An effective currency needs to be widely accepted, easy to use, and stable in value. By now most of us have recognized that cryptocurrencies fail at all three things, despite lofty ideals revolving around decentralization, transparency, and trust. But that doesn’t mean that all digital currencies or payment systems are doomed to failure. [Roni] has been working on an off-grid digital payment node called Meshtbank, which works on a much smaller scale and could be a way to let a much smaller community set up a basic banking system.

The node uses Meshtastic as its backbone, letting the payment system use the same long-range low-power system that has gotten popular in recent years for enabling simple but reliable off-grid communications for a local area. With Meshtbank running on one of the nodes in the network, accounts can be created, balances reported, and digital currency exchanged using the Meshtastic messaging protocols. The ledger is also recorded, allowing transaction histories to be viewed as well.

A system like this could have great value anywhere barter-style systems exist, or could be used for community credits, festival credits, or any place that needs to track off-grid local transactions. As a thought experiment or proof of concept it shows that this is at least possible. It does have a few weaknesses though — Meshtastic isn’t as secure as modern banking might require, and the system also requires trust in an administrator. But it is one of the more unique uses we’ve seen for this communications protocol, right up there with a Meshtastic-enabled possum trap.

One of the major difficulties in studying electricity, especially when compared to many other physical phenomena, is that it cannot be observed directly by human senses. We can manipulate it to perform various tasks and see its effects indirectly, like the ionized channels formed during lightning strikes or the resistive heating of objects, but its underlying behavior is largely hidden from view. Even mathematical descriptions can quickly become complex and counter-intuitive, obscured behind layers of math and theory. Still, [lcamtuf] has made some strides in demystifying aspects of electricity in this introduction to analog filters.

The discussion on analog filters looks at a few straightforward examples first. Starting with an resistor-capacitor (RC) filter, [lcamtuf] explains it by breaking its behavior down into steps of how the circuit behaves over time. Starting with a DC source and no load, and then removing the resistor to show just the behavior of a capacitor, shows the basics of this circuit from various perspectives. From there it moves into how it behaves when exposed to a sine wave instead of a DC source, which is key to understanding its behavior in arbitrary analog environments such as those involved in audio applications.

There’s some math underlying all of these explanations, of course, but it’s not overwhelming like a third-year electrical engineering course might be. For anyone looking to get into signal processing or even just building a really nice set of speakers for their home theater, this is an excellent primer. We’ve seen some other demonstrations of filtering data as well, like this one which demonstrates basic filtering using a microcontroller.

If you exclude certain companies like Peloton, the world of cycling technology is surprisingly open. It’s not perfect by any means, but there are enough open or open-ish standards for many different pieces of technology from different brands to interoperate with each other, from sensors and bike computers and even indoor trainers to some extent. This has also made it possible for open source software to exist in this realm as well, and the GoldenCheetah project has jumped in for all of us who value FOSS and also like to ride various bicycles from time to time.

GoldenCheetah focuses on gathering data from power meters, allowing cyclists to record their rides and save them in order to keep track of their training performance over time. It works well with sensors that use the ANT+ protocol, and once it has that data it can provide advanced analytics such as power curves, critical power modeling, and detailed charts for power, heart rate, and cadence. It can display and record live indoor-training data, and in some situations it can even run interval workouts, although not every indoor trainer is supported. There are no social features, subscriptions, or cloud requirements which can be refreshing in the modern world, but is a bit of a downside if you’re used to riding with your friends in something like Zwift.

All in all, though, it’s an impressive bit of software that encourages at least one realm of consumer electronics to stay more open, especially if those using bike sensors, computers, and trainers pick ones that are more open and avoid those that are proprietary, even if they don’t plan to use GoldenCheetah exclusively. And if you were wondering about the ANT+ protocol mentioned earlier, it’s actually used for many more things that just intra-bike wireless communications.

Although it might seem like there was a sudden step change from analog to digital sometime in the late 1900s, it was actually a slow, gradual change from things like record players to iPods or from magnetic tape to hard disk drives. Some of these changes happened slowly within the same piece of hardware, too. Take the Sony DXC-3000A, a broadcast camera from the 1980s. Although it outputs an analog signal, this actually has a discrete pixel CCD sensor capturing video. [Colby] decided to finish the digitization of this camera and converted it to output HDMI instead of the analog signal it was built for.

The analog signals it outputs are those that many of us are familiar with, though: composite video. This was an analog standard that only recently vanished from consumer electronics, and has a bit of a bad reputation that [Colby] thinks is mostly undeserved. But since so many semi-modern things had analog video outputs like these, inspiration was taken from a Wii mod chip that converts these consoles to HDMI. Unfortunately his first trials with one of these had confused colors, but it led him to a related chip which more easily outputted the correct colors. With a new PCB in hand with this chip, a Feather RP2040, and an HDMI port the camera is readily outputting digital video that any modern hardware can receive.

Besides being an interesting build, the project highlights a few other things. First of all, this Sony camera has a complete set of schematics, a manual meant for the end user, and almost complete user serviceability built in by design. In our modern world of planned obsolescence, religious devotion to proprietary software and hardware, and general user-unfriendliness this 1980s design is a breath of fresh air, and perhaps one of the reasons that so many people are converting old analog cameras to digital instead of buying modern equipment.

By now we’re all familiar with the quad-rotor design most popular among modern drones, and of course there are many variants using more or less propellers and even fixed-wing drones that can fly autonomously. We’ve even seen drones that convert from rotorcraft to fixed-wing mid flight. But there are even more esoteric drones out there that are far more experimental and use even more bizarre wing designs that look like they shouldn’t be able to fly at all. Take [Starsistor]’s latest design, which uses a single motor and an unconventional single off-center wing to generate lift.

This wing, though, is not a traditional foil shape typically found on aircraft. It uses the Magnus effect to generate lift. Briefly, the Magnus effect is when lift is generated from a spinning object in a fluid. Unlike other Magnus effect designs which use a motor to spin a cylinder, this one uses a design inspired by Savonius wind turbines where a wing is free to rotate around a shaft. A single propeller provides a rotational force to the craft, allowing this off-center wing to begin spinning and generating lift. The small craft was able to sustain several flights but was limited due to its lack of active control.

[Starsistor] went through a number of iterations before finally getting this unusual craft to fly. His first designs did not have enough rotational inertia and would flip over at speed, which was fixed by moving the propeller further away from the center of the craft. Eventually he was able to get a working design to prove his conceptual aircraft, and we hope to see others from him in the future.

Looking up at the sky just after sunset or just before sunrise will reveal a fairly staggering amount of satellites orbiting overhead, from tiny cubesats to the International Space Station. Of course these satellites are always around, and even though you’ll need specific conditions to view them with the naked eye, with the right radio antenna and only a few dollars in electronics you can see exactly which ones are flying by at any time.

[Josh] aka [Ham Radio Crash Course] is demonstrating this build on his channel and showing every step needed to get something like this working. The first part is finding the correct LoRa module, which will be the bulk of the cost of this project. Unlike those used for most Meshtastic nodes, this one needs to be built for the 433 MHz band. The software running on this module is from TinyGS, which we have featured here before, and which allows a quick and easy setup to listen in to these types of satellites. This build goes much further into detail on building the antenna, though, and also covers some other ancillary tasks like mounting it somewhere outdoors.

With all of that out of the way, though, the setup is able to track hundreds of satellites on very little hardware, as well as display information about each of them. We’d always favor a build that lets us gather data like this directly over using something like a satellite tracking app, although those do have their place. And of course, with slightly more compute and a more directed antenna there is all kinds of other data beaming down that we can listen in on as well, although that’s not always the intent.

When AI is being touted as the latest tool to replace writers, filmmakers, and other creative talent it can be a bit depressing staring down the barrel of a future dystopia — especially since most LLMs just parrot their training data and aren’t actually creative. But AI can have some legitimate strengths when it’s taken under wing as an assistant rather than an outright replacement.

For example [Aarav] is happy as a lark when birdwatching, but the birds aren’t always around and it can sometimes be a bit of a wild goose chase waiting hours for them to show up. To help him with that he built this machine learning tool to help alert him to the presence of birds.

The small device is based on a Raspberry Pi 5 with an AI hat nested on top, and uses a wide-angle camera to keep an eagle-eyed lookout of a space like a garden or forest. It runs a few scripts in Python leveraging the OpenCV library, which is a widely available machine learning tool that allows users to easily interact with image recognition. When perched to view an outdoor area, it sends out an email notification to the user’s phone when it detects bird activity so that they can join the action swiftly if they happen to be doing other things at the time. The system also logs hourly bird-counts and creates a daily graph, helping users identify peak bird-watching times.

Right now the system can only detect the presence of birds in general, but he hopes to build future versions that can identify birds with more specificity, perhaps down to the species. Identifying birds by vision is certainly one viable way of going about this process, but one of our other favorite bird-watching tools was demonstrated by [Benn Jordan] which uses similar hardware but listens for bird calls rather than looking for the birds with a vision-based system.

In our modern world full of planned obsolescence helping to fuel cycles of consumerism, the thing that really lets companies dial this up to the max is locked-down electronics and software. We all know the key players in this game whether it’s an automotive manufacturer, video game console producer, smart phone developer, or fruit-based computer company of choice, but there are some lesser known players desperately trying to make names for themselves in this arena too. Many power tool manufacturers like Milwaukee build sub-par battery packs that will wear out prematurely as [Tool Scientist] shows in this video.

Determining that these packs don’t actually balance their cells isn’t as straightforward as looking for leads going to the positive terminal of each. The microcontrollers running the electronics in these packs are hooked up, but it seems like it’s only to communicate status information about the batteries and not perform any balancing. [Tool Scientist] tested this hypothesis through a number of tests after purposefully adding an imbalance to a battery pack, first by monitoring i2c communications, measuring across a resistor expected to show a voltage drop during balancing, let a battery sit 21 days on a charger, and then performing a number of charge and discharge cycles. After all of that the imbalance was still there, leading to a conclusion that Milwaukee still doesn’t balance their battery packs.

Giving them the benefit of the doubt, it could be that most packs will be just fine after years without balancing, so the added cost of this feature isn’t worth it. This video was put out nearly a year ago, so it’s possible Milwaukee has made improvements since then. But a more realistic take, especially in a world dominated by subscription services and other methods of value extraction, is that Milwaukee is doing this so that users will end up having to buy more batteries. They already make user serviceability fairly difficult, so this would be in line with other actions they’ve taken. Or it could be chalked up to laziness, similar to the Nissan Leaf and its lack of active thermal management in its battery systems.

Thanks to [Polykit] for the tip!

One of the hardest things about owning a classic car is finding replacement parts. Especially if the car is particularly old or rare, or if the parent company is now out of business, sometimes this can be literally impossible and a new part will have to be manufactured from scratch. The same is true of bicycles as well, and there are plenty of defunct bicycle manufacturers to choose from. [Berm Peak] found a couple old rental ebikes from a company that’s not in business anymore and set about trying to get them working again. (Video, embedded below.)

Of course, unlike many classic cars, ebikes are encumbered by proprietary electronics and software that are much harder to replace than most physical components. As a result, these bikes get most of their electronics pulled out and directly replaced. This bike also had a seized motor, so [Berm Peak] replaced it with another hub motor he had in his shop. Some of the other highlights in the build include a custom 3D-printed latching mechanism for the battery’s attachment point at the frame, a 3D printed bezel for the new display and control unit, and the reuse of some of the other fun parts of the bike like the front basket and integrated headlight.

There are a few reasons for putting so much work into a bike like this. For this specific bike at least, the underlying components are worth saving; the sturdy metal frame and belt drivetrain are robust and won’t need much maintenance in the long term. It also only cost around $500 in parts to build a bike that would take around $2,000 to purchase new, so there’s some economic incentive as well. And in general it’s more fun and better for the world to fix things like this up and get them running again rather than buying something new off the shelf. And while proprietary electronics like those found on this bike are ubiquitous in the ebike world, they’re not all completely closed-source.

There’s been a bit of a virtualization revolution going on for the last decade or so, where tools like Docker and LXC have made it possible to quickly deploy server applications without worrying much about dependency issues. Of course as these tools got adopted we needed more tools to scale them easily. Enter Kubernetes, a container orchestration platform that normally herds fleets of microservices in sprawling cloud architectures, but it turns out it’s perfectly happy running on a tiny computer stuffed in a cat carrier.

This was a build for the recent Kubecon in Atlanta, and the project’s creator [Justin] wanted it to have an AI angle to it since the core compute in the backpack is an NVIDIA DGX Spark. When someone scans the QR code, the backpack takes a picture and then runs it through a two-node cluster on the Spark running a local AI model that stylizes the picture and sends it back to the user. Only the AI workload runs on the Spark; [Justin] also is using a LattePanda to handle most of everything else rather than host everything on the Spark.

To get power for the mobile cluster [Justin] is using a small power bank, and with that it gets around three hours of use before it needs to be recharged. Originally it was planned to work on the WiFi at the conference as well but this was unreliable and he switched to using a USB tether to his phone. It was a big hit with the conference goers though, with people using it around every ten minutes while he had it on his back. Of course you don’t need a fancy NVIDIA product to run a portable kubernetes cluster. You can always use a few old phones to run one as well.

Perhaps the biggest hurdle to starting a home blacksmithing operating is the forge. There’s really no way around having a forge; somehow the metal has to get hot enough to work. Although we might be imagining huge charcoal- or gas-fired monstrosities, [Shake the Future] has figured out how to use an unmodified, standard microwave oven to get iron hot enough to melt and is using it in his latest video to cast real, working tools with it.

In the past, [Shake the Future] has made a few other things with this setup like an aluminum pencil with a graphite core. This time, though, he’s stepping up the complexity a bit with a working tool. He’s decided to build a miniature bench vice, which uses a screw to move the jaws. He didn’t cast the screw, instead using a standard size screw and nut, but did cast the two other parts of the vice. He first 3D prints the parts in order to make a mold that will withstand the high temperatures of the molten metal. With the mold made he can heat up the iron in the microwave and then pour it, and then with some finish work he has a working tool on his hands.

A microwave isn’t the only kitchen appliance [Shake the Future] has repurposed for his small metalworking shop. He also uses a standard air fryer in order to dry parts quickly. He works almost entirely from the balcony of his apartment so he needs to keep his neighbors in mind while working, and occasionally goes to a nearby parking garage when he has to do something noisy. It’s impressive to see what can be built in such a small space, though. For some of his other work be sure to check out how he makes the crucibles meant for his microwave.