Greg Payne’s 3x3x3 LED cube project via etchingpathways.blogspot.com:
The basic concept is this; the cube, in this case 3x3x3, is made up of columns (9) and layers (3).On each layer, all the cathodes are connected together and in each column, the anodes are connected together. Therefore, 12 ouputs are needed to control all 27 LED’s.
By driving the layer output low and the column output high, the specific LED will turn on. Driving both the layer and column output low, will turn the LED off. By sequencing what LED is on when, you can draw different patterns. The bigger the cube, the better patterns can be drawn.
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