Mysterious Files PH

When mass-printed holograms appeared on magazines in the 1980s they were a huge novelty, before degrading to the level of kids’ stickers in the years since. At the time they were seen as not for ordinary people to make, but the truth is they can be created without lasers or an optics lab. [Jordan Matelsky] is here to show us how they can be made using as humble a device as a pen plotter.

The effect of an interference pattern from a set of fine lines in a thin film can be demonstrated at its simplest with an oily finger and a mobile phone screen, and once he’s demonstrated that he takes us through some of the theory involved in shifting the light to make an image. There are some false starts with different materials, but eventually he shows us some finished holograms scribed on the polycarbonate of a CD case. It seems you really can make a hologram with a pen plotter. If these images interest you, we’ve looked deeper into the subject in the past. Meanwhile, one of the plotter-scribed holograms can be seen below.

One of the great things of Linux as an ecosystem is that there is so much choice. Yet this is also its greatest weakness, as unlike on MacOS and Windows this means that simple questions often do not have a simple answer. The topic of distributing software is one of these vexing topics that never really goes away, with [Noam Lewis], as author of the Fresh editor, recently expressing their frustrations on this topic.

This is a familiar topic that we have covered before, mostly in the context of cross-platform installers. Whereas on MacOS and Windows you just pick any of a handful of standard installer frameworks that do roughly the same thing, on Linux you are dealing with a dizzying number of package managers, including distro-specific ones, NPM, Homebrew, Rust crates, third party repositories like Arch Linux’s AUR or stray APT repositories for Debian, and of course AppImage and Flatpak along with a host of other options.

After going through the entire list with help from the Fresh community, [Noam] ended up creating packages for all of them, and has a lot of thoughts. Since Fresh is a TUI-based editor, something like Flatpack is not a really good fit, while AppImage is just very slow due to mounting the image, which is annoying.

Overall, distro-specific solutions are just unpleasant in general, as they mean repeating the same work over and over, even if you can even get into a distribution channel. Ultimately the solution that [Noam] ended up at was to have a static binary with the musl runtime, along with an integrated updater, which is a solution that should be quite familiar for Windows users. Yet even if it fails some kind of purity test for certain Linux users, is it really a bad solution if it works for users of the software?

Now that MCUs like the ESP32-S3 are quite capable computer systems including USB host functionality, it only makes sense that you can connect USB peripherals like Logitech racing wheels to them. Of course, these aren’t basic HID USB devices, so they require a bit of setup to make them start spitting out the data updates which we’re interested in. Making this process easy is the goal of the LogiWheelHost project for ESP32-S3 by [Joel Kometz].

This single-header library supports the G29, G923, G920, G27, G25, DFGT, Driving Force Pro wheels, building on top of the EspUsbHost project. As explained in the README, these racing wheels do not start streaming all updates to their controls once powered on, but boot into a restricted mode in which only neutral or combined-axis data is sent.

To change this you need to trigger the so-called native mode switch in which far more detailed information as well as updates on extended features like separate pedals, all buttons and the gear shifter become available. This is done by sending a HID output report to the USB device, which is easy enough.

In addition to handling this detail the library also provides an API using which obtaining and using these controller states in your own code should be quite easy. Presumably the library will work on or can be ported to other ESP32 MCUs that support host USB mode, so this might be good news for anyone who is looking to do more with that old Logitech racing wheel.

A few weeks ago, we put out the call for participation for this year’s 2026 Hackaday Supercon, taking place in Pasadena, CA this November. Today was going to be the deadline, but like you, we often let things pile up and put things off, so we’re extending another two weeks until August 26th.

Which is not to say that we haven’t heard from a ton of you! We’re psyched to see so many familiar Supercon regulars on the list, but we also love to see first-timers give talks. We try to make sure that new folks get their time to shine, so if you’ve never given a Supercon talk before, or if it’s been a few years, take this as your cue to present in front of the friendliest audience of like-minded hackers around.

This year is Hackaday’s tenth in-person Superconference, and to celebrate we’ve gotten a larger venue, so more folks can watch the talks live. We’ll be running two tracks as always, and you have your choice of a 20-minute or 40-minute slot. Presenters get in free, and we’ll get you an early-bird ticket rate the submission, so don’t delay and register for your slot today! Or at least before August 26th, because we won’t extend the deadline twice.

Oh, and if you’re interested in tickets, swing by Hackaday about this time tomorrow — we’ll have some news for you.

In a few hours, there is a solar eclipse that will be visible with a track that goes from Spain up through Greenland. Too late to travel for it, but thanks to [jonty], you can find all the webcams that will have a view.

This may be ideal. No funny glasses. No looking at a projected image on a card. Of course, many, if not all, of these cameras aren’t looking directly at the sun, so it isn’t clear if you’ll be able to see the actual eclipse or just the effect it has on the surroundings.

If you prefer more science, try the NASA feed below.

Or, you could see what ESA is broadcasting from Javalambre, Spain:

Or, try the telescope view version:

Want to know what it might look like from a particular spot? Harvard has you covered. If you want to feel more realistic, try wearing some regular sunglasses while watching just for the fun of it.

We wish we could watch our eclipses from the lunar surface. Of course, you can always make your own eclipse.

It’s no real secret that battery packs for power tools aren’t the foremost when it comes to user serviceability, so if said battery pack suddenly stops charging outside of warranty, you generally just e-waste it. That’s what [The Repair Forge] could have done for the Makita battery pack in question, but instead it was opened up for a diagnosis and fix.

Rather than the charger throwing up an error with this specific battery, it would flash its red LED and run its fan, but never actually start the charging process. Apparently the charger seems to think that the battery is either too hot or cold to be charged, which already gives a big hint as to what might be wrong.

Using the open source PocketOBI tool it’s possible to query the battery, which showed that one of the internal thermistors reported the battery being at a chilly -30°C while the other a more reasonable 28°C. After popping open the pack and measuring the thermistors, the faulty one registered as infinite resistance thus confirming that it had failed.

By putting in a temporary resistor this diagnosis was confirmed, thus the next step will be to replace said thermistor. This same procedure was then used with a second battery, whose thermistor read a wild 64°C.

Overall it’s a pretty easy fix, using a 20 cent part, with the entirety of diagnosis to repair taking maybe ten minutes when using a tool like PocketOBI, itself based on the great Open Battery Information project that originally reverse-engineered the Makita battery protocol.

Gears are usually the biggest contributors to backlash in a mechanical system, but they’re far from the only culprits. Ball bearings are a less obvious source of imprecision, since any gaps between the balls and the races can lead to axial wobble. Precision mechanisms can eliminate this by pairing two ball bearings, holding the outer races fixed, and applying a preload force to the inner traces. [Chronova Engineering], however, has a different solution, for which he split a ball bearing in half.

Besides taking up more room, thermal expansion also means that it’s difficult to apply a consistent preload force between two ball bearings. Instead, to make a self-contained preloaded bearing, [Chronova Engineering] first disassembled a single ball bearing. The most difficult part of this is taking apart the ball cage; the two parts of this are normally riveted together, but he managed to find a crimped cage and pry it apart. After taking the bearing completely apart, he cut the outer trace in half along the circumference, then reassembled the bearing. The split outer trace makes it possible to press the two halves together, preloading it and removing slop.

To see how well this worked, [Chronova Engineering] replaced the the ball bearing supporting one end of the feed screw for a milling machine with this new bearing. Before the replacement, it had a backlash of 0.1 to 0.2 millimeters; after the modification, it dropped to 30 to 40 microns. This kind of bearing is already known in the machining world – four-point-contact bearings use a very similar principle – but they don’t seem to be well known.

For more about these common yet remarkable rotary mechanisms, check out our article on bearings. If, on the other hard, precision isn’t a priority, you can always 3D print ball bearings.