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4 pictures in a cube

A photo of a wooden cube, displaying an adorable creature.

This cube is supposed to be cute. When shaken, it randomly displays one of four pictures, which are carved on pieces of polycarbonate.


The display is an edge-lit LED display, such as the one here. Each piece of plastic has one of the images stratched into it, and a super-bright white LED lights the plate from the side. The images in the back are visible through the plates that are not lit.

Each display plate is bordered with aluminum foil to reduce scattered light. The outer side of the foil is painted black, whereas the inner surface is reflective to increase the brightness.

The display plates were cut of empty CD cases. The plastic is quite brittle, so I needed a few tries — fortunately the cases are ubiquitous. After that, I put each plate on a printed paper, and carved (with a utility knife) through the images that I had stolen from the internet.


Schematic diagram of the electronics.

A PIC16F689 microcontroller controls the whole thing, with a tilt switch for input. Every time a pulse occurs, the program lights up a random led and stores the random seed number to EEPROM for next use. After 15 seconds without changes, it goes to low-power sleep mode.

It has a 3.6V 1100 mAh litium battery (the same kind that is used on some motherboards), which I estimate will last up to 10 hours of continuous use or about 3000 shakes. The sleep mode takes just about 2 µA, so it is insignificant to battery life.

A finishing touch is the wooden box, with grooves to fit the dark acrylic front plate, and polished lacquer finishing.


In case you are interested, the Eagle design files, schematic and PIC assembler source code are downloadable below. You can go and find your own images, though.

– Petteri Aimonen on 16.7.2010

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