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Electric Concertina, post the IInd
A few days ago I posted about an idea for an electronic concertina, suggesting a design utilizing 12 oscillators and a bunch of frequency dividers to get the notes I needed. A counter-suggestion was made of making the concertina a MIDI-controller and feed the result into a MIDI synth to do the actual sound generation.

I looked into it.

My main objection to using an external MIDI synth is that this project is intended to be a stand-in for a concertina; I should be able to pull it out and play it where I would play a concertina, without having to carry around something to plug it into. I also don't have a MIDI synth to use.

On the other hand, it would simplify a lot of the sound generation aspects, as well as giving me otherwise unexpected flexibility: because the mapping from key to note is software-driven, it means I could capo the concertina. I could switch instruments in software, so instead of playing an accordion-sound, I could play a fiddle sound, or piano, or the acoustic equivalent of wingdings. If I could find a small enough MIDI synth, I could build it into the device.

Looking around, I found Joe Brown's blog post on an Ultra-simple MIDI Synth using VS1103b Sparkfun BOB. Sparkfun, a hobbyist electronics online retailer based in Colorado, offers a Breakout Board (BOB) for the VS1103b MIDI decoder. The BOB includes all the basic electronics needed to make it easier to work with the chip (pull down/up resistors on all inputs, power regulators to power the chip, crystal oscillator, etc), and provides connection points for all the important connections all in a nice 3cmX3.5cm board. Joe Brown combined the BOB with 5 resistors, 2 capacitors, a switch, an opto-isolator, a diode, and a MIDI connector to create a MIDI synth. The BOB is $25. This seems doable, especially combined with the Arduino I already have (but can't find).

I've downloaded Eagle, a circuit and PCB layout program, and started layout schematics. The Freeware Light version of Eagle only allows one to design 2-layer boards up to 4"x3.2", but that should be sufficient for this job. Sparkfun also works with a site which does prototype PCBs for $2.50/sq.in. + $10/order. The boards I need aren't that big, I'm thinking I could do what I need on a 2x2 board, which would cost $20 to make.

I'll continue to try to lay the boards out, as well as make decisions like should I go for pin-through or SMD (I've never done SMD, but I haven't done anything for 20+ years, so...).

And I'll make things available to you all for commentary.

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Nifty! I look forward to following the progress.

Nothing on Instructables.com?

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