Positional sensing testing

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Re: Positional sensing testing

Postby mgd49 » Tue Jun 09, 2015 5:32 pm

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.
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Re: Positional sensing testing

Postby dmitri » Tue Jun 09, 2015 6:16 pm

You should re-read point 4 right at the beginning of the first post - it explains it.
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Re: Positional sensing testing

Postby mgd49 » Tue Jun 09, 2015 7:52 pm

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 ?
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Re: Positional sensing testing

Postby dmitri » Wed Jun 10, 2015 8:42 am

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

Postby mgd49 » Wed Jun 10, 2015 5:02 pm

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 ?
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Re: Positional sensing testing

Postby dmitri » Wed Jun 10, 2015 6:23 pm

Right.
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Re: Positional sensing testing

Postby mgd49 » Wed Jun 10, 2015 7:30 pm

brilliant. I can now say that I understand the theory of positional sensing.
thanks
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Re: Positional sensing testing

Postby airflamesred » Wed Jun 10, 2015 7:35 pm

mgd49 wrote:brilliant. I can now say that I understand the theory of positional sensing.
thanks

Me too!

koby drums - Triggera krigg/Bix - megadrum - Kontakt........... Samples from all and sundry.
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Re: Positional sensing testing

Postby ignotus » Thu Feb 25, 2016 11:32 am

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.
If it ain't broken... fix it until it is.
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Re: Positional sensing testing

Postby dmitri » Thu Feb 25, 2016 12:01 pm

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