1. Creating the 4x4x4 LED matrix
The continuation of my 3D TicTacToe LED Matrix project. See Introduction.
The matrix is based on an 8×8 LED matrix design, where it’s been divided into fourths and wired to work on four levels. Here’s a diagram of an 8×8 matrix: The structure of the 3D matrix is entirely composed of the anode LED leads soldered together, the cathode LED leads soldered together and a few extra wires to make connections. Here’s a picture of the semi-final product (note: from a previous build):
Four 4×4 LED matrices need to be created. Practically any LEDs will do, as I initially just used the cheapest ones I could find, but the current build is using 350 MCD yellow ones (see shopping list). Note also that different LEDs have different lead lengths. You want lengths that are 25 mm or more. I tried using shorter length LEDs, but the resulting matrices were too small to work with. My 4×4 matrices are modeled after the above 8×8 matrix. There’s an Instructables.com project by Electronics Man where he suggests drilling holes in a board to place the LEDs properly aligned at the correct distances from each other. I used his example to make the board and securely place the 16 LEDs for soldering. However, I believe his overall LED matrix design is different from mine, and will likely not work with the circuitry and software used in my project. Here’s an OpenDocument drawing template of the 21 mm-spaced LED matrix holes that I printed out and taped on the board. I then used a punch to make a small dent at each of the sixteen points before drilling. I used a hand-powered drill starting with the smallest size drill bit and worked up in bit size until the LEDs fit snugly into the holes.
Fit the LEDs into the holes with the cathode (shorter) leads above the anode leads at about 45 degrees.
Bend the cathode leads down right at the base and push them so they’re all pointing to the top of the board.
There should be plenty of space between the anode and cathode leads. Now with small needle nose pliers bend the anode (longer) leads about 3 mm above the LED base – perpendicular to the cathode leads. They should be well above the cathodes.
Adjust all of the leads so they overlap appropriately and solder them together. Gently prod out the LEDs from the other side of the board, and you should have a very stable 4×4 matrix. Make three more identical matrices, except two should have the cathodes pointing down instead of up. The two pointing down are levels 1 & 3, the the two pointing up are levels 2 & 4.
The four matrices now need to be soldered together. I differentiate between the LEADS (the extra lead sticking out that’s not soldered to the next lead) and the LINE of soldered-together leads. It’s not straight forward so consult the following:
Top Level 4 Anode Leads: attach to anode line of Level 3. Bend the leads down so they can be soldered to the level below. Note that you can attach additional anode connections anywhere along the Level 4 anode line to the corresponding anode line below it on Level 3 – this will add support to the structure (see picture below).
Top Level 4 Cathode Leads: attach to cathode line of Level 1 (bottom). Do this last, after all of the other levels have been soldered together. You’ll need to use wire to make the connections long enough. I recommend 24 AWG.
Level 3 Anode Leads: leave alone for now.
Level 3 Cathode Leads: attach to cathode line of Level 2. As before, bend the leads down so they can be soldered to the level below, and attach addititonal cathode connections to support structure.
Level 2 Anode Leads: leave alone for now.
Level 2 Cathode Leads: leave alone for now.
Bottom Level 1 Anode Leads: bend leads up to solder to Level 2 line. Attach additional anode connections to support structure.
Bottom Level 1 Cathode Leads: leave alone for now.
I’ll admit soldering the levels together is much more of an art than a science. It’s warping a single 8×8 matrix into 4 levels and you need to be careful to solder the correct leads and lines. I still haven’t developed a technique that I’m really happy with. This picture shows the final soldered together structure including a support attachment:
Once all of the levels have been soldered together, and a few structural connections added for stability, the wires that connect the matrix to the controlling prototype board can be added. I used 8 green for the cathodes and 8 red for the anodes. Make the wires long enough to reach the board – I suggest starting with 25 cm to be sure it’s long enough. Use somewhere around 24 AWG solid (not stranded) to make it somewhat pliable. Solder these wires to the leads above that were left alone. Finally, clip all extraneous leads and wires off the matrix. Finished matrix:
Up Next: Developing The Protoboard To Control The Matrix