Zen Flute Is A Teensy Powered Mouth Theremin

May 17, 2025 by Dave Rowntree 13 Comments

An intriguing mouth-played instrument emerged—and won—at the 2023 Guthman Musical Instrument Contest hosted by Georgia Tech. [Keith Baxter] took notice and reproduced the idea for others to explore. The result is the Zen Flute Mouth Theremin, a hybrid of acoustics, electronics, and expressive performance.

At its core lies a forced Helmholtz resonator, a feedback system built with a simple microphone and speaker setup. The resonator itself? The user’s mouth. The resulting pitch, shaped by subtle jaw and tongue movements, is detected and used to drive a MIDI controller feeding an external synthesizer.

Like a trombone or classic electromagnetic theremin, the Zen Flute doesn’t rely on discrete notes. Instead, the pitch is bent manually to the desired frequency. That’s great for expression, but traditional MIDI quantisation can map those “in-between” notes to unexpected semitones. The solution? MIDI Polyphonic Expression (MPE). This newer MIDI extension allows smooth pitch transitions and nuanced control, giving the Zen Flute its expressive character without the hiccups.

Physically, it’s an elegant build. A flat speaker and microphone sit side-by-side at the mouth end, acoustically isolated with a custom silicone insert. This assembly connects to a length of clear PVC pipe, flared slightly to resemble a wind instrument. Inside, a custom PCB (schematic here) hosts a mic preamp, an audio power amp, and a Teensy 4.1. The Teensy handles everything: sampling the mic input, generating a 90-degree phase shift, and feeding it back to the speaker to maintain resonance. It also detects the resonant frequency and translates it to MPE over USB. A push-button triggers note onset, while a joystick adjusts timbre and selects modes. Different instrument profiles can be pre-programmed and toggled with a joystick click, each mapped to separate MIDI channels.

Mouth-controlled instruments are a fascinating corner of experimental interfaces. They remind us of this Hackaday Prize entry from 2018, this wind-MIDI hybrid controller, and, of course, a classic final project from the Cornell ECE4760 course, a four-voice theremin controlled by IR sensors.

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PCB Renewal Aims To Make Old Boards Useful Again

May 4, 2025 by Lewin Day 13 Comments

We’ve all made a few bad PCBs in our time. Sometimes they’re recoverable, and a few bodge wires will make ’em good. Sometimes they’re too far gone and we have to start again. But what if you could take an existing PCB, make a few mods, and turn it into the one you really want? That’s what “PCB Renewal” aims to do, as per the research paper from [Huaishu Peng] and the research group at the University of Maryland.

*The plugin quantifies resource and time savings made by reusing an old board.*

The concept is straightforward — PCB Renewal exists as a KiCad plugin that can analyze the differences between the PCB you have and the one you really want. Assuming they’re similar enough, it will generate toolpaths to modify the board with milling and epoxy deposition to create the traces you need out of the board you already have.

Obviously, there are limitations. You’ll never turn a PlayStation motherboard into something you could drop into an Xbox with a tool like this. Instead, it’s more about gradual modifications. Say you need to correct a couple of misplaced traces or missing grounds, or you want to swap one microcontroller for a similar unit on your existing board. Rather than making brand new PCBs, you could modify the ones you already have.

Of course, it’s worth noting that if you already have the hardware to do epoxy deposition and milling, you could probably just make new PCBs whenever you need them. However, PCB Renewal lets you save resources by not manufacturing new boards when you don’t have to.

We’ve seen work from [Huaishu Peng]’s research group before, too, in the form of an innovative “solderless PCB”.

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Reverse Engineering The IBM PC110, One PCB At A Time

April 6, 2025 by Tom Nardi 10 Comments

There’s a dedicated group of users out there that aren’t ready to let their beloved IBM PC110 go to that Great Big Data Center in the Sky. Unfortunately, between the limited available technical information and rarity of replacement parts, repairing the diminutive palmtops can be tricky.

Which is why [Ahmad Byagowi] has started a project that aims to not only collect all the available schematics and datasheets that pertain to the machine, but to reverse engineer all of the computer’s original circuit boards. Working from optical and x-ray scans, the project has already recreated the motherboard, power supply, modem, keyboard, and RAM module PCBs in KiCad.

Just last week the project released production-ready Gerbers for all the boards, but considering there have been 45+ commits to the repository since then, we’re going to assume they weren’t quite finalized. Of course, with a project of this magnitude, you’d expect it to take a few revisions to get everything right. (Hell, we’ve managed to screw up board layouts that had fewer than a dozen components on them.)

If you’d like to lend a hand, [Ahmad] says he could use the help. Beyond checking the boards for problems and reporting issues, he’s also on the hunt for any datasheets or other documentation that can be found for the PC110 or its components. It looks like there’s still schematic work that needs to be done as well, so if your idea of zen is figuring out how ~30 year old computers were wired up internally, this might be the perfect summer project for you.

Interestingly, our very own [Arya Voronova] has been working on creating a drop-in replacement motherboard for the Sony Vaio P using KiCad and imported board images. That hobbyists are now able to do this kind of work using free and open source tools is a reminder of just how far things have come in the last few years.

Thanks to [adistuder] for the tip.

Some Useful Notes On The 6805-EC10 Addressable RGB LED

March 12, 2025 by Dave Rowntree 9 Comments

LEDs are getting smaller and smaller, and the newest generations of indexable RGB LEDs are even fiddlier to use than their already diminutive predecessors. [Alex Lorman] has written some notes about the minuscule SK6805-EC10 series of LEDs, which may be helpful to those wanting to learn how to deal with these in a more controlled manner.

Most hardware types will be very familiar with the 5050-sized devices, sold as Neopixels in some circles, which are so-named due to being physically 5.0 mm x 5.0 mm in the horizontal dimensions. Many LEDs are specified by this simple width by depth manner. As for addressable RGB LEDs (although not all addressable LEDs are RGB, there are many weird and wonderful combinations out there!) the next most common standard size down the scale is the 2020, also known as the ‘Dotstar.’ These are small enough to present a real soldering challenge, and getting a good placement result needs some real skills.

[Alex] wanted to use the even smaller EC10 or 1111 devices, which measure a staggering 1.1 mm x 1.1 mm! Adafruit’s product page mentions that these are not intended for hand soldering, but we bet you want to try! Anyway, [Alex] has created a KiCAD footprint and a handy test PCB for characterizing and getting used to handling these little suckers, which may help someone on their way. They note that hot air reflow soldering needs low temperature paste (this scribe recommends using MG Chemicals branded T3 Sn₄₂Bi₅₇Ag₁ paste in this application) and a very low heat to avoid cracking the cases open. Also, a low air flow rate to prevent blowing them all over the desk would also be smart. Perhaps these are more suited to hot plate or a proper convection oven?

As a bonus, [Alex] has previously worked with the slightly larger SK6805-1515 device, with some good extra notes around an interesting nonlinearity effect and the required gamma correction to get good colour perception. We’ll leave that to you readers to dig into. Happy soldering!

We’ve not yet seen many projects using these 1111 LEDs, but here’s one we dug up using the larger 1515 unit.

Demonstration of the multichannel design feature, being able to put identical blocks into your design, only route one of them, and have all the other blocks' routing be duplicated

KiCad 9 Moves Up In The Pro League

February 22, 2025 by Arya Voronova 28 Comments

Do you do PCB design for a living? Has KiCad been just a tiny bit insufficient for your lightning-fast board routing demands? We’ve just been graced with the KiCad 9 release (blog post, there’s a FOSDEM talk too), and it brings features of the rank you expect from a professional-level monthly-subscription PCB design suite.

Of course, KiCad 9 has delivered a ton of polish and features for all sorts of PCB design, so everyone will have some fun new additions to work with – but if you live and breathe PCB track routing, this release is especially for you.

Continue reading “KiCad 9 Moves Up In The Pro League” →

Get Ready For KiCAD 9!

February 17, 2025 by Jenny List 58 Comments

Rev up your browsers, package managers, or whatever other tool you use to avail yourself of new software releases, because the KiCAD team have announced that barring any major bugs being found in the next few hours, tomorrow should see the release of version 9 of the open source EDA suite. Who knows, depending on where you are in the world that could have already happened when you read this.

Skimming through the long list of enhancements brought into this version there’s one thing that strikes us; how this is now a list of upgrades and tweaks to a stable piece of software rather than essential features bringing a rough and ready package towards usability. There was a time when using KiCAD was a frustrating experience of many quirks and interface annoyances, but successive versions have improved it beyond measure. We would pass comment that we wished all open source software was as polished, but the fact is that much of the commercial software in this arena is not as good as this.

So head on over and kick the tires on this new KiCAD release, assuming that it passes those final checks. We look forward to the community’s verdict on it.

Custom PCB Is A Poor Man’s Pick And Place

February 4, 2025 by Dan Maloney 8 Comments

Surface mount devices have gotten really small, so small that a poorly timed sneeze can send your 0603 and 0402 parts off to live with the dust motes lurking at the edge of your bench. While soldering such parts is a challenge, it’s not always size that matters. Some parts with larger footprints can be a challenge because of the pin pitch, and getting them to land just right on the PCB pads can be a real pain.

To fight this problem, [rahmanshaber] came up with this clever custom PCB fixture. The trick is to create a jig to hold the fine-pitch parts securely while still leaving room to work. In his case, the parts are a couple of SMD ribbon cable connectors and some chips in what appear to be TQFP packages. [rahmanshaber] used FreeCAD to get the outline of each part from the 3D model of his PCB, and KiCad to design the cutouts; skip to 7:30 or so in the video below if you don’t need the design lesson. The important bit is to leave enough room around the traces so that the part’s leads can rest of the PCB while still having room to access them.

Using the fixture is pretty intuitive. The fixture is aligned over the footprint of the part and fixed in place with some tape. Solder paste is applied to the pads, the part is registered into the hole, and you’re ready for soldering. [rahmanshaber] chose to use a hot plate to do the soldering, but it looks like there’s enough room for a soldering iron, if that’s your thing.

It’s a simple idea, but sometimes the simplest tools are the best. We’ve seen lots of other simple SMD tools, from assembly jigs to solder paste stencil fixtures. Continue reading “Custom PCB Is A Poor Man’s Pick And Place” →