Misc Hacks

4030 Articles

Walking Arm Trebuchet Is Different, But Effective

September 15, 2019 by 6 Comments

For many of us, our first encounter with the famous trebuchet was Age of Empires II, or perhaps a documentary on historical siege engines. However, many people continue to pursue builds of their very own, exploring designs new and old. The walking arm trebuchet is a good example, which uses an unconventional design to great effect.

The design eschews a rigid frame, instead consisting of simply an arm and a triangular leg assembly. The arm is held upside down, and is launched by allowing the trebuchet to collapse forward to rest on the triangular leg. The triangular leg is fitted with spikes which dig into the ground, and the arm then pivots around, launching the projectile. The design is reportedly quite efficient, similar to a floating arm trebuchet, with a very simple design. Performance was so good, it netted a clean sweep of the 2018 Vermont Pumpkin Chuckin’ festival.

There’s a wide variety of ways to go about building a trebuchet, and we’ve featured some before. You can even instrument your payloads to quantify performance. Video after the break.

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Subaru Coils Make A Great HV Power Source

September 14, 2019 by 28 Comments

High-voltage experimenters are a unique breed. They’re particularly adept at scrounging for parts in all kinds of places, and identifying how to put all manner of components to use in the service of the almighty arc. [Jay] is one such inventor, and recently came across a useful device from Subaru.

The device in question is an ignition coil from the Subaru Outback. It consists of a pair of high-voltage transformers, connected together, in a wasted-spark setup to run four-cylinder engines. Having sourced the part from a friend, [Jay] realised that with some modification, it would make a great high-voltage power source. The first job was to figure out how to remove the internal electronics that drive the transformers. In this case, it was a simple job of hacking off a chunk of the case, removing the interfering hardware. With this done, it’s possible to directly access the transformer connections.

In [Jay]’s experiments, the device is run in an anti-parallel configuration, to produce higher than normal voltages at the output. In various tests, it’s demonstrated running from both a classic 555 circuit, as well as a ZVS driver. For future projects, [Jay] intends to use this setup to drive a large voltage multiplier, also noting it can be used with Tesla coils and plasma balls with the right additional hardware.

While [Jay] doesn’t include any specific model numbers, reports are that these coils are readily available in a variety of 1990s and 2000s Subaru vehicles. Others have used similar hardware to create high voltage projects, too – this stun gun is a great example. Video after the break.

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Wall-Mounted Ground Station Tames Unruly SatNOGS Node

September 12, 2019 by 8 Comments

For many of us, ad hoc projects end up having a certain permanence to them. Think of the number of Raspberry Pis and RTL-SDRs that are just dangling from a USB cable under a desk or stuffed behind a monitor, quietly going about their business. If it ain’t broke, don’t fix it.

Some projects, though, just end up accreting past the acceptable point. This wall-mounted SatNOGS ground station is a great example of what happens when something needs to be done about the mess. The pile of stuff that [cshields] had cobbled together over time for his ground station needed tidying, so he laid hands on a new Pi 4 and a cool enclosure/breadboard called a Stegoboard. This is just a piece of acrylic with a variety of holes laid out to match every imaginable PC board, hard drive, PC motherboard, Arduino, and just about anything out there that needs mounting. To contain the mess, he mounted the Pi and a 7″ touchscreen to the Stegoboard, along with an RTL-SDR and an Arduino to control his antenna rotator. The ground station wiring is still a little rough, but worlds better than what it was, and now that it’s mounted on the wall it’ll be much easier to use.

For those not familiar with SatNOGS, check out our article back from when the Satellite Network of Ground Stations won the 2014 Hackaday Prize. In the half-decade since then, SatNOGS has only grown, with a huge following of dedicated enthusiasts pointing their antennas at the sky. We know how to pick ’em, and we’ll be selecting the 2019 Hackaday Prize winner very soon.

Thanks to [elkos] for the tip.

Custom Lego Server Case Looks As Though It Came Straight From A Data Center

September 11, 2019 by 12 Comments

The picture above appears to show two unremarkable 2U rack servers, of the kind that are probably hosting the page you’re reading right now. Nothing special there – until you look carefully and realize that the rack server case on the left is made entirely from Lego. And what’s more, the server even works.

When it comes to building Lego computers, [Mike Schropp] is the guy to call. We’ve previously featured his Lego gaming computer, a striking case wrapped around what was a quite capable machine by 2016 standards, as well as an earlier case that reminds us a little of a NeXT. His reputation for Lego-clad computers led server maker Silicon Mechanics to commission a case for a trade show, and [Mike] jumped at the challenge.

Making a home-grade machine is one thing, but supporting all the heavy drives, power supplies, and fans needed to make the machine work is something else. He used a combination of traditional Lego pieces along with a fair sampling of parts from the Lego Technics line to pull off the build, which looks nearly perfect. Sadly, the Lego unit sizes make the case slightly taller than 2U, but that’s a small quibble when everything else matches so well, even the colors. And the fact that the server works, obviously important for a trade show demo, is pretty amazing too. The power supplies are even hot-swappable!

Congratulations to [Mike] on yet another outstanding Lego creation.

Homebrew Oscillator Is In A Glass By Itself

September 7, 2019 by 8 Comments

Great things happen when we challenge ourselves. But when someone else says ‘I bet you can’t’ and you manage to pull it off, the reward is even greater. After [WilkoL] successfully made a tuning fork oscillator, his brother challenged him to make one out of a wine glass. We’ll drink to that!

First, [WilkoL] needed to find a way to make the wine glass vibrate continuously without having to stand there running a moistened finger around the edge. A piezo speaker mounted close by did the trick. Then he had to detect the sound waves, amplify them, and feed them back in.

After toying with the idea of making a laser microphone, and tossing aside the idea of a regular microphone (because squealing feedback), he settled on using light. LEDs didn’t work, probably because the light is too divergent. But he found out that by aiming a laser just right, the curve of the wine glass modulates the light, and the waves can be detected with a phototransistor.  Then it was just a matter of amplifying the the sound and feeding it back to the piezo.

In the demo video after the break, you can see the vibrations in the glass manifest once he pours in some water. As anyone who’s ever played the water glasses can tell you, this also changes the frequency. [Editor’s note: I expected a much larger change in pitch. Not sure what’s going on here.]

Speaking of, here’s a steampunky glass armonica that uses an old turntable motor to rotate the wine glass, and a pneumatic cylinder to raise and lower the water level.

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Capture A Star In A Jar With Sonoluminescence

September 6, 2019 by 18 Comments

If nothing else, [Justin Atkin] is persistent. How else do you explain a five-year quest to create sonoluminescence with simple tools?

So what exactly is sonoluminescence? The short answer is as the name suggests: a release of light caused by sound. In [Justin]’s case, he used an ultrasonic transducer to set up a standing wave at the resonant frequency of a flask of water. A drop of water is used to entrain a small air bubble, which is held in a stable position in the flask in much the same way as styrofoam beads are in an acoustic levitator. Turn off the lights and you’ll see that the bubble glows with a ghostly blue light.

What causes the glow? Good question. According to [Justin], we just don’t know for sure what causes it, although the leading theory is that cavitation of the bubble causes the trapped gas to compress and heat violently, turning into a brief bit of plasma. But there are problems with that theory, which is one of the reasons he wanted to show just how easy the process can be – now that he’s shaken out the bugs with five years of effort. It wasn’t easy getting the transducers attached and the driver circuit properly tuned, but with little more than a signal generator, an audio amp, and a spool of magnet wire, you too can make your own “star in a jar.”

We applaud [Justin]’s determination to bring this project to a successful conclusion. It’s not unlike his dogged effort to make a cold plasma torch, or even his desktop radio telescope.

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3D-Printed Film Scanner Brings Family Memories Back To Life

September 4, 2019 by 14 Comments

There is a treasure trove of history locked away in closets and attics, where old shoeboxes hold reels of movie film shot by amateur cinematographers. They captured children’s first steps, family vacations, and parties where [Uncle Bill] was getting up to his usual antics. Little of what was captured on thousands of miles of 8-mm and Super 8 film is consequential, but giving a family the means to see long lost loved ones again can be a powerful thing indeed.

That was the goal of [Anton Gutscher]’s automated 8-mm film scanner. Yes, commercial services exist that will digitize movies, slides, and snapshots, but where’s the challenge in that? And a challenge is what it ended up being. Aside from designing and printing something like 27 custom parts, [Anton] also had a custom PCB fabricated for the control electronics. Film handling is done with a stepper motor that moves one frame into the scanner at a time for scanning and cropping. An LCD display allows the archivist to move the cropping window around manually, and individual images are strung together with ffmpeg running on the embedded Raspberry Pi. There’s a brief clip of film from a 1976 trip to Singapore in the video below; we find the quality of the digitized film remarkably good.

Hats off to [Anton] for stepping up as the family historian with this build. We’ve seen ad hoc 8-mm digitizers before, but few this polished looking. We’ve also featured other archival attempts before, like this high-speed slide scanner.

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