in this instructable i am going to make a rgb led cube(charlieplex cube)
ok…what is charlieplex cube…?
Charlieplexing is a technique for driving a multiplexed display in which relatively few I/O pins on a microcontroller are used e.g. to drive an array of LEDs.The method uses the tri-state logic capabilities of microcontrollers in order to gain efficiency over traditional multiplexing. Although it is more efficient in its use of I/O, there are issues that cause it to be more complicated to design and render it impractical for larger displays. These issues include duty cycle, current requirements and the forward voltages of the LEDs.why charlie cube is differ from other cubes……?
Other cubes use shift registers, decade counters, or other components to control all the LEDs and that will increse the making cost. The charliecube can be run using only 16 digital pinsof arduino with no extra components…total cost this cube is around 9$.”

Link