[sdiy] What are these buttons?

[James Hughes]

I've got no answers for ya, but I was just flipping through the Jameco
catalog and saw this (serendipity!):
http://www.jameco.com/fmr9

If you replaced LED1 with ambient light, that would be your sensing
circuit, right? Maybe you could use another LED (not part of the
switch) to provide a reference voltage for varying ambient light
levels? It's probably a terrible idea in practice, but an interesting
hack.

On Wed, May 4, 2011 at 9:49 AM, Barry Klein <Barry.L.Klein at wdc.com> wrote:
> The Tenori-on specific document says each led has a switch.
> Did they change their design to use the sensing strategy?
> I don't get how it could work if you want a black screen or portions, and
> want it to work in daylight as well as dark.
> If this were this simple we'd just have leds on our front panels and use
> them for indicators and switches both...  (show me...)
>
> Barry
>
>
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Tim Ressel
> Sent: Wednesday, May 04, 2011 9:39 AM
> To: Speth, John; Synth-Diy
> Subject: Re: [sdiy] What are these buttons?
>
> 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_inte
> nsity.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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