classic hacks

2778 Articles

Screen-Accurate Lightsaber As A Practical Effect

November 7, 2025 by 17 Comments

The lightsaber was one of the coolest and most iconic visual effects from the original Star Wars, and people have been trying to get that particular piece of movie magic off the silver screen for about 40 years now. [HeroTech] seems to have cracked the code with their “Impossible Lightsaber”— it’s fully retractable, fully lit, and able to hit things (lightly), all while fitting into a replica prop handle.

The secret is… well, there’s more than one secret, here. The blade itself is made out of a “magician’s cane”, which is a coil of plastic that can spring outwards on demand for magic tricks. Hidden inside of it is a strip of LED lights. Of course one strip of LEDs would not be omnidirectional, and the magician’s cane is pretty floppy, but both of those problems are solved by the same idea: “I’ll try spinning. That’s a good trick.”

The spin-stabilized blade holds up to being waved around much better, and apparently the gyroscopic forces it induces are actually lore-accurate. (Who knew?) Of course fitting a motor to spin the “blade”, and another to winch it back in, along with the circuitry and batteries to drive them was no mean feat. It’s impressive they fit it all inside the replica handle; even more impressive that they fit a speaker so this prop even makes the iconic sound effects. We always wanted to see a stage production of William Shakespeare’s Star Wars, and this gives us verily, a new hope.

[HeroTech] isn’t done yet– while seemingly impossible, this lightsaber isn’t perfect, as it’s not rugged enough for full dueling. It’s also not easy to put together, and apparently can’t handle the delicate attentions of airline baggage handlers. So ruggedization and a bit of design-for-assembly are on the table for the next version. Sadly the project is not open source; they are releasing the build files to subscribers only. Given how much work must have gone into iterating to get to this point, that is disappointing, but understandable. Everybody needs to make a living, after all.

If this project seems familiar, it’s because we featured a much-bulkier previous iteration last year.

You may prefer your lightsabers to match the movie version in effects instead of visuals; if that’s the case, check out this saber that uses HHO to cut through a steel door.

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Pi-Powered Camera Turns Heads And Lenses In Equal Measure

November 7, 2025 by 11 Comments

Have you ever seen photos of retro movie sets where the cameras seem to be bedazzled with lenses? Of course you can only film via one lens at a time, but mounting multiple lenses on a turret as was done in those days has certain advantages –particularly when working with tiny M12 lenses, like our own [Jenny List] recently did with this three-lens, Pi-zero based camera.

Given that it’s [Jenny], the hardware is truly open source, with not just the Python code to drive the Pi but the OpenSCAD code used to generate the STLs for the turret and the camera body all available via GitHub under a generous CC-BY-SA-4.0 license. Even using a cheap sensor and lenses from AliExpress, [Jenny] gets good results, as you can see from the demo video embedded below. (Jump to 1:20 if you just want to see images from the camera.)

The lenses are mounted to a 3D printed ring with detents to lock each quickly in place, held in place by a self-tapping screw, proving we at Hackaday practice what we preach. (Or that [Jenny] does, at least when it comes to fasteners.) Swapping lenses becomes a moment’s twist, as opposed to fiddling with tiny lenses hoping you don’t drop one. We imagine the same convenience is what drove turret cameras to be used in the movie industry, once upon a time.

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Volumetric Display Takes A Straight Forward (and Backward) Approach

November 1, 2025 by 9 Comments

There’s something delightfully sci-fi about any kind of volumetric display. Sure, you know it’s not really a hologram, and Princess Leia isn’t about to pop out and tell you you’re her only hope, but nothing says “this is the future” like an image floating before you in 3D. [Matthew Lim] has put together an interesting one, using persistence-of-vision and linear motion.

The basic concept is so simple we’re kind of surprised we don’t see it more often. Usually, POV displays use rotary motion: on a fan, a globe, a disk, or even a drone, we’ve seen all sorts of spinning LEDs tricking the brain into thinking there’s an image to be seen. [Matthew’s] is apparently the kind of guy who sticks to the straight-and-narrow, on the other hand, because his POV display uses linear motion.

An ESP32-equipped LED matrix module is bounced up by an ordinary N20 motor that’s equipped with an encoder and driven by a DRV8388. Using an encoder and the motor driver makes sure that the pixels on the LED matrix are synced perfectly to the up-and-down motion, allowing for volumetric effects. This seems like a great technique, since it eliminates the need for slip rings you might have with rotary POV displays. It does of course introduce its own challenges, given that inertia is a thing, but I think we can agree the result speaks for itself.

One interesting design choice is that the display is moved by a simple rack-and-pinion, requiring the motor to reverse 16 times per second. We wonder if a crank wouldn’t be easier on the hardware. Software too, since [matthew] has to calibrate for backlash in the gear train. In any case, the stroke length of 20 mm creates a cubical display since the matrix is itself 20 mm x 20 mm. (That’s just over 3/4″, or about twice the with of a french fry.) In that 20 mm, he can fit eight layers, so not a great resolution on the Z-axis but enough for us to call it “volumetric” for sure. A faster stroke is possible, but it both reduces the height of the display and increases wear on the components, which are mostly 3D printed, after all.

It’s certainly an interesting technique, and the speechless (all subtitles) video is worth watching– at least the first 10 seconds so you can see this thing in action.

Thanks to [carl] for the tip. If a cool project persists in your vision, do please let us know. Continue reading “Volumetric Display Takes A Straight Forward (and Backward) Approach” →

Recreating A Homebrew Game System From 1987

October 29, 2025 by 10 Comments

We often take for granted how easy it is to get information in today’s modern, Internet-connected world. Especially around electronics projects, datasheets are generally a few clicks away, as are instructions for building almost anything. Not so in the late 80s where ordering physical catalogs of chips and their datasheets was generally required.

Mastering this landscape took a different skillset and far more determination than today, which is what makes the fact that a Japanese electronics hobbyist built a complete homebrew video game system from scratch in 1987 all the more impressive.[Alex] recently discovered this project and produced a replica of it with a few modern touches.

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All Hail The OC71

October 29, 2025 by 50 Comments

Such are the breadth of functions delivered by integrated circuits, it’s now rare to see a simple small-signal transistor project on these pages. But if you delve back into the roots of solid state electronics you’ll find a host of clever ways to get the most from the most basic of active parts.\

Everyone was familiar with their part numbers and characteristics, and if you were an electronics enthusiast in Europe it’s likely there was one part above all others that made its way onto your bench. [ElectronicsNotes] takes a look at the OC71, probably the most common PNP germanium transistor on the side of the Atlantic this is being written on.

When this device was launched in 1953 the transistor itself had only been invented a few years earlier, so while its relatively modest specs look pedestrian by today’s standards they represented a leap ahead in performance at the time. He touches on the thermal runaway which could affect germanium devices, and talks about the use of black silicone filling to reduce light sensitivity.

The OC71 was old hat by the 1970s, but electronics books of the era hadn’t caught up. Thus many engineers born long after the device’s heyday retain a soft spot for it. We recently even featured a teardown of a dead one.

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A 3D Printed 16mm Movie Camera

October 27, 2025 by 4 Comments

The basic principles of a motion picture film camera should be well understood by most readers — after all, it’s been well over a hundred years since the Lumière brothers wowed 19th century Paris with their first films. But making one yourself is another matter entirely, as they are surprisingly complex and high-precision devices. This hasn’t stopped [Henry Kidman] from giving it a go though, and what makes his camera more remarkable is that it’s 3D printed.

The problem facing a 16mm movie camera designer lies in precisely advancing the film by one frame at the correct rate while filming, something done in the past with a small metal claw that grabs each successive sprocket. His design eschews that for a sprocket driven by a stepper motor from an Arduino. His rotary shutter is driven by another stepper motor, and he has the basis of a good camera.

The tests show promise, but he encounters a stability problem, because as it turns out, it’s difficult to print a 16mm sprocket in plastic without it warping. He solves this by aligning frames in post-processing. After fixing a range of small problems though, he has a camera that delivers a very good picture quality, and that makes us envious.

Sadly, those of us who ply our film-hacking craft in 8mm don’t have the luxury of enough space for a sprocket to replace the claw.

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Magazine Transistor Tester Lives Again

October 27, 2025 by 9 Comments

One of the lost pleasures of our modern world is the experience of going shopping at a grocery store, a mall, or a drugstore, and finding this month’s electronics magazine festooned with projects that you might like to build. Sure, you can find anything on the Internet, but there’s something to be said about the element of surprise. Can any of those old projects still be of interest?

[Bettina Neumryr] thinks so. She has a hobby of finding old magazine projects and building them. Her most recent installment is a transistor tester from the June 1983 issue of Everyday Electronics.

The tester was quite a neat job for 1983, with a neat case and a PC board. It measures beta and leakage. There’s an analog meter that can measure the collector current for a fixed base current (beta or hfe). Leakage is how much current flows between emitter and collector with the base turned off.

In 1983, we’d have loved to have a laser printer to do toner transfer for the PC board, but of course, that was unheard of in hobby circles of the day. The tester seemed to work right off the bat, although there was a small adjustment necessary to calibrate the device. All that was left was to put it in a period-appropriate box with some printed labels.

We loved the old electronics and computer magazines. Usually, when we see someone working on an old magazine project, it is probably not quite a literal copy of it. But either way is cool.

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