World’s Smallest LED Cube – Again

There’s a new challenger on the block for the title of the “Worlds Smallest 4x4x4 RGB LED Cube“. At 13x13x36 mm, [nqtronix]’s Cube Pendant is significantly smaller than [HariFun’s] version, which measures in at about 17x17x17 mm just for the cube, plus the external electronics. It took about a year for [nqtronix] to claim this spot, and from reading the comments section, it seems [HariFun] isn’t complaining. The Cube Pendant is small enough to be used as a key fob, and [nqtronix] has managed to really cram a lot of electronics in it.

The LED’s used are 0606 RGB’s which are 1.6mm square, although he did consider using 0404’s before scrubbing the idea. There’s many ways of driving 192 IO’s, but in this case, Charlieplexing seemed like the best solution, requiring 16 IO’s. Unlike [HariFun]’s build, this one is fully integrated, with micro-controller, battery and everything else wrapped up in a case made entirely from PCB — inspired by [Voja Antonic]’s FR4 enclosure technique, and the LED array is embedded in clear resin.

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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 project page.

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