[sdiy] Magnetic field

[Tom Arnold]

On Sun, Aug 01, 2004 at 07:57:57PM -0700, harrybissell wrote:
> 
> I'd probably go with an optical switch setup... because the "key down" point
> could be
> made totally unambiguous.  If you use a dual phototransistor, or analog sensing
> you could get velocity as well.

I thought about that.  Oh god, I just had another idea...

I'm trying to think of ways to do this that are physically fairly easy.  I
want this to be able to be backed out easily.

So,  bounce this idea off of you.

Are you familier with the Spring-based PRatt&Reed mech?  A piece of plastic
on top pulls the 3 springs when the bellcrank moves.  Optical idea : piece
of clear plastic with a gradiant printed on it.  photocell underneath LED on
top.  You can easily get velocity but at the "On" end the gradient would
allow you to get aftertouch assuming the semi-hard rubber or felt key stop.

Problem with optical is its hard to get aligned for precise movements like
this.  We're only talking about 1/4" of action or so.  Magnetic could at
least be made auto-calibrated "Press Each C to Stop.  Press to
full-aftertouch. Release" or something.  Plus with optical there would be
parts that could wear ( my plastic sliding strip ).

I'm sure there are tonnes of excellent optical setups out there but I'm
thinking around Pratt&Reed mechs with the foundation idea that I want to be
able to return them to original.

-- 
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 - Tom Arnold -       When I was small, I was in love,                  - 
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