Vibratory Rock Tumbler Bounces On Printed Spring

April 4, 2024 by Tom Nardi 26 Comments

If you’re reading Hackaday, there’s a good chance you had a rock tumbler in your younger days. Hell, we’d put odds on a few of you having one rumbling away in the background as you read this. They’re relatively simple contraptions, and a common enough DIY project. But even still, this largely 3D printed rock tumbler from [Fraens] is unique enough to stand out.

To make a basic rock tumbler, all you really need to do is rotate a cylindrical chamber and let physics do its thing. Such contraptions are known as, unsurprisingly, rotary rock tumblers. But what [Fraens] has put together here is a vibratory tumbler, which…well, it vibrates. If this was Rockaday we might go farther down this particular rabbit hole and explain the pros and cons of each machine, but the short version is that vibratory tumblers are more mechanically complex and are generally better suited to fine finish work than rotary tumblers which take a brute force approach that tends to round off the rocks.

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A Stirling Engine From Minimal Parts

March 28, 2024 by Jenny List 5 Comments

The model Stirling engine is a staple of novelty catalogues, and we daresay that were it not for their high price there might be more than one Hackaday reader or writer who might own one. All is not lost though, because [jirka.luftner] has posted one on Instructables which eschews the fancy machined brass of the commercial models and achieves the same result with an array of salvaged parts.

The main cylinder is a former apple drops tin with a cardboard displacer, and the CD/DVD flywheel is mounted on either a 3D printed or cut out frame with the secondary cylinder cut into it. A diaphragm for the secondary cylinder is taken from a rubber glove, and the cranks come courtesy of bent wire.

A slight mystery of this design is that it appears not to have a regenerator, or heat store. This usually lies in the path between the two cylinders to improve efficiency by taking the heat from the air as it passes in-between the two, and returning it when it goes the other way. We’re guessing that on an engine this small it’s the tin itself which performs this function. Either way this is a neat little engine that shouldn’t break the bank.

If this has whetted your appetite, you’ll be pleased to hear it’s not the first Stirling engine we’ve seen made from what was lying around.

Build Yourself A Vacuum Tube VU Meter

March 22, 2024 by Lewin Day 5 Comments

Volume unit (VU) meters are cool — it’s an undeniable fact. For some reason, humans just dig lights that flash along with sounds. You can build a VU meter using LEDs, or bulbs if you’re trapped in 1972. Or, you could use special vacuum tubes. [mircemk] did just that in their latest VU meter project.

The 6E2 vacuum tube is the part for the job in this case. You might think a specialist tube like this is expensive, but they can be had for just a few dollars from online retailers. They were often used as tuning indicators, but here, they’re used as a responsive VU meter instead. However, instead of a single bar going up and down, you get a pair of bars that raise to meet in the middle.

[mircemk] explains all the circuitry required to drive the tubes, and how to hook them up to create a two-channel stereo VU meter. The final circuit largely relies on a transistor, a diode, some passive components, and a DC-DC boost supply to generate 250 V for the tubes.

The final result looks pretty neat, particularly as it’s built into an old-school blue project box. We’ve seen similar projects from [mircemk] before, too. Continue reading “Build Yourself A Vacuum Tube VU Meter” →

Modern Microcontroller Boosts Classic Logic Analyzer To New Heights

March 19, 2024 by Lewin Day 5 Comments

[Ted Fried] recently found a beautiful HP 1600A/1607A logic analyzer set. State of the art in 1975, it looks like glorious Space Age equipment today. He decided to hook it up some modern gear to put it through its paces.

Wanting to give the equipment a proper shakedown, he enlisted a Teensy 4.1 to spit a deluge of logic at the HP unit. The microcontroller was tasked with generating 32 data signals along with two clock outputs to give the analyzer plenty to analyze. The HP 1600A handled this no problem, so [Ted] kept tinkering.

His next feat was to explore the addressable “MAP” function of the unit, which allowed writing to the 64×64 pixel display. The Teensy 4.1 was easily able to send images to the display, but [Ted] isn’t stopping there. He’s got plans to do the usual thing and get Bad Apple going on the hardware.

Getting a logic analyzer to analyze logic isn’t much of a hack, sure. But it’s instructive of how to approach working with such hardware. If you want to spit a bunch of logic out fast, a Teensy 4.1 is a great choice because it’s got a ton of IO and a ton of clock cycles to tickle it with.

We enjoyed seeing this old piece of hardware light up the phosphors once more. If you’ve got your own projects going on with classic bits of HP test gear, don’t hesitate to let us know!

STM32 Draws On Scope

March 10, 2024 by Al Williams 7 Comments

Drawing on an oscilloscope’s XY mode isn’t a new idea. However, if you’ve ever wanted to give it a go, you’d be hard-pressed to find more information than the nearly hour-and-a-half video about the topic from [Low Byte Productions]. You can check out the video below.

If you prefer to jump straight into the code, there’s a GitHub page. While the code is specific to the STM32, you can apply the ideas to anything.

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Dial-Up Is Still, Just Barely, A Thing

March 6, 2024 by Lewin Day 94 Comments

In an era dominated by broadband and wireless cellular networks, it might come as a surprise to many that dial-up internet services still exist in the United States. This persistence is not a mere relic of nostalgia — but a testament to the diverse and uneven nature of internet infrastructure across the country.

Yes, dial-up internet, with those screechy, crackly tones, remains a useful tool in areas where modern, high-speed internet services are either unaffordable or unavailable. Subscriber numbers are tiny, but some plough on and access the Internet by the old ways, not the new.

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Making A Crystodyne Radio With Zinc Oxide And Cat’s Whiskers

March 5, 2024 by Maya Posch 19 Comments

Zinc negative resistance oscillator circuit. (Credit: Ashish Derhgawen)

During the first half of the 20th century radio technology was booming, albeit restricted by the vacuum tube technology of the time which made radios cumbersome in size and power needs. The development of a solid state alternative to the vacuum tube was in full swing, but the first version pioneered by [Oleg Losev] in the form of crystal radios failed to compete. Even so these ‘crystal radios’ laid much of the groundwork for subsequent research. The ease of creating this type of radio also makes it a fun physics experiment today, as [Ashish Derhgawen] demonstrates in a blog post.

In the January 1925 issue of Radio News the theory of the circuit is explained by [Oleg Losev] himself (page 1167). At the core is a material capable of negative resistance, as a non-linear (non-Ohmic) material, which means that the current passing through them decreases as voltage increases over part of their I-V curve. This enables it to work as an amplifier or oscillator. After the cessation of research on crystal radio technology by [Losev] and others, the negative resistance diode was rediscovered in 1957 with the tunnel diode.

Continue reading “Making A Crystodyne Radio With Zinc Oxide And Cat’s Whiskers” →