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seminar report on wireless inductive charging

seminar report on wireless inductive charging

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  • 1. AReport OnINDUCTIVE CHARGINGDEPARTMENT ELECTRONICS & COMMUNICATION ENGINEERINGCOLLEGE OF TECHNOLOGY AND ENGINEERINGMaharana Pratap University of Agriculture and EngineeringUdaipur (Rajasthan)Submitted to:- Submitted By:- Mr. P.C.Bapna Jai Lal MeenaAssistant Prof. B.E.FINAL YEARECE (CTAE) ECE (CTAE)ACKNOWLEDGEMENT
  • 2. Before we get thick, I would like to add heartful words for the people whohelped me a lot in the completion of my seminar .I would like to givesincere gratitude to my parents. Words are unable to express their valuesin my life.I would like to take this opportunity to express my honors, respect, deepgratitude & Regards to my guide Mr. P.C. Bapna sir, without whom helpthis seminar would not have been success. Also giving me all the support &cooperation required & for being tremendous source of my inspiration &motivation.I will be failing in my duty, if I do not my express my gratitude towardsother staff members and friends who have helped me to complete myseminar work successfully and in time.Yours FaithfullyABSTRACT
  • 3. An inductive charging system for vehicle battery chargers includes atransformer having a stationary primary coil and a secondary coil mountedon the vehicle. The primary coil is mounted in a charging station and has apower source connected therewith. When the vehicle is parked adjacent tothe charging station, the secondary coil on the vehicle is proximate to theprimary coil in the station. The power source is activated to deliver currentto the primary coil which generates a magnetic field to induce a voltage inthe secondary coil. A controller is connected with the power source toadjust the voltage delivered to the primary coil. A feedback loop betweenthe secondary coil and the controller delivers a secondary voltage signal tothe controller which continuously adjusts the power source in order tomaintain the secondary output voltage at a predetermined value.INDEX1. Introduction2. History3. Terminology3.1 DC/AC converter3.2 Split-core transformer3.3 Transmitting inductor3.4 Receiving inductor3.5 Rectifier and filter
  • 4. 3.6 Voltage regulation4. How ordinary charger work5 How inductive charger work6. Advantage7. disadvantage8. Use area of inductive charging8.1 Electric car8.2 Artificial heart8.3 Mobile charger8.4 Toothbrush8.5 Power Mats9. RefrenceIntroductionA transformer can be used to induce a current from one circuit to anothernearby circuit, due to the mutual inductance of the two circuits. The coilcarrying the power is called the primary, and the other coil is thesecondary. Current flows through the primary inductive coil and theresulting magnetic flux induces an alternating current through the magneticfield and across the secondary coil, completing the circuit. When applied toa transformer the primary and secondary coils are fixed in relation to oneanother. Using these electromagnetic properties, and patents leased byDr. John Boys of the University of Auckland, Wampfler®has developed aninductive charging system that can be used to charge a range of differentdevices. Some of the current applications of this system include the
  • 5. powering of a floor conveying system at both an Audi and a BMW engineassembly line, three sorting system distribution centers located in Europe,and an outdoor elevator in Germany.The major aim of this project is to test how the orientation of the primaryand secondary coils affects the charging rate of the batteries. The twomost important aspects of the design include a frame capable of supportingthe secondary coil in a range of orientations above the primary coil, and apositioning system capable of accurately measuring what that orientationis. This frame will simulate the underside of the bus carrying the secondarycoil. The data obtained from running these experiments will help determinethe tolerances in which the bus must be aligned with the primary coil toobtain a sufficient charge for the bus within a given time frame.Problem StatementThe Inductive Charging team has been tasked with developing andimplementing a method in which to determine the sensitivity of the chargingrate of the Inductive Power Transfer system, to the orientation of theprimary and secondary coils.
  • 6. HistoryWireless power transmission is not a new idea. Nicola Tesla demonstratedtransmission of electrical energy without wires in early 20th century. Teslaused electromagnetic induction systems. Tesla discovered that electricalenergy could be transmitted through the earth and the atmosphere. In thecourse of his research he successfully lit lamps at moderate distances andwas able to detect the transmitted energy at much greater distances. TheWardenclyffe Tower project was a commercial venture for trans-Atlantic
  • 7. wireless telephony and proof-of-concept demonstrations of global wirelesspower transmission. The facility was not completed because of insufficientfunding. Earth is a naturally conducting body and forms one conductor ofthe system. A second path is established through the upper troposphereand lower stratosphere starting at an elevation of approximately 4.5 miles.A global system for "the transmission of electrical energy without wires"called the World Wireless System, dependent upon the high electricalconductivity of plasma and the high electrical conductivity of the earth, wasproposed as early as 1904Following World War II, which saw the development of high-powermicrowave emitters known as cavity magnetrons, the idea of usingmicrowaves to transmit power was researched.William C Brown demonstrated a microwave powered model helicopter in1964. This receives all the power needed for flight from a microwave beam.In 1975 Bill Brown transmitted 30kW power over a distance of 1 mile at84% efficiency without using cables. Japanese researcher Hidetsugu Yagialso investigated wireless energy transmission using a directional arrayantenna that he designed. In February 1926, Yagi and Uda published theirfirst paper on the tuned high-gain directional array now known as the Yagiantenna. While it did not prove to be particularly useful for powertransmission, this beam antenna has been widely adopted throughout thebroadcasting and wireless telecommunications industries due to itsexcellent performance characteristics.In 2006, more recent breakthroughs were made; using electrodynamicsinduction a physics research group, led by Prof. Marin Soljacic, at MIT,wirelessly power a 60W light bulb with 40% efficiency at a 2 metersdistance with two 60 cm-diameter coils.Researchers developed several techniques for moving electricity over longdistance without wires. Some exist only as theories or prototypes, butothers are already in use.
  • 8. TERMINOLOGYFull-wave rectificationA full-wave rectifier converts the whole of the input waveform to one ofconstant polarity (positive or negative) at its output. Full-wave rectificationconverts both polarities of the input waveform to DC (direct current), andyields a higher mean output voltage. Two diodes and a centertapped transformer, or four diodes in a bridge configuration and any ACsource (including a transformer without center tap), are needed. Singlesemiconductor diodes, double diodes with common cathode or commonanode, and four-diode bridges, are manufactured as single components.
  • 9. For single-phase AC, if the transformer is center-tapped, then two diodesback-to-back (cathode-to-cathode or anode-to-anode, depending uponoutput polarity required) can form a full-wave rectifier. Twice as many turnsare required on the transformer secondary to obtain the same outputvoltage than for a bridge rectifier, but the power rating is unchanged.The average and root-mean-square no-load output voltages of an idealsingle-phase full-wave rectifier are:A very common double-diode rectifier tube contained a singlecommon cathode and two anodes inside a single envelope, achieving full-wave rectification with positive output. The 5U4 and 5Y3 were popularexamples of this configuration.Power invertersA power inverter, or inverter, is an electrical power converter thatchanges direct current (DC) to alternating current (AC); the converted ACcan be at any required voltage and frequency with the use of appropriatetransformers, switching, and control circuits.
  • 10. Working principleThe single-phase voltage source half-bridge inverters, are meant for lowervoltage applications and are commonly used in power supplies .Figureshows the circuit schematic of this inverter.Low-order current harmonics get injected back to the source voltage by theoperation of the inverter. This means that two large capacitors are neededfor filtering purposes in this design. As Figure , only one switch can be onat time in each leg of the inverter. If both switches in a leg were on at thesame time, the DC source will be shorted out.Inverters can use several modulation techniques to control their switchingschemes. The carrier-based PWM technique compares the AC outputwaveform, vc, to a carrier voltage signal, vΔ. When vc is greater than vΔ, S+is on, and when vc is less than vΔ, S- is on. When the AC output is atfrequency fc with its amplitude at vc, and the triangular carrier signal is atfrequency fΔ with its amplitude at vΔ, the PWM becomes a special
  • 11. sinusoidal case of the carrier based PWM.This case is dubbed sinusoidalpulse-width modulation (SPWM).For this, the modulation index, oramplitude-modulation ratio, is defined as ma = vc / v∆ .The normalized carrier frequency, or frequency-modulation ratio, iscalculated using the equation mf = f∆ / fc .If the over-modulation region, ma, exceeds one, a higher fundamental ACoutput voltage will be observed, but at the cost of saturation. For SPWM,the harmonics of the output waveform are at well-defined frequencies andamplitudes. This simplifies the design of the filtering components neededfor the low-order current harmonic injection from the operation of theinverter. The maximum output amplitude in this mode of operation is half ofthe source voltage. If the maximum output amplitude, ma, exceeds 3.24,the output waveform of the inverter becomes a square wave.As was true for PWM, both switches in a leg for square wave modulationcannot be turned on at the same time, as this would cause a short acrossthe voltage source. The switching scheme requires that both S+ and S- beon for a half cycle of the AC output period.The fundamental AC outputamplitude is equal to vo1 = vaN. .Its harmonics have an amplitude of voh =vo1 / h.Therefore, the AC output voltage is not controlled by the inverter, but ratherby the magnitude of the DC input voltage of the inverter.Using selective harmonic elimination (SHE) as a modulation techniqueallows the switching of the inverter to selectively eliminate intrinsicharmonics. The fundamental component of the AC output voltage can alsobe adjusted within a desirable range. Since the AC output voltage obtainedfrom this modulation technique has odd half and odd quarter wavesymmetry, even harmonics do not exist. Any undesirable odd (N-1) intrinsicharmonics from the output waveform can be eliminated.
  • 12. Used Transformer:-The construction of a simple two-winding transformer consists of eachwinding being wound on a separate limb or core of the soft iron form whichprovides the necessary magnetic circuit. This magnetic circuit, know morecommonly as the "transformer core" is designed to provide a path for themagnetic field to flow around, which is necessary for induction of thevoltage between the two windings.However, this type of transformer construction were the two windings arewound on separate limbs is not very efficient since the primary andsecondary windings are well separated from each other. This results in alow magnetic coupling between the two windings as well as large amountsof magnetic flux leakage from the transformer itself. But as well as this "O"shapes construction, there are different types of "transformer construction"and designs available which are used to overcome these inefficienciesproducing a smaller more compact transformer.The efficiency of a simple transformer construction can be improved bybringing the two windings within close contact with each other therebyimproving the magnetic coupling. Increasing and concentrating themagnetic circuit around the coils may improve the magnetic couplingbetween the two windings, but it also has the effect of increasing themagnetic losses of the transformer core.As well as providing a low reluctance path for the magnetic field, the core isdesigned to prevent circulating electric currents within the iron core itself.Circulating currents, called "eddy currents", cause heating and energylosses within the core decreasing the transformers efficiency. These lossesare due mainly to voltages induced in the iron circuit, which is constantlybeing subjected to the alternating magnetic fields setup by the externalsinusoidal supply voltage. One way to reduce these unwanted powerlosses is to construct the transformer core from thin steel laminations.
  • 13. In all types of transformer construction, the central iron core is constructedfrom of a highly permeable material made from thin silicon steel laminationsassembled together to provide the required magnetic path with theminimum of losses. The resistivity of the steel sheet itself is high reducingthe eddy current losses by making the laminations very thin. These steellaminations vary in thicknesses from between 0.25mm to 0.5mm and assteel is a conductor, the laminations are electrically insulated from eachother by a very thin coating of insulating varnish or by the use of an oxidelayer on the surface.Voltage Regulation:-A voltage regulator is used to produce a constant linear output voltage.It’s generally used with AC to DC power supply. And also it can be used aswell as a DC to DC voltage converter. To regulating low voltage, most useddevice is one single IC. 7805, 7812, 7905 etc. 78xx series are design forpositive and 79xx series are for Negative voltage regulator. 7805 is a threeterminal +5v voltage regulator IC from 78XX chips family. See 7805 pinout below. LM78XX series are from National Semiconductor. They arelinear positive voltage regulator IC; used to produce a fixed linear stableoutput voltage. National Semiconductor has also negative voltageregulator chips family, they indicate with LM 79XX. 78xx is used more than79xx because negative voltage has a few usability purposes as we see.I was previously posted a 5v regulated power supply circuit using 7805 IC,that circuit and this 7805 voltage regulator circuit is almost the same.
  • 14. Circuit diagram of 7805 Voltage RegulatorFig: 7805 Voltage Regulator Circuit
  • 15. Fig: Pin out of 7805Its output voltage is +5V DC that we need. You can supply any voltage ininput; the output voltage will be always regulated +5V. But myrecommendation is, don’t supply more than 18V or less than 8V in input.There used two capacitors in this voltage regulator circuit, they aren’tmandatory to use. But it will be best if you use them. They helped toproduce a smooth regulated voltage at output. Use electrolyte capacitorinstead of ceramic capacitor.One limitation of 7805 I have found that is its output current 1A maximum.Otherwise it is a good voltage regulator if you are happy with 1A. But ifyou need over 400mA current in output then you should use a HeatSink with IC LM7805. Otherwise it may fall damage for overheating.
  • 16. How ordinary charger workMost of the small electronic appliances we use in our homes work on relativelylow voltagesTypically 5-10 percent as much voltage as hefty electric appliances like vacuumcleaners and clothes washers.That means we generally need to use transformersto"step down" the domestic voltage so it will safely power electronic gadgets withoutblowing them up. All those chargers you have (little boxes attached to wires thatplug into things like yourMP3playerandcellphone) actually have electricitytransformers hiding inside. Its easy to understand how these simple chargers work:electricity flows into the charger from the electricity outlet on your wall. Inside thecharger, a transformer "steps down" the electricity to a much lower voltage. Thelow-voltage current then flows from the charger into the battery in your appliance.The important thing to note is that all three parts of the transformer (the primarycoil, the secondary coil, and the iron core linking them together) are containedinside the charger:
  • 18. ARTWORK: INDUCTION CHARGING: HALF THE TRANSFORMER IS IN THE TOOTHBRUSH;HALF IS IN THE STAND.THE PRIMARY COIL IS IN THE CHARGER BASE AND IT HAS AN IRON PEG ON TOPof it covered in plastic. The secondary coil is in the base of the toothbrush, whichyou stand on the iron peg. Whats the peg for? Its not just to stop the toothbrushwobbling about: its the core that links the primary and secondary coils togetherelectromagnetically. When the toothbrush is standing on the peg, youve got acomplete transformer that works by electromagnetic induction :energy flows fromthe coil in the base to the coil in the toothbrush via the iron peg that links them.The two ends of the coil in the toothbrush are simply hooked up to therechargeable battery inside.
  • 20. Electric vehicle energy storage systems are normally recharged using direct contactconductors between an alternating current (AC) source such as is found in mosthomes in the form or electrical outlets; nominally 120 or 240 VAC. A well knownexample of a direct contact conductor is a two or three pronged plug normallyfound with any electrical device. Manually plugging a two or three pronged plugfrom a charging device to the electric automobile requires that conductors carryingpotentially lethal voltages be handled. In addition, the conductors may be exposed,tampered with, or damaged, or otherwise present hazards to the operator or othernaïve subjects in the vicinity of the charging vehicle. Although most householdcurrent is about 120 VAC single phase, in order to recharge electric vehiclebatteries in a reasonable amount of time (two-four hours), it is anticipated that aconnection to a 240 VAC source would be required because of the size andcapacity of such batteries. Household current from a 240 VAC source is used inmost electric clothes dryers and clothes washing machines. The owner/user of theelectric vehicle would then be required to manually interact with the higher voltagethree pronged plug and connect it at the beginning of the charging cycle, anddisconnect it at the end of the charging cycle. The connection and disconnection ofthree pronged plugs carrying 240 VAC presents an inconvenient and potentiallyhazardous method of vehicle interface, particularly in inclement weather.In order to alleviate the problem of using two or three pronged conductors,inductive charging systems have been developed in order to transfer power to theelectric vehicle. Inductive charging, as is known to those of skill in the art, utilizesa transformer having primary and secondary windings to charge the battery of thevehicle. The primary winding is mounted in a stationary charging unit where thevehicle is stored and the secondary winding is mounted on the vehicleThere is a time varying aspect to the AC voltage, and hence there is a time-varyingaspect to the magnetic fields in both the primary and secondary transformer cores.Typically, house current in the U.S. operates at about 60 hertz (Hz), or cycles persecond. The problem with using a voltage that oscillates at 60 Hz, is that the size ofthe components in an inductive charging system is inversely proportional to thefrequency, and thus the lower the frequency of the voltage, the greater the size ofthe inductive charging system. Size is extremely critical to vehicle manufacturersbecause it is very important to automotive owners. The size and weight of an
  • 21. object directly affects the fuel mileage of the vehicle. Thus in other inductivecharging systems, high frequency voltages, normally above 10 kHz, have beenused to transfer power by radiation and tuned coils.The present invention relates to inductive proximity charging. More particularly,the invention relates to a system and method for increasing the efficiency of agapped transformer used in inductive charging of a vehicle and for regulating theload voltage of the transformer.WorkingReferring first to FIG. 1, the inductive charging system according to the inventionwill be described. The system includes a charging station 2 and transformer 4. Thetransformer includes a stationary primary coil 6 which is preferably mounted onthe ground such as the floor of a garage. The primary coil is connected with thecharging station. The transformer further includes a secondary coil 8 which ismounted on a vehicle 10. The secondary coil is mounted at a location on thevehicle so that the vehicle can be positioned adjacent to the charging station withthe secondary coil above the primary coil as shown. Preferably, the coils arearranged with their axes in alignment for maximum energy transfer. However,because axial alignment is imprecise, the inductive charging system according to
  • 22. the invention is designed to adjust the charging station to maximize energytransfer.The inductive charging system according to the invention will be described ingreater detail with reference to FIG. 2. The charging station 2 is connected with apower source 12. The power source is preferably a 220 volt AC supply operating atbetween 50 and 60 Hz. The charging station includes a power converter 14 whichis capable of converting the incoming source voltage from the power supply into avoltage of arbitrary frequency and voltage. The voltage is supplied to the stationaryprimary coil 6. Current within the primary coil generates a magnetic field 16 whichinduces a current in the secondary coil 8 mounted on the vehicle. This in turnproduces an output voltage which is delivered to a battery charger 18 in the vehicleto charge the vehicle battery.An AC capacitor 20 is connected in series with the secondary coil 8 to create aresonant circuit in order to efficiently transfer energy within the transformer and toregulate the load voltage. The resonant circuit is between the transformer leakageinductance and the capacitor. Such a circuit is useful when the transformer leakageinductance is large, as is the case for the coil arrangement according to theinvention, and must be cancelled by the capacitor in order to prevent anunacceptable voltage drop when the battery charger load is applied.The primary coil is preferably energized at a frequency corresponding to theresonant frequency of the primary-to-secondary coil leakage inductance and theseries connected capacitor. In this case, the no load voltage at the output of thetransformer will equal the input voltage multiplied by the secondary-primary turnsratio and by the coupling factor between the coils. As the secondary coil is loaded,the voltage drop at the load will be only that due to the primary and secondarywinding resistance, assuming that the primary coil is excited with a constantvoltage. However, there are many factors which alter this ideal scenario.The coupling factor between the primary and secondary coils, which dictates theoutput voltage of the transformer, depends on the relative alignment between thecoils with respect to both the axial and radial positions of the coils. If the primarycoil is energized at 220V AC for example, the secondary voltage at no load may be220V AC at a gape of three inches and perfect radial alignment. However, if the
  • 23. radial alignment is off by one-third of the diameter of the coils, the secondaryvoltage will be significantly lower. The secondary voltage might be below theacceptable range for the load or might result in excessive secondary coil current,thereby reducing the efficiency of the inductive charging system. It is thereforedesirable to maintain a regulated voltage at the load for reasonable radial and axialmisalignments of the coils.According to the invention, reductions in the secondary voltage may becompensated by adjusting the power input. Accordingly, a voltage sensor 22 isconnected with the output of the secondary coil 8 and the capacitor 20. The voltagesensor 22 generates a secondary voltage signal. A radio frequency (RF)communication device 24 is connected with the voltage sensor 22 and delivers thesecondary voltage signal to a controller 26 within the charging station 2 via afeedback loop. The controller continuously adjusts the voltage applied to theprimary coil in accordance with the secondary voltage so that the secondaryvoltage is maintained at a fixed value. Thus, the output voltage is maintained at anacceptable level regardless of misalignment of the coils or various in the gapbetween the coils. The controller also compensates for the resistive voltage drop asthe battery charger load is applied to the inductive charging system. A voltagesensor 28 connected with the output of the power converter 14 delivers a signalcorresponding to the voltage output of the power converter to the controller forfurther adjustment of the power converter to maintain an adequate voltage supplyto the system transformer.In addition to the normal variations in coupling factors that must beaccommodated, the inductive charging system must be able to accommodatevariation in both leakage reactance and series capacitance, which define theresonant frequency of the system. Variations in leakage reactance will arise due todifferences in coil geometries and due to steel or conductive material which isintroduced into the magnetic path as a result of application of the coil to thevehicle. Variations in capacitance also occur over time as the capacitor ages.In order to adjust for these variations in system resonant frequency, an algorithm isused in the controller to adjust the frequency of the voltage applied to the primarycoil. At the resonant frequency of the system, the ratio between the output voltage
  • 24. and input voltage will be at a maximum for a given current level. The controlsystem can maintain the excitation voltage frequency at the resonant frequency byperiodically applying slight variations to the excitation frequency and thenmeasuring the output to input voltage ratio. By comparing the ratio before theadjusted frequency with the ratio at the new frequency, an appropriate adjustmentcan be made to the excitation voltage frequency. Because the resonant frequencywill not, in any practical application, vary by more than approximately 10-20%from a nominal value, the adjustments to the excitation voltage frequency wouldneed to be relatively minor and performed relatively infrequently in order tomaintain the optimal value. It will be apparent to those of ordinary skill in the artthat there are a number of algorithms which may be utilized to implement thisiterative technique for maintaining the system resonance.This corresponds to approximately 8A for a 3.3 kW 400VDC charger andapproximately 16A for a 6.6 kW 400VDC charger.Power Mat 3XPower Mat 3X as shown in Figure 5 is a sleek, slim three position Wirelesscharging mat for home and office. A magnetic attraction between every receiverand each access point on every Mat assures that alignment is precise and the mostefficient charging occurs. Communication between the Mat and the Receiverallows the mat to deliver an exact amount of power for the proper length of time sothat the transfer of power is safe and efficient and no energy is wasted. When thedevice reaches full charge, power is shut off to that device, which avoidsovercharging of the devices battery as well as saves energy. Once full power isachieved andthe Auto Shut Off has occurred to save energy, the system willmonitor the status of the battery in the device. If the battery is
  • 25. used, the system will again initiate charging and return the battery to a full charge.Artificial heart (transcutneous energy transfer):With the number of cardiac patients increasing dramatically each year, thepotential for development of implantable circulatory assist devices is remarkable.Such circulatory assist devices consist of totally artificial hearts and ventricularassist devices. These devices usually require 12-35 W for operation, and they arepowered by portable battery packs and dc-dc converters. Recently, however, therehas been great interest and subsequent development of transcutaneous transfer ofelectrical energy to these circulatory assist devices. A depiction of how such asystem is implanted as represented by the Abiocor artificial heart system is shownbelow.
  • 26. Figure 1. Transcutaneous energy transmission system location of implantationDevelopment of such circuitry involves inductive coupling. Inductive couplingallows for the transfer of energy without any electrical contact. This technique isaccomplished by a power supply that employs a transcutaneous transformer. Theprimary of the transformer is to be placed externally with respect to the body. Thesecondary winding of the transformer lies underneath the skin. The spacing ofapproximately one to two centimeters between the primary and the secondary ofthe transformer contributes to the extremely large leakage inductance. This leakageinductance is much higher than the magnetizing inductance and as a result, thevoltage gain is low. Consequently, a high percentage of primary winding currentflows through the magnetizing inductance in order to reduce the voltage gain. Useof a dc-dc converter employing the resonance of the secondary side lowers theimpedance and improves the voltage gain. Below is the equivalent circuit modelfor the transcutaneous energy transmission circuit.
  • 27. Figure 2. Equivalent circuit model for transcutaneous energy transmission circuitThe circuit in Figure 2 is currently being implemented in FEMLAB. FEMLABoffers the opportunity to model the above circuit by employing the finite elementmethod to solve partial differential equations used in electromagnetics and morespecifically in the above circuitry. In the future, this FEMLAB model will beimplemented in the VTB platform. The uses of such modeling are quite expansive.The concept of transferring electrical energy wirelessly can be applied in medicalfields as well as in areas in which the transfer of energy is compromised byenvironmental conditions. Such a case exists in transferring energy to electric shipssurrounded by water. Hence, contactless energy transfer has many applications andthe future has much potential in this area.ToothbrushesSpecification1. Rotates clockwise and counterclockwise 8000rpm.2. Lasts up to14 days when brushing two mins, twice a day3. Brush your teeth for about 2mins, move the brush head between the teeth,brushing the outside first, then the inner side and finally the chewing surface.4. Wash the toothbrush with water and dry it5. For optimal result and better tooth and mouth hygiene, replace the brush headevery month6. Overall size: Height: 25mm Length: 220mm (assembled)7. Weight: 202g
  • 28. Mobile Charger:According to Apples most recent patent application, "Wireless power utilization ina local computing environment," you could soon be charging your iOS devicesimply by keeping it close to your computer system. In case this sounds toopedestrian for you, the research comes from the field of midrange wireless powertransfer physics. Near field magnetic resonance is used to power devices within
  • 29. 1meter of the power base. Without a mat or extra case.Inductive Mobile charger
  • 30. AdvantageInductive charging carries a far lower risk of electrical shock, whencompared withconductive charging, because there are no exposed conductors .The ability to fullyenclose the charging connection also makes the approach attractive where waterimpermeability is required; for instance, inductive charging is used for implantedmedical devices that require periodic or even constant external power, and forelectric hygiene devices, such as toothbrushes and shavers, that are frequently usednear or even in water. Inductive charging makes charging mobile devices andelectric vehicles more convenient; rather than having to connect a power cable, theunit can be placed on or close to a charge plate .For example, toothbrushes areguaranteed to get wet during operation. So obviously it would be quite dangerousto have a wired object that operates in a watery environment. Of course, they coulduse some system where the cord could be disconnected during operation, but thenthat would become tedious for users. In this case, inductive charging fits perfectly;theres no fiddling with a wire and more importantly, water wont pose a safetyhazard. As for using it for speakers, it depends on a lot of things. Mainly I wouldsay it depends on the number of speakers actually, since having lots of separatecharging stations might be more cumbersome than using a single inductive station.Again though, youd have to look at the efficiency, and also whether it might bepossible to use a very simple (inexpensive) multi-docking station using conductivechargers instead.
  • 31. DisadvantageThe main disadvantages of inductive charging are its lower efficiency andincreased resistive heating in comparison to direct contact. Implementations usinglower frequencies or older drive technologies charge more slowly and generateheat within most portable electronics. Inductive charging also requires driveelectronics and coils, increasing the complexity and cost of manufacturing .Newerapproaches reduce transfer losses through the use of ultra-thin coils, higherfrequencies, and optimized drive electronics. This result in more efficient andcompact chargers and receivers, facilitating their integration into mobile devices orbatteries with minimal changes required. These technologies provide chargingtimes comparable to wired approaches, and they are rapidly finding their way intomobile devices. For example, the Magne Charge system employed high-frequencyinduction to deliver high power at an efficiency of 86% (6.6 kW power deliveryfrom a 7.68 kW power draw).A toothbrush which takes about 16 hours to charge,only lasts about 15minutes. Of course, the main reason for the inefficiency is thatthe design forces the use of an inefficient transformer type of circuit (since youcant use a solid iron core to link the two circuits).The other problem is that youstill need to supply power to the base station. And so you never fully escape theneed for a conventional conductive charger in the end.Reference:1. http://answers.yahoo.com/question/index?qid=20081222154050AAANpjF
  • 32. 2. http://web.mit.edu/newsoffice/2007/wireless-0607.html3. http://en.wikipedia.org/wiki/Inductive_charging4. http://lifehacker.com/5598744/hack-an-induction-charger-to-work-with-any-cellphone5. http://www.explainthatstuff.com/inductionchargers.html6. http://www.instructables.com/answers/How-do-I-build-an-inductive-charger/7. http://en.wikipedia.org/wiki/Electric_car8. http://en.wikipedia.org/wiki/Artificial_heart9. http://en.wikipedia.org/wiki/Magne_Charge10. http://en.wikipedia.org/wiki/WiTricity11. http://en.wikipedia.org/wiki/Electromotive_force12. http://en.wikipedia.org/wiki/Electromagnetic_induction13. http://en.wikipedia.org/wiki/Rectifier