[sdiy] My Player piano roll project... refining my design

Roman Sowa modular at go2.pl
Tue Apr 11 12:17:21 CEST 2023

How precise are all rolls ever made? I mean I find it hard to believe 
that paper rolls made 100 years ago were so precisely made that paper 
edge was in +/-0.1mm tolerance distance from the lowest or top note 
hole. What I'm saying is that maybe it's better to adjust paper position 
based on actual note sensors, and don't really care about the edges? 
OTOH it might be too complex, because you'd have to monitor the 
amplitudes of all sensors, multiplying circuits complexity a few times.

As for paper edge location stability, I like Gerry's idea, it's the way 
to do it, but you may also go one step further, and use linear scanning 
sensor, the kind used in flatbed scanners, or industrial positioning 
systems. This will give you wide range of exact location info.
You could even make simplified linear scanner on your own, just put a 
bunch of small phototransistors side by side, read them all by ADC and 
calculate measured paper edge location in the micro controlling stepper 


W dniu 2023-04-09 o 17:09, Jean-Pierre Desrochers pisze:
> Hi all again,
> I’m still trying to refine my design and working on
> the paper centering process circuit.
> So far I’m using the tracker bar edge’s holes to detect
> left/right paper movements while playing the rolls.
> Those who are at the paper’s edge sides.
> The system works pretty well
> but still some rolls lacks of centering correction.
> SO I want to do some tests using Photointerrupters - Slot Type – with 
> open collector Outputs.
> Like those types:
> I’m trying to select the best accurate one to detect _paper edges_
> not the overall paper cutting the IR beam..
> Any idea of the best specifications to pick one ?
> *De :*Synth-diy <synth-diy-bounces at synth-diy.org> *De la part de* 
> Jean-Pierre Desrochers
> *Envoyé :* 23 février 2023 17:31
> *À :* Synth-diy at synth-diy.org
> *Objet :* [sdiy] My Player piano roll project... a small video demo for 
> you..
> *Importance :* Faible
> I’m not done yet with this project but this is promissing..
> https://www.youtube.com/watch?v=K7xXYqCB0AY 
> <https://www.youtube.com/watch?v=K7xXYqCB0AY>
> I let the piano roll play its song while filming.. around 4:00 duration.
> Enjoy !
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