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Old 29th January 2003, 09:31 AM   #1
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Default Alu-foil electrostatic shield

Originally posted by EC8010
You might want to use kitchen foil to cover one side of the toroid and the circumference, then run a strip of insulating tape all the way round the circumference of the toroid, then use foil to cover the other side. Solder that works on aluminium can be readily bought, but it contaminates the tip of your iron, so keep that tip for aluminium jobs.
Thanks again for this excellent tip! I purchased some of this aluminium solder labelled "Alu-Sol" today. A quick proof of concept test indicates that it works quite well soldering a tinned copper wire to plain kitchen alu-foil. I used a mini-torch with some care to heat the joint and it worked fine.

The fumes were rather unpleasant despite positioning a fan over my shoulder to blow the fumes away. I may do future jobs outdoors.

The only tricky bit left is working with the alu-foil without tearing it. In the States I could find "heavy duty" alu-foil that was extra thick at the supermarket. Here all of the alu-foil is labelled "heavy duty" even if it isn't any thicker than usual.

I'm also somewhat dubious about the core size of this little toroid. Any suggestions on how I might guesstimate its VA capacity?
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Old 29th January 2003, 09:56 AM   #2
EC8010 is offline EC8010  United Kingdom
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In the UK, "turkey foil" tends to be thicker. (Cue the inevitable jokes.)

You can usually make a stab at the rating of a transformer by calculating its volume, then comparing it to a transformer of known rating and volume. For a toroid, you will be interested in its cross-sectional area and average circumference. As you de-rate transformers, their leakage flux decreases...
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Old 29th January 2003, 10:18 AM   #3
7N7 is offline 7N7  United Kingdom
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Default Re: Alu-Shield a Little OT

Originally posted by jeff mai

The only tricky bit left is working with the alu-foil without tearing it. In the States I could find "heavy duty" alu-foil that was extra thick at the supermarket. Here all of the alu-foil is labelled "heavy duty" even if it isn't any thicker than usual.

This "Heavy-Duty" thing is very funny.

Has anyone ever seen anything labelled "Light Duty"?

I once bought a countersink bit that was labelled "Medium Duty".

No doubt you can imagine how long it lasted!

Plug them in and light them up
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Old 29th January 2003, 02:43 PM   #4
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jeff mai, may I ask why you are trying to sheild a toroid? The electrical field is very low so is the magnetic which is unaffected by the foil. If you want to sheild it you have the shield inside between primary and secondary winding, like this transformator

which has magnetic sheild outside
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Old 29th January 2003, 03:56 PM   #5
dhaen is offline dhaen  Europe
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I believe there will be a new secondary, wound over the shield.

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