Hello everyone !
I am coming here to get some help because I have a project that I would like to do and that I am surprised to find no real equivalent on the forums, and yet could certainly be usefull to other people. Most of the projects I have found about Midi protocol are about building a controller, or controling an arduino synth. I'm looking for the opposite, to control an existing machine using Midi protocol, like midification kit for 80s synths. I can deal with electronic, but I'm quite new to arduino. So I come to ask for advices.
Here is the project, I have an 80s synth, a Siel PX JR, i realy like it's sound, and I have already tweaked it to add some possibilities to it. But this model does not have Midi IN protocol, and I would like to add this capability, among other things because the keyboard is quite unpleasant to play.
The note triggering system is quite original, but not unique either I think. There are two metal bars with a small spring stuck between the two (I put pictures attached to help understanding), when you press a key the spring leaves one of the bars to go and touch the other, the flight time between the two bars defines the velocity. Rather simple.
I immediately thought of a system of transistors to close and then open the circuit according to the velocity send by Midi, with an arduino to drive everything. Quite a lot of wiring to do but not impossible either, I like challenges! I found the "Midi glockenspiel" project which in principle corresponds to what I am looking for. The problem is, my keyboard is a 72 notes model ! It is therefore not possible to drive it directly with the outputs of the arduino, without multiplexing i think.
Then i found potential solutions. (I am attaching pictures that I collected, those are inspirations, not exactly what i need), and i saw that there is a ready-made module (74HC4067) that would transform an output of the arduino into 14? That's it ? But what about polyphony? Is it possible to play chords with this solution? (the synth himself is totally polyphonic)
And then you would need an “open the circuit” signal to a first transistor, then a second “close the circuit” signal to a second transistor, for each notes, depending on the velocity of the note. Doable ? Very (too much?) complicated? I know the synth doesn't realy worth it, but... it's the point, it will be a unique model
It is also possible, if the two-transistors solution is too difficult to implement, to simply close the circuit (see attached picture), which gives a note at maximum velocity. It would be a way of simplifying things, but losing the velocity. Ideally, I would like to keep it.
Do you think this is achievable?
Don't hesitate to ask me more questions! Have a lovely day everybody.
(I have a mega or nano arduino available, a USB host shield (not necessary I think for this project, I prefer to use Midi Din IN) and I can buy the other necessary parts ...)
What do you want to do ?