A resolution of 8x8 pixels may not sound like enough for anything interesting, but with the right setup, it is possible to create beautiful, complex animations and even add some interactivity.

In the next pages I will detail the steps needed to build the low-res display you see in the video below.

Step 1: Parts and Tools

The parts needed are:
- An LED matrix driver, I used a Rainbowduino from Seeed studio
- An RGB LED matrix compatible with the Rainbowduino
- A mini USB extension cable, used to bring out the connection from the board
- A wooden box
- Foam core board or a piece of card board
- A sheet of tracing paper
- Nylon standoffs for mounting the PCB.
- Optional: volume sensor / other amplified microphone

More details are in the attached BOM

The tools needed
- A drill
- A ruler
- A pair of scissors
- A box cutter
- A Pencil
- Paint brushes and paint
- Hot glue gun
- A screw driver

You will also need some adhesive tape.

LED-matrix_BOM.xls
Download

Step 2: The Box

We will use a wooden box as the enclosure of the system.
I used a box sized 16x16x7cm, but any box big (and deep) enough will do.

- Disassemble the box - this is essential to allow easy drilling and painting
- Measure, mark and drill the holes for the PCB (3.5mm dia). Make sure that the holes match the ones on the board and that the board will be centered inside the box.
- Make the hole for the usb socket. It should be a bit bigger than the connector to leave room for glue.
- Cut a window in the lid of the box. I made it 9x9cm and used a box cutter. Using a laser cutter or a dremel tool can be easier.
- Paint the insides of the box and the lid in black. This is important to improve the contrast of the display.
- Paint the outside in whatever color you like. I used white because it looks nice and does not compete with the animations.
- Reassemble the box

Step 3: The Diffuser Screen

The diffuser screen is made of a sheet of tracing paper, mounted on a frame made of foam core or cardboard.
I chose to use tracing paper as it is cheap, easy to find and gives the right balance between transparency and diffusion.

- Cut a square of foam-core sized to match the inside of the lid. Mine was 14.5x14.5cm
- Cut a window in the center of the square which is a little bigger than the window you made in the lid. Mine was 10.5x10.5cm
- Paint one side of the frame black. Again, this is important to improve contrast.
- Cut a square of tracing paper smaller than the size of the frame but larger than the size of the window. I made it ~12x12mm
- Attache the tracing paper to the foam core frame. I used adhesive tape as wet glue deforms the tracing paper

Step 4: Assembly

Now it's time to put everything together

- Glue the female side of the USB cable to the inside of the hole on the box. Hot glue worked well for me
- Secure the standoffs to the box
- Connect the male side of the cable to the connector on the PCB
- Optionally, connect the microphone to the relevant pins on the PCB (vcc, gnd and scl/a5)
- Mount the PCB on the spacers
- Mount the LED matrix to the PCB
- Tuck the diffuser screen inside the lid - it should be held in place by friction.

Step 5: Firmware

Now comes the fun part.
The Rainbowduino includes an FTDI chip so it can be programmed exactly like an arduino duemilanove.
You will need the Rainbowduino libraries available from here.

To get started, try the examples that come with the library. There are also some example sketches I made available in this repository:
https://github.com/giladaya/arduino-led-matrix

More complex animations can be achieved using my particle system library which is available here with several examples:
https://github.com/giladaya/arduino-particle-sys

If you attached a microphone, some of the examples in this library use its input to affect the animation, as can be seen in the following videos

Try playing with the parameters of the animations or think of new ideas, it's addictive!

Note:
I picked the length of the standoffs to be 15 mm after some experimentation.
According to your specific diffuser material, you may need a different distance - experiment to get the best results.

Enjoy!