Hacking When It Counts: Spy Radios

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”

The Minimin Aims To Be The Simplest Theremin

Hackaday.io user [eagleisinsight] is a high-school hacker whose dreams of becoming a Theremin virtuoso were thwarted by the high cost of a commercial instrument. His response is the Minimin, an affordable Theremin design using a 555 and an ATMega328.

The 555 is configured as an astable oscillator running at about 5MHz and with a loop antenna attached to its timing capacitor. The parasitic capacitance of the musician’s hand against the antenna varies the frequency of the oscillation, as you would expect. In a classic Theremin the signal from the 555 would be mixed with the output from a fixed 5MHz oscillator and the sound would be generated from the difference between the two oscillators, but in [eagleisinsight]’s design the 555 clocks the ATMega328’s timer. The processor can thus read the oscillator frequency and use that value to control a waveform generator.

There is something missing from this Theremin: a second antenna for volume. For now a potentiometer does that job, but [eagleisinsight] is working on a MkII device to correct this omission, along with plans to replace the ATMega with an XMega processor whose DAC can produce a sine wave output and whose USB port can be used to enable the Minimin as a MIDI controller.

As you might expect, we’ve covered numerous Theremins over the years here on Hackaday. You can browse them all, but we’d like to draw your attention to a typical breadboard instrument using a soda can antenna, people using Theremins as Guitar Hero controllers, and Léon Theremin’s terpistone, a full-body instrument.

The Infrared Theremin

The traditional theremin is more or less an audio oscillator with two metal rods. Using proximity sensing, one rod controls the pitch of the oscillator and the other controls the volume. [Teodor Costachiou] apparently asked himself the excellent question: Why does the proximity sensor have to use capacitance? The result is an Arduino-based theremin that uses IR sensors to determine hand position.

[Teodor] used a particular type of Arduino–the Flip and Click–because he wanted to use Click boards for the IR sensors and also to generate sound via an MP3 board based around a VS1053. The trick is that the VS1053 has a realtime MIDI mode, and that’s how this Theremin makes it tones.

Continue reading “The Infrared Theremin”

Finally, a Modern Theremin

Ever wanted to own your own Theremin but couldn’t justify dropping hundreds of dollars on one? Now you can build your own, or buy it for a quintuplet of Hamiltons. The Open.Theremin.UNO project has built up antenna-based oscillator control around the ubiquitous Arduino Uno board.

So what’s the Arduino in there for? This is a digital Theremin, but check out the video below and you’ll agree that it sounds amazing and has excellent response. The aluminum antennas used for volume and pitch are attached to the top portion of the shield but it sounds like they’re not included in the kit. Don’t fret, you can use a variety of materials for this purpose. On the bottom you need to connect a speaker cable, and also a ground wire if that cable’s not grounded.

As the name implies, this is Open Hardware and we’re quite happy with the documentation on their site and the BOM (found on the GitHub repo). This design was shown off back in 2013 hiding in a pack of cigarettes. If you don’t want to build your own they’re selling kits on their site for 48 Euro delivered, or on Tindie for $55.

Okay, we’ve screwed this up so many times that we’re going to try to get it right here: the Theremin was not heard in the opening of Star Trek the original series, or in the opening of Doctor Who. It wasn’t featured in “Good Vibrations” either. As far as we can tell, it’s not used for anything in pop culture at all… but recognizing the sound and knowing what one is remains core geek knowledge.

If you want a Theremin to play using your entire body you need the Theremin Terpsitone.

Continue reading “Finally, a Modern Theremin”

Retrotechtacular: The Theremin Terpsitone

Léon Theremin built his eponymous instrument in 1920 under Soviet sponsorship to study proximity sensors. He later applied the idea of generating sounds using the human body’s capacitance to other physical forms like the theremin cello and the theremin keyboard. One of these was the terpsitone, which is kind of like a full-body theremin. It was built about twelve years after the theremin and named after Terpsichore, one of the nine muses of dance and chorus from Greek mythology.

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Theremin’s Bug: How the Soviet Union Spied on the US Embassy for 7 Years

The man leaned over his creation, carefully assembling the tiny pieces. This was the hardest part, placing a thin silver plated diaphragm over the internal chamber. The diaphragm had to be strong enough to support itself, yet flexible enough to be affected by the slightest sound. One false move, and the device would be ruined. To fail meant a return to the road work detail, quite possibly a death sentence. Finally, the job was done. The man leaned back to admire his work.

The man in this semi-fictional vignette was Lev Sergeyevich Termen, better known in the western world as Léon Theremin. You know Theremin for the musical instrument which bears his name. In the spy business though, he is known as the creator of one of the most successful clandestine listening devices ever used against the American government.

Continue reading “Theremin’s Bug: How the Soviet Union Spied on the US Embassy for 7 Years”

Using a Theremin for Medical Applications

[Eswar] is not an ordinary 16 years old boy. He figured out a noninvasive way to measure breathing in hospitals for less than $50. He is using a theremin to measure the rise and fall of a patient’s chest. For our curious readers, this touch-less instrument was invented back in 1929 by the Russian inventor [Leon Theremin]. It uses the heterodyne principle and two oscillators to generate an audio signal. One electronic oscillator creates an inaudible high pitch tone while another variable oscillator is changed by adding capacitance to an antenna.

As you can guess the space between the patient’s chest and the antennas placed around the bed forms a tiny capacitor which varies when exhaling. With three simple TTL chips and a little guessing [Eswar] had a working prototype ready to be implemented in the real world. If you’re interested in theremin, we invite you to see one of our previous articles on how to make one in a few minutes with a soda can.