TechyMagThings

The RepRapMicron (also µRepRap) is pretty much the microscopic take on what RepRap did for more macroscale manufacturing, with the most recent innovation being a UV print head, called the PIKA UV Head. What this does is use off-the-shelf optical fiber and UV LED modules to create 3D structures in-situ in a UV resin, allowing for pretty small structures to be printed, down to a resolution of about 9 µm.

More photos of prints can be found on the blog page with links to YouTube videos. It’s naturally somewhat tricky to get clean photographs of a 3D print that’s small enough to lose forever if you so much as sneeze or breathe too loudly.

For the UV head assembly a single mode fiber optical cable was used in the form of a regular patch cord that got trimmed a bit with a hacksaw. This was used in combination with a “3W” UV LED module, which may or may not be its true rating, but it was definitely able to cure the SLA resin. The used resin was regular eSun Standard Resin.

Afterwards you have to do the typical SLA post-processing, including cleaning off of liquid resin – both the part and fiber – and curing the part. So far results are pretty decent, with overhangs still being a weak spot that will be addressed in future revisions.

Anyone who’s ever built their own motors knows how tedious winding the coils soon becomes; in [Larry]’s case, the issue was even worse. He’s building his own flip-dot matrix display, and each dot uses two electromagnetic coils to flip a magnet in the dot. Rather than wind each of these by hand, therefore, he built his own coil-winding machine.

The coil winder uses two stepper motors: one to wind wire onto the bobbin, and one to move the wire guide carriage back and forth, distributing the wire evenly across the bobbin. The bobbin is held in place by a retainer, which doubles as a tie point for the end of the wire. The spool of wire rotates on a pair of bearings, and the wire is fed between two pieces of foam to provide adjustable tension. The housing is mostly 3D-printed, with some metal rods, bearings, and belt drives fleshing out the structure. On the electronics side, a Teensy controls the winder, with an OLED display and a rotary encoder for control. Before beginning on a coil, it homes the guide carriage against an end-stop switch, then winds on layers, keeping track of the number of layers applied.

We’ve seen a few coil winders here in the past, including a 3D printer adapted to winding stators. For more on this winder’s application, check out [Larry]’s flip-dot design.

The Chinese had been using large crossbows – akin to Greek and Roman ballistae – for warfare for many of the same reasons that European armies loved them. Their single, large arrow was effectively unstoppable, though this also was rather useless against large groups of infantry unless they were so kind to neatly line up. Old Chinese records mention a special kind of ammunition, called a cup arrow, or ‘storm of crows’, which involves launching many smaller arrows instead of a single large one, a feat that [Tod] really wanted to try and recreate.

In itself this doesn’t sound too complex: just grab some arrows, loosely tie them together in a bundle and slap them on the crossbow. Yet with the immense forces applied on this bundle it clearly turns out that the engineering challenge isn’t quite that straightforward, as the arrows love to scatter wildly in all directions or otherwise be rather unpredictable.

Although we can find historical references to multiple bolt siege crossbows being used, details are sparse on how the Chinese engineers addressed these aforementioned issues, so [Tod] tries a range of approaches to try and make it work on his own siege crossbow. Unfortunately he wasn’t able to make it work reliably, but he says he’ll be back with a range of improvements, with the community invited to pitch in their own ideas.

These type of weapons were very commonly used in China and surrounding nations from hundreds of years BCE to around the 16th century CE, when black powder was used to launch projectiles like fire arrows from a Huo Che or the Korean equivalent of the Hwacha, effectively multiple rocket launchers, not unlike the MLRS units seen in militaries today.

The Philips CD-i is a console with many shortcomings, and those include the power supply. For whatever reason, the engineering team decided it should use an 8P8C connector just like Ethernet. Thus, just like your Ethernet cables, it has that annoying problem of the tab snapping off all the time. [MattKC] wondered if the CD-i could benefit from a USB power upgrade instead, and set about making it a reality.

The plan was simple enough—get the CD-i running off of USB-C instead of the ungainly original power supply that shipped with the unit. Given the console runs almost exclusively off of 5 V power, it should have been pretty easy. Only, the original spec adds one little detail that makes things a bit harder. The console is designed to draw up to 3 A from the 5 V line, while also having a -5 V line at 0.2 A. If not for that negative supply, it would have been easy to run the unit off any old 15 W USB-C charger spitting out 5 V. That extra negative line complicates things, because while the negative line could be created with some supporting electronics, it’s hard to find that extra watt from most chargers. While there are plenty of higher-wattage USB-C chargers, the majority tend to use higher voltages to deliver the additional power, capping the 5 V output at 3 amps.

Thus, it was necessary to work a little harder. [MattKC] decided to build a board that would negotiate with a USB-C charger for 9 V operation to get the power budget necessary. This would then be stepped down to 5 V, while there would also be an inversion step to supply the -5 V line, too. A CH221K chip does the job of negotiating a 9 V USB-C power supply, while a TPSM84538 steps the voltage down to 5 V with the capacity to supply up to 5 A. An LT3580 chip then inverts this voltage for the 5 V line. There’s also a power switching circuit on board because the CD-i included some of that functionality in the original power brick.

If you’ve got a CD-i and you’re sick of fussing with the original power supply, this could be a great upgrade. We’ve also explored USB Power Delivery in detail before, if you need a primer.

One of the major limits of mass-produced batteries is the electrolyte. From lead-acid to lithium ion, there’s some temperature where the electrolyte will freeze and cause all sorts of problems, from cracked casings to various non-favorable chemical changes in the battery itself. But if there’ a solid electrolyte available, many of the downsides of charging and discharging batteries in extreme cold disappear. These batteries developed by NASA, for example, can survive some wild temperature swings.

The electrolytes used for these batteries are either a ceramic or polymer electrolyte, both of which are solid. In testing, the batteries could meaningfully operate at temperatures of -60° C and up to 80° C on the high end. Further, the solid electrolyte helps protect them even outside of these temperature ranges. Bringing the battery temperature down to -170° C was not enough to damage the battery at all, and using a small heater to bring the temperature back up to its operating range showed no capacity losses or other issues.

These batteries are eventually intended for use in some of the coldest places outside of Earth still accessible to humans (in theory) such as the south pole of the Moon where the temperatures regularly get that cold and stay cold for long periods, especially in permanently-shadowed craters or places on the Moon we might want to put some telescopes eventually. There are other terrestrial situations where these batteries might be useful as well, since they don’t need as much thermal management as other battery types.

For as many sensors, cameras, and computers as there are on modern cars, they ought to be a dream to poke around in and customize to one’s liking. Unfortunately they’re generally plagued by the same locked-down, proprietary software that most consumer electronics ship with, making it very difficult to interact with these systems in ways the manufacturer doesn’t approve of. There are a few exceptions to this rule, though, and [Sasha] built this system which backs up the footage from their electric car’s on-board cameras automatically to a NAS.

The system is built around a Raspberry Pi Zero 2 W which plugs directly into a USB port in the car’s glovebox. To set it up, the software only needs to be flashed onto the Pi and then it can be controlled from a smartphone. It can connect to any NAS over a variety of protocols and keeps track of what footage has been backed up, and can even automatically restart a backup if the car drives away before it has completed. It also automatically frees up space on the car’s internal drives by deleting any files that have already been synced to the NAS. All of the data is kept in the user’s control as well, and nothing leaves the LAN unless the user sets up backups to a cloud service on their own.

If you have the correct electric car and a Pi other than a Zero 2 W, [Sasha] also has a package for other Raspberry Pis that should work. Unfortunately this was designed for a specific electric car; other makes and models won’t work with this out of the box, but we hope that won’t stop others from checking out the GitHub page anyway trying to figure out what’s going on under the hoods of their car’s electrical and computer systems. Sometimes this leads to things you might not expect, like using the car itself as a video game controller.

If you’ve ever pulled apart a set of digital calipers, you’ve probably marvelled at the capacitive encoder that does all the measuring work. There’s nothing stopping you from using the same techniques yourself, as [Nick] demonstrates with an open-source capacitive encoder of his own design.

The sensor PCB works by by having a grid of eight transmitting antennas, etched into a PCB, beneath a larger receiving antenna. The transmitting antennas pulse out a pattern as the sensor PCB moves, with the signals bouncing back from the reflector PCB which is fixed in place. The varying capacitance caused by the position of the reflector elements relative to the sensor PCB varies the strength of the pulses hitting the receiving antenna. A microcontroller—in this case an STM32—can read those pulses to determine the displacement of the sensor PCB relative to the reflector down to a very fine degree. In this case, to an accuracy of 40 micrometers. Not bad!

If you need ultra-fine linear tracking for something you’re building, you might find this project very useful. Files are available on Github for the curious, along with a great explainer on exactly how the capacitive coupling becomes a positional reading. You can also study previous teardowns we’ve featured on cheap digital calipers, just to round out your education further. If you’re working on your own impressive workshop equipment, or subcomponents of such things therein, don’t hesitate to let us know on the tipsline!