The matrix

Step 2: The matrix

I will be building my own LED matrix for this project using 5mm leds and a prototyping board from Radio Shack. It should be noted that you can purchase 8x8 dot matrix led modules from several sources, including ebay. They should work just fine with this instructable.

Construction Considerations

Alignment
The LEDS need to be aligned so they face the same direction at the same angle. I found the easiest option for me was to put the body of the LED flush to the board and hold it there with a small piece of plexiglass and a clamp. I put a few LEDs in place a couple of inches away from the row I was working on to make sure the plexiglass was parallel with the prototyping board.

Rows and Columns
We need to have a common connection for each row as well as each column. Because of our row and column driver choice we need to have the anode (positive lead of the LED) connected by row and the cathode (negative lead of the LED) connected by column.

Control Wires
For this prototype I am using solid core (single conductor) hook-up wire. This will be very easy to interface with a solderless breadboard. Feel free to use a different connector type to suit your project.

Building the Matrix

1. Place the first column of LEDS in the prototyping board.
2. Double check that your polarity for each LED is correct, this will be very difficult to fix if you realize it later.
3. Solder both leads of the LED to the board. Check to make sure they are aligned correctly (not at weird angles) and clip off the cathode leads. Make sure you do not clip the anode lead, we will need that later so just leave it pointing up.
4. Remove the insulation from a piece of solid core wire. Solder this piece of wire to each cathode right at board level.

I tacked this at each end then went back and added a bit of solder at each junction.
This wire should run past your last LED to make for an easy interface when we add control wires.

5. Repeat parts 1-4 until you have all LEDs in place and all column buses soldered.
6. To create a row bus, bend several of the anode leads at a 90 degree angle so they touch the other anode leads in the same row.

There are detailed pictures of this below.
Take care not to let these come in contact with the column buses, creating a short circuit.

7. Solder the leads at each junction and clip off the excess anode leads.

Leave the last anode sticking past the final LED. This will be used to connect the row driver control wires.

8. Repeat parts 6 & 7 until all rows buses have been soldered.
9. Attach control wires.

I used red solid core wire for the rows and black for the columns.
Connect one wire for each column and one for each row. This can easily be done at the end of each bus.

Important

This LED matrix does not have any current limiting resistors. If you test this without resistors you will probably burn out your LEDs and all this work will be for nothing.