University Project.docx

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University Project – Report On

WIRELESS CHARGING USING PIEZO ELECTRIC MATERIAL Submitted to Presidency University for the partial fulfilment of the requirements for the Degree Of Bachelor of Technology in Electronics and Communications Engineering

Submitted by Ms Sharmila Krishnaswamy Mr Hareef D Mr Vijaykumar Dalali

ID No: 2016ECE053 ID No: 2016ECE063 ID No: 2016ECE065

Under the supervision of Ms. Amrutha V Nair Assistant professor Department of Electronics and Communication Engineering

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DECLARATION This is to declare that the report titled “Wireless Charging Using Piezo Electric Material” has been made for the partial fulfilment of the course - project work in the third year by us at Presidency University, under the guidance of Prof Amrutha V Nair.

We confirm that this report truly represents our work undertaken as a part of the University Project work. This work is not a replication of work done previously by any other person. We also confirm that the contents of the report and the views contained therein have been discussed and deliberated with the faculty guide.

Sharmila Krishnaswamy (2016ECE053)

Vijaykumar Dalali (2016ECE065)

Hareef D (2016ECE063)

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ACKNOWLEDGEMENT We thank God for giving us this wonderful opportunity. We are grateful to our Dean of SOE Dr K Prabhakar Reddy, our HOD (ECE) Dr Shilpa Mehta and all our senior faculties for their guidance and support. We are sincerely grateful to our project guide, Prof. Amrutha V Nair for giving us this opportunity to investigate this project topic from the seed of an idea to the present form and for the constant support and guidance in ensuring that team contributed its best towards this learning process. We appreciate her for trusting our team and constantly being available for us all the time.

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ABSTRACT The project aims to present a model of Wireless Charging Using Piezo Electric Material in a Real-Time environment. When a person runs or exerts pressure on the piezo-mat, which is mechanical in nature can be converted into electrical energy using Piezo electric material. This generated power is transferred to the device by using an open interface standard Qi, that defines Wireless Power Transfer using Inductive Charging over a distance of up to 2cm and is developed by Wireless Power Consortium.

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TABLE OF CONTENTS 1. Introduction 2. Objective 3. Methodology 4. Work Done 5. Results and Discussions 6. Conclusions 7. References

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INTRODUCTION In the recent years there has been an increasing interest in research and development of advanced smart phone technology. But as technology evolves so are the problems associated with it, and one among those is the fast draining of battery. Almost every smartphone user wishes he had more battery life. Now, imagine your phone getting charged where ever you go. This is possible by Piezo electric wireless power transfer mobile charging technique. The keys to this technique are the piezoelectricity and Wireless power transfer (WTP).

Wireless charging, also known as inductive charging, is a convenient and cablefree way to charge your electronic devices. Wireless charging operates in a near field condition in which the primary coil produces a magnetic field that is picked up by the secondary coil in the close proximity.

It requires two things:  A charger, usually in the form of puck, a mat, or a stand that connects to a power source.  A smartphone or any other electronic device that is Qi compatible with wireless charging.

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Harvesting mechanical energy from human motion is an attractive approach for obtaining clean and sustainable electric energy. When you run on a treadmill, the belt moves to the rear, requiring the user to walk or run at a speed matching that of the belt. The rate at which the belt moves is the rate of walking or running. Piezoelectricity is electrical energy produced from mechanical pressure. This mechanical pressure compresses the piezo-mat placed under the conveyor belt. When pressure is applied to the mat, a negative charge is produced on the expanded side and a positive charge on the compressed side of the piezoelectric crystal. Once the pressure is relieved, electrical current flows across the material. The speed of running generates AC voltage which maybe controlled, measured and stored.

Qi wireless charging uses a resonant inductive coupling between the sender (the charging station) and the receiver (the mobile device). A regular test signal is sent by the sender to check for the resonance change, telling the Qi enabled charger base that a Qi compatible phone is present. The sender modulates the charge and checks for the compatibility to the Qi standard. Once Qi compatibility and the energy requirement have been calculated, the charging through induction begins. During the charging, the sender and the receiver remain in contact and switch into standby mode as soon as the battery is fully charged.

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BLOCK DIAGRAM:

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GENERATION-TRANSMISSION UNIT:

RECEIVER-CHARGING UNIT:

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OBJECTIVES 1. To design a Piezo-mat that generates 5V to 10V AC voltage. 2. To design the transmitter module that will store and transmit the generated AC voltage. 3. To design the transmitter and receiver coil such that their resonant frequencies match. 4. To design the receiver module that will rectify the AC voltage to DC voltage. 5. To implement and store this electrical energy to charge a compatible device when needed.

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METHODOLOGY The design consists of two units. Generation-transmission unit and receivercharging unit.  The generation-transmission unit consists of the Piezo electric generator, capacitance bank, oscillator (555 Timer) and transmitter coil all integrated.  The receiver-charging unit consists of capacitance bank, rectification circuit and charging circuit.

The mat design consists of a pair of array of piezo electric units connected in series. The front panel and rear panel has the array of piezo electric units in a linear arrangement. The generated voltage is sent to a oscillatory circuit that produces high frequency. The receiver-charging side collects continuous energy input from the oscillator and efficiently stores their energy in the capacitor bank. During the charging process, the capacitor voltage is continuously monitored. When it reaches 5.2V the module output is enabled to supply power to a Rectifier and charging unit.

The energy from the Receiver coil is rectified, regulated and is then transferred using wireless power transfer.

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WORK DONE The mat design was made keeping in mind the structure of human feet which has two points, the heel and the toe where the pressure exerted is maximum. The piezo electric material was embedded linearly and in series. The output was observed using a LED and was measured using the multimeter. The requirement for the transmitting-receiving coil is as follows:  Inductance of coil is a function of:  Coil diameter (D) = 100mm  Wire diameter (d) = 64mm  Number of turns of coil (N) = 50  Permeability of free space (μ0) = 4π x 10−7  Relative permeability of material (μr) = 0.99994  Frequency is a function of :  Inductance of coil (L) = 0.805mH  Capacitance (C) = 0.1 μF  Resonant frequency (F) = ~ 22000 Hz  Formula for coil inductance: L = N2 * μ0 μr * (D/2) [ln (8D/d)-2]  Formula for resonant frequency: F = 𝟏/(𝟐π√LC)

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RESULTS The regulated voltage was found out to be ~5.2V, 300mA. After implementing the circuit, it was observed that a minute error in the windings of the coil leads to a mismatch in the resonant frequency. Thus, there is no continuous flow of current causing fluctuations while charging.

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CONCLUSION This report summarizes the generation, transmission, receiving and charging the electronic devices using Wireless Power Transfer. From the calculation we have concluded that this circuit gives us 40% efficiency. This circuit can charge devices that requires 5V and 300mA charging current. However, there are certain limitations to this model as the model doesn’t work beyond the given range of 2cm. Due to poor air coupling, skin effect and error in inductance of the hand winded coil, the frequency of the oscillator circuit may not stable.

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REFERENCE  Piezoelectric generator Datasheet:

www.piezo.com/prodproto4EHkit

 Design and Test of a High Power High Efficiency Loosely Coupled Planar Wireless Power Transfer System by Zhen Ning Low, IEEE transactions on industrial electronics, vol. 56, no. 5, May 2009.  Wireless Power Transfer via Strongly Coupled Magnetic Resonances by Andre Kurs, Aristeidis Karalis, Robert Moffatt, J. D. Joannopoulos, Peter Fisher, Marin Soljacic. 2008.