[sdiy] complex gesture control ?

[harrybissell]

OK I'll take "A"

You can differentiate the CV (hipass filter - probably just a single R-C) then
use a window comparator to sense when the signal changes.  Any change pos
or neg will make the derivative of the CV go outside the window.

The time constants and thresholds need to be adjusted to suit your controller.
This circuit has been done to get analog keyboard multi-triggers.

Then, trigger a re-triggerable one shot multivibrator... every time you trigger it
it resets to the beginning of the time period.

I wrote a Design Ideas for EDN a few years ago, that desrcibes one such
retriggerable mono. Google search Harry Bissell and EDN and you'll find it.

H^) harry

Fernando de Izuzquiza wrote:

> Hi all. I've been thinking about this for some time now:
> I think it would be a useful addition to controllers, to have a simple circuit that can generate
> gate/trigger/"velocity" when playing from a  sensor-type controller (joystick, ribbon, photocell,
> IR, ....any sensor)
> The joystick may be a good example: you are sending CV from any position; using A, you open a gate
> whenever the joystick is in motion. When steady for more than, say, 300ms, the gate goes low, and so
> on.
> With  B, you send a trigger whenever you make a fast gesture (sensitivity preset), and at the same
> time, a CV proportional to the "strength" of that gesture (how fast did you change the stick
> position)
>
> A- Time based gate:
> If there is no change in CV after a preset waiting time, it goes low. Then, open the gate whenever
> any change in CV is detected. Close the gate again when no activity is detected for the w. time, and
> so on. (A comparator is not enough because you need to sense motion at any position=any CV)
>
> B- "velocity" + trigger:
> If you change CV fast enough, a trigger is sent, and also a CV proportional to how fast the
> CV changed (as in PAiA Theremax, see notes at Theremax pages)
>
> I made a very simple implementation of A in software (Max-MSP) some time ago. It was useful in order
> to open and close vcas or activate the event/s I was controlling, and "mute" all activity when no
> event was produced from controller (photocells and/or theremax)
> B idea is from Theremax. I built one, and found great the gate and velocity implementation (when
> using Theremax as a CV controller)
> Implementing this two ideas will give us: 1. controller's CV output  2. an "event" gate  3. a sort
> of "staccato event" trigger and 4. a "velocity" equivalent CV, producing lively control out of just
> one controller.
>
> How could we implement this two ideas using comparators, gate delays... circuits we already have.
> Or build simple circuits... any idea wise men?
>
> Fernando
>
> f
> *