A quick course in Binary

led matrix display modules

If you enjoyed experimenting with blinking LEDs, then you’re going to love LED matrix modules. An LED matrix module consists of several rows and columns of LEDs that you can control individually or in groups. The example that we’ll use (shown in Figure 6-16) has eight rows and eight columns of red LEDs for a total of 64 LEDs.

Figure 6-16: LED matrix
In this project we’ll build one circuit, and then we’ll use various sketches to create different effects.

The LED Matrix Schematic

The schematic symbol for the matrix looks a bit complex, as shown in Figure 6-17.

Notice that the numbering of the rows and columns of LEDs does not match the order of the pins beneath the matrix; see the circled pin numbers in Figure 6-17. On the underside of our matrix, pin 1 is indicated at the bottom right. For example, in Figure 6-18, you can see a tiny 1 printed below the pin.

The pins on the LED matrix are numbered clockwise, with pin 8 at the bottom left and pin 16 at the top right. We’ll control the matrix with two 74HC595 shift registers in a way that’s similar to the method used in Project 19.
Figure 6-19 shows the schematic for our project. Resistors R1 through R8 are 560 ohms each. One shift register controls the rows of LEDs, and the other controls the columns. The LED matrix (not shown here) is connected to the outputs at the bottom of this schematic with the pin connections listed in Table 6-3.
Table 6-3: Matrix to 74HC595 link table

Row SR Pin	Matrix Pin	Column SR Pin	Matrix Pin
15	9	15	13
1	14	1	3
2	8	2	4
3	12	3	10
4	1	4	6
5	7	5	11
6	2	6	15
7	5	7	16