What's on your workbench today?

Learning and discussion
2892

This was a mostly good experience using v1.1.3. I’m not a particularly sophisticated designer, and among other things I don’t spend nearly enough time properly constraining my sketches, but FreeCAD finally felt like it has most of what I want. Toponaming seems to have been addressed well enough that I didn’t see a need to obsess over manually avoiding it, just making sketches on surfaces like I would in any other app. Then, I rely heavily on projecting features into my sketches as construction lines, and FreeCAD has finally made that intuitive; it was a nice surprise.

There are still some things I ran into on this quick design that I think would have been smoother in the Alibre install that lives on my Windows disk. First, FreeCAD still lags behind on heuristics as to whether and where I want to snap points, but that is exactly the sort of thing that I assume is very expensive to test and decide on, plus actual implementation, so I get it. Next, filleting in 2D is a pain, either imprecise or requiring a tedious use of extra construction lines to set the radius; it’s odd because 3D filleting works completely fine as a UI matter. Finally, I was trying to move a 2D feature, and it broke the parametric history in a way I couldn’t quite figure out, so I just deleted the sketch and re-did it. That last one could have been really bad, but I got lucky.

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2893

Not sure the diode on the clock line will make PS2 work as both the host and device can drive it.

Usually you implement a bidirectional level shifter on both clock and data line, a simple MOSFET with pull-up resistor on both sides.

I am not in front of my computer but can give you a capture of a schematic for a PS2 daughter board I designed if you so desire (tomorrow).

This design has been tested and proven to work in practice(using the same rp2040 as you) :slight_smile:

2894

the MMBasic firmwares are very odd little things. Various comments about them suggested the clock pin was an output pin, but I admit to being poorly educated in this area. What I will say is that it works, tested on both breadboard and soldered protoboard. I understand the main risk is that it will eventually blow the esd protection on one or both GPIO pins. The comments on how 5v-resistant the pins on an RP2040 are have suggested that it’s worse for output pins, hence the diode.

Honestly, this whole thing is an experiment, and if worse comes to worst I’ll get a new MCU and use the proper mosfet or level shifter solution, lol. I could also finally get a 2350 which is properly 5v tolerant and remove the diode altogether. :slightly_smiling_face:

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2895

Oh this is interesting for the output only clock!

If it works in practice for your case then absolutely do not touch it:)

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2896

I believe the lesson here is that electronics are magic and utterly unknowable. :slight_smile:

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2897

Totally agree!

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2898

All done and usable. The case actually fit reasonably well, with two issues. First, I had a brain fart while designing and put the opening for the rp2040’s USB port on the wrong side of the centerline, so I had to nibble away 5mm on the other side. Second, the opening for the microSD doesn’t allow for how deep I soldered it onto the perfboard. I could actually remedy that by desoldering the reader and pushing it out to hang over the edge, but for now a pull tab of masking tape is working. What did work was setting the print to have 4mm thick solid “top” surfaces (file was printed upside down), and then simply drilling out screw holes; very forgiving of any imprecision in design, measurement, or printing, lol.

Speaking of the printer, my first layer was a bit crap, but I realized the filament had snapped beyond the sensor, so I was manually trying to feed it until the gears grabbed the intact length. This project was one I’ve had on my list for a while, but I finally got around to it, and the goal of a working, non-emulated BASIC computer has been satisfied. Don’t ask me why it’s important that it not be emulated; I don’t know.

Keyboard wise, the PS/2 circuitry is still fully operational, somehow, and I remembered that I had an AT board that could be passively converted. TBH the worn out Futabas are never going to compare to a decent buckling spring, though.

Sorry not sorry about the rat’s nest under the monitor. :rofl:

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8 Likes
2899

I am testing Wingtree Puer Tea switches vs. modded Akko Bittersweet.

Using a somewhat resonant metal-cased board with PC plate and dampening.

As with the Transition Lite TKL, the Puer Tea are LOUD.

The Akko Bittersweet are noticeably different.

Bittersweets are using 50 gf 18mm Geon springs, moderately lubed with 3204. They definitely produce a ‘woody’ tone, relative to other switches.

The Bittersweets are deeper, flatter, bassier, and quieter than the Puer Tea. The Puer Tea are loud, clacky, and brighter than the Akko Bittersweet.

I would say that the Bittersweets definitely suit this particular keyboard, sound-wise. However, I slightly underestimated the ideal force for 1u keys. Earlier, I said that 50 gf 18mm might be ideal. However, I now suspect that these switches really want 52 - 55 gf 18mm. There’s a bit too much ‘rough’ tactility with the 50 gf, and return is a little subdued. So they’d probably be smoother and punchier with 5-10% heavier springs.

The Puer Tea tested well on my new SMURVE80. They weren’t as loud on a near-stock build, with JTK keycaps. That keyboard isn’t built yet. It’s looking between MX2A Brown and Puer Tea for that one.

(The Puer Tea are an interesting comparison with MX Brown. I’d say that they have bump-strength on par with pre-tooled MX1A Brown. Bump location is slightly different, but it is fairly well-defined. Puer Tea are much smoother, though, with factory 205g0. Not much scratch or leaf noise. But they may have less character on most builds than MX1A. I think that HMX and Wingtree switches ‘want’ “modern” builds, using gasket or O-ring mounts and dampening.)

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