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Toroid or molded inductor in low voltage tank?
Roy Lewallen wrote:
John Hague wrote: On Tue, 11 Jul 2006 08:29:05 +0100, Roy Lewallen wrote: Ben Jackson wrote: . . . Anyone have any tips for securing fine-wire toroids in Ugly/Manhattan construction? A dab of hot melt glue or RTV. Or a Nylon screw through the middle. Or a couple of holes in the board and a cable tie. The only thing to avoid is laying it down flat on a solid copper plane. Roy Lewallen, W7EL Roy Excuse my ignorance, but what is the problem with laying a toroid down on a solid copper plane? I thought the magnetic field was contained within the toroid and thus minimised external effects. I have completed a couple of projects recently with some of the inductors like that and didn't notice any real problem. Mind you, I guess they might have performed better if not mounted that way ) Two potential problems. One is that the field isn't completely contained. Leakage is greater with more sparsely wound toroids and ones with lower permeability cores. The second is the "one turn effect" - There's a net field equivalent to that of a single turn running circumferentially around the core. A solid plane parallel to this would act as a shorted turn. Both effects would act to lower the Q, and might be the cause of some drift or microphonics if the inductor was in an oscillator tank. But to be honest, I've never run any experiments to see just how much of a problem it might cause -- it's quite possible you could get away with it in some or even most applications. I'll put it on my list of things to do when time permits -- unless somebody else is willing to take on the job. Roy Lewallen, W7EL "One turn effect" in magnetic core computer memory? Miniature toroids single-stitched and woven with wi http://www.fortunecity.com/marina/reach/435/coremem.htm What's the Amidon number of these cores? Some electric guitar tube amps used perpendicular point-to-point wiring in 3-dimensions between terminal strips to minimize inductive and capactive crosstalk. They are amazing to see. -- LIGO: World's largest SWR meter or the world's most expensive grid dip meter?: http://www.nytimes.com/2006/05/02/sc...ce/02hole.html |
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