There's a neodymium magnet inside some old CD-ROM drives

[mtbandy]

Just thought I'd make it known, because this is something I never realised before!

Inside some old CD-ROM drives, and probably CD-RW etc etc there appears to be a 10x3mm circular neodymium with a 4.5mm hole moulded well into the spindle that the disc sits on. Obviously part of the magnetic clamp which holds the disc in while it spins it up. I only found it after some careful disection of the spindle with wire cutters!

So... old CD-ROM drives are common, so it's surely worth checking before disposing of them. Probably have more luck with newer drives (anything greater than 32x) but I'll make no guarantees either way - just reporting on what I found!

The amount of these I must have thrown away without knowing

[fungus]

Theres also two very small rectangular magnets inside th read/write head; take the lens and the coils underneath it out and theres the two magnets on a little bracket.

[mtbandy]

so there is! I always thought used drives were pretty useless for parts, but you learn something new every day. Just pulled a couple of 9x7mm neos out, slightly thicker than the ring.

Now I would say 'who is going to be the first to build the tinyest 3ph. permanant magnet alternator', but the spindle motor also from the CD drive is exactly that.

cheers!

[ghurd]

Any idea how the polarities in the donut magnets go?

Seems like it must more than 2 poles...  

Maybe the top and bottom are poles or the outside diameter... if you know what I mean.

G-

[richhagen]

Nice find, I will have to go through my junk electronics box where I threw a few broken ones over the years.  As for the tiny three phase, I found this when I took apart a small hand crank flashlight that my son broke.





Its 9 coil three phase and about 1.165 inches (2.91cm) in outer diameter.  I am not sure of the number of magnet poles, but I am guessing 12, I will have to find a compass or something to confirm.  It is crimped together, so I am reluctant to pull it apart yet (I promised to fix the light).  I see one solder connection inside, it looks like one lead from each set of three coils, so it appears to be star connected.  The magnet ring and drum rotate with the coils stationary.  It reminds me a bit of a tiny Fisher Paykel motor.  Rich