the old “brute force” power supply design — an AC step-down transformer connected to a bridge rectifier, filtered
across a large electrolytic capacitor. Better versions will
employ a linear voltage regulator IC, however, all but the
very latest switching regulator designs will draw power
continuously. Our small test bank of wall warts under no
load drew 19 watts while powering nothing at all (Figure
2). How can you minimize the parasitic power loss in your
own home? Following are some suggestions.
Classify Your Loads
This class of loads can save you energy and money
very easily. Examples of these are boom boxes, radios,
audio/visual equipment, anything that you only want
drawing power if you are actually using them. These can
simply be unplugged or switched off with a power strip to
eliminate parasitic power loss.
The majority of your wall wart loads will probably be
in the class of battery chargers. Electric screwdrivers and
power tools, razors, standby flashlights, portable laptop
computers, cell phones, portable phones — all of these are
examples of devices that are simply on charge whenever
they are plugged in.
This type of parasitic load can be put on a timer to
limit the time it spends drawing power from the utility.
Group it together with others on a common power strip
and put the strip on a timer so it is only on for a few hours
a day. If the devices are located geographically far apart,
use several timers, or an X- 10 remote control system
to power them up and down. An X- 10 switch module
will draw less than one watt in standby mode. This is a
significant savings if you are controlling several wall warts.
These are difficult to wean off power. They are
devices like your answering machine, clocks, TIVO,
fileserver, and things that may need power at any time
of the day or night. The best way to deal with these is to
simply limit the number of them.
This class of load may save you money if you reconsider
the operating environment, for example, your DSL/cable
modem and router. You would normally consider these as
mission-critical, but if you are not actually scheduling
downloads overnight, they could actually be powered off
for more than half a day. These devices usually reconnect
automatically when powered up and shutting them down
daily has the added benefit of increasing the security of
your Internet connection by forcing the re-assignment of a
new dynamic IP address on a daily basis.
All of us have experienced the VCR that blinks 12:00
am whenever it is unplugged. This class of load must be
tested. If your television forgets the channel list if it is
unplugged, you are going to be forced to supply it power
24/7. If you can unplug it indefinitely without loss of data
or settings, you can power it down without any problem
and enjoy the energy savings.
There are some interesting things you can do to
minimize or eliminate the cost of powering some loads,
especially in the battery charger class. One possibility is
solar power. Take the dusty 50 watt solar panel in your
garage out and set it up on a small inverter so it will
charge your bank of battery charger devices whenever
the sun is up. This will be completely automatic and “free”
(less the cost of the solar panel), but it will at least be
working to offset its initial purchase price. Remember
not to overload the inverter or exceed the panel power
capacity — your devices may draw full loads when initially
powered up so calculate how many you can run with your
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