[sdiy] debouncing old roland keyboard

[Karl Ekdahl]

Ok, i see...

I have build a keyboard scanning circuit from two
4051s, one giving +5v on it's common input/output and
one delivering +5v if a key was found on the give
address on the other common input/output, so i guess i
will just put this circuit at the output on one of the
4051s...

Thanks!

/Karl

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