Wall wart
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Wall wart is a slang term for certain types of power supply - typically those that are embedded in an over-sized AC plug. Other names include wall cube, power brick, plug pack, plug-in adapter, adapter block, domestic mains adapter, power adapter, or AC adapter. These are typically packaged with electrical devices that do not contain their own power supply. This can be for reasons of size of the device, keeping a source of heat remote from the device, electrical noise isolation, making one device for international sale with a variety of power sources; and due to the economics of getting devices including an internal power supply certified by government regulatory bodies, such as the FCC in the United States.
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[edit] Criticism
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These plugs have been criticized, hence the name wall wart. Problems with this type of power supply include:
- Size — The power supply may obscure other power points; some power strips attempt to relieve this problem by varying the spacing between their sockets.
- Weight — The weight of the power supply may pull it out of the power socket. This depends on the socket design of the country in question. Some power supplies are "power bricks" having a short AC cord so they can lie on the floor, thus relieving the strain at the expense of clutter. Some that hang on the wall are made long and thin, minimizing the leverage of their weight vector that pulls the plug out, at the expense of exacerbating the size problem.
Brick in-line configuration, with detachable AC cord at left
- Inefficiency — Many wall warts have low efficiency, wasting electrical energy. Some use power even when the attached device is not in use or absent. (Since wasted electrical energy is released as heat energy, an inefficient power supply will feel warm to the touch, as will one that wastes power with nothing connected.) but many of these inefficient devices are low powered (e.g. devices that are used for Battery chargers), so although they have a low efficiency, the amount of energy they waste doesn't contribute much to the overall household consumption of electric energy. Switch-mode adapters, being more efficient, will not release noticeable heat even while being used. The drawback of switch-mode adapters is that they are considerably more expensive in production.
- Inflexibility — Unlike a standard power cord, a lost or failed wart cannot immediately be replaced from the stock of a retail store, but must await delivery from the original equipment manufacturer (if the item has not yet been discontinued). A wall wart made for other equipment may be electrically compatible, but not mechanically, in which case the plug won't fit. Or, even worse, vice versa, in which case the incompatibility may destroy the equipment or ignite a dangerous fire. A few warts have a transformer but not a rectifier, being intended to supply low-voltage alternating current to a device having its own rectifier, rather than direct current. This affords additional opportunities for misconnection, malfunction, destruction and combustion.
The problem of inefficiency of power supplies has become more well known, with George W. Bush referring to such devices as "Energy Vampires".[1] Legislation is being enacted in the EU and a number of states, including California, to reduce the level of waste caused by these devices. See standby power and the One Watt Initiative.
[edit] Wart substitutes
Third-party manufacturers address the problem of diversity with aftermarket "universal AC adapters" whose voltages and polarity can be adjusted, and come with a variety of DC plugs. The user must examine the appliance to be powered, attach the correct plug, and adjust the "universal" wart correctly to make it work properly and avoid destruction by incorrect voltage or polarity. Labeling seldom mentions the need for a particular degree of ripple filtration, voltage regulation or other questions of power quality, assuming that no user would attach a "foreign" power adapter and effectively leaving such matters to chance.
USB hubs may be used, even in the absence of a computer, to power certain kinds of consumer equipment known as "USB decorations" which are intended to be powered by a computer. Such devices are bound by the half amp (2.5 watt) USB limit. Being in general non compliant to the USB standard, they may interfere with the computer peripherals for which USB was intended. Several manufacturers in the Open Mobile Terminal Platform agreed in early 2009 to make mobile phones powered by micro-USB, thus freeing users from dependence on proprietary warts and battery chargers.
Powered USB replaces wall warts for certain commercial applications, with only three different kinds of plugs for 5, 12 and 24 volts DC, thus preventing plugging in the wrong voltage. It is especially commonplace in POS terminals but is not used for consumer equipment.
A "Green Plug" system has been proposed, also based on USB technology, by which the consuming device would tell the supplying wart what kind of power to supply.[2]
Larry Page, a founder of Google, has proposed a 12 volt, 15 amp standard for almost all equipment requiring an external converter.[3] New buildings would also have 12 V DC wiring, so that in effect the wart would no longer be outside the wall.
Car batteries (12V batteries) can also come in handy as inexpensive batteries to power car adapter devices with an alligator-clip-to-receptacle Y-cable connected to a universal voltage changer since it would provide similar functionality that doesn't waste valuable AC power.
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[edit] See also
[edit] References
- ^ Bush Takes Aim at "Wall Warts" - Extreme Tech article
- ^ Green Plug tries to replace the worry warts Engadget May 2008
- ^ Treehugger Google pushes standard wart]
[edit] External links
- Survey Finds Consumers Grow Weary of Wall Warts - Power Electronics Technology article on consumer concerns about wall warts
- Google Pushes for PC Electrical Efficiency; Side Effect: No More Wall-Warts - Treehugger.com article Google proposing standardization of 12 volt systems
- Power Adapter Outlet Liberator - Method for using wall warts on cramped power strips
