Are you ready to feel old? Lemmings just turned thirty-five. The famous puzzle game first came out in February of 1991 for the Commodore Amiga, before eventually being ported to just about everything else out there, from the ZX Spectrum to the FM Towns, and other systems so obscure they don’t have the class to start with two letters, like Macintosh and DOS. [RobSmithDev] decided he needed to commemorate the anniversary with a real floating lemming.

The umbrella-equipped lemming is certainly an iconic aspect of the game franchise, so it’s a good pick for a diorama. Some people would have just bought a figurine and hung it with some string, but that’s not going to get your project on Hackaday. [Rob] designed and 3D printed the whole tableau himself, and designed magnetic levitation system with some lemmings-themed effects.

The mag-lev is of the top-down type, where a magnet in the top of the umbrella is pulled against gravity by an electromagnetic coil. There are kits for this sort of thing, but they didn’t quite work for [Rob] so he rolled his own with an Arduino Nano. That allowed him to include luxuries you don’t always get from AliExpress like a thermal sensors.

Our favorite part of the build, though, has to be the sound effects. When the hall effect sensor detects the lemming statue — or, rather, the magnet in its umbrella — it plays the iconic “Let’s Go!” followed by the game’s sound track. If the figurine falls, or when you remove it, you get the “splat” sound, and if the lemming hits the magnet, it screams. [Rob] posted a demo video if you just want to see it in action, but there’s also a full build video that we’ve embedded below.

A commemorative mag-lev seems to be a theme for [Rob] — we featured his 40th anniversary Amiga lamp last year, but that’s hardly all he gets up to. We have also seen functional replicas, this one of a motion tracker from Aliens, and retrotech deep-dives like when he analyzed the magical-seeming tri-format floppy disk.

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A lot of hacks get inspired by science fiction. When that inspiration is taken from the boob tube or the silver screen, the visual design is largely taken care of by the prop department. If, on the other hand, one seeks inspiration from the written word– like [Math Campbell] did for his smart pocket watch inspired by The Diamond Age— the visuals are much more up to the individual hacker. Though no nanotechnology was involved in its creation, we think [Math] nailed the Victorian High-Tech vibe of [Neil Stephenson]’s cult classic.

The build itself is fairly simple: [Math] started with a Waveshare dev board that got him the 1.75″ round touch display, along with an ESP32-S3 and niceties such as a six-axis IMU, an RTC, microphone, speaker, and micro SD card reader. That’s quite the pocket watch! The current firmware, which is available on GitHub, focuses on the obvious use case of a very stylish watch, as well as weather and tidal display. Aside from the dev board, [Math] needed only to supply a battery and a case.

[Math] designed the case for the watch himself in Fusion360 before sending it off to be 3D printed in stainless steel. That might not be molecular-scale manufacturing like in the book, but it’s still amazing you can just do that. Ironically, [Math] is a silversmith and will be recreating the final version of the watch case in sterling silver by hand. We’d be tempted to include a door–making it a “hunter’s case” in pocket watch lingo–to protect that amoled display, but far be it for us to tell an artist how to do his work. If you’re not a silversmith, [Math] has stated his intent to add STLs to the GitHub repo, though they aren’t yet present at time of writing.

We’ve featured smart pocket watches before, some with more modern aesthetics. Of course a watch doesn’t have to be smart to grace these pages.

Thanks to [Math Campbell] for the tip! If you’ve got time on your hands after ticking done on a project, send us a tip and watch for it to appear here.

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Typically, when we want to take images, we use an image sensor paired with some sort of lens assembly to make a picture that’s sharply in focus. However, [okooptics] is here to show us there’s another way—using Scotch tape in place of a typical lens element.

If you just put Scotch tape over an image sensor without a lens, you’ll just get a blurry image, whatever you point it at. With the right algorithms, though, it’s possible to recover an image from that mess, using special “lensless imaging” techniques. In particular, [okooptics] shows how to recreate the so-called coded aperture techniques which were previously demonstrated in [Laura Waller]’s DiffuserCam paper.

It’s complicated stuff, but the video does a great job of breaking down the optics into understandable chunks. Armed with a Raspberry Pi HQ camera covered in a small amount of Scotch and electrical tape, [okooptics] is able to reconstruct a viable image from what initially looks like a blurry mess of nothingness, with the aid of the right deconvolution maths. It’s all about understanding the point spread function of the tape versus a regular lens, and figuring out how to fight off noise when reconstructing the image.

We’ve featured previous work from [okooptics] before, too, like this impressive demonstration of light transport and reconstruction. Video after the break.

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[James]’ Mechanical Organ of Dutch origin has been around longer than he has, but thanks to being rebuilt over the years and lovingly cared for, it delivers its unique performances just as well as it did back in the day. Even better, we’re treated to a good look at how it works.

The organ produces music by playing notes on embedded instruments, which are themselves operated by air pressure, with note arrangements read off what amounts to a very long punch card. [James] gives a great tour of this fantastic machine, so check it out in the video embedded below along with a couple of its performances.

The machine is mobile and entirely self-contained. It would be wheeled out to a venue, where it would play music as long as one could keep cranking the main wheel and the perforated cardboard book containing the chosen musical arrangement hasn’t reached its end. As perforations in the card scroll by inside the machine, each hole triggers valves that operate pipes, percussion hits, and even operate animatronic figures.
Folded stacks of perforated cardboard make up the musical arrangement.
The air pressure needed to do all this comes from a reservoir fed by two bellows operated by continuous rotation of a large wheel, a job that requires a fair bit of effort. Turning that crank would likely have been the responsibility of the lowest-ranking person within reach. Today, the preferred method is a belt drive and electric motor.

The perforated cardboard arrangements mean that the machine is just as programmable today as it ever was, and happily plays classics as easily as Lady Gaga, Daft Punk, and Queen. [James] has an enormous library of music, so take a moment to listen to it play “Night Fever” by the Bee Gees and Daft Punk’s “Get Lucky”.

One interesting tidbit [James] shares is that there is a bit of artistry and skill involved in arranging music for the machine. Some instruments play immediately when triggered (such as the pipes) while others trigger after a delay (like percussion), so one needs to take all this into account when punching the cardboard. There’s a bit more info on [James]’ website about his machine and its history.

In addition to being a fascinating piece of musical and mechanical history, it is another example of just how effective of a technology punched card was. Many of us might think of early computing or even music when we think of punched cards, but the original use was in running looms and knitting machines.

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Thanks [Keith Olson] for the tip!

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Keeping an eye on remaining battery charge. (credit: Luke Maximo Bell, YouTube)
Although not a typical focus of people who fly quadcopter drones for a hobby or living, endurance flying has a certain appeal to it for the challenge it offers. Thus, as part of his efforts to collect all the world records pertaining to quadcopter drones, [Luke Maximo Bell] has been working on a design that would allow him to beat the record set by SiFly Aviation at 3 hours and 11 minutes.

By using knowledge gained from his PV solar-powered quadcopter, [Luke] set about to take it all a few steps further. The goal was to get as much performance out of a single Watt, which requires careful balancing of weight, power output and many other parameters.

Crucial is that power usage goes up drastically when you increase the RPM of the propellers, ergo massive 40″ propellers were picked to minimize the required RPM to achieve sufficient lift, necessitating a very large, but lightweight frame.

The battery packs are another major factor since they make up so much of the weight. By picking high-density Tattu batteries and stripping these down even more this was optimized for as well, before even the wire gauge of the power wires running to the motors were investigated to not waste a single Watt or gram.

All of this seems to have paid off, as a first serious test flight resulted in a 3 hour, 31 minutes result, making it quite feasible that [Luke] will succeed with his upcoming attempt at the world’s longest flying electric multirotor record. Another ace up his sleeve here is that of forward movement as well as wind provides effectively free lift, massively reducing power usage and possibly putting the 4 hour endurance score within easy reach.

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Ever wanted to know how engineers made their calculations before digital calculators were on every workbench? [Richard Carpenter] and [Robert Wolf] have just the thing—a sliderule simulator that can teach you how to do a whole bunch of complex calculations the old fashioned way!

The simulator is a digital recreation of the Hemmi/Post 1460 Versalog slide rule. This was a particularly capable tool that was sold from 1951 to 1975 and is widely regarded as one of the best slide rules ever made. It can do all kinds of useful calculations for you just by sliding the scales and the cursor appropriately, from square roots to trigonometry to exponents and even multi-stage multiplication and divisions.

You can try the simulator yourself in a full-screen window here. It’s written in JavaScript and runs entirely in the browser. If you’ve never used a slide rule before, you might be lost as you drag the center slide and cursor around. Fear not, though. The simulator actually shows you how to use it. You can tap in an equation, and the simulator will both spit out a list of instructions to perform the calculation and animate it on the slide rule itself. There are even a list of “lessons” and “tests” that will teach you how to use the device and see if you’ve got the techniques down pat. It’s the sort of educational tool that would have been a great boon to budding engineers in the mid-20th century. With that said, most of them managed to figure it out with the paper manuals on their own, anyway.

We’ve featured other guides on how to use this beautiful, if archaic calculation technology, too. We love to see this sort of thing, so don’t hesitate to notify the tipsline if you’ve found a way to bring the slide rule back to relevance in the modern era!

Thanks to [Stephen Walters] for the tip!

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Here’s the Hackaday Europe 2026 announcement that you’ve all been waiting for. But wait! This year there’s a twist, or rather two. What absolutely hasn’t changed, though, is that we’d love to see you there, and we’d love to hear about what you’ve been up to, so get your talk or workshop proposal in before March 18th.

New Place, New Time

Hackaday Europe is moving in all four dimensions! We’ll be meeting up in the absolutely lovely Lecco, Italy — just about equidistant from Milan and Bergamot, and taking place May 16th and 17th, with the traditional pre-event meetup on the night of the 15th for those who are already in town. The location is the Politecnico Milano campus, a hub of engineering nestled in the mountains.

Who is going to be speaking at Hackaday Europe? You could be! We’re opening up the Call for Participation right now, both for talks and for workshops. Whether you’ve presented your work live before or not, you’re not likely to find a more appreciative audience for epic hacks, creative constructions, or you own tales of hardware, firmware, or software derring-do.

Workshop space is limited, but if you want to teach a group of ten or so people your favorite techniques, we’d love to hear from you.

All presenters get in free, of course, so firm up what you’d like to share, and get your proposal submitted ASAP.

The Badge

We’ll be bringing the 2025 Hackaday Supercon Communicator Badge with us to Europe, so this is also your chance to get your hands on the retro-styled super sexy keyboard, LoRa module, and fantastically oblong screen. At Supercon, we ran our own custom mesh network, and it worked flawlessly, even on microwatts. We’ll be continuing the experiment in Italy, on different frequencies of course, but maybe pushing some of the transmission parameters to see how far we can go.

The user side of the badge is very accessible as well, being programmed in Micropython and supported with a sweet plug-in architecture that makes adding your own apps a breeze, or at least reasonably straightforward. And when Hackaday Europe comes to a close, you can simply reflash the badge with new firmware, and you’ve got the sweetest Meshtastic device out there.

And it wouldn’t be a Hackaday badge if it weren’t meant to be modified.

The People

The real reason to come to Hackaday Europe, though, is the other folks who come to Hackaday Europe. You’ve never seen a more interested group of hardware hackers, and that’s coincidentally also why you’d like to give a presentation. You get to tell everyone what you’re up to — it’s the ultimate ice-breaker.

At the risk of saying it again: Get your proposal in before March 18th, and we look forward to seeing you on the shore of Lake Como. (Info on tickets and more pre-conference hype coming soon.)

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Despite the best efforts of the manufacturers, there are folks out there that try to repair power tools, with [Dean Doherty] being one of them. Recently he got a Milwaukee M18 cordless planer in for repairs, which started off with just replacing some dodgy bearings, but ended up with diagnosing a faulty controller. Consequently the total repair costs went up from reasonable to absolutely unreasonable, leading to a rant on why Milwaukee tools are terrible to repair.

Among the symptoms was the deep-discharged battery, which had just a hair over 7 V while unloaded. Question was what had drained the battery so severely. What was clear was that the tool was completely seized after inserting a working battery with just a sad high-pitched whine from a stalled motor.

After replacing both bearings and grumbling about cheap bearings, the tool had a lot of drywall dust cleaned out and was reassembled for a test run. This sadly showed that the controller board had been destroyed due to the seized rotor bearing, explaining the drained battery. Replacing the controller would have cost €60-70 as it comes with the entire handle assembly, rendering the repair non-viable and a waste.

Perhaps the one lesson from this story is that you may as well preventively swap the cheap bearings in your Milwaukee tools, to prevent seizing and taking out the controller board. That said, we’d love to see an autopsy on this controller board fault.

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Thanks to [paulvdh] for the tip.

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Today, we take ice for granted. But having ice produced in your home is a relatively modern luxury. As early as 1750 BC, ancient people would find ice on mountains or in cold areas and would harvest it. They’d store it, often underground, with as much insulation as they could produce given their level of technology.

A yakhchāls in Yazd province (by [Pastaitkaen] CC BY-SA 3.0).By 500 BC, people around Egypt and what is now India would place water in porous clay pots on beds of straw when the night was cold and dry. Even if the temperature didn’t freeze, the combination of evaporation and radiative cooling could produce some ice. However, this was elevated to a high art form around 400 BC by the Persians, who clearly had a better understanding of physics and thermodynamics than you’d think.

The key to Persian icemaking was yakhchāls. Not all of them were the same, but they typically consisted of an underground pit with a conical chimney structure. In addition, they often had shade walls and ice pits as well as access to a water supply.

Solar Chimney

The conical shape optimizes the solar chimney effect, where the sun heats air, which then rises. The top was typically not open, although there is some thought that translucent marble may have plugged the top to admit light while blocking airflow. yakhchālThe solar chimney produces an updraft that tends to cool the interior. The underground portion of the yakhchāl has colder air, as any hot air rises above the surface.

Insulation and Shade

The structure uses a water-resistant mortar made of sand, clay, egg whites, lime, goat hair, and ash. This has good insulating properties, although how the Persians found this recipe is a mystery. Many also had windcatcher towers that allowed for evaporative cooling in the dry air.
Yakhchāl and shade wall at Kashmar (by POS79, CC BY-SA 4.0)
Adjacent to the yakhchāl was often a shallow ice pool protected by a shade wall to block the sun. The shade wall minimized heating from the sun. Just as the Egyptians leveraged evaporative and radiative cooling to create ice, cold nights could produce ice in the pool, which workers would harvest and store inside the yakhchāl. They could also, of course, store ice harvested from elsewhere. Even with the shade wall, though, workers had to harvest ice before sunrise.

You could think of the whole system as an RC circuit. The dome and the soil around the pit form a resistance, while the ice, cold stone, and air inside form a thermal capacitor. Thick insulating walls make a large R, and tons of ice and stone make a big capacitor. The dome shape gets less solar radiation most of the time. With a big resistor and capacitor, bleeding off charge (in this case, leaking in heat) takes a long time.

Meanwhile, ice melting effectively absorbs leftover or leaking heat. Sure, you lose some ice, although with the ice pits, on a cold and dry night, you might be able to recover at least some of it.

Why?

The Persians wanted ice for the same reasons everyone else did. They preserved food, created frozen beverages (sharbat), and even a dessert, faloodeh, that combined noodles, rose syrup, lime, and ice. There were also medical uses. Of course, having ice in the hot desert was also a status symbol.

Other Tech

In China, around 600 AD, they used saltpeter to produce ice chemically instead of simply harvesting and storing it. It would be 1748 before [William Cullen] would demonstrate producing ice using artificial means. While [Oliver Evans] described a fairly modern refrigerator in 1805, nothing like it was built until [Jacob Perkins] did it in 1834. Australian [James Harrison] was probably the first commercial ice makaer in the mid 1800s.

These days, we don’t usually ship ice around, but we still have to ship cold things. And of course, refrigerators ended the ice harvesting business.

Featured image: “kosar” by [Elyaskb]

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When World of Warcraft was launched in 2004, it became somewhat of a juggernaut in the MMORPG space. Millions of players continue to login every month. [Kelsi Davis] is one such player, but she doesn’t always log in with the regular client anymore. That’s because she put together WoWee—an open-source alternative of her very own.

WoWee is an acronym—World of Warcraft Engine Experiment. Coded in native C++, it’s a homebrewed client that uses a custom OpenGL renderer to display the game world. [Kelsi] notes that it’s strictly an “educational/research” project, built without using any official Blizzard assets, data or code. Instead, it grabs some client data from a legally-obtained install to operate and loads certain assets this way.

It’s currently compatible with the vanilla game as well as The Burning Crusade and Wrath of the Lich King expansions. It should be highlighted how much work this project has already involved—with [Kelsi] needing to recreate various functional minutae in the game, from character creation screens to weather systems and skyboxes. There’s still a lot to do, as well, like adding 3D audio support and making it more interoperable with the quest system.

It’s rare that any MMO gets an open-source client, even less so while the original game is still being actively supported by the developers. Still, we do see some creative hacks in this space.

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The Raspberry Pi has brought digital camera experimentation within the reach of everybody, with its combination of an accessible computing platform and some almost-decent camera sensors. If there’s a flaw in the Pi as a camera though, it lies in the software, which can be slow and frustrating to use. [Martijn Braam] is here with an interesting project that might yield some useful results in this direction, he’s making a Raspberry Pi studio camera.

His camera hardware is very straightforward, a Pi 5 and touchscreen with the HD camera module in a rough but serviceable wooden box. The interesting part comes in the software, in which he’s written a low-latency GUI over an HDMI output camera application. It’s designed to plug into video mixing hardware, and one of the HDMI outputs carries the GUI while the other carries the unadulterated video. We can see this used to great effect with for example OBS Studio. It’s for now a work in progress as you can see in the video below the break, but we expect that it can only get better.

The video below exposes the obvious flaw in many Pi camera setups, that the available lenses don’t match the quality of the sensor, in that good glass ain’t cheap. But we think it’s one to watch, and could provide competition for CinePi.

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