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Wireless Power for Small Appliances




WiFi and Bluetooth are wonderful technologies for freeing our portable devices from cables, except for the power cable, right?  Some vendors are ready with a new technology that will allow the charging of cell phones or other small appliances without wires.


Is that "Buck Rogers" or what?



Powercast Wireless Power


Powercast (Pittsburgh, PA) says it has a solution for wirelessly supplying portable devices.  The technique is reliable, FCC-approved (safe), and is ready for shipment later this year, Powercast technology uses an Rf wave to transmit the power for use by the device.  According to Keith Kressin, executive vice president of sales and marketing, the technology has an efficiency of better than 50% (the amount of power transmitted versus the amount actually used, so that for every 2 watts of power consumed, the device utilizes more than 1 watt of energy).  The efficiency is inversely proportionate to the distance between the transmitter and receiver.  At less than 3 feet, the efficiency is about 70%.  The energy that is wasted can be used for warming frozen foods, uh, . . . no, just kidding.


Powercast uses a signal in the 900 Megahertz band for moving the energy to the unit being charged. Other devices on the same band will not interfere with the operation; in fact, the Powercast receiver will consume any power near this frequency that enters its perimeter.  However, this technology cannot fully replace a conventional charger for most appliances. It is able to "trickle charge" over a period of time so that the energy depletion rate is slowed dramatically for low power devices. 


The idea behind the Powercast product isn't a new idea. The problem is that power transmitted in this way reflects off different surfaces, and modifies the signal.  The Powercast solution is a receiver that acts like a radio tuned to many frequencies at the same time.


The maximum power transmission is a few milliwatts at distance of 3 feet.  That should be sufficient to recharge most cell phones to a 50% level in 12 hours.  This rate is ideal for cell phones, wireless keyboards/mice, medical implants like pacemakers, and other small appliances.  The technology is not currently capable of supporting higher electricity consuming devices such as laptop computers, which currently use more than an order of magnitude more power than the Powercast system can supply.




Phillips to Market Powercast System


Phillips will be the first to market with a product utilizing the Powercast system.  The first product will be a light stick for low power lighting application.  For this application, the device will not have a battery on-board, but will receive power continuously from the Powercast system.  "If you had asked me seven months ago if this was possible, I would have said, are you dreaming? Have you been smoking something?" says Govi Rao, vice president of solid-state lighting at Phillips.


A Powercast system currently cost less that $10 to manufacture.  In many devices, implementing a Powercast solution is less expensive than implementing a battery, and in addition, is more environmentally "green".


An alternative to the Powercast technology is inductive charging.  If you have a Sonicare electric toothbrush, you already have an inductive charging system.  An inductive system is effectively a transformer, but inductive charging is more "connector less" rather than wireless.  This system requires a very close proximity between charger and device, because the efficiency drops precipitously at anything other than very short distances.  Powermat is one of several companies developing a system in the form a pad that you would put underneath the device to be charged, and that would be capable of supporting higher power devices like laptop computers.  The system is currently capable of power outputs of about 90 watts.


The Wireless Power Consortium was launched to develop standards so that charging systems and consuming devices will be able to communicate.  This is important so that the transmitter only emits power when a consuming device is present, and at the appropriate output power.  This will improve safety and efficiency.  Founding members of the consortium include Logitech, National Semiconductor, Philips Electronics, Sanyo, Shenzhen Sang Fei Consumer Communications, and Texas Instruments.



About the Author:


Brian Bradshaw is an InfoComm Certified Technical Specialist (CTS), Microsoft Certified Technology Specialist (MCTS), and CompTIA A+ Computer Technologist.  Areas of expertise include Video, HDTV, Audio, Computation, SATCOM Systems, and Communications.

Website:  http://bradshaw-vacuum-technology.com/