Russell McMahon wrote:

> > found Jaycar Australia stocking some cheap and high-
> > performance ferrite toroids
>
> The Jaycar cores *APPEAR* to be "Micrometals" products (but may not be).
> Micrometals parts have colour coded coatings to reflect the core material
> (My
> Taiwanese clones (which I had no choice in the sourcing of) work just fine
> in my application - so far.)(In fact "so far" is a major issue - powdered
> iron cores DO have an age limit

Hi Russell, when you say Jaycar toroids with coloured
coatings I think you mean their powdered iron types?
I have been buying these since 1986 in the early grey
coat, and lately in the newer green coat. They are
terrible for SMPS unless you need a lossy core for
actual "choke" use (as opposed to conversion use).

The new Jaycar toroids I was referring to are the bare
ferrite ones on catalogue page 79, these are SUPERB
compared to the powdered iron type. I've been testing
their new ferrite toroids over the last couple of weeks,
getting around 12x the inductance for the same turns
as the iron ones, and much better current/saturation
performance.

I've *hated* those lossy iron things for years, which
is why I have a heap of expensive specialty Philips
and RS ferrite cores for SMPS use. But these new ferrite
toroids outperform anything I have here including all
the ferrite toroids I have salvaged from commercial
SMPS units.

As an example the 18mm diameter ring with one layer
of 0.8mm wire (30 turns) is 800uH and 0.027 ohms.
The 25mm ring with one layer 1.0mm wire (32 turns)
is 1400uH and 0.023 ohms! I can't get figures like
these even on expensive potcores 3 times the size.

BTW I have some old powdered iron ones that *have*
rusted and split open, but some have hung in there
in use for 16 years. :o)
-Roman

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