How to connect unmounted 36 key keyboard to Arduino

[PaulRB]

@J-M-L

most likely 8 × 10

I agree this is most likely, given the 8-way and 10-way connectors. But it's just possible it could be 9x9, or 11x7. But not 12x6.

[PaulRB]

@J-M-L

I'll let the grown up provide advice :)

Yes, I'm often mistaken for a grown-up, because of my age.

I'm no musician. But what's the point of a single extra key for one note from the next octave?

Given the (probably) 10x8 matrix, they could have added a further 3 keys.

[J-M-L]

@PaulRB

what's the point of a single extra key for one note from the next octave?

Even though there are actually 12 keys (including sharps/flats) in a full chromatic octave, the term “octave” refers to this span from one note to its repetition at a higher pitch like C–D–E–F–G–A–B–C (The word “octave” comes from the Latin octavus, meaning “eighth.”)

So the extra one is to have really 3 full octaves

C–D–E–F–G–A–B–C–D–E–F–G–A–B–C–D–E–F–G–A–B–C

[Paul_KD7HB]

@hk_jh

First thing I should like to do is to read the pressing of those keys with Arduino. How should I do so?

Actually the first thing is to decide if you want to know when a single key is pressed and which one, or do you want to know when multiple keys are pressed and which ones, or if all the keys are pressed at once and which ones they are, or which keys are not pressed? That is a whole lot of keys to monitor!

[Deva_Rishi]

@PaulRB

I'm no musician. But what's the point of a single extra key for one note from the next octave?

All keyboards i know with the exception of the 88 key have a couple of octaves + 1. (25, 37, 49, 61) The 88 has 7 + 4, or to be more exact 3 + 7x12 + 1

@PaulRB

I understand the usual way is to time the delay between the first & second switches closing, for the same key. That will require some pretty fast scanning of the matrix!

The 61 key i have uses 2 contacts per key, where the first contact closes when the key is pressed and opens again when the 2nd contact closes.(or probably opens actually) A capacitor is charged through a resistor and the voltage in the capacitor determines the velocity. No super fast scanning required, just the reading of analog range.

[hk_jh]

I would like to know when ever any key is pressed. so if I pressed C middle I would like to know that, but also if I press at the same time C octave below and G octave above

[PaulRB]

@hk_jh

First thing I should like to do is to read the pressing of those keys with Arduino.

But what's the second thing? Do you want to make a MIDI keyboard for use with your PC? In that case, an Arduino Pro Micro might be a good choice. It can act as a native USB-MIDI device, so the PC recognises it as a MIDI device when plugged into a USB socket, without any extra software running on the PC.

Will a Pro Mini scan the matrix fast enough to measure the speed that keys are pressed at? I think it could, but the code for that may be quite advanced, involving direct port manipulation, hardware timers and so on.

It might be easier to use a faster Arduino (compatible) board, perhaps one based on RP2040 or SAMD21 or any other that has native-USB capability and a fast clock speed.

[Paul_KD7HB]

So, a maximum of three keys? Probably that is doable.

[alto777]

@J-M-L

is an extra key at the end

It was called a three octave C to shining C keyboard.

a7

[Deva_Rishi]

@Paul_KD7HB

That is a whole lot of keys to monitor!

That depends a little bit.

@PaulRB

Do you want to make a MIDI keyboard for use with your PC? In that case, an Arduino Pro Micro might be a good choice.

Agreed, though also just using the UART to create a 5 pin Din port is another option.

Anyway first i think you should take it apart a bit more to see how it is actually wired before i want to speculate on how to tap into in.

You could just pulse a bt-shifter with a hwTimer/ counter and and use pinchange interrupts,

@PaulRB

but the code for that may be quite advanced,

There is of course ControlSurface.h which may support more or less what you want, though i am not sure the touch-sensitivity can be maintained.

[david_2018]

I've seen people doing this same type project several times, it shouldn't be that hard to find examples.

Looks like a Korg keyboard from the numbers on the circuit board, if you have any idea what it came out of then there may be a schematic available online, that would save a lot of work.

[Paul_KD7HB]

Have you tested any of the switches for contact bounce?

[hk_jh]

@PaulRB

But what's the second thing? Do you want to make a MIDI keyboard for use with your PC? In that case, an Arduino Pro Micro might be a good choice. It can act as a native USB-MIDI device, so the PC recognises it as a MIDI device when plugged into a USB socket, without any extra software running on the PC.

to be honest I won’t mind only to use it as on off indicating pressing the keys.. If there is possible to get pressure is even better but also only on off is good for me

[PaulRB]

@hk_jh

If there is possible to get pressure is even better

That is not the "second thing" I was referring to. It feels like you didn't read my question.

[hk_jh]

Regarding the midi option?

It is not my intention

[PaulRB]

@hk_jh

I could use multiplexer CD74HC4067?

Yes, if you have one already, that is an option. You could use that to connect between the 10-way connector and 4 Arduino pins. Then connect 8 more Arduino pins to the 8-way connector. This is assuming that the keyboard is wired as a 10x8 matrix (which we do not yet know for sure, but seems most likely configuration).

Depending on the wiring inside the keyboard, you may need 8 pull-down resistors. To know this, we need to know if the anodes of the diodes are connected to the 8-way connector or the 10-way.

This diagram shows how we expect the keys and diodes are connected. This diagram shows a 4x4 matrix, but your keyboard is probably 10x8.