Realtime Guitar Fret Scanning

Started by stingray05, March 25, 2020, 05:58:03 PM

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stingray05

Hello forum,

With Teensy 3.2, I built a controller for realtime midi note recognition, but it only works with one string at the moment:

The whole thing works in a similar way to FretTrax.
Frets (are not divided!) And strings function as two contacts of a switch. The frets are connected to each other with the same resistors via a voltage divider from + 5 V to PIN A1, the strings are each connected to GND (a hex pickup is not yet used).

When the strings are gripped, a resistance measurement is triggered which the Teensy converts into Midi notes.
However, polyphony will only function to a limited extent due to the lack of split frets.

Works in the test setup with only one string so far without problems.
With more than one string I am faced with the problem that I need an additional trigger that gives me the information which string is currently being used ...

How can I implement this with Teensy, - maybe someone here has a brilliant idea?
Greetings from Germany - and please stay healthy in these difficult times!

-----

WIN 10
Cantabile Performer
Guitar Wing
Komplett 11 Ultimate
Sampletank 3
VB 99, GR 55, US 20, FC 300
MM Stingray 5 with GK Kit BG
Dingwall Lee Sklar with GK Kit BG + Graphtech Piezo

gumtown

#1
you need each string to have its own data source, via separate/insulated bridge for each string.
instead of a resistive divider and A/D for the strings, use multiple inputs (one for each fret, and one for each string), and use high speed multiplex keyboard scan techniques.
No need for split frets.
also a hex pickup for velocity recognition of each string plucked (soft/hard)
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

stingray05

#2
Quote from: gumtown on March 25, 2020, 07:18:58 PM
you need each string to have its own data source, via separate/insulated bridge for each string.
instead of a resistive divider and A/D for the strings, use multiple inputs (one for each fret, and one for each string), and use high speed multiplex keyboard scan techniques.
No need for split frets.
also a hex pickup for velocity recognition of each string plucked (soft/hard)

Hi gumtown,

First, thanks for your answer ! Nice to hear that no split frets have to be used!
but I'm not quite sure if I really understood you correctly, because I have to translate the answers with Google Translator ...

It was already clear to me that I had to use a separate data source for each string. The question is how exactly?
Can you describe that in more detail?

No matter whether I wire each fret individually or use the system with a voltage divider, in both cases I have to put GND on the strings to make a switching function possible ...
At that moment, however, I can no longer put the strings on separate entrances, or have I overlooked something important here (mistake in thinking?)?
Here the devil is obviously in the details.

An Hexpickup would initially only give me AC voltages that at least cannot be processed directly with an Arduino. I'm not sure if the teensy can do that directly?
It would be conceivable to rectify this signal, but this would also lead to further problems ...
What is the best way to proceed here?

The system with voltage divider would have the charming advantage of only having to use a single input for the fingerboard. Also means just a single connecting wire plus resistances between the frets, instead of having to lay 20 - 24 individual wires in the guitar neck ... An advantage that should not be underestimated for mounting on the instrument.

---

Another approach is that of OMB (gripping hand only):






Capacitive scanning is carried out here. In the videos you can see that all frets are connected to each other and only one wire runs to the controller.
EDIT: The strings are used individually by direct galvanic contact (without hex pickup) ...
The system should also be available for retrofitting, works completely polyphonic ...

It would be very interesting to do something like this with the Teensy ...
Maybe someone has ideas?

Apparently empty strings are also recognized ...

EDIT:
Apparently empty strings are NOT recognized (yet) ...
The system apparently does NOT (yet) recognize the volume of the strings struck.


Greetings from Germany - and please stay healthy in these difficult times!

-----

WIN 10
Cantabile Performer
Guitar Wing
Komplett 11 Ultimate
Sampletank 3
VB 99, GR 55, US 20, FC 300
MM Stingray 5 with GK Kit BG
Dingwall Lee Sklar with GK Kit BG + Graphtech Piezo

billbax

Good post stingray05 8)

I can see a lot of possibilities for basic writing using this system.  Trio+ has a rival maybe.

Bill

stingray05

#4
Quote from: billbax on March 27, 2020, 06:56:13 AM
Good post stingray05 8)

I can see a lot of possibilities for basic writing using this system.  Trio+ has a rival maybe.

Bill

Hi Billbax,

Hope you are well ?

I didn't even know the Digitech Trio yet - I had to search for ...

For OMB, however, I was not interested in the automatic accompaniment - I find the approach of triggering Midi notes in real time much more interesting - although so far only for the gripping hand ...

I would like to hear from the specialists present here whether and how something can be implemented with the Teensy ...

That's exactly why I had a post next, https://www.vguitarforums.com/smf/index.php?topic=28192.0, asked if the TouchSense PINs can also be used as a slider for Teensy (if yes, how?) ...

Greetings from Germany - and please stay healthy in these difficult times!

-----

WIN 10
Cantabile Performer
Guitar Wing
Komplett 11 Ultimate
Sampletank 3
VB 99, GR 55, US 20, FC 300
MM Stingray 5 with GK Kit BG
Dingwall Lee Sklar with GK Kit BG + Graphtech Piezo

admin

#5
OMB Thread is here
https://www.vguitarforums.com/smf/index.php?topic=24725.msg179318#msg179318

https://onemanband.backerkit.com/hosted_preorders/project_updates#updates

During 2019 Winter NAMM, I ran into the developer who was simply showing it off at a coffee stand ( no official booth )




I told him we have been talking about since Nov 2018 here at VGuitarforums  - even showed him the link
https://www.vguitarforums.com/smf/index.php?topic=24725.msg179318#msg179318

He was taken aback as he assumed his attendance at Jan 2019 Winter NAMM was the very 1st public announcement of the system , I invited him to join and spread the news of OMB to 29,000 High Tech GUitarists  - but nothing ever developed and he still is unaware of our forum.

They use Facebook
https://www.facebook.com/pg/OMBguitars/posts/?ref=page_internal