Dot Matrix 8x8 (2 color)

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LNM2088BEG2C Datasheet    Size: (274.19 KB)

The way you actually control them is like this:

ROW ---1-2-3-4-5-6-7-8
Column-2
---------3
---------4
---------5
---------6
---------7
---------8
You have to active a + pin and a - pin to light one of the lights (say for example the 6th led in the 2nd row, you would have to activate a positive charge on pin 6(or pin that goes to that column) and a negative charge on pin 2 (or pin that goes to that row

You will have two different positive pins for each led. One for one color and one for the other, however they use the same negative line.

Look at my 3x3 sketch in Fritzing:


This is the way it looks on the breadboard (in fritzing) but here is what it looks like in real life (Sorta)


Now then with these two things taken into account, you know you can't switch on and off a negative port on the arduino, so to sidestep this, you use a transistor OR a chip like the MAX7219CNG or a 74HC238, but for your understanding you should consider the theory of using the transistor.

You can use a transistor as a switch, and the beautiful thing about it, is it's an indirect switch which means you can switch positive OR negative signals on or off. So what you are doing is using the transistor as a sort of "negative switch", so you can switch on any positive and/or negative pins on the led matrix that you want at any given time.

Another way you could look at it is an old school time table.


Say you needed to get to LED number 42 (dont mind that there are other numbers the same.....) you need to put a positive charge on Row 7 and a negative charge onColumn 6.

Hope that helps!

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