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electronic practice concertina


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On 7/31/2022 at 11:21 AM, Richard Mellish said:

I would be interested in your design, particularly what you used to sense bellows (real or virtual) pressure and direction.


Analogue differential pressure sensor and normal bellows. My box was built around a repurposed cheap, german made anglo. This gives the full information about bellows expression and direction, which was then utilised for bisonoric functionality (I fiddled with a concept of bisonoric Hayden based layout for a bit) and volume modulation or MIDI velocity in case of piano mode. 


It was a nice experiment, but as Don wrote above, ultimately you need real action and hal switches to make a decent instrument, so unless you need MIDI input for music production it isn’t exactly worth it. Baffled acoustic ’tina played softly is way better as a quiet practice instrument than a ‚cut corners’ e-tina. 

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I help to run a community workshop including running a weekly electronics drop in session.  A couple of weeks ago one of our members asked if I could help with a midi concertina design.  At this stage he didn't know that I play the concertina (I tend to keep music and engineering lives separate.)

 

I started with 15 small buttons mounted on a pcb just to get the electronics sorted but of course the feel wasn't right being click switches and with just a couple of extra switches to indicate directions the bellows.  The resultant midi signal was sent to a convenient Yamaha synth module which was lying about. 

 

Then I acquired a batch of "press to break" push switches.  These produce a signal immediately the button starts to move and then there is about 3mm travel after that.  The spring pressure is a little bit high but quite comparable with the button on my Wheatstone 1950s 40 button C/G.

 

Draw up the hex ends and switch positions and laser cut 3mm ply boards, leaving space for the Arduino nano, a strain gauge to connect the ends together along with a small HX711 electronic module to connect it and later a small oled display.

 

The result is in the attached pictures. Not fully enclosed so you can see some of the innards.

The small switch enables you to go into "setup mode" where some of the buttons are used to change, pitch, octave, sensitivity and program number. Also the shape of the response curve for pressure to volume which I haven't yet fully explored.

 

There's a video of me playing it at https://youtu.be/XSPmpdLq0fc

Be kind, this is just the accordion patch in Yamaha MU15 synth and me getting used to the feel of the thing including how the strain gauge responds.

 

It feels strange, not moving, and there's an urge to reach for the air button as your hands are close together but of course it's not necessary.

 

 

Howard Mitchell

 

IMG_0939.jpg

IMG_0940.jpg

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Howard, I love the simplicity of your build. It looks like a very budget-friendly setup, and my impression is that it strikes a good balance between cost and function. Obviously it doesn't perfectly replicate the feel of an acoustic concertina, but in my opinion that's a nice-to-have feature and not essential to the purpose of a midi instrument. Would you be willing to share details of your design, like source code or links to specific electronic components?

Edited by Steve Schulteis
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6 hours ago, Steve Schulteis said:

Would you be willing to share details of your design, like source code or links to specific electronic components?

Steve,

I’d be happy to publish details.  Give me a little time to put something together ( some parts of it are in my head!). 

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I've put a schematic, an Arduino .ino file and 2 .dxf files for the hex ends with holes for the switches in a dropbox at - 

 

https://www.dropbox.com/scl/fo/mhjby3ht9931ijvjbtpge/h?dl=0&rlkey=6vaxarmjt0zd28jz2kphnjpyu

 

The code needs a bit of tidying up and optimisation but it works as is.

 

Here are links to the load cell, the switches and the oled display.

 

https://www.ebay.co.uk/itm/254500986126

https://www.switchelectronics.co.uk/black-on-off-miniature-momentary-push-to-break-switch-spst

https://www.ebay.co.uk/itm/203920721729

 

Mitch

 

 

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2 hours ago, Howard Mitchell said:

Here are links to the load cell

Which 'weight' of load cell did you go with?  Would you stick with that weight if you built another one?

 

I wonder if two fairly heavy springs between each end of the load cell and the concertina ends would give it a better feel? Or even two load cells with a spring between them.

 

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1kg. It’s sensitive enough at the low end and doesn’t peak at the high end. 
 

I wondered about springs or maybe foam buffers. They might affect the response time when changing bellows direction. 
 

I’m working at the moment at making the ends further apart and at an angle to mimic the way I normally play. Also plugged it into a computer with your concertina sound font.   Had to modify the code as the Logic Audio sampler doesn’t recognise “all note off”. 

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Those switches have a  (reasonably good) lifetime expectancy of >=10,000 depressions but they will fail at some time.  Can they take a push on connector so that replacing a switch does not require electronic surgery?

 

Dammit, I am feeling the urge to revive my earlier abandoned project.

Edited by Don Taylor
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My (mechnically crude) version uses just such a load cell. I tried a 5 kg one then changed to a more sensitive one. I think it's 2 kg but I can't see its marking. I have it rigidly attached to the left-hand keyboard and have tried various arrangements for connecting it to the right-hand keyboard and allowing some play, none of which have yet satisfied me. That is one of the ergonomic aspects not yet resolved. The other is the 1.57 N operating force of the switches, which with the small diameter (3.4 mm) of their buttons makes them a bit uncomfortable to play. I thought about replacing them by switches with a lower operating force and/or gluing larger caps onto them but temporarily shelved the project before coming to a conclusion on that.

 

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I should add that the purpose of mine is not quiet or silent practice but the ability to have the sounds of different instruments controlled by a concertina-style keyboard rather than an off-the-shelf piano-style one.

Edited by Richard Mellish
Corrected a typo
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I did build a MIDI 40 key ES concertina a couple of years ago using hall-effect sensors and magnets in the keys. I also made a 30 key anglo, which I never quite finished. Both played via an APP on an I-Phone and got their power through the USB line. For a while the ES MIDI worked via bluetooth:

 

Concertina 2.0

 

I since have been working on a system to convert one of Aeolas to midi without tempering with the original instrument...

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Very impressive work on all these (past and present) and I'll just put my penny's worth here:  I have used the Striso (singular) for a couple of weeks, and the extra dimensions of control offered by the silicone buttons make a huge difference to me in terms of creative potential/sound variety/bent notes/and all.  I don't yet see any prices or shipping dates for the actual Striso Duet we've seen and heard Didie play so well, but I can imagine simple hobby-shopping an hour or two to make the triangular frame, and with a pair of Striso Boards at uder $1K USD, that power is a bargain, IMHO.  My little old iPad could probably play both simultaneously (since it plays the Striso and another MPE controller now) and the whole package, from scratch/brand new, with a smallish PA system, would be about $1600 USD.  Not cheap, perhaps, but compared to any other Hayden Duets of such broad range (122 buttons, with adjustable overlap and all) well, there aren't any, are there?

 

So, in my electronic ignorance, can anyone like Howard or others "spec" a button that allows for the kind of wobbly, "wah-wah" and other switching options that the Striso offers?  That would let me save up for the Striso Duet!

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4 hours ago, David Colpitts said:

So, in my electronic ignorance, can anyone like Howard or others "spec" a button that allows for the kind of wobbly, "wah-wah" and other switching options that the Striso offers?  That would let me save up for the Striso Duet!

Piers, the originator of the Striso, told me this about the buttons:

 

"The note buttons are force sensitive resistor based, on top of the circuit board is carbon foil of which the resistance lowers when more pressure is exalted on the buttons. Each button has 3 pads underneath to create the direction sensitivity." *

 

I have been very tempted by the Striso system but was a bit concerned about the longevity of this system.  However, Didie has been playing his (a lot!) for over a year now so maybe he can comment on any problems.

 

My other concern is that the dual Striso board version is a lot of buttons (122), I think that I would prefer something much smaller with maybe 50-60 buttons.

 

-----------

 

* Added later.  Thinking about Piers description above, and doing a little Googling, I suspect that he is using a single sheet of Velostat, which is a conductive carbon foil made by 3M, and that each button is permanently wired so that when pressed it can potentially pass a current through the Velostat under the button.  Underneath each button and the Velostat are three little electical contacts ('pads').  Each of these pads are connected so that when the button above them is pressed then one, or more, of the pads makes a circuit through the Velostat to the button.  The resistance of each of these circuits will vary depending on how hard the button is pressed and this resistance can be used by a microcontroller to know which button was pressed and by how much (volume, pitch and timbre).  Each button to pad connection is a separate force sensitive resistor that can be measured.  A  Striso board  would have 61x3 = 183 FSRs!!!  I have no idea how Piers would manage this number of FSRs. Anybody?

 

FSRs  are not terribly accurate at measuring a variable resistance, but that would not matter in this case - they would be good enough.  They do react quickly to changes in pressure and that is important for this sort of application.

 

I do wonder about the longevity of the Velostat but the stuff is dirt cheap and I think that it should be possible to set it up to be replaceable.

 

Edited by Don Taylor
Added my supposition on how the Striso works.
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Thanks, Don, for the excerpts and explanations.  I learn here, each and every day.  And, FYI, the older "Striso Box" model has fewer buttons on the left, and there may be a couple of not-quite-done examples in Piers' shop (for so I  he wrote me) but they represented a bit of a dead-end in the evolution of the project, at least not compatible with new software, as I understand it.  But, perhaps a winner for some here?  My latest thought is to make a hybrid sort of frame-up, with the Striso as the right hand and my bought-and-paid-for QuNexus Red as the left.  I can set it for two octaves below, and use it as a bass side, or some such.  Not Hayden layout, but simple enough for some basic leftism.  But the Striso has whetted my appetite.  For that matter, you clever types can probably re-configure some "extra" Striso buttons to just play other instruments and effects and???  Maybe Didie has already done such?

 

Anyway, thank you for all your information.  And, if one considers the interest for silent practice as well as performance electronica, the market may be a bit bigger than some speculate?  Or maybe not.

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David

 

Perhaps you could perform a test for me on your Striso.

 

Try pressing successively more buttons simultaneously, 2 then 3, 4 and all the way up to 10 (shriek!). 

 

Do the buttons all sound at the same time and is there a point when it will not recognise more buttons and just sounds a smaller number of buttons, or it maybe that the buttons are all recognised but that there is a slight delay as you add more buttons. 

 

Or maybe Piers has figured out how to multiplex all of those signals so that they all sound together fast enough that you cannot hear any delays.

 

Hmmm.  I guess that I am assuming that your iPad can respond to that many signals at the same time, but in any case it would be interesting to know what happens.

 

Don.

Edited by Don Taylor
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Sure, Don, though the Striso I am falling for is a generous loan from a friend.  But to answer your question, it sounds to my modestly trained ear that all buttons sound without delay.  And, doesn't he list "15 note polyphony" or am I confusing that with something else.?

 

For my purposes, in what passes for normal play, absolutely no issues with delays in sounding.  Matter of fact, a nice change from slower-to-respond bass notes on my acoustinc machines.

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