At 10:40 PM 2/14/2008, you wrote:
>On Thu, Feb 14, 2008 at 6:40 PM, Spehro Pefhany <speff@interlog.com> wrote:
> > At 07:13 PM 2/14/2008, you wrote:
> >
> >  >Yep, that's right. UL-met wall warts solve a lot of costs, but they
> >  >aren't "slick".
> >  >
> >  >Look at it like this... UL simply wants to see if the product will ca=
use
> >  >a fire.  If
> >  >you use a wall wart , all the fire-susceptible stuff is in an
> >  >already-tested box, and
> >  >you are golden (as long as your product is within the rating of the
> >  >wall-wart). UL
> >  >doesn't care if it even WORKS, they ONLY care if it causes or sustain=
s a
> >  >fire.
> >
> >  You sure about that? I bet I could cause a real fire with a UL-approved
> >  12V 1.5A wall wart, and not once exceed the ratings.... any takers?
> >
>
>Sure, I've seen it done with a 6.3V, 1A wart.  Just "trickle" charge a
>li-ion battery.

LOL. Even without a Li-ion cell...

I used a rather puny 1.25A 12V SMPS wall-wart sold by CUI. Measured out
about 12' of AWG 39 wire, calculated to give a current of about 1.2A at
20=B0C (dropping as the temperature rises). I was a little generous with the
wire and the resistance measured 10.6 ohms, for a current of 1.13A.

First attempt failed-- too spread out. I wound it on a toilet paper tube--
it got hot, but not hot enough.

Second test had the same length and gauge of wire in a much smaller volume,
and it succeeded in creating smoke, and then open flames, within a total
time of less than 10 minutes.

So, if you use an approved adapter but your factory uses a non-fire-retarda=
nt
grade of plastic for the housing moldings, for example, you *could* be putt=
ing
lives in danger.

Test 1
http://server2.hostingplex.com/~zstoretr/test1s.jpg
http://server2.hostingplex.com/~zstoretr/test1.jpg

Test 2
http://server2.hostingplex.com/~zstoretr/test2s.jpg
http://server2.hostingplex.com/~zstoretr/test2sm.jpg
http://server2.hostingplex.com/~zstoretr/test2f.jpg


Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the rewar=
d"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com




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