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

Gerry Murray synthimuse at gmail.com
Mon Apr 10 02:34:31 CEST 2023


Hi JP

There's definitely no reason you can't try it with one sensor.
It depends on how your positioning mechanism works and how 
proportionally it needs to deal with paper position errors.
Certainly, if you do it with minimal hardware and you are confident that 
the software can deal with it all, please do what you feel will work 
best for you.

Best wishes

Gerry


On 10/04/2023 01:20, Jean-Pierre Desrochers wrote:

> Hi again Gerry,*//*
>
> *//*
>
> */> Hi JP/*
>
> */> Another attempt at attaching the image. This time as a gif./*
>
> */> Hope you can open it./*
>
> It worked !
>
> */> I think if you use two sensors, you have the increased accuracy 
> that comes from two signals when balanced./*
>
> */> If you use one sensor, you would be comparing the signal to a 
> reference voltage but the sensor signal could vary with temperature or 
> supply variations. /*
>
> */> Using two sensors, each would be equally affected by temperature & 
> voltage variations and this would reduce the system error./*
>
> The idea of using only one sensor was without any opamp at all.
>
> Only the sensor’s open collector output to a micro-controller..
>
> Here again are my thoughts on that:
>
> But what about using only one sensor at the right paper side??
>
> If the output is low (IR beam passes , Paper too far left) move the 
> paper right
>
> If the output is high (IR beam hidden,  Paper too far right) move the 
> paper left
>
> This way the centering will continually look for the output 
> ‘transition’ position
> to ‘consider’ the paper is at the right position..
>
> But ONLY at the transition position.
> But doing so the centering will ALWAYS be working.. but that could be OK
> for a very precise centering..
>
> **********************************************************
>
> *De :*Gerry Murray <synthimuse at gmail.com>
> *Envoyé :* 9 avril 2023 19:16
> *À :* Jean-Pierre Desrochers <jpdesroc at oricom.ca>
> *Cc :* 'synth-diy mailing list' <synth-diy at synth-diy.org>
> *Objet :* Re: [sdiy] My Player piano roll project... refining my design
>
> Hi JP
>
> Another attempt at attaching the image. This time as a gif.
>
> Hope you can open it.
>
> I think if you use two sensors, you have the increased accuracy that 
> comes from two signals when balanced.
>
> If you use one sensor, you would be comparing the signal to a 
> reference voltage but the sensor signal could vary with temperature or 
> supply variations.
>
> Using two sensors, each would be equally affected by temperature & 
> voltage variations and this would reduce the system error.
>
> That's just the way it seems to me.
>
> Happy to hear others views.
>
> Best regards
>
> Gerry
>
> On 10/04/2023 00:03, Jean-Pierre Desrochers wrote:
>
>     Clever idea too !
>
>     But what about using only one sensor at the right paper side??
>
>     If the output is low (IR beam passes , Paper too far left) move
>     the paper right
>
>     If the output is high (IR beam hidden,  Paper too far right) move
>     the paper left
>
>     This way the centering will continually look for the output
>     ‘transition’ position
>     to ‘consider’ the paper is at the right position..
>
>     But ONLY at the transition position.
>     But doing so the centering will ALWAYS be working.. but that could
>     be OK
>     for a very precise centering.. Hmmm..
>
>     *De :*The SynthiMuse <synthimuse at gmail.com>
>     <mailto:synthimuse at gmail.com>
>     *Envoyé :* 9 avril 2023 17:27
>     *À :* Jean-Pierre Desrochers <jpdesroc at oricom.ca>
>     <mailto:jpdesroc at oricom.ca>
>     *Cc :* synth-diy mailing list <synth-diy at synth-diy.org>
>     <mailto:synth-diy at synth-diy.org>
>     *Objet :* Re: [sdiy] My Player piano roll project... refining my
>     design
>
>     Hi JP
>
>     I should have been clearer earlier on so I've attached a scribbled
>     image of my idea.
>
>     There's no need to invert one of the signals. You just need to get
>     nice linear values from 2 sensors and put them into a differential
>     amplifier. This will give you a DC value that will tell you the
>     position error and you can use it to drive the correction mechanism.
>
>     Obviously, if the signal from the two sensors are equal, then the
>     paper is perfectly centred.
>
>     I hope this helps.
>
>     Best wishes
>
>     Gerry
>
>     On Sun, 9 Apr 2023, 17:24 Jean-Pierre Desrochers,
>     <jpdesroc at oricom.ca> wrote:
>
>         Very good idea.
>
>         If I understand correctly their would be 2 sensors close to
>         each other
>
>         but set a little apart from each ones. (But on one of the two
>         paper sides only)
>
>         If so there would be some kind of detected ‘notch’ or ‘peak’
>
>         to tell the paper is correctly placed right ?
>
>         But when this peak or notch disappears how can I know which
>         direction to move the paper
>
>         and correct its position ?
>
>         I would need the same tandem on the other paper edge.. ?
>
>         ******************************************************************************
>
>         De : Synth-diy <mailto:synth-diy-bounces at synth-diy.org> De la
>         part de Gerry Murray via Synth-diy
>
>         Envoyé : 9 avril 2023 11:20
>
>         À : mailto:synth-diy at synth-diy.org
>
>         Objet : Re: [sdiy] My Player piano roll project... refining my
>         design
>
>         Hi JP
>
>         I would recommend two of these sensors operated in linear
>         mode, with a small difference in their physical position and
>         invert the signal from one of them.
>
>         From these two signals you would get a 'detent' differential
>         signal that would tell you the lateral error and allow you to
>         adjust the horizontal position of the paper more accurately.
>
>         Best wishes
>
>         Gerry
>
>         On 09/04/2023 16:09, Jean-Pierre Desrochers wrote:
>
>         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 mailto:synth-diy-bounces at synth-diy.org De la
>         part de Jean-Pierre Desrochers
>
>         Envoyé : 23 février 2023 17:31
>
>         À : mailto: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
>
>         I let the piano roll play its song while filming.. around 4:00
>         duration.
>
>         Enjoy !
>
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