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

[Colin f]

> So I'm thinking (dangerous, I know)...might it be easier to 
> put together a
> keyboard with photo interrupter type switches?

> 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. 

I'm thinking you could use bundles of fibre optics with shutters on keys
to build a scanning matrix keyboard using only 8 LEDs and 8
photo-transistors, and design an interface circuit so it could directly
replace an exisiting scanned diode matrix. Each column activates an LED
that is split to 8 shutters, and each shutter in a group has another
fibre optic cable behind it that feeds one of the photo-transistors.
Might be too much loss in the optics though.

Colin f