[sdiy] debouncing old roland keyboard

[Czech Martin]

A AND gate has an output o and two inputs i1 and i2.

tie i1 and i2 together.
wire them to your contact.
Now the output should toggle according to the contact.
Add a resistor from o to i1/i2. 1Meg is a starting
value, depends on contact.
Now the output should be debounced.

Instead of an AND gate, two inverters in series or a
buffer (noninverting) can be used. 

A hex CMOS buffer would be conveniant, since you need so many
of them for all those keys.

m.c.

-----Original Message-----
From: Karl Ekdahl [mailto:_nial_ at yahoo.com]
Sent: Donnerstag, 3. Juli 2003 15:52
To: Czech Martin; synth-diy at dropmix.xs4all.nl
Subject: RE: [sdiy] debouncing old roland keyboard


Ehm....   ...i'm learning so maybe a little sketch on
the exact connections.. ?

/Karl

 --- Czech Martin <Martin.Czech at Micronas.com> skrev: >
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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