2023 Halloween Hackfest: Organ-playing Skeleton Livens Up Halloween

October 30, 2023 by Donald Papp 3 Comments

Every hacker appreciates how off-the-shelf parts can be combined into something greater, and [bryan.lowder] demonstrates this beautifully with his organ-playing skeleton, a wonderful entry to our 2023 Halloween Contest!

Skelly the 3-foot-tall novelty skeleton animatedly plays Bach’s Toccata and Fugue in D Minor while perched at an old (and non-functional) Hammond organ. The small animatronic skeleton has canned motions that work very well for mock organ playing while an embedded MP3 player takes care of playing the music.

That’s not to say the project didn’t have its challenges. Integrating off-the-shelf components into a project always seems to bring its own little inconveniences. In this case, the skeleton the MP3 player both expect to be triggered with button pushes, but taping the button down wasn’t enough to get the skeleton moving when power was applied. [bryan] ended up using relays to simulate button pushes, and a 555 timer circuit to take care of incorporating a suitable delay.

As [bryan] puts it, “a technical tour de force it ain’t, but it is practical and it works and it was done on time” which is well said. Watch Skelly in action in the video, embedded below. There’s also a second video showing the homebrewed controller and MP3 player, both concealed under Skelly’s robe.

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Rotating Necked Guitar Looks Difficult To Play

October 30, 2023 by Richard Baguley 20 Comments

Have you ever looked at a guitar and thought “Nah, that’s way too easy to play.”[Mattias Kranz] seems to have done, so he built the 360 Guitar, a new instrument with a circular, rotating neck. The rotating neck means that it can have more strings than most: we think that it has sixteen, but it’s hard to tell. Anyway, it has a lot of strings and looks utterly impractical, which makes it an exciting project.

The basic idea is intriguing: take a conventional guitar design and replace the fretboard with a rotating pillar. Perhaps even stick a motor in there to rotate it on command. Each of the strings is mounted along this pillar using standard string retainers and tuning pegs, with frets along the pillar. Because you can fit so many strings, you can use all of the standard strings for a bass and treble guitar, plus a few extra like the thickest bass string available and the thinnest guitar strings. It’s like a four-dimensional Chapman Stick.

[Mathias] is still working on the project as you can see in the video below the break, so we will be interested to see what new design aspects he comes up with, like the plan to use a motor to rotate the neck. [Mattias] has built a few instruments that we have featured before, like the Helium guitar, which replaces the resonant cavity with a helium balloon, and the Plasma Piano, a combination of piano and tuned plasma coil.

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Upgraded Toy Guitar Plays Music

October 25, 2023 by Bryan Cockfield 1 Comment

Getting the finishing details on a Halloween costume completed is the key to impressing friends and strangers alike on the trick-or-treat rounds. Especially when it comes to things like props, these details can push a good Halloween costume to great with the right touches. [Jonathan]’s friend’s daughter will be well ahead of the game thanks to these additions to a toy guitar which is part of her costume this year.

The toy guitar as it was when it arrived had the capability to play a few lackluster sound effects. The goal here was to get it to play a much more impressive set of songs instead, and to make a couple upgrades along the way as well. To that end, [Jonathan] started by dismantling the toy and investigating the PCBs for potential reuse. He decided to keep the buttons in the neck of the guitar despite their non-standard wiring configuration, but toss out the main board in favor of an ESP32. The ESP32 is tasked with reading the buttons, playing a corresponding song loaded on an SD card, and handling the digital to analog conversion when sending it out to be played on the speaker.

The project doesn’t stop there, though. [Jonathan] also did some custom mixing for the songs to account for the lack of stereo sound and a working volume knob, plus he used the ESP32’s wireless capabilities to set the guitar up as a local file server so that songs can be sent to and from the device without any wires. He also released the source code on the project’s GitHub page for anyone looking to use any parts of this project. Don’t forget there’s a Halloween contest going on right now, so be sure to submit the final version of projects like these there!

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Commodore Datassette Does Barbershop Quartet

October 20, 2023 by Kristina Panos 3 Comments

Okay, now this is just plain fun. [Linus Åkesson] modified a Commodore Datassette player to move its “mouth” and, when quadrupled, sing a clever barbershop tune called “Sweet End of Line” that’s a play on “Sweet Adeline“, a top hit from the summer of 1903.

What? Let us explain. Those with Commodore 64s who lacked disk drives often had the Datassette — a magnetic storage tape device, or cassette player used to load and save files. But they couldn’t open the doors themselves with a keypress, and they certainly couldn’t sing barbershop.

First off, [Linus] redirected the current that drives the magnetizing tape head through a speaker coil instead. Then he replaced the motor with a servo that opens the lid from the inside. A simple rubber band pulls the lid back shut. Software-wise, [Linus] is using a timer interrupt to run code that toggles the output signal, the rate of which determines the pitch.

Don’t worry — all of these modifications are reversible, so no Datassettes were truly harmed in the making. Don’t forget to check out the brief build/demo video after the break.

We’ve seen our share of tape players, but we’d never seen one with a crank until recently.

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Low-Cost Electret Microphone Preamplifiers

October 16, 2023 by Bryan Cockfield 8 Comments

Before the invention of microelectromechanical system (MEMS) microphones, almost all microphones in cell phones and other electronics were a type of condenser microphone called the electret microphone. The fact that this type of microphone is cheap and easy enough to place into consumer electronics doesn’t mean they’re all low quality, though. Electret microphones can have a number of qualities that make them desirable for use recording speech or music, so if you have a struggling artist friend like [fvfilippetti] has who needs an inexpensive way to bring one to life, take a look at this electret microphone pre-amp.

The main goal of the project is to enhance the performance of these microphones specifically in high sound pressure level (SPL) scenarios. In these situations issues of saturation and distortion often occur. The preampl design incorporates feedback loops and an AD797 opamp to reduce distortion, increase gain, and maintain low noise levels. It also includes an output voltage limiter using diodes to protect against input overload and can adjust gain. The circuit’s topology is designed to minimize distortion, particularly in these high SPL situations.

Real-world testing of the preamp confirms its ability to handle high SPL and deliver low distortion, making it a cost-effective solution for improving the performance of electret microphones like these. If you want to go even deeper into the weeds of designing and building electret microphones and their supporting circuitry, take a look at this build which discusses some other design considerations for these types of devices.

Screech Owl Is A Tribute To The Eowave Persephone

October 12, 2023 by Lewin Day 6 Comments

The Eowave Persephone was a beautiful thing—a monophonic ribbon synth capable of producing clean, smoothly varying tones. [Ben Glover] used to own a nice example that formerly belonged to Peter Christopherson, but lost it in the shifting sands of time. His solution was to build one of his own from scratch.

It’s a simple build, but the final result puts out a nice pleasant sound.

Known as the Screech Owl, the build is based around a custom shield designed to suit the Arduino Leonardo. The primary control interface is a Softpot 500 mm membrane potentiometer, layered up with a further thin film pressure sensor which provides aftertouch control. The Leonardo reads these sensors and synthesizes the appropriate frequencies in turn.

All the electronics is wrapped up inside a tidy laser-cut enclosure that roughly approximates the design of the original Eowave device. [Ben] noted the value of services like Fiverr and ChatGPT for helping him with the design, while he also enjoyed getting his first shield design professionally manufactured via JLCPCB.

It’s a tidy build, and in [Ben’s] capable hands, it sounds pretty good, too. We’ve seen some other great ribbon controlled synths before, too. Video after the break.

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Dial Up A Tune On The Jukephone

October 10, 2023 by Kristina Panos 9 Comments

What do you do when you find a nice corded phone with giant buttons out in the wild? You could pay $80/month for a landline, use a VOIP or Bluetooth solution instead, or do something a million times cooler and turn it into a jukebox.

Now when the receiver is lifted, [Turi] hears music instead of a dial tone or a voice on the other end. But playback isn’t limited to the handset — there’s a headphone jack around back.

To listen to a track, he can either dial one in directly, or call up a random track using one of the smaller buttons below. A handy directory organizes the tunes by the hundreds, putting children’s tracks between 1-99 and the intriguing category “hits” between 900-999.

The phone’s new guts are commanded by a Raspberry Pi Pico, which is a great choice for handling the key matrix plus the rest of the buttons. As you may have guessed, there’s an DF Player Mini mp3 player that reads the tracks from an SD card. Everything is powered by a rechargeable 18650 battery.

Jukephone is open source, and you’ll find more pictures on [Turi]’s blog post. Be sure to check out the very brief build and demo video after the break.

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