Wind-Powered iPhone Battery Charger - Lab Report Example

Wind powered iPhone Battery Charger Table of Contents Introduction 2 2.Objective 3 3.Proposed Design 4 4.Design Solution – Component Identification7 5.Implementation 15 6.Advantages & Benefits 15 7.Limitations: 17 8.Conclusion 18 Kaltschmitt, Martin., Streicher, Wolfgang., Wiese, Andreas. Renewable energy: technology, economics, and environment. 2007. Berlin Heidelburg: Springer. 19 Gussow, Milton. Theory and problems of basic electricity. McGraw-Hill Professional 19 1. Introduction The demand for mobile or cellular phones among common people is every increasing, leading to a high competition among the mobile phone manufacturers. In order to sustain and to maintain their level of success in the business, the competitors try to implement their innovation and creativity to the products to the best of their capability. This has brought in millions of products in the mobile phone market with varied features and technologies till date. Among them, smart phones are the latest innovation which builds in all the common functionalities of a mobile phone in addition to the high end functionalities like internet surfing, high resolution touch screens, enhanced media players, GPS and so on. And these functionalities are endless over time, with the invention of a new technology, a new functionality gets added in. Though new features are being added time to time, the level of usability has always been given a major focus thereby maintaining the size and weight of the device, making the modern smart phones handy and user-friendly. However, building in all the features of almost a modern computer into this sort of a smart mini handheld device has brought in a real challenge in the mobile phone industry. Some manufactures design the unit with a power (battery) backup of approximately 7 hours (call time), and extending it to 15 hours on standby. As people are aware of these power backup constraints, they always tend to carry their battery power charger handy whenever they plan to be out of home for a long time. This would help them to stay connected as far as there is a source of power to charge the unit whenever the battery gets low, but arriving at a place where they find no power units to charge the device, would really worsen the scenario especially when there is a critical need to make a call or surf the internet to find some information or view route map for the journey through GPS. The only source of availability would be the nature. An analysis of how helpful would it be if we could charge up the battery using the energy available from this nature would of course is a point of thought emerging out from the minds at that moment. In this project, the discussed scenario has been captured into a working model, which would not only provide a new solution to power charging but also contribute to the path towards an eco-friendly environment. 2. Objective The objective of this project is to develop a handheld portable iPhone charger that operates on available wind power and would solve this sort of low battery issues when people find no source of power sockets, and to develop a new eco-friendly way of charging. Though there are wide ranges of products available on smart phones world-wide, I have chosen iPhone as my point of study due to its high level of attraction among people. Moreover iPhones offers a wide range of application like mail exchange, fastest internet browser, 3G call facility, GPS and loads of business application downloadable from the apple store. All these facilities keeps a businessmen in touch with the business even on the move, a student to browse their educational materials from the internet, a person driving his vehicle to look for the destination route in the map and so on. Hence apart from keeping oneself stay connected with home or network, it also acts as guide or a medium of communication between people and the world around for all their needs. In order to ensure that, these multiple benefits and services a man realises should be realisable anytime and anywhere irrespective of environment, this eco-friendly charger is designed, which purely relies on the wind power which is an inexhaustible and renewable source of energy. 3. Proposed Design The principle behind the working of wind powered iPhone charger is the fact that electrical energy can be generated from wind energy and that the wind energy can be easily extracted by employing wind turbines. Hence the device would have a small turbine at the front which would generate wind energy, a generator which would convert this wind energy into electrical energy and an Integrated Circuit that supplies the generated electrical power to the iPhone. The simplified block diagram of the working model would be as shown in the fig.1: Fig1. Simplified block diagram of wind-powered iPhone charger Principle of working: The kinetic energy present in the moving wind can produce electrical energy when a suitable wind energy generator device is employed. A typical wind energy generator consists of a turbine and a generator. The kinetic energy from the blowing wind causes the blades of the turbine to rotate thereby generating mechanical energy which is directly dependent on the speed of the air flow. This causes the shaft of the generator to rotate thereby creating electrical energy as per the theory of electromagnetic induction. The voltage generated is then processed through a series of electronic circuits to match the requirement of the device which is an iPhone here. In real scenarios, in case of low winds, the speed of the rotor is further increased by the inbuilt gear mechanism in the turbine. The device is also be provided with an efficient control mechanism such that it does not get deteriorated with increase in wind speed. This combination of rotating blades and the gear mechanism and control mechanism forms an effective turbine and they can convert the kinetic energy in the wind into a valuable mechanical energy that can drive the generator in a safe and efficient manner. Turbines: As explained above, a turbine converts the kinetic energy in the wind into mechanical energy. The typical components of a turbine would include a rotor which rotates upon wind flow, a stand to hold the rotor, a gear mechanism to gear up the speed, a control mechanism to safeguard the rotors during heavy winds and cables to connect to the generator. Fig 2 shows the expanded view of a tiny turbine and its working principle. Fig 2. Expanded view of the turbine showing the parts The blades form the major part in the turbine, which plays the real role in the energy conversion process. Each time they rotate based upon the direction and the speed of the wind, it generates a mechanical energy which is passed through the connection coils on the rod or the shaft that is present in between the turbine and the generator. Generator: Turbine is connected to the generator via a small connecting rod or a shaft with coils over it which is connected to the shaft of the generator. The purpose of the generator is to convert the incoming mechanical waves into electrical power. Generators have a long shaft with coils over it which in turn is covered by magnets. The principle behind the working of generator is the electromagnetic induction theory by Michael Faraday, which states that if a conductor “cuts across” the lines of magnetic force or if lines of force cut across a conductor, an emf, or voltage is induced across the ends of the conductor. Fig 3 shows the internal structure of a generator along with how it is connected to the turbine. Fig 3 Internal Structure of a generator showing the principle of working When the blades of the turbine rotate upon wind direction, it enables the connecting shaft to rotate in a direction opposite to it. Since the connecting shaft is coupled to the internal shaft of the generator, the movement of the copper wire present in the shaft inside the magnets generates the voltage or electrical energy to flow across the wire. This electric energy is passed through the integrated charging circuit to process it to achieve the desired voltage required to charge an iPhone. Integrated Circuit(IC) for the Charging circuit: The overall purpose of this IC is to convert the electrical power from the generator into a desired steady voltage to charge the iPhone. The circuit would start with a rectifier which converts the ac voltage from the generator in a dc voltage. However this voltage would not be sufficient enough to charge an iPhone. Hence, the rectifier should be followed by 3 more circuits: one would be a step up dc-to-dc convertor which would step up the voltage generated from the rectifier into a desired voltage, a voltage regulator to ensure a constant voltage supply and the other would be a voltage divider which provides the appropriate voltages to the four pins of the iPhone’s USB port. Fig 4 shows the block diagram of the charging circuit. Fig 4 Block diagram for the Charger IC 4. Design Solution – Component Identification Turbine The amount of wind power a turbine can generate is the derivative of the kinetic energy created by the flowing wind on the direction of the turbine with respect to time. If ρw is the density of the wind that flows with a velocity of u, then the power available from the wind Pw is given by the equation: Pw = ρwAu3 * Cp * Ng * Nb where ‘A’ is the rotor swept area, Cp is the coefficient of performance and Ng & Nb are the efficient of generator and the gearbox or bearing efficiency. Since one of the major design goals of this project is to make the device handy and portable, we have designed a simple turbine mechanism for wind energy generation using small fan-like PVC blades (shown in fig 5) which can be directly screwed to the rotor of the generator through the holes present in it. The speed of rotation of blades would be directly proportion to the wind speed. Fig 5 PVC blades used for wind generation Generator Though there are many dc generators available in the market, which can be directly used in this system, simplifying the design by eliminating the need for ac to dc conversion. The rpm required for electrical power generation in a dc generator would be very high as compared with the ac generators. Since wind flow is not constant throughout the year, designing a system which would operate even on low wind is highly desirable in this context. Hence an ac generator is implemented using a stepper motor. A Stepper motor consists of a stator, rotor and conducting coils. Stator is the stationary part of the motor made of soft metallic core wounded by a couple of coils and it acts as a surrounding case for the motor. Rotor is the central rotating part of the motor that are made of permanent magnets attached to a shaft. This permanent magnet is in the shape of a circular disc that surrounds the rotor shaft, and is placed such that the north and the south poles are interlaced together. Simple design of motor would include only two poles while complex motors use multiple poles. The movement of the rotors inside the stator causes a flow of electrical energy in the coils of the stator. Generally, the stepper motors are driven by a pulse of current to make a rotational movement thereby converting mechanical energy from the applied electrical energy. However, rotating the shaft would cause a pulse of current to flow in the coil windings making the motor work in the reverse manner. This characteristic of the motor is employed here to act as a generator. As the turbine blades are directly connected to the rotor shaft of the stepper motor, it causes the shaft to rotate thereby driving the motor to generate electrical energy by inducing current flow in the coils. The output current is not a constant but would be an alternating one going positive when the coil moves towards the magnetic pole and going negative upon moving away. Since stepper motors generally operate with four phases at 900 intervals each, such that when one goes down to zero the other would reach the maximum. This is an added advantage as the output produced can be easily rectified to produce a much flatter DC. Choosing a stepper motor with higher number of steps would decrease the rpm required to drive them in order to generate a minimum sufficient amount of electrical power. Typically, only 200rpm would be sufficient to produce a decent output compared to other generators which would require 10 to 15% more rpm to produce the same amount of electrical power. TSM15 - Permanent Magnet (PM) Stepper Motor shown in fig 6 is used here. This is very small in size measuring only 15mm and consists of 4 wires as shown in fig7 which makes the wiring with other circuits much easier. Fig 6 Stepper Motor employed in the circuit design Fig 7 Stepper Motor employed in the circuit design Charger Circuit Rectifier: As described above, the output voltage from the stepper motor is an ac voltage which is proportional to the wind speed. This voltage has to be rectified to a dc in order to proceed further. A basic rectifier consists of two pair of diodes in the form of a bridge. Using the fact that the diodes allows current only in one direction, when the cathodes of the diodes are connected together and the anodes are connected to the output of the ac transformer output wires, it can create a positive dc at that junction. From the above figure (7), the stepper motor has two transformers with four output wires. Hence the rectifier circuit for this requirement would need two such bridge circuits. Thus the overall rectifier circuit is built using four pair of diodes that are directly connected to the four pins of the stepper motor as shown in fig 8. Rectifier diode 1N4004 is used for this purpose. Fig 8 Rectifier connection with the stepper motor Step up dc-dc convertor: The voltage from the rectifier would be very low and not be sufficient enough to charge the iPhone, which requires a 5V dc. In order to increase the voltage level to the required amount, we employ a step dc-to-dc convertor which is a circuit designed to boost up the input dc Voltage. A handy IC MAX756 available in the market is used here for this purpose. It has 8 pins and can convert very low voltages of upto 0.7V to a constant 5Vdc. The device is shown in fig 9 and the circuit design obtained from the data sheet is shown in fig 10 Fig 9 Step up dc to dc convertor Fig 10 Circuit diagram for the Step up dc to dc convertor IC Voltage regulator: Though the voltage coming from the step up convertor is a constant dc, it may have any fluctuations due to various unexpected reasons resulting in undesired effects. Thus it is necessary to ensure a constant voltage to the iPhone in order not safeguard the internal circuitry of both the mobile phone as well the charger device. Hence a voltage regulator circuit is also added in the circuit to achieve maximum stability of the system. Handy voltage regulators are available in the market that comes with 3 pins. Since the requirement here is a 5V dc, L7805C shown in fig 11 is used which supplies a constant 5V dc and can handle an input voltage of up to 10V. This ensures maximum protection of the phone circuits on high voltage issues. Fig 11 L7805C -Voltage Regulator Voltage divider: The voltage obtained from the regulator has to be supplied to the 4 pins of the USB charging port of the iPhone as per the correct requirement. In order to do so, 4 points should be created such that at each point, the voltage is tapped to match that of the requirement for its connected pin. This can be done using a voltage divider. Voltage divider is a circuit which when provided with an input voltage, it produces a fraction of its input voltage as its output. This fraction may also be unity, in which case, the output will be equal to the input. This is achieved by connecting two resistors R1 and R2, the values of which are chosen as per the requirement for the output voltage. The equation governing the relationship between input voltage Vin, output voltage Vout and the two resistors is given by; Vout = Vin In our case, the four voltage requirements for the USB pin shown in fig 12 are 5V, 2.5, 2 and 0 for each pin respectively. Hence the resistor values are chosen as shown in Fig 13. Fig 12 USB pin details Fig 13 Voltage Divider These four wires are screwed to the USB adapter in the right order to form a USB jacket which can be directly plugged into the USB port of the iPhone. 5. Implementation The above circuits are implemented in a small PCB board. The circuit board along with the stepper motor is enclosed in a plastic case with the fan in front and the USB jack behind. The completed device looks like fig 14. Fig 14 Completed design of the device 6. Advantages & Benefits The advantages of using this eco-friendly charger can be summarised in terms of various areas of interest. Effective utilisation of renewable energy: Wind is an inexhaustible and renewable source of energy which is universal. Implementation of system which can effectively utilise this type of energy would be a better choice towards saving the existing electrical energy available around us. The demand for electrical energy is ever increasing and tones and tones are electricity is generated each hour globally to meet this demand using various power generation methods. Using natural resources like wind energy for the power generation can minimize the risk of shortage in supply owing to shortage or unavailability of resources used for power generation. Eco friendly: Since the device operates on wind which is a natural resource, it serves as a pure source of energy. Many power generation methods employ combustion of fossil fuels like coal or natural gases, which not only dirties the environmental air, but also pollutes water which impairs the animals and plants live to a very bad extreme. Use of nuclear fuels is not so safe. On the other hand, use of renewable energy will avoid this sort of issues as it is very pure and safe. Moreover it aids in conserving this sort of fossil fuels for future use. Cost effective: Wind energy is available around us with free of cost. The system required to generate power using this technique could be implemented with a very less cost compared with other methods. In this implementation for the device, the overall cost is very low compared to buying the actual electrical charger device for the circuit. Thus this device is very cost effective. Stability and Reliability: The device is built with robust components. The blades are designed with PVC, the circuit and motor is covered with robust plastic case. This ensures the device to be reliable and the USB connecting jacket that comes with this device makes sure that the system is maintained with necessary physical stability. Portability: As the device is a USB type self supported device, it does not rely on any fixed structures like any other wind generators which are fixed firmly to a stand. Moreover none of the components used in the device is dependent on any fixed source of input; the input for each component would purely depend only on its previous component. First component being the fan blades and the input to the rotating blades are the external wind, the device ensures complete portability. Compatibility The device acts as a USB charger and hence it can be used as a replacement for the actual charger without any extra devices mounted on the existing charging port of the iPhone. Thus the device is compatible with the existing provision for the charger in the iPhone. Safety Above all the advantages mentioned, the device offers a very safe method of charging the iPhone. The power output from the wind generator is process through a series of electronic circuits which ensures a steady output. The regulator present in the device further enhances the stability of the output voltage. Thus charging the iPhone with this device is very safe and does not cause any damage to the expensive internal circuits of the iPhone. 7. Limitations: The power generation from this device is not constant and is solely dependent on the external wind flow. It can be as low as zero to as high as a big storm. Thus the wind generators would not produce the same amount of electrical energy at all times. Sometimes it produces a high voltage and sometimes no voltage at all. Though regulators are employed to handle high voltage fluctuations, the device would not turn ON if it produces no voltage at all. This may make the device obsolete in case of extreme low winds. Care should be taken such that the device is operated at least with little amount of wind supply for the stepper motor to rotate. Moreover the power generation using the renewable energy such as wind would generate power much slower than the other generation methods using fossil fuels; hence the time taken to charge the iPhone using this device would be high as compared with the charging of the same device using an electrical charger. 8. Conclusion Thus the wind operated iPhone charger was designed and implemented successfully. Though the design started with a simplified model for the device, the in depth analysis on various components required for each circuit has lead to a more complex circuitry for device. However efficient use of already available ICs for step up dc to dc convertor and voltage regulator has reduced the complexity in design. The plastic case around the circuit and the stepper motor ensures maximum protection to the circuit under various environmental conditions. The size of the fan blades is also kept low to match the overall size of the entire device. This device would not only help people to charge their iPhones on low battery but also helps to maintain a pollution free environment. The device can be further enhanced by incorporating an additional circuit in order to ensure at least a minimum level of voltage generation at all times irrespective of the wind conditions. We have seen from the limitation section that the device may not serve the intended objective when the wind flow around them is extremely low. This can be done by employing a gear mechanism in between the fan and the stepper motor which can drive the rotor even at very low winds. Moreover, heavy winds like storm may result in large supply of wind power to the stepper motor. This can be avoided by incorporating a sort of control mechanism between the blades and the rotor such that the air flow is maintained at a constant value equal to the maximum speed that the motor can handle. However implementing these types of additional devices will increase the size of the charger. Thus incorporating all the functionality while maintaining the maximum efficiency would be a challenging task in the overall design of the device. References Kaltschmitt, Martin., Streicher, Wolfgang., Wiese, Andreas. Renewable energy: technology, economics, and environment. 2007. Berlin Heidelburg: Springer. Gussow, Milton. Theory and problems of basic electricity. McGraw-Hill Professional Mathur, Jyotirmay., Wagner, Hermann-Josef. Introduction to wind energy systems: basics, technology and operation. Springer Moczala, Helmut et al. Small Electric motors. England: Redwood books. Horowitz, Paul., Hill, Winfield. The art of electronics. 2001. UK: Cambridge University Press. Read More