Hacking my arm prosthesis to output CV so that it plugs into my synth [video] | Hacker News Reader

Hacking my arm prosthesis to output CV so that it plugs into my synth [video]

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125 pointsmiobrien27 comments

Previously on HN (46 comments, 2 months ago):

https://news.ycombinator.com/item?id=22342314

The below comment there from horentis got me thinking.

> This is incredible. I think the next step from here - technology wise I mean - is figuring out how devices can tap into this without needing to lose a limb.

Accessibility mode, but not as I have seen it before.

From what I got out of his explanation, is that his prosthesis listens to the nerve signals that would control the muscles of a left hand (which he doesn't have). So, I think you could hook up a similar detector to your own arm for similar effects, its just that your arm would twitch along with your commands.

I suspect the reason we don't see these built for able-bodied people is that its easy to contact the fingers to buttons and knobs and read the muscle activations through these cheap, well-understood pieces of hardware. Might be slower than his input method though.

Good lord.

I guess I knew this was possible, but seeing it in practice is something else entirely.

I wonder if it’s output unipolar 0-10v or bipolar -5/+5 and how that “feels” to the user.

Most CV signals can be positive or negative. For instance, there's a standard for pitch CV that's 1 volt per octave. 0 volts might be middle C (whether it is would vary depending on the synth and/or position of tuning knobs), and -1 volt would be an octave below middle C. (There's another hz/volt standard used most notably by the Korg MS-20 where 0 volts == 0 hertz, but it hasn't caught on as widely.)

If the prosthetic adapter only outputs positive voltage, you could just turn the knob corresponding to the CV being controlled to its lowest setting (assuming there is a knob and it is summed with rather than bypassed by the jack).

Right. I guess my question is more around the actual sensation and expressiveness when using it.

Is it simply “the more I tense up the muscle the higher the voltage”?

Is it able to be more or less expressive than say a Cv joystick or a high quality ribbon controller.

This is so fucking amazing. The “mind control” DJ is definitely a concert I would attend. I wonder how much extendable is the prototype.

I know I'm not fun, but everything is "mind control". When you turn the knobs on a synthesizer you control the music with your mind (not your hands). You can also mind control the music with other devices such as an xy-pad https://en.wikipedia.org/wiki/Kaoss_Pad, if you've ever tried it, the result is about the same as what you can ear in the video.

So this is "mind control" in the same way that a trackpad can be used to mind control the pointer on the screen. It's a device that allows you to control two continuous variables with (almost) no physical effort. And yes it's connected to the nerves, but what can you do with this that you can't do with a joystick or a pad?

Oh. Thanks for, "explaining it". And also way to miss the point completely.

Oh come on it is not that obvious. At least it took me a while to realize that this was not a superpower.

But you're right, I know I'm missing the point. I don't care, I can't help, I need to know: can this guy do something that I cannot do with a trackpad?

It’s obvious we didn’t truly believe about “magic” mind control. He’s a handicapped person that can do something truly amazing thanks to tech skills.

Even though we all possess the same electric signals let me tell you. Unless you can chop your arm off you will never be able to do the same thing with your bloody trackpad.

When I saw the video, I thought "wow there are so many crazy things that I could do with this". Now I realize: probably not so much that I cannot already do with a bloody trackpad. This is just something I wanted to share.

Of course this guy's story is inspiring.

Haha yes! The funny thing is that with fingers, one can still observe the nerve signals getting turned into CV. With this guy, it's not possible.

Wow, that's a really cool project! I love the modular design of the prosthesis that allowed the hand to be quickly exchanged with the CV output module. I wonder how many independent signals you could learn to control using this type of interface? I suspect at least ~5 per arm (>=1 per finger), similar to the fingering used for piano/guitar/etc?

While it isn't remotely as cool as controlling CV with you mind... someday I should convert my Nintendo Power Glove into denkitribe's SynthGlove[1] MIDI controller.

[1] https://www.youtube.com/watch?v=qpLkX7X37D4

I was thinking, I'd consider hacking off an arm if I could control a machine with the stub, and then I realized, one likely does not need to remove any appendages to interact with such a mind body interface. The future is coming.

It's happening! I'd say we're no more than five years away from a computer interface that integrates with your existing fingers.

> a computer interface that integrates with your existing fingers

Like ... a keyboard?

Imagine how much faster you could type if you interacted through muscle twitches or directly through brain impulses. No latency from pressing/releasing keys.

This would be a step beyond a keyboard. Imagine letting kids learn it while they're young. Your WPM is limited by the speed of your mind!

> Your WPM is limited by the speed of your mind!

I mean... it already is. This tech is highly unlikely to surpass keyboards for a few reasons:

1) It needs to be customized for each user.

2) It needs really special hardware to read an accurate signal, especially if there's no open channels to connect to via a missing limb.

3) The accuracy / speed tradeoff for muscle twitches vs. touch typing can't possible be that good. The signal to noise ratio of brain impulses is bad.

4) The limiting factor on wpm typed for any original work of non trivial length is going to be your thinking of the idea, not your typing of it.

5) Imagining the tech worked perfectly, such an interface would probably be very mentally draining to use. Typing out a passage is easy to imagine doing, but editing existing text? I feel exhausted just thinking about it.

Yeah, that's the joke.

Awesome. I wonder how much control he has over the output. I assume it's easy for him to hit min or max, but can he be accurate in the middle?

I imagine each of the sensors are binary - either picking up a signal or not - so it probably depends on what "speed" he has set the "knob turning" to be, and he sets it in the middle by holding on a sensor for a mid-range amount of time.

Most fine precision motor skills are made with a orchestra of opposing muscle stimuli.

It'll be interesting one day to see fully-integrated humans with these digitally controlled devices. I imagine the human brain will be easy to train to operate, say a cell phone, especially if it's integrated at a very young age.

https://news.ycombinator.com/item?id=22342314

This is so rad- I love that the prosthesis designers are so excited to work with him on this. Really need to ditch those cables for bluetooth though.

I wonder how many channels he can get up to.

This is exactly the type of content I come to HN for.

That is fucking rad.

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