The Fascinating Waveguide Technology Inside Meta’s Ray-Ban Display Glasses

October 9, 2025 by 25 Comments
The geometric waveguide glass of the Meta Ray-Ban Display glasses. (Credit iFixit)
The geometric waveguide glass of the Meta Ray-Ban Display glasses. (Credit iFixit)

Recently the avid teardown folk over at iFixit got their paws on Meta’s Ray-Ban Display glasses, for a literal in-depth look at these smart glasses. Along the way they came across the fascinating geometric waveguide technology that makes the floating display feature work so well. There’s also an accompanying video of the entire teardown, for those who enjoy watching a metal box cutter get jammed into plastic.

Overall, these smart glasses can be considered to be somewhat repairable, as you can pry the arms open with a bit of heat. Inside you’ll find the 960 mWh battery and a handful of PCBs, but finding spare parts for anything beyond perhaps the battery will be a challenge. The front part of the glasses contain the antennae and the special lens on the right side that works with the liquid crystal on silicon (LCoS) projector to reflect the image back to your eye.

While LCoS has been used for many years already, including Google Glass, it’s the glass that provides the biggest technological advancement. Instead of the typical diffractive waveguide it uses a geometric reflective waveguide made by Schott, with the technology developed by Lumus for use in augmented reality (AR) applications. This is supposed to offer better optical efficiency, as well as less light leakage into or out of the waveguide.

Although definitely impressive technology, the overall repairability score of these smart glasses is pretty low, and you have to contest with both looking incredibly dorky and some people considering you to be a bit of a glasshole.

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Motors Make The Best Knobs With SimpleFOC

October 9, 2025 by 17 Comments

The worst thing about a volume knob is that, having connected it to a computer, it might be wrong: if you’ve manually altered the volume settings somewhere else, the knob’s reading won’t be correct. [I Got Distracted] has a quick tutorial on YouTube showing how to use a BLDC, a hall effect sensor, Pi Pico and the SimpleFOC library to make a knob with active haptic feedback and positioning.

We covered the SimpleFOC library a few years ago, but in case you missed it, it’s, well, a simple library for FOC on all of our favorite microcontrollers, from Arduino to ESP to Pico. FOC stands for field-oriented control, which is a particular way of providing smooth, precise control to BLDCs. (That’s a BrushLess DC motor, if the slightly-odd acronym is new to you.) [I Got Distracted] explains exactly how that works, and shows us just how simple the SimpleFOC project is to use in this video.  Why, they even produce their own motor controllers, for a fully-integrated experience. (You aren’t restricted to that hardware, but it certainly does make things easy.)

The haptic feedback and self-dialing knob make for an easy introductory project, but seeing how quick it hacks together, you can doubtless think of other possibilities. The SimpleFOC controller used in this video is limited to relatively small motors, but if you want to drive hundreds of kilowatts through open source hardware, we’ve covered that, too.  

Arguably, using a motor as a knob isn’t within the design spec, and so could almost qualify for our ongoing Component Abuse Challenge, had [I Got Distracted] thought to enter.

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2025 Component Abuse Challenge: The Sweet Sound Of A Choking Transformer

October 9, 2025 by 13 Comments

The Component Abuse Challenge is dragging all sorts of old, half-forgotten hacks out of the woodwork, but this has got to be the most vintage: [KenS] started using a transformer as a variable choke on his speakers 55 years ago.

The hack is pretty bone-dead simple. A choke is an inductor in an audio (or any other) circuit designed to, well, choke off higher-than-desired frequencies. We featured a deep dive a few years back if you’re interested. An inductor is a coil of wire, usually (but not necessarily) wound around a core of iron or ferrite. A transformer? Well, that’s also a coil of wire around a core… plus an extra coil of wire. So when [KenS], back in his salad days, had a tweeter that a was a little too tweety, and no proper choke, he grabbed a transformer instead.

This is where inspiration hit: sure, if you leave the second winding open, the transformer acts like a standard choke. What happens if you short that second winding? Well, you dampen the response of the first winding, and it stops choking, to the point that it acts more like a straight wire. What happens if you don’t short the second winding, but don’t leave it wide open? [KenS] stuck a potentiometer on there, and found it made a handy-dandy variable choke with which to perfectly tune the tone response of his speakers. Changing the resistance changes the rate at which high frequencies are choked off, allowing [KenS] to get the perfect frequency response with which to rock out to Simon & Garfunkel, The Carpenters and The Guess Who. (According to the Billboard Top 100 for 1970, those are who you’d be listening to if you had conventional tastes.)

While we can’t say the transformer is really being tortured in this unusual mode, it’s certainly not how it was designed, so would qualify for the “Junk Box Substitutions” category of the Component Abuse Challenge. If you’ve made similar substitutions you’d like to share, don’t wait another 55 years to write them up– the contest closes November 11th.

Transformer image: Hannes Grobe, CC BY-SA 4.0.

2025 Hackaday Component Abuse Challenge

2025 Component Abuse Challenge: Load Cell Anemometer

October 9, 2025 by 22 Comments

When you think anemometer, you probably don’t think “load cell” — but (statistically speaking) you probably don’t live in Hurricane Country, which is hard on wind-speed-measuring-whirligigs. When [BLANCHARD Jordan] got tired of replacing professionally-made meteorological eggbeaters, he decided he needed something without moving parts. Whatever he came up with would probably qualify for the Component Abuse Challenge, but the choice of load cells of all things to measure wind speed? Yeah, that’s not what the manufacturer intended them for.

In retrospect, it’s actually a fairly obvious solution: take a plate of known area, and you’re going to get a specific force at a given air speed. The math isn’t hard, it’s just not how we normally see this particular measurement done. Of course, a single plate would have to be pivoted to face the wind for an accurate reading, which means moving parts– something specifically excluded from the design brief. [Jordan] instead uses a pair of load cells, mounted 90 degrees to one another, for his anemometer. One measures the force in a north-south axis, and the other east-west, allowing him to easily calculate both wind speed and direction. In theory, that is. Unfortunately, he vibe coded the math with ChatGPT, and it looks like it doesn’t track direction all that well. The vibe code runs on an ESP32 is responsible for polling data, tossing outliers, and zeroing out the load cells on the regular.

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Colorful parachutes at different levels of expansion

Holy Parachute Out Of Kirigami

October 9, 2025 by 15 Comments

If you have a fear of heights and find yourself falling out of an airplane, you probably don’t want to look up to find your parachute full of holes. However, if the designer took inspiration from kirigami in the same way researchers have, you may be in better shape than you would think. This is because properly designed kirigami can function as a simple and effective parachute.

Kirigami, for those unfamiliar, is a cousin of origami where, instead of folding, you cut slits into paper. In this case, the paper effectively folds itself after being dropped, which allows the structure to create drag in ways similar to traditional parachute designs. Importantly, however, the stereotypical designs of parachutes have some more severe drawbacks than they appear. Some major issues include more obvious things, such as having to fold and unpack before and after dropping. What may be less obvious are the large eddies that traditional parachutes create or their ease at being disturbed by the surrounding wind.

The kirigami chutes fix these issues while being easier to manufacture and apply. While these are not likely to be quite as effective for human skydiving, more durable applications may benefit. Quoted applications, including drone delivery or disaster relief, worry more about accuracy and scalability rather than the fragile bones of its passenger.

Clever and simple designs are always fun to try to apply to your own projects, so if you want to have your own hand, make sure to check out the paper itself here. For those more interested in clever drone design to take inspiration from, look no further than this maple seed-inspired drone.

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Meshtastic: A Tale Of Two Cities

October 9, 2025 by 76 Comments

If I’m honest with myself, I don’t really need access to an off-grid, fault-tolerant, mesh network like Meshtastic. The weather here in New Jersey isn’t quite so dynamic that there’s any great chance the local infrastructure will be knocked offline, and while I do value my privacy as much as any other self-respecting hacker, there’s nothing in my chats that’s sensitive enough that it needs to be done off the Internet.

But damn it, do I want it. The idea that everyday citizens of all walks of life are organizing and building out their own communications network with DIY hardware and open source software is incredibly exciting to me. It’s like the best parts of a cyberpunk novel, without all the cybernetic implants, pollution, and over-reaching megacorps. Well, we’ve got those last two, but you know what I mean.

Meshtastic maps are never exhaustive, but this gives an idea of node density in Philly versus surrounding area.

Even though I found the Meshtastic concept appealing, my seemingly infinite backlog of projects kept me from getting involved until relatively recently. It wasn’t until I got my hands on the Hacker Pager that my passing interest turned into a full blown obsession. But it’s perhaps not for the reason you might think. Traveling around to different East Coast events with the device in my bag, it would happily chirp away when within range of Philadelphia or New York, but then fall silent again once I got home. While I’d get the occasional notification of a nearby node, my area had nothing like the robust and active mesh networks found in those cities.

Well, they say you should be the change you want to see in the world, so I decided to do something about it. Obviously I wouldn’t be able to build up an entire network by myself, but I figured that if I started standing up some nodes, others might notice and follow suit. It was around this time that Seeed Studio introduced the SenseCAP Solar node, which looked like a good way to get started. So I bought two of them with the idea of putting one on my house and the other on my parent’s place down the shore.

The results weren’t quite what I expected, but it’s certainly been an interesting experience so far, and today I’m even more eager to build up the mesh than I was in the beginning.

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Google Japan Turn Out Another Keyboard, And It’s A Dial

October 9, 2025 by 20 Comments

There’s a joke that does the rounds, about a teenager being given a dial phone and being unable to make head nor tail of it.  Whether or not it’s true, we’re guessing that the same teen might be just a stumped by this year’s keyboard oddity from Google Japan. It replaces keys with a series of dials that work in the same way as the telephone dial of old. Could you dial your way through typing?

All the files to make the board, as well as a build guide, are in the GitHub repository linked above, but they’ve also released a promotional video that we’ve put below the break. The dials use 3D printed parts, and a rotary encoder to detect the key in question. We remember from back in the day how there were speed dialing techniques with dial phones, something we’ve probably by now lost the muscle memory for.

We like this board for its quirkiness, and while it might become a little tedious to type a Hackaday piece on it, there might be some entertainment for old-timers in watching the youngsters figuring it out. If you’re hungry for more, we’ve covered them before.

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