Be Still, My Animatronic Heart

Fair warning for the squeamish: some versions of [Will Cogley]’s animatronic heart are realistic enough that you might not want to watch the video below. That’d be a shame though, because he really put a lot of effort into the build, and the results have a lot to teach about mimicking the movements of living things.

As for why one would need an animatronic heart, we’re not sure. [Will] mentions no specific use case for it, although we can think of a few. With the Day of Compulsory Romance fast approaching, the fabric-wrapped version would make a great gift for the one who stole your heart, while the silicone-enrobed one could be used as a movie prop or an awesome prank. Whatever the reason, [Will]’s build is a case study in incremental development. He started with a design using a single continuous-rotation servo, which powered four 3D-printed paddles from a common crank. The four paddles somewhat mimicked the movements of the four chambers of the heart, but the effect wasn’t quite convincing. The next design used two servos and complex parallelogram linkages to expand each side of the heart in turn. It was closer, but still not quite right.

After carefully watching footage of a beating heart, [Will] decided that his mechanism needed to imitate the rapid systolic contraction and slow diastolic expansion characteristic of a real heart. To achieve this, his final design has three servos plus an Arduino for motion control. Slipped into a detailed silicone jacket, the look is very realistic. Check out the video below if you dare.

We’ve seen plenty of animatronic body parts before, from eyes to hands to entire faces. This might be the first time we’ve seen an animatronic version of an internal organ, though.

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Additive, Multi-Voice Synth Preserves Sounds, Too

For his final project in [Bruce Land]’s microcontroller design class, [Mark] set out to make a decently-sized synth that sounds good. We think you’ll agree that he succeeded in spades. Don’t let those tiny buttons fool you, because it doesn’t sound like a toy.

Why does it sound so good? One of the reasons is that the instrument samples are made using additive synthesis, which essentially stacks harmonic overtones on top the fundamental frequency of each note. This allows synthesizers to better mimic the timbre of natural, acoustic sounds. For each note [Mark] plays, you’re hearing a blend of four frequencies constructed from lookup tables. These frequencies are shaped by an envelope function that improves the sound even further.

Between the sound and the features, this is quite an impressive synth. It can play polyphonically in piano, organ, or plucked string mode through a range of octaves. A PIC32 runs the synthesizer itself, and a pair of helper PIC32s can be used to record songs to be played over. So [Mark] could record point and counterpoint separately and play them back together, or use the helper PICs to fine-tune his three-part harmony. We’ve got this thing plugged in and waiting for you after the break.

If PICs aren’t what you normally choose, here’s an FPGA synth.

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A STM32 Tonewheel Organ Without A Single Tonewheel

The one thing you might be surprised not to find in [Laurent]’s beautiful tonewheel organ build is any tonewheels at all.

Tonewheels were an early way to produce electronic organ sounds: by spinning a toothed wheel at different frequencies and transcending the signal one way or another it was possible to synthesize quite an array of sounds. We like to imagine that they’re all still there in [Laruent]’s organ, albeit very tiny, but the truth is that they’re being synthesized entirely on an STM32 micro controller.

The build itself is beautiful and extremely professional looking. We were unaware that it was possible to buy keybeds for a custom synthesizer, but a model from FATAR sits at the center of the show. There’s a MIDI encoder board and a Nucleo development board inside, tied together with a custom PCB. The UI is an momentary encoder wheel and a display from Mikroelektronika.

You can see and hear this beautiful instrument in the video after the break.

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A Fleet Of Pressure Washers Powers This Interactive Public Fountain

Public art installations can be cool. Adding in audience interactivity bumps up the coolness factor a bit. Throw civic pride, dancing jets of water, music, and lights into the project, and you get this very cool pressure washer powered musical fountain.

The exhibit that [Niklas Roy] came up with is called Wasserorgel, or “water organ”, an apt name for the creation. Built as part of a celebration of industry in Germany, the display was built in the small town of Winnenden, home to Kärcher, a cleaning equipment company best known for their line of pressure washers in the distinctive yellow cases. Eight of the company’s electric pressure washers were featured in the Wasserorgel, which shot streams of water and played notes in response to passersby tickling the sturdy and waterproof 3D-printed keyboard. The show was managed by an Arduino with a MIDI shield, which controlled the pressure washers via solid state relays and even accepted input from an anemometer to shut down the show if it got too windy, lest the nearby [Frau Dimitrakudi] be dampened.

The video below shows how engaging the Wasserorgel was during its weeks-long run in the town market square; there’s also one in German with build details. And while we can’t recall seeing pressure washers in public art before, we do remember one being used as the basis of a DIY water-jet cutter.

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Ask Hackaday Answered: The Tale Of The Top-Octave Generator

We got a question from [DC Darsen], who apparently has a broken electronic organ from the mid-70s that needs a new top-octave generator. A top-octave generator is essentially an IC with twelve or thirteen logic counters or dividers on-board that produces an octave’s worth of notes for the cheesy organ in question, and then a string of divide-by-two logic counters divide these down to cover the rest of the keyboard. With the sound board making every pitch all the time, the keyboard is just a simple set of switches that let the sound through or not. Easy-peasy, as long as you have a working TOG.

I bravely, and/or naïvely, said that I could whip one up on an AVR-based Arduino, tried, and failed. The timing requirements were just too tight for the obvious approach, so I turned it over to the Hackaday community because I had this nagging feeling that surely someone could rise to the challenge.

The community delivered! Or, particularly, [Ag Primatic]. With a clever approach to the problem, some assembly language programming, and an optional Arduino crystalectomy, [AP]’s solution is rock-solid and glitch-free, and you could build one right now if you wanted to. We expect a proliferation of cheesy synth sounds will result. This is some tight code. Hat tip!

Squeezing Cycles Out of a Microcontroller

Let’s take a look at [AP]’s code. The approach that [AP] used is tremendously useful whenever you have a microcontroller that has to do many things at once, on a rigid schedule, and there’s not enough CPU time between the smallest time increments to do much. Maybe you’d like to control twelve servo motors with no glitching? Or drive many LEDs with binary code modulation instead of primitive pulse-width modulation? Then you’re going to want to read on.

There are two additional tricks that [AP] uses: one to fake cycles with a non-integer number of counts, and one to make the AVR’s ISR timing absolutely jitter-free. Finally, [Ag] ended up writing everything in AVR assembly language to make the timing work out, but was nice enough to also include a C listing. So if you’d like to get your feet wet with assembly, this is a good start.

In short, if you’re doing anything with hard timing requirements on limited microcontroller resources, especially an AVR, read on!

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Vintage Organ Donates Parts For Two New Instruments

It’s often hard to know what to do with a classic bit of electronics that’s taking up far too much of the living room for its own good. But when the thing in question is an electronic organ from the 1970s, the answer couldn’t be clearer: dissect it for its good parts and create two new instruments with them.

Judging by [Charlie Williams]’ blog posts on his Viscount Project, he’s been at this since at least 2014. The offending organ, from which the project gets its name, is a Viscount Bahia from the 1970s that had seen better days, apparently none of which included a good dusting. With careful disassembly and documentation, [Charlie] took the organ to bits. The first instrument to come from this was based on the foot pedals. A Teensy and a custom wood case turned it into a custom MIDI controller; hear it in action below. The beats controller from the organ’s keyboard was used for the second instrument. This one appears far more complex, not only for the beautiful, hand-held wooden case he built for it, but because he reused most of the original circuitry. A modern tube amp was added to produce a little distortion and stereo output from the original mono source, with the tip of the tube just peeking above the surface of the instrument. We wish there were a demo video of this one, but we’ll settle for gazing at the craftsmanship.

In a strange bit of timing, [Elliot Williams] (no relation, we assume) just posted an Ask Hackaday piece looking for help with a replacement top-octave generator for another 1970s organ. It’s got a good description of how these organs worked, if you’re in the mood to learn a little more.

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Ask Hackaday: How Do You DIY A Top-Octave Generator?

One of the great joys of Hackaday are the truly oddball requests that we sometimes get over the tip line. Case in point: [DC Darsen] wrote in with a busted 1970s organ in need of a new top-octave generator, and wondered if we could help. He had found a complicated but promising circuit online, and was wondering if there was anything simpler. I replied “I should be able to get that done with a single Arduino” and proceeded to prove myself entirely wrong in short order.

So we’re passing the buck on to you, dear Hackaday reader. Can you help [DC Darsen] repair his organ with a minimum amount of expenditure and hassle? All we need to do is produce twelve, or maybe thirteen, differently pitched square waves simultaneously.

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