Uses a technique I’ve never heard of called “voltage triangulation” to create a touchpad effect from a conductive/resistant plane.
So, I was thinking - could you use a copper plane of a PCB panel as the resistance surface to create an X/Y plane interface module? Seems like that could work really well with the large Kosmo panels, although it’s a lot more work and needs a microcontroller for something which can be trivially accomplished with two knobs. Though it would allow you to modulate two parameters with a single finger, making for more expressive playing.
Still, could be nifty! Just throwing that out into the ether…
“You’ll need to choose a material with a reasonably high resistance.” Copper is not noted for that.
I’m guessing, though, you could design a PCB with traces to eight contact points for the touchpad, and then paint the touchpad onto it with conductive paint.
A touch surface might be of interest for something like a small desktop synth. For a modular, it seems to me a joystick would serve better.
you could design a PCB with traces to eight contact points for the touchpad, and then paint the touchpad onto it with conductive paint.
I thought this too, but I think it might still work with bare copper. As long as there’s any differentiable signal, the neural network should be able to train on it.
The joystick is definitely more “pro”, mostly I just think it’s neat when the panel becomes part of the instrument, like in your Mikrophonie. There’s also a slightly difference in how it could play, since a joystick will always have “tweens”, you couldn’t play a discrete arpeggio with a joystick.
I was a researcher at university in a project where I tried to create a conductive plastic that had resistance that varied with pressure. I think the idea was to make mobile phone covers that could sense how user is handling them. Technically it worked, it was plastic infused with extremely small nanocarbon particles which conducted electricity, and applying pressure forced them closer together and lowered the resistance. Big problem was that it was very inconsistant and even 10% of carbon completely annihilated any durability and rigidity of the plastic and you could just crust them in your had. But for this kind thing with solid backplate it could work. If you also figure out how to solder metal leads to the plastic…
Not that this helps in any way with this, I just remembered that.
For capacitive XY input laptop touch pads of a certain vintage still had ps2 serial interfaces available and it would not surprise me if some still do. That said usb host mode is starting to be a common microcontroller feature and touchpads should use a standard HID interface.
I’m pretty sure this is what the Korg kaossolator mini? (The small one) was using.
but that also made me think: given that cheapo touch controllers from Aliexpress start in the single-digit price range, it’d be a waste to use it to make a small XY pad… it’d be great to use it instead for something huge, maybe a big piece of scrap metal with the proper resistance, something that’d really make for a good visual performance.
also, speaking of capacitive / resistive PCB stuff… has there ever been a good guide on how to design those for use in synths? only ever found bits of info here and there. one day i’d love to bring to life alternative layouts i have in mind using tech similar to the arturia microfreak
These things are literally manufactured in their millions. In general, using something off the shelf is more consistent and reliable than homebrew stuff (but again, homebrew gives you “I made this” satisfaction). When I fiddled with VHS ribbon controllers years ago it was finicky and hard to get a repeatable result.
That reminds me, I’ve actually got a Pimoroni Skywriter HAT sitting in a box somewhere.
It’s a 3D capacitive gesture/proximity sensor, about the size of a playing card. It is designed for the Pi but it uses I2C so it can probably talk to any capable microcontroller. I reckon it could be shoved behind a non-conductive Kosmo panel without too much hassle. (they’re currently on sale at the above link too)
Interesting concept, I’m curious to see where this thread goes.