My Oscilloscope Uses Fire

December 12, 2018 by Al Williams 16 Comments

If you want to visualize sound waves, you reach for your oscilloscope, right? That wasn’t an option in 1905 so physicist [Heinrich Rubens] came up with another way involving flames. [Luke Guigliano] and [Will Peterson] built one of these tubes — known as a Rubens’ tube — and will show you how you can, too. You can see a video of their results, below. Just in case a flame oscilloscope isn’t enough to attract your interest, they are driving the thing with a theremin for extra nerd points.

The guys show a short flame run and one with tall flames. The results are surprising, especially with the short flames. Of course, the time base is the length of the tube, so that limits your measurements. The tube has many gas jets along the length and with a sound source, the height of the flames correspond to the air pressure from the sound inside the tube.

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A $4 Ultrasonic Theremin Looks Cheesy On Purpose

November 10, 2018 by Al Williams 6 Comments

We don’t think [bleepbit] will take offense when we say the “poor man’s theremin” looks cheesy — after all, it was built in a cheese container. Actually, it isn’t a bad case for a simple device, as you can see in the picture and the video below. Unlike a traditional theremin, the device uses ultrasonics to detect how far away your hand is and modifies the sound based on that.

There are also two buttons — one to turn the sound off and another to cycle through some effects. We liked how it looked like a retro cassette, though. The device uses a cheap Arduino clone, but even with a real Arduino, the price wouldn’t be too bad. However, the price tag quoted doesn’t include a few connectors or the speaker that appears in the schematic. There’s a note that the model built uses a jack instead of a speaker, but it would be nice to include both and use the kind of jack that disconnects the speaker when you plug speakers or headphones in.

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The Portable, Digital, Visual Theremin

November 1, 2018 by Brian Benchoff 6 Comments

The theremin is, for some reason, what people think of first when they think of electronic musical instruments. Maybe that’s because it was arguably the first purely electronic musical instrument, or because there’s no mechanical analog to something that makes sound simply by waving your hand over it. This project takes that idea and cranks it up to eleven. It’s a portable synthesizer that’s controlled by IR reflectors. Just wave your hand in front of it, and that’s what pitch is going to sound.

The audio hardware for this synth is, like so many winners in the Musical Instrument Challenge in this year’s Hackaday Prize, based on the Teensy and its incredible Audio library. The code consists of two oscillators and a pink noise generator. Pressing down button one activates the oscillators, and the frequency is determined by the IR sensor. Button two cycles through various waveforms, while the third and fourth buttons shift the octaves up and down. The output is I2S, and from there everything is out to an amplifier and speaker.

Of course, it’s really not a musical instrument unless it looks cool, and that’s where this project is really great. It’s a fully 3D printed enclosure that actually looks good. There’s an 8×8 LED array to display the current waveform, and this is something that could actually be a product instead of a project. It’s a great synth, and we’re happy to have it in the running for the Hackaday Prize.

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NES Controller Slider-Based Light Theremin

March 20, 2018 by Kristina Panos 1 Comment

Having never use a 555 before, [lonesoulsurfer] decided that his first foray into the world’s most popular and versatile IC would be to use a 555 to make beautiful chiptunes. For that, we commend him. He found [Dean Segovis]’ Slidersynth light-based Theremin and got to work building his own version it and stuffing it into a (knockoff!) NES controller.

For the uninitiated, a Theremin is a touch-less synthesizer that uses human capacitance and a pair of antennae to control oscillation and amplitude. In a light-based Theremin such as this one, the oscillation is controlled by the intensity of photons from a white LED and their interaction with a light-dependent resistor, also known as a photocell or ‘squiggly resistor’.

The oscillations themselves are created by wiring up the 555 as an astable oscillator, and the pitch is controlled with a potentiometer mounted on the back. It has a small built-in speaker, but [lonesoulsurfer] replaced the B button with a 3.5 mm audio jack so he can plug it into a powered speaker and really rock out. We’ve got his demo tape queued up after the break.

We love pocket instruments around here. If you prefer brass and woodwinds, this pocket woodwind MIDI controller just might draw your lips into an O.

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Theremin In Detail

September 9, 2017 by Al Williams 4 Comments

[Keystone Science] recently posted a video about building a theremin — you know, the instrument that makes those strange whistles when you move your hands around it. The circuit is pretty simple (and borrowed) but we liked the way the video explains the theory and even dives into some of the math behind resonant frequencies.

The circuit uses two FETs for the oscillators. An LM386 amplifier (a Hackaday favorite) drives a speaker so you can use the instrument without external equipment. The initial build is on a breadboard, but the final build is on a PCB and has a case.

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FabricKeyboard Is Piano, Theremin And More

June 17, 2017 by Steven Dufresne 6 Comments

Two researchers of Responsive Environments, MIT Media Lab, have put to together a device that is an amazing array of musical instruments squeezed into one flexible package. Made using seven layers of fabrics with different electrical properties, the result can be played using touch, proximity, pressure, stretch, or with combinations of them. Using a fabric-based keyboard, ribbon-controller, and trackpad, it can be played as a one-octave keyboard, a theremin, and in ways that have no words, such as stretching while pressing keys. It can also be folded up and stuffed into a case along with your laptop, and care has even been taken to make it washable.

Layer one, the top layer, is a conductive fabric for detecting proximity and touch. The twelve keys can work independently with a MPR121 proximity touch controller or the controller can treat them all as one, extending the distance the hand can be and have it still work. Layer two is just a knit fabric but layers three to six detect pressure, consisting to two conductive layers with a mesh fabric and a piezo-resistive fabric in between. The piezo-resistive fabric is LTT-SPLA from eeonyx, a knit fabric coated with the conductive polymer, polypyrrole (PPy). Layer seven consists of two strips of knitted spandex fabric, also coated with PPy, and detects stretching. Two strips of this are sewn on the bottom, one horizontal and one vertical. You can see and hear the amazing sound this all produces in the video below.

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Hacking When It Counts: Spy Radios

August 12, 2016 by Dan Maloney 33 Comments

World War II can be thought of as the first electronic war. Radio technology was firmly established commercially by the late 1930s and poised to make huge contributions to the prosecution of the war on all sides. Radio was rapidly adopted into the battlefield, which led to advancements in miniaturization and ruggedization of previously bulky and fragile vacuum tube gear. Radios were soon being used for everything from coordinating battlefield units to detonating anti-aircraft artillery shells.

But it was not just the battlefields of WWII that benefitted from radio technology. From apartments in Berlin to farmhouses in France, covert agents toiled away over sophisticated transceivers, keying in coded messages and listening for instructions. Spy radios were key clandestine assets, both during the war and later during the Cold War. Continue reading “Hacking When It Counts: Spy Radios” →