The Dangerously Delightful Homemade Rockets Of Thailand

Every once in a while, we here at Hackaday stumble across something that doesn’t quite fit in with all the other amazing hacks we feature, but still seems like something that our dear readers need to see as soon as possible. This video of homemade rockets in Thailand is one of those things.

It comes to us from our friend [Leo Fernekes], who documents a form of amateur rocketry that makes the Estes rockets of our youth look pretty tame. It’s far easier to watch than it is to describe, but for a quick summary, the rockets are bamboo rings with a steel pipe across the diameter. The pipe is packed with homemade gunpowder and provided with nozzles that create both thrust and rotation. When ignited by torches touched to seriously sketchy primers, the rocket starts to spin up, eventually rising off the launch pad and screwing itself into the sky on a twisting column of gray smoke.

At three or four meters across, these are not small vehicles. Rather than letting a steel pipe plummet back to Earth from what looks like several hundred meters altitude, the rocketeers have devised a clever recovery system that deploys a parachute when the rocket motor finally melts through some plastic straps. The use of banana tree bark as a heat shield to protect the parachute is simple but effective; which is really the way you can describe the whole enterprise. [Leo] has another way to describe it: “Dangerously negligent madness,” with all due respect and affection, of course. It looks like a big deal, too — the air is obviously filled with the spirit of competition, not to mention the rotten-egg stench of gunpowder.

Should you try this at home? Probably not — we can think of dozens of reasons why this is a bad idea. Still, it’s amazing to watch, and seeing how much altitude these cobbled-up rockets manage to gain is truly amazing. Hats off to [Leo] for finding this for us.

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Practical Transistors: JFETs

Transistors come in different flavors. Tubes used an electric field to regulate current flow, and researchers wanted to find something that worked the same way without the drawbacks like vacuum and filament voltages. However, what they first found — the bipolar transistor — doesn’t work the same way. It uses a small current to modulate a larger current, acting as a switch. What they were looking for was actually the FET — the field effect transistor. These come in two flavors. One uses a gate separated from the channel by a thin layer of oxide (MOSFETs), and the other — a junction or JFET — uses the property of semiconductors to deplete or enhance carriers in the channel. [JohnAudioTech] takes a decidedly practical approach to JFETs in a recent video that you can watch below.

The idea for the FET is rather old, with patents appearing in 1925 and 1934, but there were no practical devices at either time. William Shockley tried and failed to make a working FET in 1947, the same year the first point-contact transistor appeared, which was invented while trying to create practical FETs. In 1948, the bipolar junction transistor hit the scene and changed everything. While there were a couple of working FETs created between 1945 and 1950, the first practical devices didn’t appear until 1953. They had problems, so interest waned in the technology while the industry focused on bipolar transistors. However, FETs eventually got better, boasting both very high input impedance and simplified biasing compared to bipolar technology.

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An electric eraser built into a mechanical pencil

Power Up Your Pencil With The 30,000 RPM Erase-O-Matic

There are some inventions that look completely pointless to the untrained eye: who would ever need a motorized garbage can, an electric pencil sharpener or a battery-powered eraser? Quite often, it turns out that there is some niche use case where such tools make complete sense, as is the case for motorized erasers. Having a tiny piece of rubber spinning at high speed gives artists and drafters a way to very precisely delete or lighten bits of their drawing, something that’s nearly impossible to do with a regular eraser.

[Franklinstein] however decided to design a high-speed eraser integrated into a mechanical pencil that brings the whole concept straight back to the pointless category, although not without showing off his advanced engineering skills. The Erase-O-Matic contains a miniature electric motor sourced from a quadcopter, together with an ultra-small lithium-ion battery and a power switch. The spinning bit is held by a tiny bearing, with the whole setup covered by a machined aluminium housing.

Tests with a laser tachometer show a rotational speed of about 30,000 RPM, which is almost three times as fast as a commercial electric eraser. And although it has very good erasing performance, it also wears out its tip in a few seconds, so a bit less speed could actually make this device more useful. If you’re planning to build one of these yourself, you might want to first read our primer on small DC motors.

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The Great Euro Sat Hack Should Be A Warning To Us All

Military officials and civilian security researchers have been warning us for years: cyberattacks are becoming a very real part of modern warfare. Far from being limited to military targets, cyberattacks can take out everything from vital public infrastructure to commercial and industrial operations, too.

In the early hours of February 24, as the Russian invasion force began raining missiles on Ukrainian cities, another attack was in progress in the digital realm. Suddenly, satellite terminals across Europe were going offline, with many suffering permanent damage from the attack.

Details remain hazy, but researchers and military analysts have pieced together a picture of what happened that night. The Great Euro Sat Hack prove to be the latest example of how vulnerable our digital infrastructure can be in wartime.

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Screenshot of the website, showing the sidebar with technology types on the left, and an entry about modifying LCD polarizers on the right, with a video showing an art piece using LCD polarizers

Alternative Display Technologies And Where To Find Them

[Blair Neal] has been working on an information database for artists and hackers – a collection of non-conventional display technologies available to us. We’ve covered this repository before, six years ago – since then, it’s moved to a more suitable platform, almost doubled in size, and currently covers over 40+ display technology types and related tricks. This database is something you should check out even if you’re not looking for a new way to display things right now, however, for its sheer educational and entertainment value alone.

[Blair] doesn’t just provide a list of links, like the “awesome-X” directories we see a lot of. Each entry is a small story that goes into detail on what makes the technology tick, its benefits and fundamental limitations, linking to illustrative videos where appropriate. It’s as if this guide is meant to give you an extensive learning course on all the ways you can visualize things on your creative journey. All of these categories have quite a few examples to draw from, highlighting individual artworks that have made use of any technology or trick in a particular way.

If you’re ever wondered about the current state of technology when it comes to flexible or transparent displays, or looked for good examples of volumetric projection done in a variety of ways, this is the place to go. It also talks about interesting experimental technologies, like drone displays, plasma combustion or scanning fiber optics. Overall, if you’re looking to spend about half an hour learning about all the ways there are to visualize something, this database is worth a read. And, if there’s a display technology the author might’ve missed and you know something about, contributions are welcome!

Someone setting out to compile information about an extensive topic is always appreciated, and helps many hackers on their path. We’ve seen that done with 3D printer resin settings and SMD part codes, to name just a few. What’s your favourite hacker-maintained database?

Bottoms Up: Soda Can Help With Almost Any Project

If there’s any one thing that the average hacker is short on at a given moment (besides chips), it’s transient small part storage. Just as new projects are built from small parts, diagnostics and teardowns of commercial equipment invariably result in small parts. We think [amenjet] may have the answer — small parts holders made from the bottoms of soda cans.

You start by cutting the bottom off of an empty can however you like. In the first video after the break, [amenjet] scores the can on what could be a purpose-built jig before cutting along the line with tin snips, but you could use regular scissors if that’s all you have. Then it’s just a matter of shoving it into the circle around the perimeter of the print to secure the sharp edge.

The underside of the print is graduated and ends with a small hole fit for a disc magnet. To keep the prints from scratching the table, [amenjet] covered the bottoms with crushed velvet. After making about a dozen of these things, they CNC’d a tray to hold three of them, which you can see in the second video. Each cavity in the tray is lined with more crushed velvet for elegance and stability.

Between the concavity of the can bottom and that little lip, it should be particularly easy to actually retrieve a tiny part from the pile and grab on to it. Between the utility and the recycled aspect, this could easily be an entry into the second Challenge of the 2022 Hackaday Prize, which runs now until Sunday, June 12th. This round is all about reusing, recycling, and revamping anything and everything to keep it out of the landfill. Start your entry today!

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The STM32 Makes For A Cheap DIY USB Soundcard

Soundcards used to be giant long 8-bit ISA things that would take up a huge amount of real estate inside a desktop computer. These days, for most of us, they’re baked into the motherboard and we barely give them a second thought. [Samsonov Dima] decided to whip up a cheap little sound card of their own, however, built around the STM32.

The soundcard is based specifically on the STM32F401. readily available on the “Green Pill” devboards. A digital-to-analog converter is implemented on the board based on two PWM timers providing high-quality output. There’s also a simulated software sigma delta ADC implemented between the audio streaming in via USB and the actual PWM output, with some fancy tricks used to improve the sound output. [Samsonov] even found time to add a display with twin VU meters that shows the audio pumping through the left and right channels.

Without test gear on hand, we can’t readily quantify the performance of the sound card. However, as per the Youtube videos posted, it appears more than capable of recreating music with good fidelity and plenty of fine detail.

If you need a cheap, simple USB sound card that you can hack away on, this might be the one for you. If you need something more suitable for a vintage PC, however, consider this instead. Video after the break.

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