Velocity sensing keyboard circuit modification

[caguaman]

I found a disassembled midi controller keyboard.

I wanted to use it connecting some switches as keys but the circuit there is different from what I have seen (Note: I'm a begginner and I have not seen many keyboards PCB's). It has 2 switches per key. From the info I could find, this is used for velocity sensing (not sure). Does anybody know if there's any way to convert this double switch key into a single switch? I cannot figure out how this double switch works.

Also does anybody know where can I find a schematic of this configuration?



Thanks!

[J M Fahey]

Never seen one, but out of the top of my mind, they are probably arranged as to close one before the other. That time difference gives you a speed reference.
In that case, they would not be replaceable by a single switch, unless you were not interested in velocity data, only on key closed, pitch, whatever.
It's just an educated guess, might be well off track.

[caguaman]

Never seen one, but out of the top of my mind, they are probably arranged as to close one before the other. That time difference gives you a speed reference.
In that case, they would not be replaceable by a single switch, unless you were not interested in velocity data, only on key closed, pitch, whatever.
It's just an educated guess, might be well off track.

Thanks J M Fahey.

Yes, seems like it uses time difference between the activation of the switches. Now, do you know if there is a simple way to use only one switch and delay the signal that goes the second switch circuit in order to emulate the activation of 2 switches one after the other? I assume this will give a constant velocity but at least probably could make the keyboard work.

Thanks,

[J M Fahey]

No, not really.
I'm sure somebody who is into keyboards will chime in.
This is a great Forum, but maybe "out there" you'll find another one which is more specifically into that area.
Good luck.

[Enzo]

The switches are matrixed, and there are two sets of them.

What exactly are you trying to accomplish and what is the equipment? DO you even need velocity?

Juan is correct, the two switches close one after the other, the difference in time between them is coverted into the speed the key was travelling, and interpreted then as how hard the note was played.

It SEEMS like you want to make remote buttons to key certain individual notes.

SOme possible tricks: Is max velocity OK? Note simply p-lays its loudest, as if you struck the key hard. Depending on the system, of the second switch is stuck shut, then when teh first switch closes, it instantly sees the other and assumes max velocity. Not all will do that. You might also be able to tie the two together on a key and get the same result.

And how about the controller function itself, can you turn the velocity OFF?


It may be tempting to try to convert this thing, but even some pretty basic drum machines have each button assignable as a note number on the scale. ANd that is as simple as setting a parameter for each button. Try it, connect the MIDI out of a drum machine to the MIDI in of some keyboard. Now when you strike a drum button, or play a drum pattern, the MIDI sound circuits will play the pattern in the keyboard voice.