Wireless Charging by Rachin Jindal

7/31/2019 Wireless Charging by Rachin Jindal

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Presented By

Rachin Kumar JindalEC-B (G1)

08ESKEC062


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ContentsIntroduction

Design Overview

Transmitter

Antenna

Receiver

Testing and DataProblems with this Device

Possible Improvements

Advantages

Disadvantages

Application

Conclusion


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Introduction

Portable electronic devices are very popular now a days.As the usage of these portable electronic devices is

increasing, the demands for longer battery life are also

increasing. These batteries need to be recharged or replaced

periodically.It would be convenient not having to worry about charging or

changing the batteries and still have a working device. The

advantage of this device is that it can wirelessly charge up the

batteries which can save time and money in a long run for the

general public.


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DesignOverview

This wireless battery charger is designed to operate at 900MHz In this system, a power transmitter acts as the power

source. It will transmit power to the receiver side. And then,

the rectifier circuit in the receiver will convert the RF/

microwave signal into DC signal. After the DC signal is

produced, the charging circuit will store the power into the

battery.


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Block Diagram Of Wireless Charger


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It is a 900 MHz video/audio transmitter. Heres thespecification of the transmitter.

12V DC, 900 mA

Output Power: 3 Watts

Operating Frequency: 900 MHz

Connector Type: SMAFemale

OutputImpedance: 50

Transmitter


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The antenna plays a very important role. To charge abattery, a high DC power signal is needed. there are

many considerations to choose the correct parts for

the design. The considerations of choosing the

appropriate antenna are:

Antenna

1. Impedance of the antenna

2. Gain of the antenna


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Taking the above design specification in consideration, itis found that Yagi antennas fit our specification. Above

is a picture of the Yagi antenna.


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The impedance of the Yagi antenna matches with the output

impedance of the power transmitter and input impedance ofthe rectifier circuit.

Non-matching impedance between circuits can cause a

tremendous power loss due to signal distortion. Since the

output impedance of the transmitter is 50 , the antenna

should also have 50 impedance.

The higher of the Yagi antenna gain yields a better result of

the design. However, higher gain will also increase the cost

and the size of the antenna.

WhyYagi antenna :-


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Receiver

The receivers main purpose is to charge an battery.

A simple battery charging theory is to run current through the

battery, and apply a voltage difference between the terminals

of the battery to reverse the chemical process. By doing so, it

recharges the battery.


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Full-wave Rectifier Circuit

D1 D2

D3

D4


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A full-wave rectifier is chosen due to its simplicity and

efficiency in converting the AC signal.

The full-wave rectifier is consisted of four diodes. Since the

power received by the receiver will be relatively low and the

signal frequency is high.

the diodes are required to have a very low turn on voltage

and operating frequency at 900 MHz For this reason, aSchottky diode is chosen for the design.

At the output of the rectifier, the signal is not a fully DC

signal yet. Thus, by adding a capacitor and a resistor can

smooth out the output to become DC signal.


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The final design of the wireless battery charger consists of:

these major components:

1.Transmitter

2. Yagi antennas

3. Full-wave rectifier circuit

4. RC circuit5. Battery holder


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Problems with this device

Even though the frequency was set on 900 MHz, the results

did not meet our expectations.One of the difficulties is the power insufficiency from the

transmitter.

The output power of the transmitter was theoretically 3

Watts, but when it is measured using the spectrum analyzer,

it only gave us 1 Watt output.

With that insufficient output from the transmitter and the

loss from the medium, we got only 90 mW from the antennaon the receiver side. With that small input power, our circuit

did not have enough power.


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PossibleImprovements

There are several possible ways to improve our design in

order to increase the power output :

One way is to use multiple rectifiers. By doing so,

more power is getting rectified by these multiple

rectifiers in the circuit.


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HighGainParabolic Antenna

By using a high gain parabolic antenna This parabolic antenna

will be able to transmit power from the transmitter with a muchhigher gain, and receive approximately seven times greater

power than the Yagi antennas .


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Advantages

We can charge our battery without physical contact whenthere are no Power outlet around.

In the case of constant power supply is needed this device is

very useful.


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Charging has lower efficiency as compared to the chargingthrough direct contact.

Device also requires some circuits that increase

manufacturing complexity and cost.

It did not give enough current output to charge the batteryin a short time.

Disadvantages


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Wireless charging is already being used in some electronics

devices like mobile phones.Similar technology is being used to recharge electronic

toothbrushes and even power tools

Its is used for implanted medical devices that require

periodic or even constant external power SupplySuch like pacemaker which is used to set uneven heart beats

of the patient .if such person is in this charging zone then its

pacemaker get charged continuously.

Its used in electric cars if such cars are passing through fromcharging zone then no need to be replaced its battery

frequently.

Applications


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ConclusionAs the wireless technology is getting popular nowadays

the demand of battery is also increasing. The battery

needs to be recharged or changed eventually. This

wireless battery charger will eliminate all the hassle

with the battery. But power loss and efficiency are the

major problems in this technology.

As for now, there are no known companies which

develop the wireless battery charger. This means that

the opportunity is very big. Also, people tend to spendmore money for convenience. It gives more reason that

this device will have a very good market.


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Wireless Charging by Rachin Jindal