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Marc345 Offline OP
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Many optical sensor systems in higher end DPs nowadays seem to use optical fibers for transmitting the sensor data. Examples:

* https://www.bechstein-digital.com/de/vario-connect/
* Yamaha AvantGrand (AFAIR)
* Kawai Novus (AFAIR)

Are there any particular reasons for that?

Is it easier to scan all key position sensors via optical means?

Does it remove electromagnetic interference?

Last edited by Marc345; 11/12/21 06:24 PM.

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I can't find that information in the page you link, but the Bechstein system looks nice. I have a Kawai ATX3 system which is similar/identical to the sensor system in the Novus I think. No idea if the wires are optical. I always assumed copper but haven't actually paid attention when looking at it. There is a connector between the wires from the sensors and the wires to the processing unit. This is needed if you want to take the action out. That connector looks like a 'normal' one. But haven't checked in detail.

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The question isn't clear (to me). Are you asking about the use of optical sensors, or are you asking about the use of fiber optics to convey the detected signals?

The former is because, and I have no data for this, optical sensors are more reliable, and provide more precision than the rubber/graphite electronic switches, and the latter is presumably a design or component availability decision.

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Originally Posted by pianogabe
I can't find that information in the page you link

You can see it on their pictures. To me it seems like they are using some of the fibers to transmit the light source, and others in the same bunch of fibers to pick up the reflections.

Originally Posted by spanishbuddha
The question isn't clear (to me)

The title is pretty clear: it's about the connection.

Part of the question is also a concern regarding the transformation of all that scanning bandwidth into a digital signal. ADCs are beasts on their own and usually you don't have like 88-176 pieces of them connected to some processing unit. So I guess there may be some sort of muiltiplexing going on, a very fast switching between the signals. Maybe there are optical variants that are simply better than their usual electric counterparts? Do we know of someone who checked what those manufacturers actually did with their optical sensor system, ie. how they implemented them?

p.s. here is what I found related to AvantGrand: https://forum.pianoworld.com/ubbthr...avantgrand-n1x-hands-on.html#Post3077968

Last edited by Marc345; 11/13/21 05:34 AM.

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The AvantGrand definitely uses bundles of fiber cabling. I'm pretty sure the Novus doesn't. The NV has optical sensors and transmitter components SMT mounted directly to a PCB that has slotted holes for the hammer-shank "fins" or shutters to pass through. No fiber cables anywhere.


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That's something I'm especially curious about:

[img]https://postimg.cc/F7x4qww0[/img]

What exactly is this device?


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Originally Posted by Marc345
That's something I'm especially curious about:

[img]https://postimg.cc/F7x4qww0[/img]

What exactly is this device?
Looks like a optical (on the back) / electrical (on the right) converter to me.
The optical cables seem to be plastic type optical fiber which is normal for short range communication (similar SPDIF on audio equipment): they have much higher attenuation per length but it's ok since the link is short.
Only for longer links (fiber to the home, switch stations, trunk fiber networks) glass fiber will be used.


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Originally Posted by TonyDIGITAL
Looks like a optical (on the back) / electrical (on the right) converter to me.
The optical cables seem to be plastic type optical fiber which is normal for short range communication (similar SPDIF on audio equipment): they have much higher attenuation per length but it's ok since the link is short.
Only for longer links (fiber to the home, switch stations, trunk fiber networks) glass fiber will be used.

So, it's essentially a few dozen fiber optic receivers like

https://www.mouser.de/ProductDetail...?qs=sGAEpiMZZMudkDON%252B1gPs78B52tIpnYn

packed on one board? I have been trying to find receivers that handle a few dozen single-mode input fibers, but either this is done outside of the receivers (time-based interleaving?), or I haven't found the proper term for them yet. Also, that receiver seems to be of the on/off type, not a continuous (ADC like) type as I'd expect being used in the AvantGrand series.

Last edited by Marc345; 11/13/21 07:51 AM.

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Hello,

Originally Posted by Marc345
... or I haven't found the proper term for them yet.

Just from the top of my head, not being an expert: a term may be 'Opto couplers'?

Cheers and happy learning,

HZ

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Originally Posted by Marc345
Also, that receiver seems to be of the on/off type, not a continuous (ADC like) type as I'd expect being used in the AvantGrand series.
The actual sensor on the NU1(X) is not on/off, and has changed across releases but is a varying graded (diffraction) type of grating. So for example the NU1 uses dots and the NU1X uses lines. I have not seen the other models, but they have a key sensor that is probably the same, and a hammer sensor which is probably on/off.

Last edited by spanishbuddha; 11/13/21 10:37 AM.
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Something like ADS92x4R Dual, Low-Latency, Simultaneous-Sampling SAR ADC has 2x 3MSPS (6 million samples per second at 16 bit resolution). Only problem is: how do I connect 88 or double that amount of gray sensors to it? Are there some time-based interleaving mechanisms out there that is compaitble with that sampling rate? I guess one would also need to use the ADC as a time source for that.

Last edited by Marc345; 11/13/21 11:10 AM.

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I think it more likely that they use a simple on off scheme and measure the time between.

There are proximity sensors that spit out the distance and even velocity as digital outputs.

The fiber optic cables might simply be easier to mount and align within the framework of a piano mechanism


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