Symmetry For Beginners – The Rubik’s Cube

Symmetry is everywhere in our natural world. Just take a look at your hands, a butterfly, or a sunflower.  It’s easy to pass off the idea of symmetry and symmetric structures as a simple quirk of existence, and to pay it little mind. If this is your view, I can assure you it will no longer be by the end of this series. If we force ourselves to look beyond the grade school applications of symmetry, we find a world rich in connections via many different types of symmetric identities. One of the most interesting is Gauge Symmetry, which lies at the heart of Quantum Electrodynamics, or QED (we’ll get into this a bit later in the series). Several branches of higher level mathematics study symmetry in detail, allowing a host of sciences, from physics to chemistry,  to view difficult problems and theories from a different perspective.

The subject matter of the ideas explored in symmetry is complicated, and not well known outside of academia and the theoretical sciences. It is the goal of this series of articles to simplify some of the concepts that underpin the study of symmetry, so that the average hacker can gain a basic (and I mean basic) understanding of this fascinating body of knowledge, and put it to use in future projects.  We’ll start things off by taking a look at a machine that has crossed the Hackaday server many times – those nifty Rubik’s Cube solvers. Just how do those things work anyway?

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Real-time Driving Of RGB LED Cube Using Unity3D

RGB LED cubes are great, but building the cube is only half the battle – they also need to be driven. The larger the cube, the bigger the canvas you have to exercise your performance art, and the more intense the data visualization headache. This project solves the problem by using Unity to drive an RGB LED cube in real-time.

Landscape animation RGB Cube - smallWe’re not just talking about driving the LEDs themselves at a low level, but how you what you want to display in each of those 512 pixels.

In the video, you can see [TylerTimoJ]’s demo of an 8x8x8 cube being driven in real-time using the Unity engine. A variety of methods are demonstrated from turning individual LEDs on and off, coloring swaths of the cube as though with a paintbrush, and even having the cube display source image data in real-time (as shown on the left.)

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Resistance Is Futile: Balancing Cubes Are Taking Over!

It’s been a while since we’ve seen a balancing cube, but as different companies and universities start making them, we’re excited to see how they continue to develop. This one doesn’t really have a catchy name, but its designers [Erik Bjerke] and [Björn Pehrsson] call it a Nonlinear Mechatronic Cube.

Very similar to Cubli — the first self-balancing cube inside of balancing cubewe remember seeing — this cube can jump up from surfaces, “walk” and balance in any orientation.

The system features an IMU to determine orientation, three gyros powered by beefy 70W motors, three bicycle brakes powered by servo motors, and a microprocessor to control it all.

The way it balances is quite obvious with the gyros, but the ability to jump comes from the rapid breaking of the “reaction wheels”, allowing for a sudden impulse of force that is powerful enough to reorient the entire cube. The interesting part is how both systems are actually controlled individually with separate control systems.

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Converting A GameCube Controller To USB

The GameCube controller is a favorite among the console enthusiasts new and old, and with Nintendo’s recent release of the Smash Bros. edition of this controller, this is a controller that has been in production for a very, very long time. [Garrett] likes using the GameCube controller on his PC, but this requires either a bulky USB adapter, or an off-brand GameCube ‘style’ controller that leaves something to be desired. Instead of compromising, [Garrett] turned his GameCube controller into a native USB device with a custom PCB and a bit of programming.

First, the hardware. [Garrett] turned to the ATtiny84. This chip is the big brother of the ubiquitous 8-pin ATtiny85. The design of the circuit board is just under a square inch and includes connections for the USB differential pairs, 5V, signal, and ground coming from the controller board.

The software stack includes the micronucleus bootloader for USB firmware updates and V-USB to handle the USB protocol. There are even a few additions inspired by [Garrett]’s earlier shinewave controller mod. This controller mod turns the GameCube controller into a glowing hot mess certain to distract your competitors while playing Super Smash Bros. It’s a great mod, and since [Garrett] kept the board easily solderable, it’s something that can be easily retrofitted into any GameCube controller.

Building The World’s Smallest RGB LED Cube

What’s the smallest RGB LED cube? A 1x1x1 cube is easy, but it’s a stupid joke and we’ve heard it before. No, to build the smallest LED cube, you’ll have to stuff 64 RGB LEDs into a cubic inch, like [Hari] did with his miniscule LED cube.

A single column of Charlieplexed LEDs. Note the resistor for scale.
A single column of Charlieplexed LEDs. Note the resistor for scale.

One might think that individually addressable RGB LEDs are the way to go with an LED cube this small. Anything else would hide the LEDs behind a mess of wires. This isn’t the case with [Hari]’s LED cube – he’s using standard surface mount RGB LEDs for this build. But how is he connecting the things?

The entire build was inspired by the a much earlier project, the Charliecube. This LED cube, like [Hari]’s uses Charlieplexing to condense all the connections for a column of LEDs to only four wires. Repeat that sixteen times, and [Hari] built himself a tiny, one-inch cube of glowey goodness.

The cube itself was built with a PCB backplane designed in Eagle and fabbed at OSHPark. The LEDs are driven by an Arduino Nano. If you’d like to build your own, or you’re a masochist for dead bug soldering, you can grab all the design files over on [Hari]’s hackaday.io project page.

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Robot Solves Rubik’s Cube In Just One Second

Some of the fastest Rubik’s cube solvers in the world have gotten down to a five second solve — which is quite an incredible feat for a human — but how about one second? Well, [Jay Flatland] and [Paul Rose] just built a robot that can do exactly that.

The robot uses four USB webcams, six stepper motors, and a 3D printed frame. The only modification to the Rubik’s cube are some holes drilled in the center pieces to allow the stepper motors to grip onto them with 3D printed attachments.

The software is running off a Linux machine which feeds the data into a Rubik’s cube algorithm for solving. In approximately one second — the cube is solved.

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CubeSat Challenge Winners Show Interesting Design Approaches

The winners are in for the GrabCad CubeSat Challenge, which asked designers to rethink the way that CubeSats are built. These tiny 10 cm square satellites are the hot thing in orbit, and the competition was looking for new ways to build and pack more into this tiny space. The winners offered some fascinating new approaches to building CubeSats, and some excellent design lessons that anyone can use.

The winner was FoldSat, by [Paolo Minetola]. His excellent design is a 3D printed folding case for a satellite that is built from just two 3D printed parts. The case can be snapped together and offers multiple ways to mount electronic components and sensors inside. [Paolo] estimates that it could save 40% time and 30% materials from existing CubeSat casings, which means more space inside and more time to build. It is an excellent example of how 3D printing can make things cheaper, easier and better, all at the same time.

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