Instructables

Step 6: The anatomy of a LED cube

We are going to be talking about anodes, cathodes, columns and layers, so lets take a moment to get familiar with the anatomy of a LED cube.

An LED has two legs. One positive (the anode) and one negative (cathode). In order to light up an LED, you have to run current from the positive to the negative leg. (If i remember correctly the actual flow of electrons is the other way around. But let's stick to the flow of current which is from positive to negative for now).

The LED cube is made up of columns and layers. The cathode legs of every LED in a layer are soldered together. All the anode legs in one column are soldered together.

Each of the 64 columns are connected to the controller board with a separate wire. Each column can be controlled individually. Each of the 8 layers also have a separate wire going to the controller board.

Each of the layers are connected to a transistor that enables the cube to turn on and off the flow of current through each layer.

By only turning on the transistor for one layer, current from the anode columns can only flow through that layer. The transistors for the other layers are off, and the image outputted on the 64 anode wires are only shown on the selected layer.

To display the next layer, simply turn off the transistor for the current layer, change the image on the 64 anode wires to the image for the next layer. Then turn on the transistor for the next layer. Rinse and repeat very very fast.

The layers will be referred to as layers, cathode layers or ground layers.
The columns will be referred to as columns, anode columns or anodes.
 
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llb4433 years ago
shouldn't the bottom left comment read: "An 8x8 image is flashed first on layer 0" or am i missing something?

p.s. Great istructable. love the videos and pics, very helpful...
T-Prime llb4431 year ago
I believe you are correct. 8x8 grid for a total of 64 points.
x-pecado3 years ago
The current flows from the negative (cathode) to positive (anode), because the positive side has fewer electrons than the negative. As the atom tends to be neutral, this condition of more electrons on one side and less of the other causes the electrons to migrate to the positive (fewer electrons) when a short circuit.
You're describing electron flow. His description in the instructable is correct for current flow. The standard modern definition of current is the flow of positive charge, so it's in the opposite direction to electron flow. (Note that if you have "holes" or positive charges moving, as in some conductors, then the current would be in the same direction as those particles. That's why it's easier, at the macroscopic level, to just talk about the net movement of positive charge, and not worry about what the particles are doing. So that's why electrical engineers just say current and don't think about electrons.)
You're both right. Current can be describe either way, they are just two conventions to describe the same effect. Personally, I was trained with the Electron Flow model.