@FreeCAD Mechanical logic gates for hands on learning during the Great American Teach In.

@FreeCAD I've been busy in #FreeCAD making design after design for a DIY remotely operable variable capacitors with an eye to designing something that is easy and reasonably inexpensive for anyone to make. I think I'm getting close to something I'm satisfied with. Most people don't need this, but it's actually pretty useful in #HamRadio. Hams tend to scrounge for large variable capacitors and then bend their designs to fit whatever they can turn up; this is parametric so a ham can choose desired parameters, get some PCBs printed, buy some common parts, 3d print a few others, and have a working butterfly capacitor.The trickiest part will probably be the workflow from FreeCAD design into #KiCAD to create the gerbers to send off to make the PCBs. That will take some manual work for anyone who wants to change the design parameters, beyond just changing some numbers in a VarSet.This is about 120mm on a side. It uses printed PCBs for the fixed capacitor plates, PTFE film for the dielectric, and laser-cut copper for the rotors. A 3d-printed 60-tooth GT2 pulley for the effector (don't want metal there; it will change the behavior of the capacitor!) and a 16-tooth pulley on a nema17 pancake stepper to drive it. I haven't modeled the belt, but that's kind of the trivial part to imagine, I hope!

@FreeCAD Finally printing at least the first iteration of my solar charge control and battery power distribution box for #HamRadio POTA that I shared early versions of last week and have been tweaking in FreeCAD on and off in the meantime.Two battery busses, each with both an XT60M and PowerPole connection. Each bus is intended for only one battery, though.One XT60M connector for a solar panel connected to a charger, which can be connected to either battery bus or disconnected. The solar charger has a USB-A output as well. A relay (internal, not visible in this model) protects the solar charger from being connected to the solar panel unless it is connected to one of the battery busses.Two device buses, each with three fuses protecting five device power ports, for a total of eight XT60F and two PowerPole connections.One 65W USB-C PD converter with a USB-A socket that can charge a laptop.Each device bus and the USB-C converter can be independently switched between the two battery busses or disconnected entirely.Not part of this box, but the solar panel also has USB-A and USB-C power supplies built in.The design was exploratory and is not the cleanest or more parsimonious or highest-performing modeling, but such as it is, it is available at https://gitlab.com/mcdanlj/SolarPowerBoxI can't imagine anyone else wants to make this, and the planned schematic is not drawn let alone shared, but some of the parts might be useful. I did make them in a dev build of FreeCAD, so they are untested in the stable 1.0.1 release.

I came up with a layout for my solar charge controller power distribution box that I think will work.This is ridiculously over-complicated. Two battery busses, two appliance busses (each with two XT60 and one PowerPole) that can be switched between the battery busses, the solar controller can be switched between battery busses, and even a USB-C PD adapter that will boost the 12V nominal batteries up to 20V at 65W to power a laptop, and can also be switched between battery busses. There's room in here for filters, too; I plan common-mode chokes on both sets of connections to the solar charge controller, though I haven't modeled them.I'm still trying to decide whether to use the caps on the fuse sockets. Probably not, since this isn't weatherproof anyway due to the opening for the charge controller, and if I don't put caps on the fuses, I think I can mount them so they don't stick as far out of the box, and the fuses will be easier to change. So right now I'm only partway through modeling cutouts in the box.I'm still not 100% certain I really should make this, but... I've already purchased basically all the parts I need, so sunk cost fallacy here I come! Hmm, there's room on the far side to add more XT60 connectors, but I might be running out of fuse sockets!