[sdiy] Keyboards good for scrap / repurposing?

sleepy_dog at gmx.de sleepy_dog at gmx.de
Mon Feb 19 12:26:34 CET 2018

Mikko Helin wrote:
> You could make optical scanner for any keyboard like an acoustic piano.
> https://hackaday.com/2010/10/07/playing-piano-with-optical

Ah! I have been thinking about optical scanning for a while, such a 
thing should worst case get dirty (dust?)  and need to be cleaned, but 
may last forever, eh?
And probably one could also implement (poly) aftertouch with this, two 
birds one stone.

And Roman:
Thanks for the warning about "plastic springs", that doesn't sound very 

- Steve

> 19.2.2018 10.59 "Roman Sowa" <modular at go2.pl <mailto:modular at go2.pl>> 
> kirjoitti:
>     That's exactly how keyboard scanning is done in old organ consoles
>     you all are talking about now. Not in every one, but usually in
>     Ahlborn, one of the major european organ makers. The HC138 decoder
>     is already mounted on the PCB with rubber contacts.
>     I heard from many organ repairmen that rubber contacts fail first,
>     especially in Fatar keyboards. They literally fall apart. Probably
>     not an issue for casual mono synth player, but those kind of
>     organs are heavy banged every day with 10 fingers.
>     Don't bother looking for old broken toy synths, they all have keys
>     made so one octave is made of 2 pieces of plastic, one white with
>     8 keys and the other one black with 5 keys. And the piece of
>     plastic that holds it together is also back support and return
>     spring. This is also the case in entry level Yamaha digital pianos.
>     Roman
>     W dniu 2018-02-19 o 01:29, rsdio at audiobanshee.com
>     <mailto:rsdio at audiobanshee.com> pisze:
>         Steve,
>         Since you are writing your own firmware, you might be
>         interested in one simple way to reduce the number of GPIO pins
>         needed. Since the Columns in a matrix of switches are only
>         ever active one at a time, you can use a CMOS 3-to-8 decoder
>         chip. That requires only 3 GPIO pins, but generates 8 Column
>         strobes. The 4-to-16 variations of the chips come in both
>         active high and active low variations (I seem to recall that
>         the 3-to-8 do not). You can just hard-wire the Enable pin so
>         that one Column is always active (unless that screws up some
>         part of your circuit that is shared), and then your firmware
>         can increment a binary variable that is directly written to
>         the GPIO port as 3 or 4 bits, as appropriate.
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