[sdiy] Touch Controllers

[The Proteus]

Scott,

	Originally, ribbon controllers IIRC were a filament of
grounded wire put over a strip of resistive material. Wherever you touched
created a basic potentiometer, and also gave you a similar tactile
response to that of "tapping" a guitar. I've never worked with older
units, but I did have experience while working on E-Mu's XL-7.
	Nowadays, touch strips are either re-designed from the ground up
(as in the case of the Kurzweil touch strip), or they're bought from the
same companies that make trackpads and similar substrates. I've seen
products used from Interlink Electronics (www.interlinkelec.com) to create
both resistive strips and touch pads for drum machines. Also, another
popular domestic source is Spectra Symbol corporation
(www.spectrasymbol.com) for resistive elements like pitch ribbons. These
are primarily resistive touch-strips, other companies make capacitive as
well as optical strips. 
	One really cool technology I was exposed to was the tactex pad
from tactex controls. It's basically a mesh of fiber-optic cable with a
urethane pad on top of it. There's an emission matrix and a scanning
matrix that not only can sense x/y position, but also pressure applied to
the pad as well. This is better in one major way for musical instruments: 
You can actually have multiple fingers down on the element at the same
time, and it will read multiple points on the element. Polyphonic trigger
control, assigning different instruments to different areas of the pad,
all are possible with this. 
	So, this is more of an overview of touch-pad technology, which all
have applicaiton on pitch ribbons. That's all I've got that would be
useful for the DIY crowd at the moment... most of the other sources I know
have too high of a minimum order quantity, or NRE costs that would be
prohibitive for us DIY folk to use the products seriously.

Best Regards,

Prot

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On Mon, 20 Jan 2003, Scott Evans, Gen Mgr wrote:

> Hello all,
> 
> After reading the interest in the ribbon controller ideas, I got to 
> thinking about touch controlled interfaces such as the Buchla 100 and 
> 200 interfaces as well as the Serge TKB. I had opportunity to use the 
> Buchla 100 controllers years ago, but I have never seen inside one of 
> these fun devices. Has anyone in the DIY community done any development 
> on these? Or perhaps some information on how the mechanics work? I 
> believe these are variable capacitance devices. I would love to build 
> something of this nature. Any guidance would be appreciated.
> 
> Scott
> 
> 
>