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

[Tim Parkhurst]

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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