@Rod,
The ratio follows the often mentioned (on the huge OU forumj thread) 2:1 ratio. The coil being twice as large as the core. However, the magnets are only what I have from hard drives or CD-Rom drives and so that's why you often see a couple more on the back etc.
The plastic middle former piece that surrounds the core creates a distance to the coil itself. In other words, the coil doesn't sit right on the core, it has a plastic layer between. The bobbins themselves are wound to give a 2:1 ratio and that is about the way they sit anyway with their plastic end pieces.
I tend to use a small spacer of something non metallic on the backs of them now, after reading about outputs increasing like that. The optimal distance for such spacing to a magnet is, I believe, just at the change over from repulsion of the rotor magnets to attraction of the core. The downside of that, is that the magnets fall off the back unless glued !
The ratio follows the often mentioned (on the huge OU forumj thread) 2:1 ratio. The coil being twice as large as the core. However, the magnets are only what I have from hard drives or CD-Rom drives and so that's why you often see a couple more on the back etc.
The plastic middle former piece that surrounds the core creates a distance to the coil itself. In other words, the coil doesn't sit right on the core, it has a plastic layer between. The bobbins themselves are wound to give a 2:1 ratio and that is about the way they sit anyway with their plastic end pieces.
I tend to use a small spacer of something non metallic on the backs of them now, after reading about outputs increasing like that. The optimal distance for such spacing to a magnet is, I believe, just at the change over from repulsion of the rotor magnets to attraction of the core. The downside of that, is that the magnets fall off the back unless glued !
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