for implementing a simple state server in Node.js, which [Hans] adapted for this project by adding some conditional statements that analyze the status of the current game.

These functions fire off serial commands to the attached Arduino, which in turn controls the WS2812B LEDs. The Arduino code takes the information provided by the HTTP server and breaks that down into various lighting routines for different conditions such as wins and losses. But things really kick into gear when a bomb is active.

[Hans] wanted to synchronize the flashing LEDs with the beeping sound the bomb makes in the game, but the API doesn’t provide granular enough data. So he recorded the audio of the bomb arming sequence, used Audacity to precisely time the beeps, and implemented the sequence in his Arduino code. In the video after the break you can see that the synchronization isn’t perfect, but it’s certainly close enough to get the point across in the heat of battle.

With the special place that Counter-Strike occupies in the hearts of hackers and gamers alike, it’s little surprise people are still finding unique ways to experience the game.

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Analyzing CNC Tool Chatter With Audacity

When you’re operating a machine that’s powerful enough to tear a solid metal block to shards, it pays to be attentive to details. The angular momentum of the spindle of a modern CNC machine can be trouble if it gets unleashed the wrong way, which is why generations of machinists have developed an ear for the telltale sign of impending doom: chatter.

To help develop that ear, [Zachary Tong] did a spectral analysis of the sounds of his new CNC machine during its “first chip” outing. The benchtop machine is no slouch – an Avid Pro 2436 with a 3 hp S30C tool-changing spindle. But like any benchtop machine, it lacks the sheer mass needed to reduce vibration, and tool chatter can be a problem.

The analysis begins at about the 5:13 mark in the video below, where [Zach] fed the soundtrack of his video into Audacity. Switching from waveform to spectrogram mode, he was able to identify a strong signal at about 5,000 Hz, corresponding to the spindle coming up to speed. The white noise of the mist cooling system was clearly visible too, as were harmonic vibrations up and down the spectrum. Most interesting, though, was the slight dip in frequency during the cut, indicating loading on the spindle. [Zach] then analyzed the data from the cut in the frequency domain and found the expected spindle harmonics, as well the harmonics from the three flutes on the tool. Mixed in among these were spikes indicating chatter – nothing major, but still enough to measure.

Audacity has turned out to be an incredibly useful tool with a broad range of applications. Whether it be finding bats, dumping ROMs, detecting lightning strikes, or cloning remote controls, Audacity is often the hacker’s tool of choice.

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Wishing The Family A Sinusoidal Christmas

When it’s time to put together the annual Christmas card, most families take a few pictures of the kids, slap on a generic greeting, and call it a day. It used to be fairly common for the whole family to get dressed up and pose for a special Christmas picture, but who has the time anymore? It’s not like we have hours and hours to slave over a unique and memorable gift we can mail out to a dozen (or more) people.

Unless you’re [Chris Wolsey], anyway. Rather than take the easy way out and simply mailing some pictures of his daughter out to friends and family, he recorded her giving a Christmas greeting and turned the waveform of her voice into a framed physical memento. Way to wreck the curve for the rest of us, [Chris].

Evolution of the printed waveform.

As it turns out, getting sound into CAD software isn’t exactly straightforward. To start, he made a recording of his daughter saying the words “Happy Christmas From the Wolsey Family” with Audacity, and then took a screenshot of the resulting waveform. This screenshot was then brought into Adobe Illustrator and exported to SVG, which Fusion 360 (and most other CAD packages) is able to import.

Now that the wave was in Fusion 360 he could scale it to a reasonable size, and use the revolve function to bring it into three dimensions. Cutting that object in half down the length then gave [Chris] a shape which should, theoretically, be printable on his FDM printers. But unfortunately, it wasn’t so easy. His personal Anet A8 had a tough time printing it, and the Prusa i3 MK2 at work didn’t fare much better. In the end, he had to make the leap to SLA, getting the shape printed on a Form 2 via 3D Hubs.

With the finalized shape in hand, [Chris] just need to put them into production. Printing them all via 3D Hubs wasn’t really an option, so he decided to make a mold and cast them in resin. He printed up a mold box, and after fiddling around with the mix a bit, was able to settle on a resin which allowed him to de-mold the shapes just 30 minutes after pouring.

Finally, he made frames for each cast waveform, and printed up a little label explaining just what the recipient was looking at; even going as far as showing which word corresponded to which section of the shape.

This is a fantastically executed and documented project, and while it’s too late to whip up your own version this year, we have no doubt they’ll be a few people “borrowing” this idea next time the holidays roll around.

It’s never too early to start planning for next Christmas. We’ve covered unique takes on the traditional holiday card before, as well as a sleighful of holiday decorating projects.

Detect Lightning Strikes With Audio Equipment

One of the driving principles of a lot of the projects we see is simplicity. Whether that’s a specific design goal or a result of having limited parts to work with, it often results in projects that are innovative solutions to problems. As far as simplicity goes, however, the latest project from [153armstrong] takes the cake. The build is able to detect lightning using a single piece of equipment that is almost guaranteed to be within a few feet of anyone reading this article.

The part in question is a simple, unmodified headphone jack. Since lightning is so powerful and produces radio waves in many detectable ranges, it doesn’t take much to detecting a strike within a few kilometers. Besides the headphone jack, a computer with an audio recording program is also required to gather data. (Audio is often used as a stand-in for storing other types of data; in this case, RF information.) [153armstrong] uses a gas torch igniter as a stand-in for a lightning strike, but the RF generated is similar enough to test this proof-of-concept. The video of their tests is after the break.

Audacity is a great tool for processing audio, or for that matter any other data that you happen to be gathering using a sound card. It’s open source and fairly powerful. As far as lightning goes, however, it’s possible to dive far down the rabbit hole. Detecting lightning is one thing, but locating it requires a larger number of weather stations.

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Dirt Cheap Motor Balancing And Vibration Analysis

Ever the enterprising hacker and discerning tool aficionado, [Chris] knows the importance of “feel”. As a general rule, cheap tools will shake in your hand because the motors are not well-balanced. He wanted a way to quantify said feel on the cheap, and made a video describing how he was able to determine the damping of a drill using a few items most people have lying around: an earbud, a neodymium magnet, scrap steel, and Audacity.

He’s affixed the body of the drill to a cantilevered piece of scrap steel secured in a vise. The neodymium magnet stuck to the steel interrupts the magnetic field in the earbud, which is held in place with a third hand tool. [Chris] taped the drill’s trigger down and controls its speed a variac. First, [Chris] finds the natural frequency of the system using Audacity’s plot spectrum, and then gets the drill to run at the same speed to induce wobbling at different nodes. As he explains, one need not even use software to show the vibration nodes—a laser attached to the system and aimed at a phosphorescent target will plot the sine wave.

Just for fun, he severely unbalances the drill to find the frequencies at which the system will shake itself apart. Check it out after the break.

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