[sdiy] Need some advices... cd4049 touch switches

Tom Bugs admin at bugbrand.co.uk
Fri Jan 24 20:16:44 CET 2014


Not sure about that particular ..
(I remember looking at the Chatterbox years ago before I understood very 
much - I figured later that probably the opamps should be powered with a 
bipolar supply - that wasn't clear when I originally read it..)
Anyways,,,
Paia have some ideas:
http://www.paia.com/ProdArticles/touchsw.html -- a bit more complex
http://www.paia.com/ProdArticles/dual-ribbon-howto.htm -- this actually 
has a pair of simple touch-switches in the design
Maybe helpful, I hope

On 24/01/2014 18:15, Jean Bender wrote:
> Hello !
>
> I'm turning around some schematics, and i found this one :
> http://yusynth.net/archives/WirelessWorld/Chatterbox-1976.pdf
>
> I'm not interested yet by the formant filters, but.. the touch
> sensitives switches ( shown on P6, on the whole schema). I don't
> really figure how they work. I've tried to breadboard one with my
> cd4049UBE, but it doesn't seem to do anything.
>
> I'm powering my breadboard with a 13,3v supply. With the bias built as
> shown in the schematic, i can get around 6v at the CD4049 inverter
> input, when i'm touching the points, it's going down, but i don't have
> nothing at the output. Still at 0, touching points or not.
>
> Could somebody explain me how it should work ? I mean, i think i get
> the idea, but i can't see where i'm wrong. Maybe my component ?
>
> Anyway, if you have ressources about body controls and way to build
> touch switches, i'm really interested..
> Thanks !
>
> Jean
>

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