I made this a over a year ago. Just thought I'd share it with you. Video http://www.youtube.com/watch?v=dt_WGIWt5G8Tutorial Ok, this is quite complicated, so i will do my best to help you understand. First off, I took a hard drive and removed the disks, so that all that remains is the armature. The armature uses an electromagnetic coil suspended between two high power magnets. When an electrical current is sent through the electromagnetic coil, the armature moves in one direction. When you switch the poles ,put (+) to (-) and (-) to (+), the arm moves in the other direction. This can be compared to a speaker, which has a magnet suspended in a coil. A speaker works by osculating, switching from (+) to (-), very fast, producing audible sound/music. Now what do you think would happen if you hooked your stereo up to the hard drive armature? It acts as a speaker. YES THE HARD DRIVE IS NOW A SPEAKER!!! All I did was attach a laser pen to this armature. When the armature osculates, the laser moves respectively. To give it the cone/rotating effect, I used a nice shiny hard drive disc and slightly offset it. When the disc spins it makes tiny circles. When the laser hits the disc the light bounces and projects circles on whatever. When the wave is portrayed over time (the rotation) it shows a visual display of sound. All of this cost me only $5 worth of material: An old 256MB Hard Drive - $3 , An old laser pointer - 2$, Hours of pointless entertainment - Priceless.
show us more off you room!!!! we want to see it and that laser thing is pretty cool i love how it looked like a cone of red light