Tuna tin toroid shield?

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hodad

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Jun 4, 2004
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Didn't someone around these parts try this once?  It may have been at the old place as a search nets me no info.  I seem to remember someone suggesting taking care that the screw through the middle of the toroid not touch the can.  Don't remember how well it supposedly worked.  I'm working on something that might benefit from a tuna tin toroid shield, so I figured I'd ask & see if anyone remembers or knows more.

Tom
 
May stink when hot tho......It should work shouldnt it....I made a mic in a biscuit tin also a cat food can & a metal drink bottle none of which humm..Good luck.
 
Unlikely to do much in shielding.
However it will cause the toroid to burn out if you connect to to the case with a bolt through the centre since it creates a shorted turn on the transformer.
 
Any kind of metal shield will do fine for electrostatic shielding - but mu-metal or heavy iron is needed if it's electromagnetic shielding you're after.

So it depends on what your actual hum-problem is about - both variants are common.

Jakob E.
 
Electrostatic? You mean a can over a dc charged device?

I'm not sure I understand.
 
Electrostatic, i.e. inteference-by-capacitative-coupling. This is the main problem in high-impedance circuits, like electromagnetic interference is in transformer circuits.

Jakob E.
 
I had a chat with Dave from Altran, about toroid-induced problems. He said what they do for some customers/applications is make a strip of the same metal as the toroid core, and wrap it around the trafo. This seems to help with induced EMI problems. Have 0 experience with this.
 
Yes, that helps. Also special winding techniques can help to minimize stray fields - something with winding forwards, then ½this backwards, then forwards again. All these tricks can add up to some 35dB difference in interference from a standard trafo to a special wound one (on a bad day - yes, I've been there.)

Jakob E.
 

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