Hacked Prosthesis Leads To Mind-Controlled Electronic Music

As amazing as prosthetic limbs have become, and as life-changing as they can be for the wearer, they’re still far from perfect. Prosthetic hands, for instance, often lack the precise control needed for fine tasks. That’s a problem for [Bertolt Meyer], an electronic musician with a passion for synthesizers with tiny knobs, a problem he solved by hacking his prosthetic arm to control synthesizers with his mind. (Video, embedded below.)

If that sounds overwrought, it’s not; [Bertolt]’s lower arm prosthesis is electromyographically (EMG) controlled through electrodes placed on the skin of his residual limb. In normal use, he can control the servos inside the hand simply by thinking about moving muscles. After experimenting a bit with an old hand, he discovered that the amplifiers in the prosthesis could produce a proportional control signal based on his inputs, and with a little help from synthesizer manufacturer KOMA Electronik, he came up with a circuit that can replace his hand and generate multiple control voltage channels. Plugged into any of the CV jacks on his Eurorack modular synths, he now has direct mind control of his music.

We have to say this is a pretty slick hack, and hats off to [Bertolt] for being willing to do the experiments and for enlisting the right expertise to get the job done. Interested in the potential for EMG control? Of course there’s a dev board for that, and [Bil Herd]’s EMG signal processing primer should prove helpful as well.

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Muscle Your Way Into Music

Inspired by an old Old Spice commercial, [Juliodb96] decided he too wanted to make music by flexing his muscles. An Arduino and a MyoWare sensor did the trick. However, he also tells you how to make your own sensors, if you are so inclined. You can see the instrument in action in the video below.

If you use the ready-made MyoWare sensors, this is a pretty easy project. You just respond to sensor input by playing some notes. If you decide to roll your own, you’ll have some circuit building ahead of you.

In particular, the signal conditioning for the sensors involves filtering to eliminate signals not in the 20 Hz to 300 Hz passband, several amplifiers, a rectifier, and a clipper. This requires 3 IC packages and a handful of discrete components.

Unlike the original commercial (see the second video, below), there are no moving parts for actuating actual instruments. However, that wouldn’t be hard to add with some servo motors, air pumps, and the like. This may seem frivolous, but we had to wonder if it could be used to allow musical expression for people who could not otherwise play an instrument.

This isn’t the first time we’ve seen the MyoWare in action. We’ve even talked about signal processing that is useful for this kind of application.

Listen To Your Body

[John Miller] has the perfect response next time he complains about an ache or pain and one of his friends says, “You should listen to your body!” As you can see in the video below, he already does. Using two 9V batteries and some instrumentation amplifiers, [John] built an electromyography (EMG) rig.

If you haven’t heard of EMG, think of EEG or EKG, but for muscles instead of your brain or your heart. The LT1167 amplifier is well-suited for this application and even has a data sheet showing how to create an EMG circuit. [John] also used some more garden-variety op amps and the ubiquitous LM386N chip for audio amplification.

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Recording Functioning Muscles To Rehab Spinal Cord Injury Patients

[Diego Marino] and his colleagues at the Politecnico di Torino (Polytechnic University of Turin, Italy) designed a prototype that allows for patients with motor deficits, such as spinal cord injury (SCI), to do rehabilitation via Functional Electrical Stimulation. They devised a system that records and interprets muscle signals from the physiotherapist and then stimulates specific muscles, in the patient, via an electro-stimulator.

The acquisition system is based on a BITalino board that records the Surface Electromyography (sEMG) signal from the muscles of the physiotherapist, while they perform a specific exercise designed for the patient’s rehabilitation plan. The BITalino uses Bluetooth to send the data to a PC where the data is properly crunched in Matlab in order to recognize and to isolate the muscular activity patterns.

After that, the signals are ‘replayed’ on the patient using a relay-board connected to a Globus Genesy 600 electro-stimulator. This relay board hack is mostly because the Globus Genesy is not programmable so this was a fast way for them to implement the stimulator. In their video we can see the muscle activation being replayed immediately after the ‘physiotherapist’ performs the movement. It’s clearly a prototype but it does show promising results.

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This DIY Wearable Assist Goes Beyond Traditional Therapy

Bodo Hoenen and his family had an incredible scare. His daughter, Lorelei, suddenly became ill and quickly went from a happy and healthy girl to one fighting just to breathe and unable to move her own body. The culprit was elevated brain and spinal pressure due to a condition called AFM. This is a rare polio-like condition which is very serious, often fatal. Fortunately, Lorelei is doing much better. But this health crisis resulted in nearly complete paralysis of her left upper arm.

Taking an active role in the health of your child is instinctual with parents. Bodo’s family worked with health professionals to develop therapies to help rehabilitate Lorelei’s arm. But researching the problem showed that success in this area is very rare. So like any good hacker he set out to see if they could go beyond the traditional to build something to increase Lorelei’s odds.

What resulted is a wearable prosthesis which assists elbow movement by detecting the weak signals from her bicep and tricep to control an actuator which moves her arm. Help came in from all over the world during the prototyping process and the project, which was the topic of Bodo Hoenen’s talk at the Hackaday SuperConference, is still ongoing. Check that out below and the join us after the break for more details.

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EMG Tutorial Lets You Listen To Your Muscles

What with wearable tech, haptic feedback, implantable devices, and prosthetic limbs, the boundary between man and machine is getting harder and harder to discern. If you’re going to hack in this space, you’re going to need to know a little about electromyography, or the technique of sensing the electrical signals which make muscles fire. This handy tutorial on using an Arduino to capture EMG signals might be just the thing.

In an article written mainly as a tutorial to other physiatrists, [Dr. George Marzloff] covers some ground that will seem very basic to the seasoned hacker, but there are still valuable tidbits there. His tutorial build centers around a MyoWare Muscle Sensor and an Arduino Uno. The muscle sensor has snap connectors for three foam electrodes of the type used for electrocardiography, and outputs a rectified and integrated waveform that represents the envelope of the electrical signal traveling to a muscle. [Dr. Marzloff]’s simple sketch just reads the analog output of the sensor and lights an LED if it detects a muscle contraction, but the sky’s the limit once you have the basic EMG interface. Prosthetic limbs, wearable devices, diagnostic tools, virtual reality — the possibilities are endless.

We’ve seen a few EMG interfaces before, mainly of the homebrew type like this audio recorder recruited for EMG measurements. And be sure to check out [Bil Herd]’s in-depth discussion of digging EMG signals out of the noise.

All About Biosignals

DIY medical science is fun stuff. One can ferret out many of the electrical signals that make the body run with surprisingly accessible components and simple builds. While the medical community predictably dwells on the healthcare uses of such information, the hacker is free to do whatever he or she wants.

A good first start is to look at the relatively strong electrical signals coming off of the heart and other muscles. [Bernd Porr] has put together a simple bioamplifier circuit, and his students have made a series of videos explaining its use that’s well worth your time if you are interested in these things.
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