MIDI concertina keyboard: button boards arrived

[caj]

I've been taking a cheap-and-fast MIDI concertina project and gradually improving it.  Previously I 3d-printed a homebrew position sensor for the bellows, which seemed to work well.

 

Now, for the buttons.  The current box uses a 5x6 ortho keypad from Adafruit, which is really cool but hard to play:  firstly because the buttons are in a rectilinear grid, second because they are spaced apart about 2cm center-to-center (see picture.)  I like the performance of the cherry key switches, however, so I fabbed up a PCB to hold a bunch of keys in a more appropriate concertina layout.  The boards just arrived from JLCPCB (other picture.)

 

The keys in each column are now 1.5cm center to center, and the same between columns (and I can bring the columns closer together by 1mm.)  That's still a tiny bit wider than my Crabb, but this allows me to use cherry switches.  As a project, it means that a hobbyist can upload the files to JLCPCB to get them in the mail a week later, and buy the switches, and only a bit of soldering is required.

 

I'll be installing the parts over the next week, pretty much as they arrive.  The board has the traces for reading the buttons so there will be fewer wires to pop out and it will look less like a science project.  I also opted for a key footprint to solder the keys down directly, rather than soldering in sockets for hot-swappable switches.  It only took a little playing to realize that the key switches are best held down securely.

 

 

 

[SIMON GABRIELOW]

Looks very scientific indeed🌝

[Richard Mellish]

For my MIDI concertina project I decided that the buttons had to be in the same positions as on my real concertinas. Cherry switches are too big for that spacing so I ordered some from Mouser Electronics, https://www.mouser.co.uk/ProductDetail/688-SKHHBW which are 6 mm square with buttons 3.4 mm diameter.

The operating force is 1.6 N, and in use I have found them a bit uncomfortable so I am considering replacing them by a version with lighter operating force and/or fitting them with caps of larger diameter.