[sdiy] keyboard contacts

[fmg]

Hi All,

I recently bought a dead toy organ/synth (Casio CTK-100) for a few
coins. I have no intention to repair it but to make a CV keyboard
with it. It's a standard key size 4 octave keyboard with a 7x8 diode
encoded matrix.
While checking the diode matrix I noticed that there is enough
space below (~1.5 square inch section, constant along keyboard length)
to put a series of contacts in there.

Now, what kind of contacts?  I dig for simple contacts in shops and
all guys tell me the same: "...years they are no longer in market" and
offered me opto and reed switches as alternative. They are not
expensive (alone) but a purchase for 4 octaves is something I can't
afford at the moment, then I decided to go diy and make my own contacts.

I made a "contact test" in workbench with different metal wires:
tin/lead, brass, silver, copper, stainless steel, gold, and found
the main problem is not the contact resistance but bouncing noise.
About electric resistence I can say that all this metals are good, (for
a home project, I know one or another list member could burn me for this
statement), but bouncing was a real headache with all of them.

After several tries I found that polishing the metal surface reduce
considerably the bounce noise. I used paper (no sandpaper, just paper),
then a piece of cotton cloth and silk to get a mirror-like surface.
The result was a considerable attenuation in bounce noise, specially
for copper, brass and gold. The other metals didn't understand what
I made and insisted on staying noisy.

I made a short "hall of fame" list of metals regarding bouncing with
copper as best and stainles steel at worst place. I will not post this
list cause it's surely wrong due to my crappy way of measure, but I can
to affirm that copper showed the best figure, beating even gold-plated
pins I took from an aerospace connector.

Well, to not keep boring the list:

- Will it worth the effort to hand-make all the contacts?
- Does anyone in this list made it before?
- Did they work as expected?
-  ...even after a year?

I will appreciate your thoughts about. I don't want a uC solution, but
if there is no other chance...

Thanks in advance, (and sorry for my english)

Fabio Gonzalez