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

[Roman]

>keyboard with photo interrupter type switches? They're very reliable,

I had that idea years ago, have bought lots of photo interrupters
and still no time to finish it.
My idea was to use no solid plate to interrupt the light, but gradually changing darkness printed on foil. I made PCB design with dense traces changing thickness from 1 to 10 mils. After making photomask it looked not too good, but now there may be other ways to make such gradual thing.
Anyway, when such thing crosses photo-interrupter slot, we can obtain velocity info by reading current from phototransistor like we would do in 2-contact keyboard. Set 2 thresholds and voila.
And what's more interesting, we get aftertouch from each key too.
I'm only affraid it might be difficult to select so many optos with similar light/current response.

Roman