My new cheap hot air soldering station arrived, along with some solder paste that turned out to be leaded (I forgot to check). Tried it out and holy shit it's like magic! This is a game changer for micro USB connectors.

I tried it out on a pointing stick PCB and it's a big improvement over my dodgy hand soldering. It also saved a board I had written off because it was too much of a pain to fix the USB connector.

Mutilating a keyboard and keycaps for the next prototype on the pointing stick project.

Drilling a hole for the pointing stick only cut 2 traces so it should be easy enough to fix with a couple of mod wires.

Made a bit more progress on the pointing stick project before I realised I only have one strain gauge left. I did order more but the order got cancelled.

The mod wires went fairly smoothly, although I still hate stripping magnet wire. Haven't checked that they work - that would be a good idea because this mod is likely to be permanently glued on. Perhaps I should use hot glue to be safe.

I also printed and heavily ground away at a new mount for strain gauges.

Major progress on the pointing stick project today! I actually managed to build it into a keyboard!

Started by redesigning the strain gauge mount to clear the keycaps, then printed and assembled it. That went smoothly but took a while.

It turned out the keys I bought are plate mount so they lack the little pegs that go into the PCB! But they'll do - this is just a prototype, the keys aren't the important thing here.

Initial testing feels good but it's late so I'll try it tomorrow!

Unfortunately I found out that there's something wrong with the pointing stick board I soldered with the hot air station. I can't burn the Arduino bootloader on it with a setup that works for the first one I put together. Can't see anything wrong with it, so it might just be that I killed the chip while soldering it :(

Programmed some keys on my keyboard to be mouse buttons and the pointing stick is now usable!

It's a little bit too high - I keep hitting it while typing H and I just found out that I type B with my right hand instead of my left. It would be easier not to hit it if the keyboard had a slight split.

With this longer stem on the pointing stick I am noticing drift starting to happen. That gives me a reason to look at correcting it.

Today I'll design a little nub for the top of the stick!

I'm still working on the code for the pointing stick, but it looks like I've managed to (physically) break the Y-axis. That was the one with a dodgy strain gauge that I just put some hot glue over.

Hopefully if I lift off the pads I can just glue another gauge on top and not lose too much sensitivity.

Turns out the strain gauge I replaced probably wasn't the one that had an intermittent connection - replacing the top gauge in the photo didn't fix the problem of the pointer jumping around.

If you look closely you can see the bottom one's left contact has broken off after I poked it.

Basically these strain gauges are not something that'll work for a device in production. The gauges themselves are fine, but the heat of soldering messes with the pads and it's a fiddly manual process.

@yngmar Probably, yeah! I think the extra height that would add might be a bit annoying, and it seems odd for something that should be permanent. I'd rather find something I can surface mount on a PCB that acts as a strain gauge when it's stretched

@gbrnt I mean something like this (random pic off images search that illustrates what I mean):

I expect there is some flexing going on so these might last better than soldered contacts?


@yngmar Hmmm, this might be a good step in between what I have now and integrating the strain gauges onto the PCB. I'm still not a fan of manually gluing the strain gauges in place, but spring fingers would at least take the pain out of connecting to them!

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