Originally Posted By: rockstar_not
Whenever I've trashed hard drives, which has been somewhat rare - I keep them on a shelf, I've used it as a lesson to my kids as to how they work (if I can get the case open in a reasonable time).

There is a bit of magic for them seeing the platters and the tiny little read/write heads on the arms - and telling them that all of the music, photos, school assignments, etc. actually exist as little magnetic deviations on the platters and the little arms are what put them there and read them off.


There is a rather popular hack that I have used with kids in the summer school program. All you need is an old hard drive, platter does not even have to be able to spin, because all that is used is the headarm and its magnetic motor movement. And a low level and cheap laser pen pointer.

Locate the two connections to one of the two coils that move the head arm, found at the end of the flexy, disconnect from the drive's electronics and connect to the + and - speaker terminals of any small audio amplifier.

Now the headarm will move in response to any audio or music played through the amplifier.

Attach a small piece of glass mirror to the head end of the headarm using superglue.

Figure out a way to mount the laser pointer such that it is pointing at the headarm mirror. I use rubber bands to do that.

And, with the lights dimmed, you have a laser lightshow:



More than just watching the pattern that music makes, if you hook up a small mixer and microphone to the amplifier, the kids juswt love to see the patterns they can generate with their own voice.

The one thing that they sometimes can't wrap around is that this is an ANALOG situation and not Digital. Great time to show the difference and explain. At my summer school classes, that's when we get to delve off into an old record turntable, a few old records, and our tone arm and amplifier becomes a sewing needle taped to the corner of a piece of printer paper handheld above the spinning record. And they hear the sound of the record. Then I use one of my laptops and SP/DIF output to let them hear the digital sound of an mp3 file using a song the kids love at the time, and let them hear the digital nasty instead of the actual sound. That leads off into their first delvings into the 1's and zeros thang.

ADULT SUPERVISION on this one at all times, you must ot let them ever try to shine laser light directly into their own or other children's eyes. I pocket the little laser pointer and also disconnect the leads from coil to speaker, taking the alligator leads with me. That way, they can't start it up without resorting to a rather lot of procurement and learning first, avoids that happening when I'm not around.

--Mac

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