I'm not too keen on electromagnetic specifics.  About all I know is that
when a conductor cuts through magnetic field lines, at an angle, then a
current is generated.  You are correct, in theory, because the field
lines the conductor is generating are circular (around) the conductor,
and in theory would cut through the coils parallel to the coil (also a
circle).  Therefore no current should be generated in the coil, since
the lines  are 'cutting' through the coil at an angle of zero.

So, no, I don't understand all the issues in relation to this specific
design.  You can find PCB mounted current transformers that require a
single conductor going through them as well.  Perhaps they use a
different coil configuration than what I've described:
http://www.crmagnetics.com/newprod/ProductView.asp?ProdName=CR8750
Gives a pretty good picture of how they work.

Perhaps the original article called for two loops of the main conductor
to pass through the coil.  In any case, if the original poster has
trouble making a homebrew coil work, the products offered by the
manufacturer above and many others would do the trick.  On the main page
they have pictures of current transformers with built in LEDs just as
indicators.

-Adam

John N. Power wrote:

>        How did he get that to work? Wrapping wire around one conductor
>      does not make a transformer. The "secondary" wire is at right angles
>      to the "primary"; there is no coupling between them.
>
>
>
>

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