[sdiy] Reading holes (voids) on piano paper rolls.. using Photo-transistors and PIC micro..

[Jean-Pierre Desrochers]

Rutger,

This is a nice suggestion I’ve thought about..
But I need a LIVE piano reader who will play ‘real time’
what is on the srolling paper and directly put notes
on a MIDI output connector..
It will not be an ‘archiving’ reader..
Thanks anyway.



 

De : Rutger Vlek <rutgervlek at gmail.com> 
Envoyé : 15 novembre 2022 15:42
À : Roman Sowa <modular at go2.pl>
Cc : Jean-Pierre Desrochers <jpdesroc at oricom.ca>; SDIY List <Synth-diy at synth-diy.org>
Objet : Re: [sdiy] Reading holes (voids) on piano paper rolls.. using Photo-transistors and PIC micro..

 

Hi Jean-Pierre,

 

So nice to see another player piano fan here! I have been interested in mechanical musical instruments since early age and have some experience in arranging music for them, particularly for mechanical organs.

 

Recently I bought a Steck pianola, which is still awaiting restoration.

 

I've been thinking about your problem, and was curious to hear if you have considered an alternative route without the need for custom electronics. With a modern smartphone on a stand, it should be possible to capture a movie of the pianoroll while playing. With modern computer vision techniques (AI is my daytime job, though not computer vision specifically) it should be possible to recognize the holes in specific areas and convert the information MIDI. I did a quick calculation of the spatial resolution, and think that with a common framerate of 60 fps you have around 1mm accuracy between frames when the roll is at its max speed of 13 feet per minute. Additional accuracy might be possible when identifying the exact start/end of a hole in each frame.

 

Rutger 

 

Op zo 13 nov. 2022 12:31 schreef Roman Sowa <modular at go2.pl <mailto:modular at go2.pl> >:

One thin heated wire in front of the holes would indeed be most elegant 
solution, but I'm also not sure if those wavelengths are in range of 
optotransistor sensing. And what is more important, such solution would 
not block ambient light in any way, so you could play it from the 
distance with a flashlight :)

It's no problem for JLC to make 5mm wide long PCB filled with SMD IR 
LEDs, and IMHO it is cute. Maybe even 5mm will be too narrow to block 
ambient light, so maybe more like 10mm sounds like good choice. And on 
the back side you can put some art-deco graphics to match the aesthetics 
of entire instrument.

Roman

W dniu 2022-11-11 o 15:58, Jean-Pierre Desrochers pisze:

(...)
> I was thinking of something else that could work..
>
> Heat is Infrared so.. Using a heating element wire over all the brass 
> bar holes
> could be seen as a LEDS array but smaller in width (no PCB).
> This wire just heated a little could be glued in a plexiglass 
> transparent Bar
> placed over the brass reading bar.??
> Or use some kind of diffused incandescent light all over the scrolling 
> paper
> that has infrared specs close to 940nm.. ?
>
> But I’m about sure heating wire spectral wavelength would be far from 
> my needed 940nm..
>
> Hmmm…
>
>

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