Korg NanoKontrol DIY Modification Question

[JimJhn]

I am going to take the guts of a Korg NanoKontrol and turn it into the brains of a custom midi-controller interface.

My plan is to use it as a machine-room brain with lots of RJ45 or 1/4" or 1/8" jacks, then attach pedals, small fader controllers, etc. as needed.

Basically just take the slide and rotary pots off of it, as well as the switches (and hopefully LEDs), and connect them to jacks that will plug into footswtiches, pedals, fader boxes, etc. as needed.

It's a nice platform because Korg did a nice job with the editor software to program it, and it gives me 18 possible faders and 18 possible switches (hopefully with LEDs).

I'm just getting started, but one of my first questions is about switches?

I want an 8-switch foot pedal. I can jumper the switches on the circuit board and attach remote momentary switches.

The switches on the circuit board I can jumper, then connect to a remote pedal with 8 momentary spst switches.

Would that mean, though, 16 wires going to the remote switch-pedal?

RJ45 cables have 8 wires, so I guess I could use two RJ45 cables, but could I somehow have all of the switches share the same ground or something, and get away with less cabling?

Thanks!

 

[capacitorless]

I had one of these (albeit the 2nd version) but it's no longer here or I would tear into it. Cool idea!

I would start by measuring the resistance between pads. From here, it looks like the inner set of 'teeth' are connected with a trace at the top. I'm guessing, but it might turn out that one side of the outer pads are all connected to ground (or a supply voltage), and the other sides are individually scanned, so those wires would need to be separate of course. If there's a common ground (or supply), that would reduce those connections down to a single wire. I wonder if the cable's shield could be used for that purpose?

Same with the potentiometers - they all might/should have a common ground and common supply voltage. I would expect the wiper to not be common (scanned using an ADC), but the sides are likely either connected to a common ground, or a common supply voltage.

You might find that all of these controls (pots and switches) share a common ground, for that matter.

Schematics would help, but I would say not mandatory

 

[JimJhn]

Hey thanks or the reply!

I guess I can just try a mock-up of the common ground?

I already have it open, so I can try some tests.

 

[JimJhn]

I just found this schematic of the NanoKontrol;

http://zeninstruments.blogspot.com/2017/09/korg-nanokontrol-schematic-new-firmware.html

 

[capacitorless]

Good find! It looks like the switches might be multiplexed like a musical keyboard, so more complex. Looking at it now.

Edit: no more complex than the way it's usually done nowdays when designing with lots of switches, eg using multiplexers & select lines with diodes. A midi keyboard uses the same tech

 

[capacitorless]

It looks like there's a common connection to each bank of 8 switches, so there's a way to consolidate things. The way it's multiplexed, you'll probably need an rj45 connector per bank of 8, assuming there's a shield available (otherwise, a 9th wire).

The photos of the switch assembly show what looks to be two pairs of pads per switch? If so, I'm guessing that's for operability; the membrane switches on the NanoKontrol 2 were soft (as they usually are) and required a firm press to actuate.

The sliders and pots look normal; they are all supplied by the same Vcc and ground, with each set of 8 wipers going to a multiplexer (there are three select lines at the top right of each mux chip + the output line that goes to an A/D input on the Mega323 chip). The last set of slider/pot wipers go directly to A/D inputs on that Mega323, but look like they also use the same Vcc and ground as the others.

Edit: since the buttons are muxed (constantly getting voltage/no voltage multiple times a second), testing for voltage/ground is going to give funky results Best I think that can be done is to measure for continuity, and use that mapping to figure out what's common (and what isn't) on the board's pads.

Another tack could be to build the board into your footpedal, and run a long usb cable to your system. I don't know the max length offhand, but I do know there are active usb extender cables that give some significant additional length.

 

[JimJhn]

Hi thank you so much for this!

I am going to put it on a table this weekend and test some configurations with the common ground.

I don't really need 8 switches, 7 would be fine really, and then it would all fit on one ethernet cable.

It's just to switch between favorite amp models/settings of the Strymon Iridium to get to them faster.

I have such problems using long USB cables.

Actually problems with USB in general!

I think I've tried every powered-hub on the market, and still regularly have USB problems with all of the peripherals here in both studios.

So ethernet sounds like the way to go.

I was actually looking at the possibility of using HDMI cables in the future, which evidently have 19 pins.

I saw there are HDMI terminal-block breakouts. That and RJ45 are both common enough, cheap, and have allot of pins.

But back to this...thanks so much for looking at the schematic. I don't know how to read them yet...trying to learn, so I really appreciate it!

 

[capacitorless]

All good. I'm a rank newbie relative to the serious genius that is here

The switch multiplexing technique isn't friendly to the typical newbie The pots are more straightforward though. All just fyi.

 

[JimJhn]

Thanks for that!

I'm trying to get my head around the idea of multiplexing!

I'm going to try some combos with the NanoKontrol tomorrow.

It's not like I'll blow something up or anything (at least I hope not!).

I do wish I was doing this to a NanoKontrol 2 instead of the original one I ave here.

The Mk 2s evidently will do Mackie Control, so I could do a lighted punch in/out switch with one.

I have been able to get a button to toggle record with the LED working, but you have to make sure the light is off at the start of a session. It doesn't know if you are in record or not, it just toggles the LED every time you hit the button.

 

[capacitorless]

I'll be doing something similar to a Line6 FBV Shortboard. Same thing (kinda) - the MkII unit does do midi, original unit does not, which is what I have. The original design has better footswitches, and it was really cheap (it came in a pile of other stuff for like $35 plus the cost of driving) in unknown condition. I'll be converting it to midi and probably fitting a modern OLED screen in it, and using it as a stage controller. A project for another day - I'm way way behind in some other efforts.

I'll likely use a SBC that I have here (Arduino clone) and I'm not sure yet if I'll need to multiplex the switches. If I do I'll either link to a resource I find online, or post a simple writeup here.

In the interim, here's an explanation that drives 16 LEDs:

https://www.instructables.com/Multiplexing-with-Arduino-and-the-74HC595/
Gotta love the internet!

 

[JohnRoberts]

With a VOM you can measure for commonality between the switch footprints. One side of each is probably ground.

JR

 

[JimJhn]

With a VOM you can measure for commonality between the switch footprints. One side of each is probably ground.

JR

Can I ask how I would do that? I do have a multimeter here, but again I'm just learning how to use this stuff. Thanks!

 

[JohnRoberts]

The "O" from VOM is Ohms. On the low Ohms scale measure the resistance between the switch footprints. Footprints that are connected together with PCB copper traces would measure zero ohms, in theory. In practice they will measure more than 0 Ohms, but not much more since the way those switches work is by completing an electrical circuit when shunted by a metal dome switch, or conductive rubber puck from a molded keypad.

JR

 

[capacitorless]

To add to that, if you are brand new to a multimeter, there will be a setting for ohms that may be labeled with an omega symbol. If you touch the two leads together, you'll see something like 0.0 (or 0.1 - the surface of the leads could be a little dirty) on the display. With that knowledge, you can touch one lead to one pad, and the other to another pad, and figure out which ones are directly connected via a pc board trace.

There may be a continuity setting, which might be labeled with a symbol indicating audio; I have a meter somewhere that says "CONT" on it. If you touch the leads together and hear a beep, that would make it easier/quicker to do the mapping.

 

[JohnRoberts]

+1 If your multimeter has an audible continuity test mode that will be easier for tracing out connections since you don't have to watch the meter while probing.

JR

 

[JimJhn]

Hey thank you so much for all of this!

I read all of this, and then looked at some articles on measuring.

I'm still trying to get my head around this, but I think this is the time to actually learn something instead of blowing it off and handing it to someone with a blank look.

 

[JimJhn]

OK I bought a few rj45 terminal-block jacks, and I am going to start down this path. Thanks so much not just for the specific information, but also the general information on electronics. It really is so nice and generous!