Building A Lego Paper Shredder

Sometimes we need to destroy documents before throwing them away for security reasons, and shredders are a primary way of achieving that. If you don’t have your own, you might consider building your own, like [Brick Experiment Channel] did using Lego.

First attempts at shredding a small slip of paper with interlocking gears were a failure, merely crumpling the paper in an attractive rippled manner. As the “Top Secret” piece of paper says, “If you can read this, the shredder didn’t work.” Adding more gears managed to gouge a couple holes in the paper, but it was still far from effective. Continuing down this path further only stalled the Lego motor.

A redesign with different sized gears did eventually manage to tear the paper into large chunks. One set of gears would hold on to the paper while a following set would tear away a section. A further modification combined this method with using bevel gears as a sort of blade, and improved shredding performance further, to the point where the paper was torn into satisfyingly tiny fragments.

It’s a fun little build, even if it won’t come close to taking on a full page of A4. It’s a great example of what can be achieved when you set a simple goal with readily measurable outcomes, in this case, the legibility of the original message on the paper.

We’ve seen a few shredders around here before too. Video after the break.
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Clock Testing Sans Oscilloscope?

Like many people who repair stuff, [Learn Electronics Repair] has an oscilloscope. But after using it to test a motherboard crystal oscillator, he started thinking about how people who don’t own a scope might do the same kind of test. He picked up a frequency counter/crystal tester kit that was quite inexpensive — under $10. He built it, and then tried it to see how well it would work in-circuit.

The kit has an unusual use of 7-segment displays to sort-of display words for menus. There is a socket to plug in a crystal for testing, but that won’t work for the intended application. He made a small extender to simplify connecting crystals even if they are surface mount. He eventually added a BNC socket to the counter input, but at first just wired some test leads directly in.

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Making A Locket From A Coin

Some countries have strict laws around the destruction or alteration of issued currency, but then again, some countries don’t. Citizens of those in the latter category may enjoy undertaking a build similar to this locket created by [Elier Olivos], crafted from a large coin.

A compass is first used to mark out a line on the coin’s perimeter, before it is cut in half with a fret saw. Once the two halves of the coin are smoothed out, it’s then time to heat them and quench them so they’re more malleable for pounding into a slightly domed shape. Metal rings are then fabricated and added to each half to give the locket some depth.

A hinge is then carefully made and fixed into the edges of the coin halves, giving the closed coin an almost seamless outside appearance. A small latch installed on the inside helps hold the locket closed. The final touches are to attach a loop for affixing the locket to a chain for the wearer, and to polish the inside of the locket up to a mirror shine.

[Elier] makes the build look easy through a combination of his amazing skills with his hands and the help of a some esoteric tooling. It can be very relaxing to take in a video of a master at work, and we’ve seen some great examples recently. Video after the break.

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You Can Build Your Own Sushi Train

According to [Garage Avenger], in Norwegian culture it’s considered impolite to ask for things to be passed across a dinner table, so much standing and reaching is the course of the day. To assist in reducing the effort required, he set about building his own sushi train device to solve the problem, giving equal condiment access to all!

The system is capable of taking plenty of weight from heavy dinner bowls, altogether quite different than relatively-light sushi dishes on plastic plates.

The system is actually relatively simple, relying on a Wemos D1 Mini controlled by a Blynk app to run the show. Mechanically, a large drive gears is turned by a stepper motor to drive the wooden conveyor chain that actually makes up the “sushi train.” The chain links ride on a bed of Norwegian one krone coins acting as rollers.

The result is a working table-sized sushi train that really does carry plates around well. It didn’t stop people leaning over [Garage Avenger] at the dinner table, but it makes a great centerpiece on the dinner table for sharing dishes like tacos.

We’ve seen similar table technology, the Lazy Susan, around these parts before. Video after the break.
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A Wireless Headphone Charger Without The Wireless

We’re all used to the idea of wireless charging, usually in the form of an induction coil on which a mobile phone or other appliance can be placed for a top-up. Not every battery-powered appliance has a built-in wireless charging coil though, meaning that despite the tech being available we all still have a jumble of wires.

[Sergio Costas] has a simple solution to conjuring wireless charging from thin air in his headphone stand, which conceals a set of charging contacts. It’s by no means a new idea and it might seem like an obvious hack, but it undeniably does away with the wires and we like it. After all, if it were that obvious, none of us would have that mess of chargers.

The headphones in question are a Bluetooth wireless pair, and the charging contacts have been brought out via a voltage regulator and a bridge rectifier to a pair of copper tapes along the sides of the headband. These mate with matching contacts in a 3D printed holder to which 12 VDC has been applied. Perhaps he’s just reinvented the springy contacts you’ll find on any cordless home phone, but it’s unquestionably a charger without wires.

Meanwhile if you have a conventional wireless charger, how do you know it’s working?

The Metal 3D Printing Hack Chat Brings The Heat

At this point, it’s safe to say the novelty of desktop 3D printing has worn off. The community has largely come to terms with the limitations of extruded plastics, and while we still vehemently believe that it’s a transformative technology, we’ll admit there aren’t too many applications where a $200 USD printer squirting out PLA is truly the best tool for the job.

But rather than looking at today’s consumer 3D printer market as the end of the line, what if it’s just the beginning? With the problems of slicing, motion control, and extrusion more or less solved when it comes to machines that print in plastic, is it finally time to turn our attention to the unique problems inherent in building affordable metal printers? Agustin Cruz certainly thinks so, which is why he took to the Hack Chat this week to talk about his personal vision for an open source 3D printer that can turn powdered metals into solid objects by way of a carefully controlled electron beam.

To be clear, Agustin isn’t suggesting you toss out your Creality anytime soon. Metal 3D printing will always be a niche within a niche, but for applications where even advanced engineering plastics like PEI and PEEK simply won’t do, he argues the community needs to have a cheap and accessible option. Especially for developing and low income countries where traditional manufacturing may be difficult. The machine he’s been working on wouldn’t be outside the capabilities of an individual to build and operate, but at least for right now the primary target is hospitals, colleges, and small companies.

The Chat was full of technical questions about Agustin’s design, and he wasn’t shy about tackling them. Some wondered why he decided to sinter the metal powder with an electron gun when solid-state lasers are cheap, easily available, and relatively straightforward to work with. But while the laser might seem like the easier solution on the surface, Agustin points out that using a magnetically focused electron beam gives his printer some unique capabilities.

For example, he can easily defocus the beam and pass it over the entire build plate to pre-heat the powder. The steerable beam doesn’t require mirrors either, which not only reduces the weight and complexity of the machine, but in theory should allow for faster print speeds. The beam can be moved in the X/Y dimensions with an accuracy of 0.01 mm, and while the beam diameter is currently a respectable 0.5 mm, Agustin says he’s working on bringing that down to 0.1 mm for high detail work. The temperature at the focal point of the beam is between 1,400 and 1,500 °C, which he notes is not only hot enough to melt the powdered metal, but can also weld stainless steel.

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Hackaday Podcast 159: Zombie Killer Or Rug Maker, 3D Printed Rims, 1950s Drum Machines, And Batteries On Wheels

Join Hackaday Editor-in-Chief Elliot Williams and Managing Editor Tom Nardi as they look back on the best hacks and stories of the previous week. There’s plenty in the news to talk about, though between faulty altimeters and the ongoing conflict in Ukraine, it isn’t exactly of the positive variety. But things brighten up quickly as discussion moves on to 3D printed car wheels, a fantastically complex drum machine from 1958, a unique take on the seven-segment flip display, and a meticulously designed (and documented) coffee machine upgrade. Somewhere in there a guy also recreates a rare German anti-air rocket launcher from WWII, but it’s all in the name of history. We’ll also tackle two very different forms of electric propulsion, from the massive wheeled batteries popping up in garages and driveways all over the world to high-efficiency thrusters for deep space missions.

Direct Download (~60 MB)

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

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