Dept. Of Electrical & Computer Engineering Dept. Of Electrical & Computer Engineering
Abstract
Mobile phones have become part of our daily lives with continued technological advancement geared towards designing them to mimic computers (Suh, Lee, & Vu, 2014). This has created increased functionality in most of the mobile phones leading to increased power usage. The current mobile phones as well as the next generation mobile phones now require more energy in order to fully support their increased functionality for reasonable periods. Moreover, the research into long-life batteries seems to have reached its limits (Maeght et al, 2013). This therefore presents the need to come up with an alternative form of charging mobile phones to support their increased functionality.
The objective of the proposed project is to design a wireless mobile phone charging system that will charge the mobile phones through electrical mutual induction thereby increasing their power usage time. This is based on the idea that the convenience of mobile phones will continue to be limited for as long as charging systems with wires are used. Therefore, the objective of the proposed wireless mobile phone charging project is to make mobile phones more convenient by eliminating the restrictions brought about by charging systems with wires.
The proposed approach is to use capacitors, resistors, copper coils, transformer, voltage regulator and diodes to create a transmitter and receiver that will be used to charge the mobile phone. The transmitter is to be connected to a power source to create a time-varying electromagnetic field that will be directed towards a receiver which will be used to convert the electromagnetic energy into AC or DC electric current which will then be utilised by the mobile phone (electrical load). The coil will act as an antenna that produces the electromagnetic field. A second induction coil connected to the phone will take the power in the time-varying electromagnetic field and convert it into electric current that will charge the battery (Sun, Xie & Zhihua, 2013).
Background and Significance
A wireless charging system will work based on the concept of inductive charging or wireless charging. Wireless charging is done using an electromagnetic field to transfer energy between the charging station and the electrical device (Shinohara, 2014). The wireless charging systems is made up of a power station that creates a magnetic field which is used to transfer energy from the power station to the moveable rechargeable device (Buckley et al, 2009). Induction charging is the transfer of power from a high voltage source to a lower voltage source such as a mobile phone through electromagnetic fields. To do this, the power station has to have a primary winding that induces an electromagnetic field into the secondary coil that is located inside the mobile phone using the process of mutual induction.
Wireless energy transmission or wireless power transfer was discovered as far back as the 19th century when Andre-Marie discovered that electric current creates a magnetic field and developed the Ampere’s circuital law to explain how it works. In 1831, Michael Faraday also developed the Faraday’s Law of Induction to explain the electromagnetic force that is induced in an electrical conductor by a magnetic flux that is time-varying. It is from these discoveries that the wireless power transfer has been developed. In the past two decades, wireless power transfer has been used to power or charge electrical devices in instances where the interconnecting wires are seen to be hazardous, inconvenient or are not possible due to the design of the device. To do this, a transmitter device is connected to the mains supply or any other power source and transmits power through electromagnetic fields created in space to a receiver device placed at a distance. The transmitted energy through electromagnetic fields is then reconverted to electrical power to be utilized by the receiver devices (Agbinya, 2012). This technology has been used in devices such as RFID tags, electric toothbrush chargers, medical devices such as the artificial cardiac pacemakers and smartcards. Currently, the focus is on creating wireless charging systems that will charge mobile phones as well as other mobile computing devices like digital music players and tablets. With technological advancement, more and more Information Technology devices have developed from heavy fixed devices to stationary high-speed mobile devices for convenience purposes. However, there is one function of these devices that has remained constant-all these mobile devices have to be chained to a plug socket on the wall at one point within the day for hours for charging purposes.
The significance of the wireless mobile phone charging system is that it will eliminate the need for a separate charger as well as provide increased convenience in phone usage (Potter, McInyre, & Middleton, 2008). The charging system will also be environment friendly and easy to operate. However, the wireless charging system can only work for short distances and will rarely be used for long distances. In case long distance charging becomes necessary, the number of inductors needs to be increased to ensure efficient current transfer.
Budget
a.)
b.) Justification
The induction coil will be of use in transmitting electromagnetic waves through the magnetic fields created in space. The second induction coil will act as a receiver. The transformer will be used to step down voltage to the usable 12V AC required in charging the mobile phone’s battery. A bridge rectifier will be used to convert the 12v AC to 12V DC and the capacitor used to filter the ripples to create a steady DC current to be used to charge the mobile phone (Electronics Hub, 2013). The first part of the circuit contains a transformer that steps down the voltage from the mains supply source into the induction coil to create the transmitter circuit. This circuit produces an electromagnetic field with the waves moving from the transmitter to the receiver circuit. The receiver circuit contains a second induction coil which picks up the electromagnetic waves by mutual induction and converts them to power. A rectifier bridge circuit converts the 12V AC to 12V DC current and the capacitor smoothens the ripples to create a steady current to be used to charge the mobile phone’s battery.
Circuit Diagram
References
Agbinya, Johnson I., Ed. (2012). Wireless Power Transfer. River Publishers. ISBN 8792329233. Comprehensive theoretical engineering text.
Buckley, J., O’Flynn, B., Barton, J., & O’Mathuna S.C. (2009) A highly miniaturized wireless inertial sensor using a novel 3D flexible circuit. Microelectronics International 26(3), pp. 9-21.
Electronics hub (2013) Wireless Mobile Battery Charger Circuit. (Online). Retrieved from http://electronicshub.org/wireless-mobile-battery-charge-circuit/
Maeght, F., & Rasolomampionona, D., Cresson, P., & Favier, P. (2013) Wireless supervision on a photovoltaic recharging station. Compel 32(1), pp. 192-205.
Potter, A.B., & McIntyre, N., & Middleton, C. (2008) How usable are outdoor wireless networks? Canadian Journal of Communication 33(3), pp. 511-524.
Shinohara, Naoki (2014) Wireless Power transfer via Radiowaves. John Wiley & Sons. Pp. Ix-xiii. ISBN 1118862961
Suh, I.S., Lee, M.Y., & Vu, D.D. (2014) Prototype design and evaluation of an FSAE-based pure electric vehicle with wireless charging technology. International Journal of Automative Technology 15(7), pp. 1165-1174.
Sun, Tianjia; Xie, Xiang; Zhihua, Wang (2013). Wireless Power Transfer for Medical Microsystems. Springer Science & Business Media. Pp. 5-6. ISBN 1461477026
