[sdiy] Opto-switch Kybd (was Reed and Switch)

[Theo]

I did this for my organ pedal keyboard using CNY17.
There are two "contacts" per key
and the outputs of the opto interrupters are multiplexed to 082 used as
comparators.
Works ok. But still have to implement velocity (has only been 2 or 3 years),
so I don't know about possible problems with the finer timing needed for
velocity.

Used small PCBs that hold electronics for 4 keys at a time,
when one print is scanned the leds of next print are tuned on.
So 16 leds are on at the same time.

Ambient light was no problem.
However just to be sure the sensors are placed so that no direct light can
reach them.
And when a key is pressed down,
a piece of plastic L profile on the top of the pedal keeps the gap closed.

Theo


----- Original Message -----
From: Tim Parkhurst <tparkhurst at siliconbandwidth.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Friday, December 12, 2003 12:49 AM
Subject: [sdiy] Opto-switch Kybd (was Reed and Switch)


> So I'm thinking (dangerous, I know)...might it be easier to put together a
> keyboard with photo interrupter type switches? They're very reliable,
> wouldn't cross trigger, wouldn't broken or otherwise affected by
vibration,
> and I have seen them in Digi-Key for as little as 50 cents each. Prolly
get
> them for even less if you could find a good surplus deal. I'm also
thinking
> you would want to:
>
> 1) Mount them 'sideways' so that any dust or dirt would fall through the
> slot, rather than into the slot.
> 2) Multiplex them so that all 30, 40 or 50 LED's are not ON all the time.
A
> pretty trivial matter though if you're already building a scanning matrix
> type keyboard.
> 3) Keep them in the dark so that ambient light doesn't bug them (or use IR
> sensors). Again a trivial matter unless you're trying to clone a Gleeman
> Pentaphonic Clear. Actually, I've used these sensors on industrial robots,
> and because of the wavelengths they use and the shape of the slot, they
are
> fairly immune to all but the brightest direct light. Shouldn't be a
problem
> when mounted inside a housing and below a keyboard.
>
> Any thoughts?
>
>
> Tim Servo
> "Imagination is more important than knowledge." - Albert Einstein
>
>
>
>
>
>
>
>
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