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

Mon Apr 10 01:16:18 CEST 2023

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>
> *Envoyé :* 9 avril 2023 17:27
> *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
>
> 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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