Here's a few generations of the hybrid switch design. The latest design adds a slope, so that the capacitive sensing copper tape is parallel to the tape you touch, when the switch is closed. I haven't tested it yet, but it should make it more sensitive.

These new thinner silicone o-rings are much better for the return spring. It's enough to pull the button back up, but provides a lot less resistance to pushing the button down.

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I'm updating the Ploopy BTU mod for the new design with a larger ball, and Rhino has decided to cause me pain.

This little pink circle means there's an extremely tiny edge in the model that's only connected to one surface. I've tried rebuilding all the surfaces except the complicated one which makes up the whole top of the trackball. Obviously I'm trying to avoid that, but the naked edge is still there after rebuilding them.

The shoulder pain from my first dose of the vaccine is subsiding now after the second day. It was never bad enough to stop me doing stuff, so that's nice! This first dose has felt pretty much like any flu jab I've had.

To keep my arm moving we did some desk shuffling! My partner had a huge new (second hand) desk so I got the old one. Lots of (bad) cable management!

I'm getting the hang of FreeCAD's Link functionality - here's the finger buttons mount with the new hybrid buttons linked in. It's not yet set up as a proper assembly with mates - they're just positioned by coordinates.

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Got myself a mini scanner for sketches, a Fujitsu S1100i. It's pretty neat! Works on linux after downloading a SANE driver for the S1100 and renaming it. It'll take a while to figure out the best settings for sketches, though.

It's been a while since I attempted digital sketch rendering, so I drew up some form ideas for the electro-sax on paper, then took a photo and added colours in Krita.

It took a very long time - I need lots of practice!

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The new button design works just as well! The feel is definitely better, although I still need to make some adjustments as my tolerances were too loose.

I might also tweak it so that it's angled slightly upward by default instead of being flat. The 6mm travel is maaaybe a little more than is needed to feel right, too. I might bring it down to 5mm just to reduce the height.

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I improved the hybrid button design a little. The return stop now doesn't push into the case, which should remove the rubbing against layer lines that I was feeling.

It's also got a longer travel, which should be closer to a real sax (that may or may not be a good thing).

Time to print it and find out what's wrong with it!

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First attempt at a hybrid button for the electro-sax: It feels pretty nice! It'll be closer to a real sax in that the activation is at the end, when the valve finally closes.

This is a mod of the microswitch design to add nice surfaces for copper tape. The Teensy capacitively senses on the bottom part, and your finger makes contact with the top part.

It can actually sense whether you're touching as well as whether you've pressed, which might be handy!

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It was hard to tell from small test sections whether the microswitch-based buttons actually felt good for the electro-sax. So I put together another cardboard prototype!

The verdict: Once they're mounted on an echoey box, these keys are way too clicky. Like distractingly clicky. It's also not nice having the activation at the start of the stroke. On a real sax it's mostly at the end.

Also black was not a good filament colour choice for parts I actually want to take photos of.

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Recompiling FreeCAD got it working again. Here's a cross-section of the button holder design. The pink and green parts are printed in one go, the grey part is the microswitch.

There are a few issues with this design. It's a little scratchy where the layer lines of the two parts rub together, and it varies from print to print.

The microswitch is mounted to stripboard glued to the bottom, which is not great because the glue is all that stops it falling off. Ideally it would be held by some plastic.

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Nice to see my CPU actually being fully utilised for once (I don't compile things very often)

I'm not convinced by the touch buttons on the electro-sax, and I had a few microswitches laying around, so what about using those for the keys?

I 3D printed some little button assemblies and a frame to hold 4 of them in place. I didn't try a print-in-place pivot on the buttons - instead there's a hole to insert a small bit of filament.

The action of the switches is quite smooth, and maybe low enough pressure to be usable. It's worth a try.

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It didn't take long to build a touch-sensitive version of the electro-sax! This is definitely nicer to build than soldering a key matrix with diodes, but the analog sensors aren't quite as nice to deal with on the code side.

The key thing is that it works! I'm not actually sure whether I prefer the buttons or the capacitive sensors. I need to tweak the sensor calibration a bit before I'll be able to tell.

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A bit more playing around with touch sensing on the Teensy. It's a little stripboard keyboard which can only play a C arpeggio! It only uses one touch sensing pin along with a 4067 analog multiplexer to get 16 touch inputs.

That's enough for all the keys currently on the electro-sax, plus two more octave keys and... I dunno, two more to do something.

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Taking a break from breath sensing to try out the Teensy. The built in touch sensing is very neat!

I might use this with an analog multiplexer to make a touch-sensitive version of the electro-sax

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Maybe this is the cause - the response is really non-linear. It jumps very slightly above the 0 point, then sits level as I keep blowing more, then suddenly jumps up before increasing linearly.

The other graph is me playing a piece - it looks alright to be honest, so maybe it's not the non-linearity, it's something in my program?

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