Positional sensing testing

[mgd49]

Hi there,
sorry to resurrect this 6-feet-under thread, but I tried to understand how the schematic shown in the first post can help one deal with positional sensing. I searched here, and also over the internet, also re-learning the basics about OpAmps, ... I still can't see how the output of this circuitry gives us a "positional sensing" information.

maybe the software part required is more important than the circuit itself, if so, can someone explain the overall chain to me, so that I can go sleeping less idiot than this morning ?

Cheers.

[dmitri]

You should re-read point 4 right at the beginning of the first post - it explains it.

[mgd49]

Hi Dimitri,

point 4 says :

The first half wave of a signal from a pad should be positive, e.g my Pintech mesh snare is such pad. Most of other mesh pads out there, like Roland, Drumtec and etc, produce a negative first half wave. This is a schematic of a precision rectifier required for such pads (a Pintech mesh snare will of course work with it as well):

ok, but this doesn't explain how this enables a human person with programming skill to define a strike's position on the pad. this is were I'm stuck right now. I understand that this is required, but not why ?

[dmitri]

Because built-in ADCs can work only with positive voltages and only the first half wave bears information about hit position.

[mgd49]

ok,
so all the work is done via software, based on the output signal of the dual OpAmp chain. the software measures the time the signal spends going down from peak to zero; based on this you estimate the position from center to rim. right ?

[dmitri]

Right.

[mgd49]

brilliant. I can now say that I understand the theory of positional sensing.
thanks

[airflamesred]

brilliant. I can now say that I understand the theory of positional sensing.
thanks

Me too!

[ignotus]

Hi,

I've been setting up my snare for positional sensing, and I've got it working pretty well, but there's something I've noticed and I don't know if this happens to anyone else:

The pointy symbol moves across the screen correctly indicating the position on the snare, and if I do a roll I get the changing sounds in AD. All fine. But if I do a single hit on the centre and then a single hit right at the edge, the module detects the position fine, but the first hit on the edge sends a cc message for a centre hit (subsequent hits are then correct); and the same vice versa: I hit the edge (gives edge sound) and then hit the centre, and the first hit gives an edge sound, even though the pointy arrow correctly indicates a centre hit. Again, subsequent hits after the first hit send the correct cc message.

Just wondering if anyone else noticed this. If you do a roll across the surface you can't notice it, but it happens every time with single hits, going straight from centre to edge and vice versa.

[dmitri]

Can you post a MIDI Log screenshot with incorrect CC messages sent?