hardware and software for electronic music 
Sat, Sep 01, 2012, 09:32

Diy soundplane with conductive wire and raspberry pi

hi,

I might make a diy soundplane this winter and I was wondering whether using conductive wire instead of copper strips would work or would it break the concept?

also I was wondering if the dielectric silicone rubber is absolutely necessary?

lastly, do you think the raspberry pi would have the processing power needed for the signal processing?(sending osc data via ethernet)

Thanks for the shared knowledge I wish I could support you by buying a soundplane, but can't afford it!

Sun, Sep 09, 2012, 12:02

All the surface area of the strips is needed. It's a parallel plate capacitor on each junction. So a wire would not give any appreciable surface area.

If you want to make something different but based on the same principe, it's easy to experiment with. I would try setting up a single-point sensor and seeing what happens.

I don't know much about raspberry pi. Probably just about any computer could do one junction. As you do more it takes more processing power, and it takes a pretty fast DSP to do what the Soundplane does (8 x 64).

Thu, Nov 20, 2014, 13:12

The raspberry pi can now do this more effectively by calculating the FFT with the GPU:
http://www.aholme.co.uk/GPU_FFT/Main.htm
http://www.raspberrypi.org/accelerating-fourier-transforms-using-the-gpu/

But how would you the signals in and out? The most I can see is 2 IO with the Wolfson sound card (for which you currently have to download a special raspbian image, find a patched kernel for your distribution or patch the kernel yourself)

Sun, Dec 21, 2014, 15:44

The Raspberry Pi might be able to handle the calculations if it had an extensive, high-speed conversion module added. The Soundplane manages 4 million D/A conversions per second for the 32 carrier frequencies, and 2 milion A/D conversions per second for the 16 sensor channels. The 32x16 converter channels are arranged as 64x8 on the physical surface.

As Randy said, the Pi could handle a smaller array, but you do need substantial area to create the capacitive plates, not just wires.

The dialectric rubber is not strictly necessary, but you absolutely need to have some mechanism for the capacitive plates to change distance from each other. That's how the pressure sensing works - by precisely measuring the change in distance between two (or more) capacitive plates.