Sewing machines have a mechanism for winding thread onto the bobbins that go 
under the table. They also have an adjustable thread tensioner device that 
works by spring loading two convex washers against one another. Your thread 
(er, wire) goes between the two washers and the spring tension is adjusted 
appropriately to produce the required drag on the it.

Perhaps you could subvert that?

You would, of course, have to add some sort of turns counter.

Bob Ammerman 

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