[sdiy] push button CV wanted

[Tim Parkhurst]

> -----Original Message-----
> From: Roy J. Tellason [mailto:rtellason at blazenet.net]
> Sent: Wednesday, May 19, 2004 10:27 AM
> To: synth-diy at dropmix.xs4all.nl
> Subject: [sdiy] push button CV wanted
> 
> I have an application in mind for which I'd like the user interface to be
a
> couple of push buttons,  one that would raise and the other one of which
> would lower a control voltage.  Ideally,  some sort of interlocking would
> make it do nothing if both buttons were pressed at the same time.  Any of
you
> folks know of a circuit that'll do this?  Or have any ideas as to how it
> might be implemented?
> 
One solution might be...

Push buttons -> debouncing -> up/down binary counter -> R/2R D/A converter

One push button would step the counter up and the other would step the
counter down. The debouncing circuit would produce a short pulse when a
button was pressed, and whichever button was pressed first would "win" (this
would implement the 'lockout' against pressing both buttons). This solution
would give you a stepped CV, limited by the resolution of the D/A converter.
However, a 6 bit converter (when set up properly) gives you 64 steps, and if
the overall range of the D/A is 5 volts, then you get 1 step = 1 note. As a
side note, this is how some quantized sequencers work (check the Oberheim
mini sequencer, and the ARP sequencer uses a similar scheme). 

Hope this helps / inspires.

Cheers!

Tim (pushing my own buttons) Servo

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