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Old 02-14-2014, 12:26 AM
gyula gyula is offline
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Join Date: Apr 2007
Posts: 820
Quote:
Originally Posted by thx1138 View Post
I finally got my hard drive magnets ....
...

So maybe the hard drive magnets won't work. ...
Hi,

Hard drive magnets are magnetized in an unusual way with respect to "normal" magnets. They have two unlike poles on one side and also two unlike poles on the other side of their thickness. Here is video to show this:
How To Find The Polarity Of Hardrive Magnets - YouTube

For simple tests to find the neutral zone you could use soft iron like a keeper, no real need for a ferrite rod yet. The latter will be needed when you want to take out power from the coil wound on the keeper (to reduce eddy current which is bound to occur in a soft iron piece unless you use transformer laminations or indeed ferrite rod).

For the neutral zone, you need one pole say S from a rod or disk-like magnet facing one end of the keeper and the other pole say N from another rod or disk magnet while an iron yoke also bridges the other side of these two magnets (as a horse shoe shape does). In case of a hard disk magnet this 'one S - one N pole' facing the keeper cannot be achieved becasue there are always two poles at the edges of such magnets.

Gyula
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