Stir plate magnet orientation

[gotbags-10]

Just pulled two magnets out of a hard drive. I guess first thing is should I use 1 or 2? I have a 1 7/8" stir bar. Already built and tested my fan speed controller.
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[Black Island Brewer]

I've not been successful using stirbars that big on my DIY plates, but I used your bottom configuration. I'd be inclined to try the first configuration - I might revisit that on my two plates.

 

[NewBrewB]

I use one magnet... in a wooden cigar box and a 2" stir bar works great with a 2L flask

 

[schematix]

I don't know how that style of magnet is magnetized, but you want a N up on one side, and a S up on the other. Stir bars have an N end and a S end so the opposing polarities will couple together. Whether that takes 1 magnet or 2 depends on how it was magnetized.

This is pretty easy to test with 2 magnets. Put 2 ends together, if they attract, then you have a N-S pair. If they repel you either have N-N or S-S. Check a few more orientations and you should know the how the poles are aligned.

I bought my magnets from this company, and they have a really good diagram showing some possibilities: https://www.kjmagnetics.com/magdir.asp

This link shows how hard drive magnets are configured: http://physics.stackexchange.com/qu...um-hard-drive-magnet-it-appears-to-vibrate-in

 

[vNmd]

Ditto on the one magnet in a cigar box. It does work great, but remember there are different size magnets that come with different drives. I had some fairly old drives that had relatively small magnets. I had a newer larger capacity drive that had a much larger magnet. You might put everything together in whatever box you are going to use, without the glue, and see how well the bar stays put with one magnet.

 

[GrayHiker]

Magnet size and orientation make a difference. Check out my post here:

https://www.homebrewtalk.com/showthread.php?t=525583