Writing words by waving LEDs

I asked my little brother if I could destory is Harry Potter Powercaster toy. He agreed (it hasn't been used in years). What did I get out of it?

7 LEDs on a stick. Said stick waves back and forth. If you switch the LEDs on and off fast enough (and precisely/accurately enough), you can write words. Cool, I think. I want to hack that.

After some ripping apart, I get to the wires and such. It appears there are 8 wires going to the LEDs. Probably a commond GND and a +5V (or whatever) for each LED. Almost. It turns out there's a common +5V, and a GND for each LED. Oh well. It just makes things backwards.

The common positive lead goes into +5V (with resistor, of course). LEDs 1-7 go into pins 2-8. When the pin is LOW, the LED is on, when the pin is HIGH, the LED is off. Simple enough.

http://youtube.com/watch?v=mqfjrxsNJ54 (writes "HI")

http://youtube.com/watch?v=JN6xnTHElDQ (writes "WOOT")

Current poor, uncommented code: http://pastebin.ca/837605

I feel like this is okay progress for yesterday. Hopefully today will be more awesome.

TODO: Add a photodiode/phototransistor setup so I can accurately time the period of the arm. Figure out how to use the coils to make the arm swing. None of this finger crap. Add computer controlled-ness. Add horizontal/vertical scrolling. (Figure out how to encode the data better + Have the computer do the work)

EVENTUALLY: Make a giant one. Stop using tape to hold wires into the headers.

Alright. I'm going to go plug my soldering iron in.

Nice hack ivong! Have you seen the POV kits that adafruit sells? POV stands for Persistance Of Vision, the effect that the LEDs exploit to write text in air. You might want to hack the wand and spokePOV kits there to make even cooler displays. I was thinking about how to use the spokePOV to make a hemispherical display. spokePOV mounts on a bicycle wheel, and you can mount more than one to get the effect at lower speeds. OR - you could offset each of the additional ones to create more "scan lines". Or to combine colors. If you turned the wheel horizontal, then turned it into a dome, you would have the kind of display I am thinking about building this year (prototyping it with 3 spokePOV kits). But I'm to busy right now with robots to build it. Sigh.