[sdiy] What are these buttons?

[dancemachine]

When I owned a tenori-on, the buttons definitely needed to be pressed
to activate.  it was a light touch but seemed to be a physical
switch/button of some sort.  I am only reporting on my own memory, and
have no idea how the device works internally.

On Wed, May 4, 2011 at 12:39 PM, Tim Ressel <madhun2001 at yahoo.com> wrote:
> O ho!  So that is what they are up to!  I've never played with one so I had no
> idea they were not buttons at all. Thanks a bunch!
>
> --TimR
>
>
>
>
> ----- Original Message ----
> From: "Speth, John" <John.Speth at coherent.com>
> To: Synth-Diy <synth-diy at dropmix.xs4all.nl>
> Sent: Wed, May 4, 2011 9:24:48 AM
> Subject: Re: [sdiy] What are these buttons?
>
>> I just saw the Tenori-On and am wondering what those buttons are?
>> I'd like to
>> use some lighted buttons in a project but the ones I have seen are
>> very
>> expensive.
>
> I wondered about the Tenori-on too.  It's been discussed here before.  At that
> time I collected two very relevant PDFs about the technology.  You can find them
> temporarily at this dropbox:
>
> http://dl.dropbox.com/u/23053666/nime2006_172.pdf
> http://dl.dropbox.com/u/23053666/nime2006_342.pdf
>
> LEDs have a lesser known function as crude photo detectors when they are reverse
> biased.  Capacitance is a function of light energy.  I'm sure there are many
> ways to measure capacitance but a really simple way is to do it as described in
> this EDN article:
>
> http://www.edn.com/article/462289-LED_senses_and_displays_ambient_light_intensity.php
>
>
> The beauty of using an LED as a photo sensor is that you can multiplex the
> detect function with the illumination function and emit light with it when
> you're not measuring its capacitance.  I've experimented with the method
> described in the EDN article.  It works.  I didn't attempt the illumination
> multiplexing idea but I think it's feasible.
>
> It sure looks like the Tenori-on uses those methods to do its tricks.  It's a
> cool use of dirt cheap LEDs.  I suppose the cost challenge becomes obvious when
> you consider how to drive 256 LEDs faster than human eye persistence and detect
> touches rapidly enough using those same LEDs.
>
> JJS
>
>
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