[sdiy] Keyboard Encoder Experiments...

[Roy J. Tellason]

On Monday 11 February 2008 17:31, Peter Keller wrote:
> On Mon, Feb 11, 2008 at 10:24:34PM +0100, Ben Stuyts wrote:
> > How about hall-effect sensors?
>
> How about an aligned IR emitter/detector pair where the emitter is
> attached to the key and the detector is fixed to the case and one or both
> have a narrow field of power.

Not a good plan for the long term,  as anything moving a LOT with wires 
attached is eventually going to have problems with those wires.  As evidenced 
by some Lowrey organs that I worked on way back when I first started that had 
an intermittent connection to a light bulb they were moving in an expression 
pedal,  which doesn't move anywhere near as much as a manual key would.

Look at what the organ mfrs did,  they have good reasons,  and lots of 
experience!

Hammond later on did something which involved a fixed emitter and sensor setup 
(some had multiple sensors) and a movable shutter going in between them.  The 
nifty part about this is that you can tailor the profile of that shutter so 
that it compensates for any inherent nonlinearity in the setup.  You can also 
control the aperture for both ends,  making a fairly narrow beam,  narrower 
than what the emitter puts out,  making any variances there go away,  too.

Stacking these in close proximity might be a hassle,  but if the key operates 
a small lever that then moves the shutter you could stagger them on adjacent 
keys.

I've thought for some time now that an optical keyboard might be kinda nifty,  
but never did feel quite ambitious enough to get around to seriously trying 
to fabricate one.

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
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