[sdiy] debouncing old roland keyboard

[Czech Martin]

These rubber keyboards are about the uggliest things
invented since the A bomb. 
Many Roland keyboards are disfunctional because of these.

I guess you just want the "key pressed" information,
and no velocity. In this case, use a CMOS AND gate,
with a feedback resistor -say- 1Meg. This will
help, cause this creates a simple FF with hysteresis.
Perhaps the resistor has to be changed.

This is an old circuit from the days when wires where
used in keyboard contacts.

m.c.

-----Original Message-----
From: Karl Ekdahl [mailto:_nial_ at yahoo.com]
Sent: Donnerstag, 3. Juli 2003 15:13
To: synth-diy at dropmix.xs4all.nl
Subject: [sdiy] debouncing old roland keyboard


Hello all, i've got an old Roland S-50 keyboard that
i'm trying to make into a cv keyboard but there's (of
course) a problem: it's in pretty bad shape so i get
trigger bouncing all the time. This is a pretty big
problem since i control a memory writeenable pin with
the gate. It can be a lot of triggers coming while
depressing/releasing they key, thus putting the memory
into writeenable and storing the wrong key.

I've put a cap inbetween the gate and ground and it
works most of the time but i still get the wrong key
stored sometimes.

Does anyone have any good deboucing circuits, or maybe
cleaning tips for the keyboard....

Another small thing that comes into my mind is, how
much power does the triggers within this kind of
keyboard (normal rubber trigger thingy) take?

/Karl

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