Here's a video of it in action. They're tricky to capture video of (particularly when using a cheap digital camera), but it gives you a rough idea:
This is an incredibly simple project to put together, thanks largely to the LEDs: I use RGB LEDs with color-changing circuitry built right into the package. You just provide power, and the LEDs cycle through red, green, blue, and various combinations thereof. One aspect of these LEDs is that the timing is slightly different in each one, so while they start out in sync, they quickly fall out of phase. I consider this a feature, not a flaw, as it results in the emergence of interesting, seemingly unpredictable patterns.
No soldering is required, just some crimping and a bit of hot glue.
The parts are easy to obtain online, but I also offer kits through Make Magazine's online store, the MakerShed, for $15:
Step 1: Parts and Tools
The screen: I used 4 x 3 piece of scrap translucent white plastic. Velum from the paper department of your local art store works perfectly as well.
5 x 4 matboard frame with a 2" x 3" window: You can get a piece of black mat board cut to these dimensions in any framing store for a few bucks, or cut one yourself from suitable material, such as stiff black cardstock.
Battery case for 2 AA batteries w/ wire leads and power switch: These can be purchased online from Jameco, part #216120, and can likely be found at Digikey.com or Mouser.com as well. Similar battery holders can also found at Radio Shack, but you may have to solder a simple power switch into the circuit yourself.
3 RGB color-changing LEDs: I get these here: http://stores.ebay.com/Amigo-Of-China. Look for "5mm RGB LED Slow Colour Change." Make sure you get the clear ones, as the diffused ones don't work as well for this specific project (but you can do other cool things with them!) Everything on this store seems to come with free resistors, which you don't need for this project, but hey, free resistors.
2 butt splices: (tee hee... butt splices). These can be found at Radio Shack; something in the range of 18-20 gauge or thereabouts works well. I use the non-shrink-wrap-coated ones, but the coated ones should work fine. You can also get these from Jameco, part #494469, but the minimum order is 100.
Also shown in the picture: Glue Dots. These come with the kit, and are used as an alternative to hot glue to attach some parts together. These can be found in a craft supply shop (you should get the largest, tackiest (stickiest) ones they have), but a hot glue gun works just as well for these steps, and is nice to have anyway when it comes time to "customize" your LED artwork.
You will also need 2 AA batteries, and some scotch tape.
TOOLS (not shown)
Wire clippers and strippers: these may be needed for cutting and trimming the wire leads on the battery case.
Scissors or similar cutting implement if you are going to cut your own screen or mat board.
Hot glue gun: As mentioned above, glue dots can be used instead of hot glue for attaching some parts, but the glue gun is useful for the optional (but highly recommended) step of customizing your artwork.
Step 2: Assemble the Frame
Flip your mat board frame (or equivalent) over so you're looking at the "back." If you are using a stiff piece of plastic as your screen, position one edge so that it is close to one wide edge of the frame (as in the picture); this will be the "bottom" of the frame, and the battery pack needs something solid to attach to. If you are using velum, position it higher so that as much of the bottom edge of the frame is exposed (when using velum, you will want to attach the battery pack directly to the mat board).
Next, tape the left and right edges of the screen to the back of the frame. Make sure the tape does not overlap with the window, or it will show through when the screen is illuminated from behind.
Step 3: Prepare the LEDs
Take a close look at one of the LEDs, and note that one of the wire leads is longer than the other. The longer lead is the positive lead. Gently bend the positive lead about 15 degrees. Do the same with the other (negative) lead.
Bend the remaining 2 LEDs in the same way.
Step 4: Crimp the LEDs
Hold your 3 LEDs side-by-side, so that the 3 positive leads are parallel. Place a butt splice over all 3 positive leads. With your pliers, squeeze the butt splice where it encloses the 3 LED leads, being careful not to crimp the opposite site of the splice. Apply enough pressure so that the 3 leads are held solidly in place.
It's very important that you remember which are the positive LED leads; you may want to mark this splice with a small piece of tape. If you get confused, each LED lens has a little flat spot next to the negative lead. Now gather the negative leads, and place the other butt splice over all 3 leads. Again, give it a good squeeze, being careful only to crimp the LED side of the splice.
Step 5: Wire LEDS to the Battery Case
Take the end of the red wire lead from the case and insert it into the open end of the butt splice that is attached to your positive LED leads. With your pliers, squeeze the splice firmly over the red wire. Next, insert the black wire in the other splice, and squeeze.
Now gently bend the leads at each splice, so it looks like the picture. It is very important that the two splices never touch, if they do, it will prevent your LED Art from lighting up, and quickly drain the battery.
Step 6: Test the LEDs
Open up the battery case. Sometimes these cases have little retaining screws to hold them shut, in which case you'll need a small phillips head screwdriver to remove it. Pop in a couple AA batteries, close the case, and switch it on.
The three LEDs should immediately turn on, and begin to change color. If they don't, here are some troubleshooting tips:
If some but not all of the LEDs turn on, you probably have one or more LEDs in backwards; that is, you didn't line up all of the positive LED leads. You may need to pull off the crimp with a pair of pliers, or cut it off \with a wire cutter. There should be enough extra LED lead to re-crimp, but you'll probably need more butt splices, which can be found at Radio Shack.
If none of the LEDs light up, you may have reversed all of the LEDs (i.e., attached the red wire where the black wire should be, and vice versa). Rather than pull or cut the splices apart, put the batteries into the holder in reverse.
Still no luck? It could just be a bad connection. Try cutting off the crimps, re-stripping the wire, and re-crimping w/ new butt splices.
Step 7: Attach LEDs to the Case
This step explains how to use the glue dots that come with the kit to attach the LEDs to the battery case. Alternately, you may use a small dab of hot glue, which is actually slightly sturdier once it's set.
Gently peel the strip of glue dots open, being careful not to touch the blobs of glue, or get them stuck on anything (they're like way sticky). Cut the backing so you have a single dot, and affix it to the case, near the switch.
Press firmly, and peel off the backing (if needed, use your finger to help the glue dot stick to the case, but try not to touch the glue more than necessary).
Now firmly press one of the crimped splices (it doesn't matter which) against the glue dot.
Step 8: Test the "Display"
Now it's time to get a sense of how your LED Art will look, and make any adjustments or alterations. Dim the lights, put the switch on the case in the on position, and hold the frame up to the LED/case assembly, so that it projects onto the back of the frame.
Take a look at the front of the piece, and see how the colors and patterns change over time. You can adjust how your piece looks by gently repositioning the LEDs.
Step 9: Optional (Recommended): Distort the LEDs With Hot Glue
Without any further changes, your LED Art piece will cycle through seemingly endless patterns of light and color. You can further modify the appearance of your piece by dribbling a small amount of hot glue on the LED lenses. Instead of seeing individual red, green, and blue spots on the screen, you can create more interesting and complex patterns.
Plug in your glue gun and give it a few minutes to heat up. If you're a kid, you definitely need to get some adult supervision for this part!
Carefully drizzle small amounts of glue on the LEDs. Let the glue cool, and see how it looks when projected against the screen. Give it a few minutes to let the LEDs cycle through their various colors. Feel free to experiment, as it's easy to peel the cooled glue off the lens and try something different!
Step 10: Attach the Case and Frame
Once you're happy with how it looks, use the remaining glue dot to attach the frame to the battery case (hot glue works too). Apply the dot to the front of the case. Peel off the backing, and attach to the lower edge of the frame, where the plastic screen extends all the way to the edge of the mat. Apply some pressure to make it stick.
You now have a one-of-a-kind piece of LED artwork... enjoy!
I really like working with these LEDs, and they have a lot of creative possibilities. Here are some links to flickr sets of projects I created with them in the past, which this Instructable is based on: