Isomorphic keyboard

[Patrik Lindholm]

Hello! I saw this keyboard: http://wiki.lvl1.org/Isomorphic_Keyboard
I'm interested in building something similar, but currently I don't have much knowledge about this subject, so I'd like to know
if it's possible to get more information on this keyboard; what components were used, how the PCB was designed, how the keys were made,
the dimensions of the keys ect. That would be very helpful for me to get started!

Thanks in advance :)

[Nathan Armentrout]

Replied privately.

[Tim Gillespie]

The bottom of the keys were CNC milled from 12mm black acrylic sheet, the edges of the top side were rounded off using a standard router with a roundover bit and a jig, a dimple was added to the center of the key using a cove bit for a router and another jig.  The keys were then spray painted.

I think I had a DXF of the keys and gerber files for the PCBs, if I can dig them up I'll add them to the wiki

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[Patrik Lindholm]

Awesome, thank you :) So they are 12mm in "height" then, do you know the width/radius of the buttons? Do you remember what kind of tactile button was used for the velocity sensing? And what type of Cherry switch was used? I was thinking about using Cherry brown, but I'm not sure which one would be ideal for this purpose.

It would be awesome to see more videos of the final version. :) I've found only one video so far:
https://firstbuild.com/blog/post/maker-monday-playing-a-honeycomb/71/

The buttons doesn't seem to be very loud. Does the tactile buttons affect the feeling of each key in some way,
like can you sense an extra bump when the tactile button is pressed?

Cheers!

[Tim Gillespie]

The switch details are at the bottom of the wiki:

Tactile Switch: Panasonic EVQ-Q2B03W

Cherry Switch: MX1A-11

You definitely want to use a Cherry switch without tactile feedback (we used black), because that feedback will happen before the switch bottoms out and the switch needs to bottom out in order to press the 2nd switch.

We chose the tactile switch to have an activation force as low as possible so that it would minimize the feel of the extra bump when it bottoms out.  You can feel it if you are thinking about it, but it isn't very noticable, we also were able to reduce it by adding small discs of self adhesive silicone sheet to the top of the tactile switch.

[Patrik Lindholm]

Awesome! Good information :) Thanks! What about the width of the buttons?

I'm thinking about the possibility to hand wire it, instead of using PCBs, because I know nothing about PCBs.
I guess you guys had that knowledge. Do you think it's possible to hand wire, or would you recommend using PCBs anyway? I'm going to have around 350 buttons, and perhaps some extra sliders and stuff. Still haven't decided on what board to use.

Cheers!

[Christopher Cprek]

Hand-wiring is probably not an option. 

The tactile switches are SMD components and, more importantly, require consistent distance and placement above the Cherry switch. Otherwise the code for velocity sensitive timing won't work correctly. If the distance is off by even 1mm, it'll make each key have wildly different MIDI note velocities for the same strike force.. if it even strikes at all.. Using two PCBs, we could add in washers as spacers to get the right distance between the board and keep it consistent. 

Trick is, with 350 keys, your boards will have to be huge. With 192 keys, our boards were about 2 x 1.5 feet. You'd want to do boards in modular blocks. I think we would have done the same in hindsight. The trickiest part of that will be keeping the layout compact, while still having room for headers to interconnect. But the benefit is that if you are new to PCBs, a small modular board will be great for learning and the layout is a fairly simple matrix.

Best of luck!

Cheers!

[Patrik Lindholm]

That's probably true, if there were difference in distances between the cherry and tactile button then it would require calibration in the software in order to have the same MIDI velocities.

Actually, my design has 310, I counted again. :) Yes, I could probably make them modular, but I wouldn't mind having just 2 PCBs like you have. It would probably be 3 by 1,75 feet then.

Here's my layout: http://i64.tinypic.com/w7obqe.png

Are there any limitation on how many buttons can be registered/played at once in your design/PCB?

So if I'm going to go for the PCB approach, is there any PCB designing programs that you can recommend? It looks like your PCBs are designed for Cherry switches?

The wiring and the various components looks quite complex, I have no idea what's going on there, or how to connect it to an Arduino or whatever board I will use. :) I'm not into electronics at all, I just want this instrument!

What can you tell me about the manufacturing of the hexagonal buttons? They look really cool! I was thinking about 3D-printing, but perhaps there are other ways. A 3D-printed key wouldn't have such a smooth surface I guess.

Thank you alot for your answer, looking forward to your next one :)

Cheers!

[Brad Luyster]

Another thing to keep in mind, a lot of PCB houses have panel size limits right around 24" x 18" :-)

[Tim Gillespie]

I added a couple photos so the wiki of my finished unit

[Patrik Lindholm]

Very beautiful. :) You made a very good job indeed!

About the bottom PCB, did they also mount the tactile switches for you?

[Patrik Lindholm]

New image url: https://i.imgsafe.org/9b1ae9b.png

[Patrik Lindholm]

Hello again! Did you find your PCB files? :) Would be very helpful to have a look at those! I've found some footprints for cherry keys and stuff, but not for the tactile switches. And by looking at your files I would understand better how to connect everything!

Thanks in advance!
Patrik

[Tim Gillespie]

I have attached a Zip of the gerbers for the boards we ordered.  I will warn you, I think there are a couple mistakes that we had to rework.   The worst one was that soldermask was covering the pads for the tact switches, so don't order any PCBs of these gerbers without modifying the soldermask, but should be fine for a reference

[Patrik Lindholm]

Thank you so much! :) This will be really helpful! So this design allows all of the keys to be registered at the same time, or is there any maximum key press number?

I will only use this as a reference since I have another layout in mind: https://i.imgsafe.org/9b1ae9b.png

I reckon it might be difficult to make it modular, since there's wires and stuff going around the keys everywhere.