Bearing Witness: Measuring The Wobbles In Rotary Build

July 21, 2025 by Matt Varian 5 Comments

3D printing has simplified the creation of many things, but part of making something is knowing just how much you can rely on it. On the [BubsBuilds] YouTube channel, he built a cheap rotary table and then walked through the process of measuring the error inherent in any rotating system.

Starting with a commercial rotary table, [BubsBuilds] decided he wanted a rotary stage that was both lighter and had provisions for motorized movement. Most of the rotary build is 3D printed, with the large housing and table made from PETG, and the geared hub and worm gear printed on a resin printer. The bearings used to support the worm gear are common skateboard bearings. There is also a commercial thrust bearing and 49 larger 9.5 mm ball bearings supporting the rotating tabletop.

There are three different types of runout to be measured on a rotating stage: axial, radial, and angular. Axial runout is fairly straightforward to discern by measuring the vertical variation of the table as it rotates. Radial runout measures how true the rotation is around the center of the table. Angular runout measures how level the table stays throughout its range. Since these two runouts are tied to each other, [BubsBuilds] showed how you can take measurements at two different heights and use trigonometry to obtain both your radial and angular runout

This is a great walk-through of how to approach measuring and characterizing a system that has multiple variables at play. Be sure to check out some of the other cool rotary tables we’ve featured.

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Reverse Engineering A ‘Tony’ 6502-based Mini Arcade Machine

July 21, 2025 by Maya Posch 15 Comments

The mainboard of the mini arcade unit with its blob chip and EEPROM. (Credit: Poking Technology, YouTube)

For some reason, people are really into tiny arcade machines that basically require you to ruin your hands and eyes in order to play on them. That said, unlike the fifty gazillion ‘retro consoles’ that you can buy everywhere, the particular mini arcade machine that [David Given] of [Poking Technology] obtained from AliExpress for a teardown and ROM dump seems to have custom games rather than the typical gaggle of NES games and fifty ROM hack variations of each.

After a bit of gameplay to demonstrate the various games on the very tiny machine with tiny controls and a tiny 1.8″, 160×128 ST7735 LC display, the device was disassembled. Inside is a fairly decent speaker, the IO board for the controls, and the mainboard with an epoxy blob-covered chip and the SPI EEPROM containing the software. Dumping this XOR ‘encrypted’ ROM was straightforward, revealing it to be a 4 MB, W23X32-compatible EEPROM.

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Researching Glow-Powder Left A Few Scars

July 20, 2025 by Brian McEvoy 34 Comments

Content warning: Human alteration and scalpels.
General warning: We are not speaking as doctors. Or lawyers.

If you watch sci-fi, you probably do not have to think hard to conjure a scene in a trendy bar where the patrons have glowing make-up or tattoos. That bit of futuristic flair was possible years ago with UV-reactive tattoo ink, but it has the unfortunate tendency to permanently fade faster than traditional ink. [Miana], a biohacker, wanted something that could last forever and glow on its own. After months of research and testing, she presents a technique with a silica-coated powder and scarification. Reddit post with graphic content.

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Remembering Chiptunes, The Demoscene And The Illegal Music Of Keygens

July 20, 2025 by Tyler August 38 Comments

We loved keygens back in the day. Our lawyers advise us to clarify that it’s because of the demo-scene style music embedded in them, not because we used them for piracy. [Patch] must feel the same way, as he has a lovely historical retrospective out on “The Internet’s Most Illegal Music” (embedded below).

After defining what he’s talking about for the younger set, who may never have seen a keygen in this degenerate era of software-by-subscription, [Patch] traces the history of the jaunty chiptunes that were so often embedded in this genre of program. He starts with the early demoscene and its relationship with cracker groups — those are coders who circulate “cracked” versions of games, with the copyright protection removed. In the old days, they’d embed an extra loading screen to take credit for the dastardly deeds that our lawyer says to disavow.

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Hackaday Links: July 20, 2025

July 20, 2025 by Dan Maloney 10 Comments

In the relatively short time that the James Webb Space Telescope has been operational, there’s seemingly no end to its list of accomplishments. And if you’re like us, you were sure that Webb had already achieved the first direct imaging of a planet orbiting a star other than our own a long time ago. But as it turns out, Webb has only recently knocked that item off its bucket list, with the direct visualization of a Saturn-like planet orbiting a nearby star known somewhat antiseptically as TWA 7, about 111 light-years away in the constellation Antlia. The star has a significant disk of debris orbiting around it, and using the coronagraph on Webb’s MIRI instrument, astronomers were able to blot out the glare of the star and collect data from just the dust. This revealed a faint infrared source near the star that appeared to be clearing a path through the dust.

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The Open-Source Multimeter: The HydraMeter

Designing An Open Source Multimeter: The HydraMeter

July 20, 2025 by John Elliot V 23 Comments

Our hacker [John Duffy] wrote in to let us know about a video he put together to explain the design of his open-source multimeter, the HydraMeter.

If you’re interested in how the circuitry for a voltmeter, ohmmeter, or ammeter might work, this video is a masterclass. In this long and detailed video, [John] walks us through his solutions to various challenges he had while designing his own multimeter. We covered this multimeter last year, and this new video elaborates on the design of the HydraMeter which has been a work in progress for years now.

The basic design feeds voltage, current, and resistance front-ends into an Analog to Digital Converter (ADC), which then feeds into a microcontroller and out to the (detachable) display. You can find the KiCad design files on the GitHub page. There is also a write-up on hackaday.io.

The user interface for the meter is… opinionated, and perhaps not to everyone’s taste. In the video, [John] talks a little bit about why he made the UI work the way that it does, and he noted that adding a rotary range switch is a goal for version 2.0.

Thank you, [John], for putting this video together; it is an excellent resource. We look forward to seeing version 2.0 develop soon!

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When A Record Player Doesn’t Work Due To Solid State Grease

July 20, 2025 by Maya Posch 24 Comments

Normally, mechanical devices like record players move smoothly, with well-greased contact surfaces enabling the tone arm to automatically move, the multi-record mechanism to drop down a fresh disc, and the listener to have a generally good time. Unfortunately, the 1972-era ITT KP821 record player that [Mark] got recently handed by a friend wasn’t doing a lot of moving, with every part of the mechanism seemingly frozen in place, though the current owner wasn’t certain that they were doing something wrong.

Fortunately, this record player was in exceptionally good condition.. The primary failure was that the BSR record player mechanism, with its many touching metal surfaces, was suffering from a bad case of solidified grease. Although this is easily fixed with some IPA and a lot of elbow grease, the biggest trick with these mechanisms is putting it back together after cleaning, with many seemingly randomly shaped parts and every single E-clip that the manufacturer could design for and source at the time.

With that complete, this just left some pot cleaning and replacing a busted fuse in the amplifier section. The selenium rectifier was still functional, as were the SGS TAA621AX1 audio amplifier ICs. Despite the age of this ‘portable’ record player, both its BSR mechanism and the twin speakers that are part of the record player are in remarkably good condition. Much like with a car, it seems that you just have to swap out the liquid-y elements before they turn into a solid.

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