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

[Oakley Sound]

The Prophet T8 famously uses opto sensing for its keyboard.

Top tip: Don't try to fix a T8 in sunlight. The fluctuating light
falling on the opto sensors when the lid is off causes the uproc to
crash. Most annoying.

One of the Ensoniq keyboards used a better method. This involved each
key having a ferrite block on it. As the key moved close to a flat PCB
with coiled traces on it. The change in inductance in the relevant coil
caused the processor, via some nifty interfacing, to realise a key was
being depressed. I think it could do poly AT too.

Regards,

Tony Allgood                         www.oakleysound.co.uk

Oakley Modular Synthesisers      Penrith, Cumbria, England