How The Turntable Paradox Works

Leave most objects on top of a turntable, and set it spinning, and they’ll fly off in short order. Do the same with a ball, though, and it somehow manages to roll around on top for quite some time without falling off. [Steve Mould] set about unpacking this “Turntable Paradox” in a recent YouTube video.

In the basic case, the fact that the ball rolls is what keeps it on the turntable. As the turntable spins, the ball spins in the opposite direction, as per Newton’s first law of motion. As long as the ball is allowed to roll up to the same speed as the turntable, it will pretty much stay in place in the absence of any other perturbing forces.¬†In the event the ball is nudged along the turntable, though, it quickly ends up in a more complicated circular motion, orbiting in a ratio to the speed of the turntable itself. [Steve] explains the mechanisms at play, and dives into the mathematics behind what’s going on.

Sometimes, demonstrations like these can seem like mere curiosities. However, understanding physical effects like these has been key to the development of all kinds of complicated and fantastical machinery. Video after the break.

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Glue-on nails with vinyl record pickups pierced through them that are used on a vinyl record

The Sound Of Nails On Black Vinyl Records

[Victoria Shen] modifies glue-on nails to give her the ability to play vinyl records with her fingers. Details are light but from the many glamour pictures, it looks like she pushes record player needles through glue-on nails with thin pickup wire that then presumably goes to an audio jack for amplification.

Photograph of hand with record needs through glue-on nails

[Victoria] experiments with novel musical tools for use in her art and performances. Be sure to check out the videos of the nails in action. The combination of “scratching” and ability to alter the speed of vinyl with the free fingers creates a weird and eerie experience.

Using her “Needle Nails”, [Victoria] has found she’s able to play multiple records simultaneously (Nitter). Thanks to the different diameters of 33, 78 and 45 vinyls, she’s able to stack them up while still keeping her fingers on them.

Glove like musical instruments are nothing new but the novel use of fashion, glamour and technology allow [Victoria Shen] the freedom to create something uniquely weird and cool, so much so that Beyonce used it in a video shoot for Vogue (Nitter).

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Is 3D Printing Up To A Turntable?

Thanks to a feature by Prusament¬†because it uses their filament, we’ve been interested to read about the SongBird turntable from the British outfit Frame Theory (Note: at time of writing, they have an expired certificate). It’s a commercial product with an interesting twist for the Hi-Fi business: buy the completed turntable or buy a kit of parts and print the rest yourself.

We’re always interested to see new things here at Hackaday but we’re not in the business of promoting commercial products without a tech angle. This turntable has us interested then not because it happens to be 3D printed but because it’s instantly raised our curiosity over how suitable 3D printing is as a medium for a high quality audio component. Without descending into audiophile silliness we cannot overstate the effect that rigidity and mass of turntable components has on its audio quality. Take a look at this one we featured in the past for an extreme example.

So looking more closely at the design, we find that the chassis is aluminium, which makes sense given its visibly thin construction. Close examination of the photos on their site also reveals the tonearm to be made of carbon fibre tube, so it’s clear that they’ve put some effort into making a better turntable rather than a novelty one. This does raise the question though: manufacturing practicalities aside could you 3D print the whole thing? We think that a 3D printed chassis could replace the aluminium one at the cost of much more bulk and loss of the svelte looks, but what about the tonearm? Would one of the carbon-fibre-infused filaments deliver enough stiffness? It would be particularly interesting we think, were someone to try.

Automatic Turntable Makes Photogrammetry A Cinch

Photogrammetry is a great way to produce accurate 3D models of real objects. A turntable is often a common tool used in this work as it helps image an object from all angles. [Peter Lin] wanted a way to run the photogrammetry process with minimal human intervention, and set about building an automated turntable setup.

The build relies on a smartphone to take images of the physical object. The phone is triggered to take photos by an ESP8266, which fires the shutter via the phone’s audio socket. The microcontroller then turns the turntable on for a short period of time after each shot, rotating it by a set angle.

The build still requires objects to be repositioned in various orientations on the turntable now and then, in order to capture the top and bottom areas that would otherwise be obscured. However, the grunt work of taking the photos and rotating the objects is now entirely automated.

It’s a useful build for anyone that finds themselves regularly imaging objects to create 3D models. The results of [Peter]’s rig look great, and as a bonus come with life-like textures ready to go. We’ve seen some other great photogrammetry builds before, too. Video after the break.

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Know Audio: Get Into The Groove

The legendary Technics SL1200 direct-drive turntable, as used by countless DJs. Dydric [CC BY-SA 2.5)], via Wikimedia Commons.
The legendary Technics SL1200 direct-drive turntable, as used by countless DJs. Photo by Dydric CC-BY-SA 2.5
For me, the vinyl record player is the spiritual home of my audio listening experience, probably because I’m of the last generation to grow up when vinyl was king. The 12″ album, with its full-size sleeve and copious sleeve notes, used to be an integral part of musical enjoyment that hasn’t been adequately replicated in the age of streaming.

And like anyone who became an adult while CD players were still expensive luxury items, I started my journey into Hi-Fi with a turntable set-up that sounded pretty good. Since a new generation have in recent years rediscovered vinyl, it’s once again something that should be part of any review of audio technology.

I would have started this piece with a full run-down of the constituent parts of a good turntable, but since that’s a piece that I wrote back in 2017, it’s time to investigate some of the audiophile claims about vinyl recordings. It’s fair to say that this is an area where a lot of complete rubbish is spouted by people who should know better, and that’s something I find immensely entertaining to poke fun at. Buckle up. Continue reading “Know Audio: Get Into The Groove”

Better 3D Scans Through A Slowed Down Turntable

3D scanners aren’t cheap, and the last thing you want to see after purchasing one is bad data. But that’s what [Dave Does] and others were getting from their Revopoint POP scanners until some communal brainstorming uncovered the reason: the motorized turntable that came with the Kickstarter edition of the product was spinning too fast for the software to accurately keep track of the object. So he decided to replace the stepper motor controller in his turntable and document the process for anyone else who’s scanner might be struggling.

Plenty of room for expansion.

In the video below, [Dave] pops open the plastic case of the turntable and reveals a pretty sparse interior. There’s an incredible amount of empty space inside, and even some mounting studs to screw down new components, should you want to get into some hardcore upgrades. But for his purposes, a generic stepper motor controller that featured a potentiometer to adjust the speed was enough. He found a suitable board online for around $5 USD, and got to designing a 3D printed bracket that mates up to the existing screw holes on the turntable.

But it’s not exactly a drop-in replacement. For one thing, you’ve got to pop a hole in the side of the enclosure for the potentiometer knob to stick out of. You’ve also got to solder wires coming from the original DC jack and power switch to the new board to get it hooked up, but at least the motor plugs right in. In the video below, you can see [Dave] demonstrate the impressively deep throttle capability of the new driver.

If you’d rather build than buy, we’ve covered some impressive DIY turntables in the past that could fit the bill nicely, from automatic models that handle camera control to fully 3D printed versions that you’ve got to crank yourself.

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Anything Becomes A Clock

Clocks are a popular project around here, and with good reason. There’s a ton of options, and there’s always a new take on ways to tell time. Clocks using lasers, words, or even ball bearings are all atypical ways of displaying time, but like a mathematician looking for a general proof of a long-understood idea this clock from [Julldozer] shows us a way to turn any object into a clock.

His build uses AA-powered clock movements that you would find on any typical wall clock, rather than reaching for his go-to solution of an Arduino and a stepper motor. The motors that drive the hands in these movements are extremely low-torque and low-power which is what allows them to last for so long with such a small power source. He uses two of them, one for hours and one for minutes, to which he attaches a custom-built lazy Suzan. The turntable needs to be extremely low-friction so as to avoid a situation where he has to change batteries every day, so after some 3D printing he has two rotating plates which can hold any object in order to tell him the current time.

While he didn’t design a clock from scratch or reinvent any other wheels, the part of this project that shines is the way he was able to utilize such a low-power motor to turn something so much heavier. This could have uses well outside the realm of timekeeping, and reminds us of this 3D-printed gear set from last year’s Hackaday prize.

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