Small magnets needed for position sensing

[kipiib]

I'm looking for small magnets that can be mounted on a turnscrew or rotating shaft. They are going to be used by a Hall sensor to detect position. I'm looking for magnets that could be as small as 1/18". Any ideas where I can find something like this?

 

[sreid]

Search the web for "Rare Earth Magnets." There are a number of online suppliers. If you need quanties for production try Magnetic Component Engineering.

 

[IRstuff]

Another possibility is the plastic kitchen magnet. While they come in sheets, the fields alternate spatially with less than 1/20" pitch.

You could simply snip off a small piece. Or, you could wrap the whole assembly with a piece and get more information about the exact position.

Or you could go another route and use a rotary encoder, e.g., potentiometer or resolver, and get tons of position information with high accuracy and precision.

TTFN

 

[gordonl]

I bought some small rare earth magnets on EBAY, small size but lots of flux! (Relatively speaking)

 

[amorrison]

Consider options

1.Having a needle/straightpin/turnscrew assembly in contact with a PM at the base mount. Some of the magnetic lines will appear at the tip.
2. Magnetize the turnscrew or turnscrew nut permanetly


Try to eliminate "problems" before trying to solve them.

 

[sreid]

Any chance you could use a commercially available proximity sensor? You'd then only have to cut the sensing tooth on the shaft. The DC prox sensors (often) use a Hall sensor back loaded with a magnet.

 

[aspearin1]

AlNiCo magnets can apparently be extruded. I believe they can reach diameters as low as 0.010". Do a google search on AlNiCo, and Arnold Magnets (something like that) should pop up. They claim the extrusion technology.

aspearin1

 

[jbartos]

Suggestion: Visit

http://www.thomasregister.com

and type Magnets under Product or Service, which will return 222 companies to approach to with your magnet specifications

 

[UKpete]

If you go for rare earth (high energy) magnets there are a couple of problems to look out for:

SmCo are very brittle, they crack and chip very easily
NdFeB corrode so they need coating after any machining

We have used both types for Hall probe sensors on brushless motors, they do give plenty of flux. The size used is 3.0mm thick and about 4mm square, mounted in a non-magnetic (titanium) retainer. I think the airgap between the magnets and the hall sensors is about 1-2mm.

 

[jbartos]

Suggestion: Visit

http://www.stanfordmagnets.com/magnet.html

http://www.rare-earth-magnets.com/

http://www.dansdata.com/magnets2.htm

http://www.shinetsu-rare-earth-magnet.jp/e/rem.shtml

etc. for more info