International Journal of Engineering Technology, Management and Applied 1
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www.ijetmas.com April 2017, Volume 5 Issue 4, ISSN 2349-4476
UNWIRED CHARGING TRULY WIRELESS
WORLD
DR. K. UMADEVI
HOD / Dept. Of EEE
Sengunthar Engineering
College
ANUP C J
III Year
Department of EEE
Sengunthar Engineering
College
SHRUTHI. S
III Year
Department of ECE
Dr. N.G.P. Institute of
Technology
ABSTRACT:
Yes, now we can forget wires even for charging. My mobile have been switched off, my Laptop
computer have no charging …….no such questions! Can we imagine the life without electrical wires?
From now answer to this question is Yes. The methods proposed in the present paper though utilizes
contrasting technologies for wire less transmission of power namely „power cast technology‟ and
„eCoupled technology‟ are presented in the name of “unwired charging”, Which will facilitate to
Transfer power without using wires.
The efficient low-range power can be transmitted to any device which uses that range of power by the
technique used in this concept called “power casting”. This technology uses radio frequency waves for
carrying power.
The efficient mid-range power can be transmitted to any device which uses that range of power by the
technique used in this concept called “eCoupling”. This technology uses electro magnetic coupling for
carrying power.
Now a days there is a Rapid development of autonomous electronics like Laptops, Cell-phones,
House-hold robots and all the above devices typically rely on chemical energy storage(Battery) .As
they are becoming daily needs to present generation, Wireless energy transfer would be useful for
many applications as above and they need low-range and mid-range energy. This is the main reason to
prepare this concept.
INTRODUCTION:
In our day-to-day life we use laptop computers, cell phones, digital cameras, voice recorder,
portable printer, MP3players all plays a significant role. But the major limitation is that they
have to be charged regularly which is possible only by connecting the device to the supply
through electrical Wires. More often it looks like snakes ……cables, cables…..and more
cables… as shown
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DR. K. UMADEVI, ANUP C J, SHRUTHI. S
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www.ijetmas.com April 2017, Volume 5 Issue 4, ISSN 2349-4476
But this dream of wire less charging might be possible very soon, by means of technology
explained below. Unless this concept is not implemented we can‟t really call the world as
really wire free world. This is because although wireless mantra is a old concept over the
world we still need electric wires and chemical batteries for purpose of charging and
transmitting power.
TECHNOLOGY:
Power casting technology:
The Basic Idea:
If we walk a few meters from where we are standing now we will probably be cutting
across at least a dozen radio waves zipping invisibly across our room that is how common
they are…. So common that we barely spare time to even think about them seriously!
Radio frequencies are foundational for most devices we use today right from TVs and
radios to mobile phones. But we ever think of how powerful the radio frequencies are?
The simple example that makes radio frequency identification (RFID) superior to barcodes
is that they can store more data, they can be read and written to, they can be re-used etc., but
what makes all this possible? How is RFID chip able to survive on its own, woven into some
product or person, isolated from the rest of civilization? It is because the chip is able to charge
itself through the radio waves transmitted by the transceiver when reading or writing.
Basically this is a simple example of the energy carrying property of radio waves
 Then why cannot RF (Radio Frequency) be used to power devices?
If we have a Base station that draws power from a power line and keeps transmitting
it as radio waves and all our mobile devices have receivers that can receive these radio waves
and convert them into DC current, that‟s pretty much a wire less powering system. That is one
base station can charge quite number of devices-provided they all have the receivers built into
them this is precisely how the power cast system works
TECHNOLOGY BEHIND THE POWER:
The mess of wires, those power strips overloaded with transformers and maddening gadget
connectors half a nanometer from perfection may all soon be a thing of the past.
The power cast wireless power platform consists of a transmitter called „power caster‟ and a
receiver called „power harvester‟. The „power caster‟ can double the effective range,
compared to normal RF transmitters and a power harvester can harvest up to 70% of the
theoretical maximum power with in the range and convert it into dc current for the device to
use. The power harvester is a chip about half the size of an ordinary battery used for charging
and must be accompanied by a small antenna whose size varies according to the frequency of
transmitted power. It can fit quite comfortably into the battery compartment of most devices,
and many devices could use the case itself as the antenna. Of course small tweaks in the
circuitry of the device will be needed to connect the power harvester to it.
The power harvester is available in various models for multiple frequency ranges, voltage
requirements sizes and so on. The design can fully customized according to the requirements.
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www.ijetmas.com April 2017, Volume 5 Issue 4, ISSN 2349-4476
Any device fitted with a power harvester gets charged automatically whenever it is with in the
range of power caster and any number of „power harvesting devices‟ can be placed within the
range of single power caster. This does not give rise to problems like cancellation and
interference because power caster neither causes nor is affected by such problems. In-fact, the
power harvesters actually outwit noises by making use of them.
POTENTIAL POWER HARVESTERS:
All the devices cannot be powered using power cast system only devices that work on AA,
AAA batteries or cell batteries can make use of this wire less power system. Power cast is
designed to power devices with very low power. Sensor networks, hearing aids, headsets etc.,
are ideally suited for this technology basically any device which requires small battery (to be
recharged) are requires very little power for direct powering (such as Light Emitting Diode
LED) is suitable for taking advantage of power cast technology. Power cast technology is
designed to provide milli watts of power to devices with in an effective range of the
transmitter.
Radio waves are in fact energy. They are already used to send and receive cell phone,
television, radio, and „Wi-Fi‟ signals every day. Those waves spread out in all directions until
they reach an antenna that is tuned to the appropriate frequency. Power cast's wireless power
platform uses a "Power caster" transmitter circuit running on conventional current to
broadcast a low-power radio signal at a predetermined frequency. The smaller "Power
harvester" receiver circuit which can be embedded in any low-power device then uses that
energy to recharge or can even replace the device's battery.
The Power cast solution is able to maximize power transfer by using a much broader area
of the RF spectrum, the 900-MHz band. While not necessarily a replacement for a
conventional charger, the technology will be able to "trickle charge" a variety of electronics
over a period of time so that their energy is never fully depleted.
As with a traditional AM/FM radio, the closer one is to the tower transmitting the signal,
the better the reception. Power cast's wireless platform operates using a similar principle. The
wireless power platform can harvest a few milli watts of energy within a meter of the source,
in this case the transmitter. That is enough energy to charge a single depleted cell phone
battery about half way overnight. The solution will also be ideal for devices with small
batteries such as watches, hearing aids, wireless keyboards and mice, and game controllers,
all of which could be continuously charged. But there are limits to the charging capabilities
the Power cast platform. Larger devices will not be able to make use of this „power cast‟
technology solution simply because they require too much power. In fact, the size limit for
now seems to be at the cell phone level for effective charging.
eCoupled technology:
The Basic Idea:
The basic concept behind this is Magnetic Resonance. Two resonant objects of the same
resonant frequency tend to exchange energy efficiently, while dissipating relatively little
energy in extraneous off-resonant objects. In systems of coupled resonances, there is often a
general “Strongly Coupled” regime of operation. If one can operate in that regime in a given
system, the energy transfer is expected to be very efficient. Midrange power transfer
implemented in this way can be nearly omni directional and efficient, irrespective of the
geometry of the surrounding space, with low interference and losses into environmental
objects. The above considerations apply irrespective of the physical nature of the resonances.
Magnetic resonances are particularly suitable for everyday applications because most
of the common materials do not interact with Magnetic Fields, so interactions with
Environmental objects are suppressed even further. We were able to identify the strongly
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www.ijetmas.com April 2017, Volume 5 Issue 4, ISSN 2349-4476
coupled regime in the system of two coupled magnetic resonances by exploring Non-radiative
(near-field) magnetic resonant induction at Megahertz frequencies.
Experimental Design:
Our experimental scheme consists of two Self-resonant coils. One coil (source coil) is
coupled inductively to an oscillating circuit; the other (device coil) is coupled inductively to a
resistive load. Self-resonant coils rely on the interplay between distributed inductance and
distributed capacitance to achieve resonance.
The coils are made of an electrically conducting wire of total length „l‟ and crosssectional radius „a‟, wound into a helix of „n‟ turns, radius „r‟, and height „h‟. There is no
exact solution for a finite helix in the literature, and even in the case of infinitely long coils,
the solutions rely on assumptions that are inadequate for this system. So here the method
implemented is simple Quasi-static model to find the parameters. Those are in Electro
Magnetic equations.
Efficiency of the System:
The efficiency of the system is nothing but the ratio of output power to input power.
The output power is nothing but the device power rating and input power is sum of the power
dissipated by source, power loss due to decay and output power.
Efficiency=Pw / (Ps+Pd+Pw)
The experiment done in 7th June, 2007 by the Massachusetts Institute of Technology,
Cambridge gives the result that in order to get 60W approximate power is the output useful
power with 40% efficiency. They resonated the circuit at ≈9.9 MHz so that they developed
the power is transmitted up to 8 times greater than the radius of the coil used.
ADVANTAGES OF ABOVE TECHNOLOGIES:
 The need for batteries and numerous redundant adaptors which consists of toxic
substances like nickel, cadmium, mercury are reduced. This reduces the electronic
waste.
 There is no need for alkaline batteries which are to be recharged regularly.
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DR. K. UMADEVI, ANUP C J, SHRUTHI. S
International Journal of Engineering Technology, Management and Applied 5
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www.ijetmas.com April 2017, Volume 5 Issue 4, ISSN 2349-4476

Complexity and risk of electric shorts reduces as we are not using any electrical
wires.
Unaffected by the day night cycle, weather or seasons.
This is an eco friendly and the system poses no health hazards what so ever as the
power limits.
It is a boon for the devices which use low-range and mid-range power



COMPARISON BETWEEN ABOVE TECHNOLOGIES:
 Power cast technology is suitable for only low range power, while eCoupled
technology is suitable for both low-range and mid-range powers
 Power cast technology is effective even though the distance between transmitter and
receiver is high but major limitation of eCoupled technology is air gap should be low.
 As eCoupled technology is based on magnetic resonance it could be easily effected
by presence of Ferro magnetic materials in its path.
 In eCoupled technology as the device is close to the charging source it is able to
provide more power than while charging using RF.
 Inductive method gives higher power at shorter distances but power cast system
though gives low range power it transmits even at longer distances.
 In eCoupled technology the resonance condition should be satisfied, if any medium
error is there possibility of power transfer is affected, while as power cast system uses
radio waves it is independent of medium around it.
 In power cast technology any number of power harvesting devices can be placed with
in the range of single power caster. It is not possible in case of eCoupled technology
CONCLUSION:
From the above discussion we can conclude that no technology can be perfectly ideal
by making use of best ideas in the technologies and working in conjunction with them we
can achieve wireless power transmission very sooner. This reduces the risk of using
electrical cables and redundant adaptors. Each of the above system has its own pros and
cons and one needs to decide based on one‟s needs.
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