USB device interfering AM radio

M

Man-wai Chang

The supply has a floating secondary. The transformer provides
isolation from the line side, making it safe.
.... snipped ...
Have fun,

More homework for me. :)

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
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M

Man-wai Chang

You could operate the LED from rechargeable batteries, but where
is the challenge in that ? :)

It's also not durable. :)

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
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M

Man-wai Chang

For your curiosity:

I hooked up a wire to the ground pin of a 13A UK plug, then connected
the other end of the wire to the wire mesh shield of the USB cable.
The noise was gone immediately!

Though building a simple power supply is interesting, the simplest
solution to the interference problem has been found.

I wonder how US power grid handles the issue of AM interference from
AC-DC converters with just 2 pins in their AC sockets....



--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.38
^ ^ 19:32:01 up 6 days 23:06 0 users load average: 1.05 1.09 1.08
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P

Paul

Man-wai Chang said:
For your curiosity:

I hooked up a wire to the ground pin of a 13A UK plug, then connected
the other end of the wire to the wire mesh shield of the USB cable.
The noise was gone immediately!

Though building a simple power supply is interesting, the simplest
solution to the interference problem has been found.

I wonder how US power grid handles the issue of AM interference from
AC-DC converters with just 2 pins in their AC sockets....

My test with the A.M. portable radio shows, they don't :-(

But my problem was emissions from the body of the adapter,
and not the wire cord. Your problem actually sounds different
than mine. Your problem might be attenuated a bit with ferrite.

I'm amazed the grounding was enough!

Paul
 
M

Man-wai Chang

But my problem was emissions from the body of the adapter,
and not the wire cord. Your problem actually sounds different
than mine. Your problem might be attenuated a bit with ferrite.

I'm amazed the grounding was enough!

My mistake calling that pin the GROUND pin resulting in a bit of
confusion.. It should be called EARTH.

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
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P

Paul

Man-wai Chang said:
My mistake calling that pin the GROUND pin resulting in a bit of
confusion.. It should be called EARTH.

We have the same scheme here. Three prongs on the plug. The
third prong is a safety ground connected to earth. My current
house has the three pronged outlets. (Not all of our plugs
are this ugly :) Many are molded and nicer looking.)

http://www.mcmelectronics.com/content/productimages/s4/4012023.jpg

Not all homes here, have three prong outlets. The home I was
born in, only has two prong outlets. This presents a problem
with things like computers. If you were to use a computer with
a three prong plug in that house, you'd get a mild shock every
time you touched the metal of the computer chassis, as well
as touching any other object in the vicinity that is at earth
potential. That is because there is no way to connect the
safety prong of the computer, to earth.

My grandmother's home, by comparison, was so old, the wiring
consisted of two separate wires, suspended on porcelain insulators
at regular intervals. (I presume that was in the walls, as well as
exposed in the basement.) As a kid, I think I was in the basement
once, and saw something similar to the concept pictured here. (The
basement was so dirty, it's not a place I would stay for long. It
was like a dungeon down there.) These aren't the exact insulators,
but they're similar in concept. This home didn't have any heavy
electrical loads in it, no central heating or central air conditioning.
It was heated with stove oil (bottled oil, heater in hallway), and
cooking was on a wood stove. The heaviest load was probably when
using an electric kettle (in later years). I think my grandmother's
house has been demolished, so is no longer a safety issue for anyone :)

http://images.oldhouseweb.com/stories/bitmaps/10327/knob-and-tube-2.jpg

There is no need in our country, to upgrade the wiring, as an old
installation of decrepit nature, is "grandfathered" and allowed
to continue to exist. Due to the amount of damage to walls and the
like, necessary to change it.

My current home, is the one on the right. The one on the left, is
similar to the house I was born in. In the one on the left,
a desktop computer would give you a shock, from leakage current
that has no place to go. To plug a three pronged computer into
a two pronged outlet, you buy a "cheater" adapter which has
the safety prong missing. The second picture shows a "cheater"
in usage, and why the safety earth ends up "floating".

http://s3.amazonaws.com/atimg/1127383/home-hack-three-prong-outlet_rect540.jpg

http://www.vincehuston.org/images/adapter_3_prong_vlh.gif

Paul
 

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