This instructable is on a sound activated RGB Led Matrix made from RGB Led's and house hold items. The LED Matrix uses three 4-bit Binary Counters and one 4-bit Shift register (for the ground leads on the RGB LED's) to make the lights go in a jumbled hi - low mixed up count for cool effect.

Step 1: Parts, Tools, and Prices

I have a lot of the parts lying around so this build was very cheep. I spent about 15 - 20 bucks on a 100 count of RGB LED's I got from Ebay. and about 10 to 15 on the circuit board and IC's at Fry's Electronics in AZ. I used my Arduino as a 5V Power supply you could use a USB cable instead of the Arduino also an old PC Power Supply will work even better.

PARTS:
** QTY: 28 RGB LED's (from Ebay came with Resistors)
** QTY: 3 74LS193 (from Fry's Electronics)
** QTY: 1 74195 4-bit Shift Register (from Fry's Electronics)
** QTY: 1 Cardboard Box To Cut up
** QTY: 1 10FT RJ45 Cable to be striped for wire's (had lying around but you can get it any were since its to be striped go to local Good Will or yard sale supper cheep and maybe free)
** QTY: 20pk HOT Glue Sticks (Home Depo)
** QTY: 1pk solder (Fry's Electronics)

TOOLS:
** BOX CUTER
** Soldering Iron
** breadboard
** Hot glue gun
** Wire strippers
** BIC PEN

Step 2: Build the 4 X 7 RGB LED Matrix

To Start you need to measure and cut out the piece of cardboard your going to use as your frame and REG LED holder. I went with a 8" by 14" roughly, and then drew out 28 2" by 2" squares. To make the holes just the right size for the RGB Led's I used the head of a classic BIC pen. Place the RGB LED's in there holes and hot glue on place. Once the hot glue has cured then bend the RGB LED's leads to the cardboard. Spreading them apart as well. Get your soldering iron ready to solder some wire.

To have the matrix affect be possible you need to wire the RGB LED's a certain way. Going from Top to Bottom looking at the back side top left hand corner square, starts row 4 column 1, in this row which will be the same for all rows you will need to have all the ground leads from the RGB's soldered together in a line or row. Then in this column this will be the same for all columns you need to connect all the Color leads in a line or column. The Red leads all get soldered in a separate column, all the blue leads get soldered in a separate column, and all the green leads get soldered in a separate column.

To prevent a short you need to hot glue all wires and RGB LED's leads in place. I added Ducked tape as a backing cause ducted tape is cool for around the house projects.

Step 3: Building the Circuit to Control the Matrix

I started with 7447 chips but that was to much wire work so I ended up just using the 4-bit binary counters as my HI - LOW switches and a Shift Register for HI - LOW on the ground leads. Really basic wiring up on the breadboard did a search in Google for the data sheets of the chips for there pin outs, and added a TIP31 transistor which is commonly used as a switch for on off or in my case HI - LOW , I used the audio out port on my computer and an aux cable and used the Tip31 transistor as my clock pulse to have the 4-bit binary counters count up and down. My RED leads count up, my GREEN leads count down, my BLUE leads count up, and the 4-bit Shift register receives the data from the BLUE leads 4-bit binary counter and applies that to the ground leads. Then you just sit back and watch the magic happen :)

http://youtu.be/mpPYGqsZuYk