[sdiy] More elegant trigger derivation?

[media.nai at rcn.com]

I have a very similar circuit on Larry's page.  You should be able to OR in
the gate with a diode and two resitors.

At 7:49 PM +0000 09/19/02, sbernardi at attbi.com wrote:
>
>I've been thinking about Harry's idea of deriving a
>trigger by differentiating the control voltage. So, I
>run the CV into a differentiator, which outputs a
>positive or negaitive going pulse depending on whether
>the the CV went up or down. Then this goes into a window
>comparator, because I don't care what the polarity is, I
>just want to indicate that it has changed. Say we set
>the window threshholds at +/- 100mV.
>I also want to generate a trigger when the gate goes
>high regardless of whether the CV changes (i.e., you
>could press the same note multiple times). So I run the
>gate into a positive edge detector and OR it with the
>window comparator output. Then I use this to trigger a
>oneshot such as a 555 to generate the actual trigger.
>This can all be done with an op amp, a dual comparator,
>some logic gates, and a 555. Seems like a lot of parts -
>is there a simpler, more elegant way to do this?