What Matters 2 Me

The continuation of my 3D TicTacToe LED Matrix project.  See Introduction and Part 1.

The 4x4x4 LED matrix is controlled by a Maxim MAX7219 display driver IC.  Using the MAX7219 reduces the number of Arduino pins needed to control and power the matrix from 16 down to 5.  The 3D TicTacToe sketch uses the Arduino Matrix library by Nicholas Zimbetti and simple coding from his hello_matrix sketch.  This library should already be included with all up-to-date arduino installations.  The design of the protoboard is based on Michael Margolis’s Arduino Cookbook project 7.13 “Controlling an Array of LEDs by Using MAX72xx Shift Registers” and the Maxim MAX7219 datasheet.

Shopping List:

• printed circuit board
• MAX7219 display driver IC
• 33 kΩ resistor
• 0.1 μF capacitor
• 10 μF capacitor
• 24 AWG solid wire in various colors (I used 22 AWG and the resulting LED matrix / protoboard connection is extremely stiff)
• box with lid (I used a $2 white cigar box from Michaels)

Connections:

To power the matrix connect the Arduino’s 5V pin directly to the MAX7219 V+ (pin 19) and through a ~30 kΩ resistor to ISET (pin 18).  I used a 33 kΩ resistor on mine.  Connect the Arduino’s GND to the MAX7219 GND pins (4 and 9).  Insert 0.1 and 10 μF capacitors between the 5V and GND to prevent noise spikes.

To control the matrix connect Arduino pins 4, 5, and 6 to the MAX7219 pins 12 (LOAD), 13 (CLK), and 1 (DIN), respectively.

The anode wires of the LED matrix will be connected to the MAX7219 SEG pins A-G, plus SEG DP, while the cathode wires will be connected to DIG pins 0-7.  Use 24 AWG wires that are long enough to reach where they need to go on the LED matrix.  Mine were a bit long at ~20 cm, but the extra should fit in the box you use or can be trimmed later.  I suggest using one color for the anode and a different color for cathode.  Solder 8 wires of one color to SEG pins A-DP and the 8 other wires to DIG pins 0-7.

If you want a nice looking 3D matrix display you’ll want a box to contain the Arduino, protoboard and wires, and a top for the LED matrix to sit on.  I used the same printout as used to drill the board holes to determine where to drill small holes in the cigar box top for the wires.  You’ll only need the seven side holes, but make the corner hole about 1.5x as big as the others.  Once the wires are soldered to the protoboard, thread them through the appropriate holes of the cigar box top.  Connect the wires to the appropriate lines on the LED matrix.  You’ll probably want to attach the wires temporarily to the LED matrix for testing before permanently soldering them.

Below are shots of the protoboard.  I know they’re difficult to make out with the gaggle of wires everywhere, and so I’ve taken shots from various directions.

Shot A: shows 33 kΩ resistor from pin 18 to 5V, and pin 19 straight to 5V.

Shot B: difficult to see pins 4 (buried) and 9 to GND

Shot C: MAX7219 pins 12 (LOAD) and 13 (CLK)

If you have any questions, need further assistance or require additional pictures or diagrams, please let me know in the comments and I’ll do my best to address them.

Up Next: Programming the Arduino To Play 3D TicTacToe