[sdiy] keyboard contacts

[harrybissell]

Hi Fabio

well... recall the original PAiA 2720 synthesizer had heys made from
piano wire with shirt buttons for keys. and the next thing was to replace
it with a professional keyboard.

You could make your own... but direct keying will have contact bounce.
I'd suggest beryllium copper for the key springs, because of the flexing
involved. Usually these would be gold plated as well.

Can't you find an old home console organ to rape for the keyboard... or
maybe
take apart one of those worthless Yamaha CS-80 synths for parts

(just kidding about the CS-80, flamesuit ON :^)

fmg wrote:

> 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