Play Robotic Bongos using your Household Plants

[Kirk Kaiser] isn’t afraid to admit his latest project a bit strange, being a plant-controlled set of robotic bongos. We don’t find it odd at all.  This is the kind of thing we love to see. His project’s origins began a month ago after taking a class at NYC Resistor about creating music from robotic instruments. Inspired to make his own, [Kirk] repurposed a neighbor’s old wooden dish rack to serve as a mount for solenoids that, when triggered, strike a couple of plastic cowbells or bongo drums.

A Raspberry Pi was originally used to interface the solenoids with a computer or MIDI keyboard, but after frying it, he went with a Teensy LC instead and never looked back. Taking advantage of the Teensy’s MIDI features, [Kirk] programmed a specific note to trigger each solenoid. When he realized that the Teensy also had capacitive touch sensors, he decided to get his plants in on the fun in a MaKey MaKey kind of way. Each plant is connected to the Teensy’s touchRead pins by stranded wire; the other end is stripped, covered with copper tape, and placed into the soil. When a plant’s capacitance surpasses a threshold, the respective MIDI note – and solenoid – is triggered. [Kirk] quickly discovered that hard-coding threshold values was not the best idea. Looking for large changes was a better method, as the capacitance was dramatically affected when the plant’s soil dried up. As [Kirk] stood back and admired his work, he realized there was one thing missing – lights! He hooked up an Arduino with a DMX shield and some LEDs that light up whenever a plant is touched.

We do feel a disclaimer is at hand for anyone interested in using this botanical technique: thorny varieties are ill-advised, unless you want to play a prank and make a cactus the only way to turn the bongos off!

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The Hard Drive MIDI Controller

[shantea] builds MIDI controllers, and after a successful first endeavor with a matrix of buttons and knobs, he decided to branch out to something a little bit cooler. It’s called Ceylon, and it’s effectively a turntable controller built from an old hard drive.

As a contrast to the first MIDI controller, this would be a stripped-down build, with just three faders, LEDs for eye candy, a pair of pots for gain control, and a hard disk surrounded by six anti-vandal buttons. The hard disk is the star of the show, acting as a rotary encoder.

When manually spun, the hard disk generates a few phases of sinusoidal waves. The faster you spin it, the higher the amplitude and frequency. These signals are far too weak to be sampled directly by a microcontroller, and for digital control – as in, MIDI – you don’t need to read the analog signals anyway. These signals were turned digital with the help of an LM339 quad comparator. With two of these comparators and signals out of the hard disk that are 90 degrees out of phase, quadrature encoding is pretty easy.

The software for this MIDI controller is based on the OpenDeck Platform, a neat system that allows anyone to create their own MIDI controllers and devices.  It’s also a great looking board that seems to perform well. Video below.

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Ro-Bow, The Violin Playing Robot

There are robots that will vacuum your house, mow your lawn, and keep their unblinking electronic eyes on you at all times while hovering hundreds of feet in the air. How about a robot that plays a violin? That’s what [Seth Goldstein] built. He calls it a ‘kinetic sculpture’, but there more than enough electronics and mechatronics to keep even the most discerning tinkerer interested.

There are three main parts of [Seth]’s violin-playing kinetic sculpture. The first is a bow carriage that draws the bow across the strings using an electromagnet to press the bow against the strings. The individual strings are fingered with four rubber disks, and a tilting mechanism rotates the violin so the desired string is always underneath the bow and mechanical fingers.

As far as software goes, the Ro-Bow transforms MIDI files into robotic mechanization that make the violin sing. From what we can tell, it’s not quite as good as a human player; only one string at a time can be played. It is, however, great at what it does and is an amazing mechanical sculpture.

Video Below.

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Arduino Synth Guitar Really Rocks

[Gr4yhound] has been rocking out on his recently completed synth guitar. The guitar was built mostly from scratch using an Arduino, some harvested drum pads, and some ribbon potentiometers. The video below shows that not only does it sound good, but [Gr4yhound] obviously knows how to play it.

The physical portion of the build consists of two main components. The body of the guitar is made from a chunk of pine that was routed out by [Gr4yhound’s] own home-made CNC. Three circles were routed out to make room for the harvested Yamaha drum pads, some wiring, and a joystick shield. The other main component is the guitar neck. This was actually a Squire Affinity Strat neck with the frets removed.

For the electronics, [Gr4yhound] has released a series of schematics on Imgur. Three SoftPot membrane potentiometers were added to the neck to simulate strings. This setup allows [Gr4yhound] to adjust the finger position after the note has already been started. This results in a sliding sound that you can’t easily emulate on a keyboard. The three drum pads act as touch sensors for each of the three strings. [Gr4yhound] is able to play each string simultaneously, forming harmonies.

The joystick shield allows [Gr4yhound] to add additional effects to the overall sound. In one of his demo videos you can see him using the joystick to add an effect. An Arduino Micro acts as the primary controller and transmits the musical notes as MIDI commands. [Gr4yhound] is using a commercial MIDI to USB converter in order to play the music on a computer. The converter also allows him to power the Arduino via USB, eliminating the need for batteries.

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Play Music with your Painting Using Teensy

[sab-art], a collaboration between [Sophia Brueckner] and [Eric Rosenbaum], has created a touch-sensitive musical painting. Initially, basic acrylic paint is used for the majority of the canvas. Once that is dry, conductive paint is used to make the shapes that will be used for the capacitive touch sensing. As an added step to increase the robustness, nails are hammered through each painted shape and connected with wiring in the back of the painting. These wires are then connected to the inputs of a Teensy++ 2.0, using Arduino code based on MaKey MaKey to output MIDI. The MIDI is then sent to a Mac Mini which then synthesizes the sound using Ableton Live.  Any MIDI-processing software would work, though. For this particular painting, external speakers are used, but incorporating speakers into your own composition is certainly possible.

A nice aspect of this project is that it can be as simple or as complex as you choose. Multiple conductive shapes can be connected through the back to the same Teensy input so that they play the same sound. While [sab-art] went with a more abstract look, this can be used with any style. Imagine taking a painting of Dogs Playing Poker and having each dog bark in its respective breed’s manner when you touch it, or having spaceships make “pew pew” noises. For a truly meta moment, an interactive MIDI painting of a MIDI keyboard would be sublime. [sab-art] is refining the process with each new painting, so even more imaginative musical works of art are on the horizon. We can’t wait to see and hear them!

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Ask Hackaday: Bringing Your Design to Market

While many of us have made and documented our open source projects, not many of us have tried to sell our design to the masses. [Scott] developed, marketed, and “bootstrapped” a cool looking MIDI controller. Now, before you get your jumpers in a bunch – the project is completely open source. [Scott] documented the entire process of not only the design, but the trials and tribulations of bringing it to market as well. Calculating costs, FCC testing and the many other challenges of bringing a consumer electronics device to market are all detailed in his blog. Join me while we look at the highs and lows of his interesting and eventually worthwhile journey.

Putting yourself into a game where orders are in the tens of thousands, with hundreds of thousands of dollars changing hands is not easy when you’re just a guy with an idea and a soldering iron. [Scott] was up for the challenge, however. He quickly realized that much of the margin is spent on advertising and to cover risk. On his last order, some of the paint was chipping off. He had to fix the paint and repackage everything – all at his cost.

He also talks about the learning process of product design along the way. His original idea was to make a volume controller, but couldn’t sell a single one. He was forced to redesign the software into the MIDI controller as it exists today. He tried to launch a Kickstarter, but was rejected. This turned out to be a good thing, however, because he would have wound up kickstarting a product that didn’t work.

For advertising, he relied on Google and made some extremely detailed tutorials for his product. Many of them can be used for other MIDI controllers, and often come up in Google searches. Smart. Very smart.

Be sure to check out the video below, where [Scott] gets into some capacitive touch design theory, and talks about how not to cut your final product in half while on the CNC.

Have any of you ever tried to mass produce and sell one of your designs? Let us know in the comments!

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Modular 555 Synth is Controlled by MIDI

[Atdiy and Whisker] aka [The Tymkrs] have created a  MIDI controlled 8 note modular synthesizer. (YouTube link). The project was designed to highlight some of the modules they have available at their Tindie Store. Essentially, the synthesizer is 8 classic Atari Punk Console (APC) tone generators. Each APC is made up of two 555 chips, rather than the 556 used in the original design. The APCs are tuned to a Pentatonic scale, with the 8 notes covering 1.5 octaves. [Whisker] added a single potentiometer which controls all 8 of the monostable oscillators at once. Tweaking this knob gives the synth that classic Atari Punk Console sound we’ve all come to know and love.

The 8 APC outputs are routed to once side of an AND gate. The other side of the AND gate is connected to a 74hc595 shift register. A Parallax Propeller processor converts MIDI note data into a serial stream that can be daisy chained across several ‘595 shift registers. The outputs of the 8 and gates are mixed to a single combined output, which goes out to [The Tymkrs] studio amplifier.

Like many [Tymkrs] videos, this one ends with a MIDI driven jam session, outlining how the circuit would sound in a song. Click past the break to see it all in action!

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