[sdiy] Info request (longshot) - Technics keyboard mech/encoder

[Steve Lenham]

> There are most likely a set of two rubber contact switches per key.   They 
> are made in such a way that one of the two contacts always makes  contact 
> before the other one does. <snip>

Many thanks Chris and Michael for your replies.

You are of course correct - I feel a bit daft for not working it out myself. 
What fooled me is that on this unit there is only one row of rubber buttons, 
but removing a key reveals that each does seem to contain two switch 
contacts.

Interestingly, this does mean that the two switches are physically very 
close together - in the order of 10mm horizontally, though there is perhaps 
also a small internal height difference (getting the PCB off to measure it 
looks like a lengthy process!) - so the counters must be running at quite a 
rate to measure the correspondingly small time interval. On the other hand, 
if the interval is close to the bottom of the key travel, the measured 
velocity might be a better approximation of "hardness".

Perhaps this is a job for Spartanman, the new SDIY superhero...

While I generally agree with Michael that metal contact are nicer, the 
rubber switches might play into my hands on this occasion. My particular 
area of interest is poly-AT (all those who can't afford a CS80, unite) and I 
was hoping to use this mechanism as a testbed. A conductive polymer contact 
offers the possibility of conversion to a linear pressure sensor - try doing 
that with a metal busbar.

I'm still interested if anyone has any knowledge of the existing Technics 
encoder.

Cheers,

Steve L.