Probably you have reached this page because you have seen one of the video clips on led cubes, which are spread in the internet, and you have decided to build one by yourself.
Well, I am happy to let you know that you have got to the right place. Here you will find my notes, the pictures for crafting, the source code for the software that I developed for controlling the cube, and many demonstration videos.
Before you start, please read the whole instructable. This is advisable to have a global view of the project.
Prior to enter in the practical steps, a short theoretical introduction is necessary to well understand what we are talking about.
How the cube is made:
The dimensions of the cube will be 8 led by 8 led, by 8 led, for a total of 512 leds. The whole structure will be based on a wood board.
The concept of persistence of vision:
In this project we will exploit the persistence of vision. This phenomenon is a feature of the human eye and is responsible for the illusion that a movie is not composed by individual still images. All the animations are based on this biological dis-functioning of the human eye. If we can switch on and off the leds in a sufficiently quick time, (a few milliseconds) they will appear as if they were simultaneously on.
We use the persistence of vision because simultaneously switching all the cube leds on would require a very high electric current (in ampere). Actually, if we consider that the high brightness leds of this project require about 20 mA, we can calculate that 512 leds would require 10.24 A. This high current is hard to manage. So, what we do? We switch on a cube layer at each time! In this way the current consumption will never exceed 1.28 A (20 mA x 64 leds), which is easily supplied by a good voltage transformer. Let us suppose that we want to make the cube appear as completely switched on. To achieve that we simply have to switch on the different layers one by one at high speed. To a human eye the cube will appear as completely lighted.
How to control each led:
In order to independently control each led, we divide the cube into horizontal layers and vertical columns.
All the leds of a horizontal layer will have the cathodic contact (-) in common.
All the leds of a vertical column will have the anodic contact (+) in common.
Overall, it will be necessary to control 8 cathodic contacts to select the layers and 64 anodic contacts to select the columns. The combination layers by column will select and switch a single led.
The 8-bit shift registers:
The shift registers are composed by 1-bit memory cells connected one each other. At each clock impulse, they allow the bit flowing from a cell to the next-one. The registers used in this project are SIPO (serial input-parallel output) type. The data are charged one by one through the input bits and the output bits are simultaneously collected from the 8 outlets.
To power the cube and the control circuit it is necessary a power supplier with the following specifications:
- voltage: 5 volts (stabilized)
- current: 2 ampere (4 is better)
The finished cube functioning.