On Jun 13, 11:25 pm, m kinsler wrote:
On Jun 13, 10:53 pm, mm wrote:





On Wed, 13 Jun 2007 14:51:20 -0400, "Zephyr" an address @ some place

.com wrote:
Hey folks,

I'm curious about power consumption of things like the power supply for my
dell laptop
its and AC/DC adaptor, and when the unit is charging my laptop it gets quite
warm.
from that I infer that its using a fair amount of power.

now, if I leave it plugged into the wall, but remove the laptop, it does
not heat up, but.
there is a little light on it that indicates it is receiving power.
aside from that little light, is it using any significant amount of power?
The label on the unit says the input is 1.5a

same question goes for my cell phone chargers 0.2a

I understand that some of these things do use power constantly, but... how
much?

Good question. Not only the ones with wall warts, those black
"adaptor" boxes that plug into the wall with a cord coming out of
them, but many radios etc. with the transformers inside, have no
switch in the primary of the power transformer, and they are ON all
the time.

For electronic reasons I don't well understand, when there is no
current in the secondary of a transformer, there is higher impedance
in the primary of the transformer, so less current flows even through
the primary. The heat one can feel, that you feel, the waste heat
would be iiac the same percentage of energy used, as when the device
is running and there is current through the secondary.

From your touch, it sounds like the current is a lot lower, but otoh,
it's on all the time if the thing is plugged in, even for things that
are only used an hour a year.

Does anyone know what the percentage is, or how much these things use
when off?

xposted to sci.electronics.repair

I found this link but it doesn't get into the Nitti gritty I was looking
for

http://gizmodo.com/gadgets/gadgets/c...mpire-slayer-a...

Dave- Hide quoted text -

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Well, there's been a lot of discussion on this. Essentially, when
there's no load on the phone charger or other appliance, it's like
having an inductance across the power line of your house. There will
be some very small current flow, but only because it's not a perfect
inductance. All of the energy used in these wall transformers when
they're just idling is dissipated in the form of heat in their black
plastic case, so you can get an idea of how much power they're using
by just feeling them. It's not really very much. Note that you'll
have a tough time measuring the power drain with a multimeter, because
both current and voltage will show rather high readings. But since
they're almost 1/4 cycle out of phase, there's almost no power being
dissipated, and only a good power meter will take this into account.
(This problem is the basis for a lot of free energy claims, you'll be
happy to note.)

In general, wall transformers aren't a big deal.

And don't forget, in winter you don't mind a little heat radiating, so
there really is no waste, unless you have them plugged in the attic or
something.