ABSTRACT:
This project is designed to ensure that our cell phones never run out of juice by letting us charge it while we are on our daily walk and getting some exercise and thereby getting two jobs done at the same time. The basic idea is about converting a part of the bio-mechanical energy spent in our day-to-day lives (while walking) into a usable form and storing it to charge low-power battery-operated devices.
INTRODUCTION:
Mobile phones are used widely in our everyday lives giving us the freedom to communicate anywhere and at anytime. Equipped with various facilities, it is available to people of all classes. The affordable price range and the easy application make it a pleasure to use. Besides communication, they also have various other services programmed in them. The latest mobile phones are incorporated with features like MP3 players, high resolution camera, high sound quality, 3G technology and the list goes on. The mobile phones have become a hit among all classes of people from kids to teenagers to adults allowing them to enjoy a tech-savvy lifestyle. These phones are considered as style statement and give a sophisticated touch to your profile.
The utility of this device is no longer unknown. The rate of sales growth in India shows that nearly six million people buy cells every month in India. In fact this is the largest growing market in the world. An expected target of 800 million buyers by 2011, does not seem to be impossible.
Although the extensive use of mobile phones have placed us in a completely new arena but the core of all the mobile phones have remained constant and that?s the battery and the charging of this battery. The majority of cell phones use built-in batteries that can be recharged with a charger and an electrical outlet. But if the charger is improperly used, it may stop operating and even cause dangerous situations. We? rely heavily on our cell phones for various applications, so we need to realize how important it is to have enough battery power to make accomplish our needs. Fortunately, companies have created so many different types of cell-phone chargers so that we can easily and conveniently charge our batteries.
These chargers come in five basic varieties:
Wall Chargers
? Of all the types of cell-phone chargers, wall chargers are the most common. An AC wall adapter is included with your cell phone when you purchase it.
Car Chargers
?? Car chargers plug into the cigarette lighter outlet or accessory outlet in your vehicle, allowing you to charge your cell phone while you drive. Car chargers come in three varieties: fast chargers, rapid chargers and trickle chargers. All three types allow you to use your cell phone while the battery is charging. The primary difference is the speed of charge. Use fast chargers with caution. If you do not unplug your cell phone as soon as the battery is charged, the battery can overheat and become damaged.
Desktop Chargers
? Desktop chargers, also known as docking stations, contain a base with one or more slots to hold your cell phone or other electronic devices. These chargers typically connect to your computer with a USB cable. One drawback of desktop chargers is that you cannot use your cell phone while it is charging.
Emergency Chargers
? Emergency chargers generally require AAA batteries. They do not give enough power to charge your cell-phone battery completely, but you can get at least a half-hour of talk time in the event of an emergency.
Green Chargers
? Some companies have begun manufacturing green chargers. Numerous companies, such as ElectroHiFi and IST SideWinder, produce crank chargers that permit you to charge your cell phone by turning a crank. These chargers typically produce small amounts of power, enough to make an emergency call. Solio has a solar-powered charger that can also use USB ports or wall outlets if there is not enough sunlight. Nokia has created a bicycle charger that allows you to charge your cell phone as you pedal your bike.
The disadvantages of using conventional portable chargers for the purpose of charging mobile phones include the conventional portable chargers' requirement of a power supply, which is very impossible in the conditions of no power or low voltage. This causes fluctuation in the electromagnetic field of the battery. Since it uses electricity, you should be very careful while handling the charger. Thus the user?s safety is not guaranteed while using a conventional portable charger.
Turning apart from the conventional methods of charging the battery of our mobile phones, this project aims at introducing a new way of mobile phone charging and also conserving energy.
WORKING PRINCIPLE:
This device has to be worn below the knee cap on one leg and a light string is attached to the other leg. The strides taken help in pulling and retracting the string, which is further attached to a dynamo that generates about 3.5 Watts; enough to charge low-powered devices such as our mobile phones. This device captures the energy by connecting an electrical generator to leg movements. When the person extends the gap between the legs, power is generated by a gear that turns and spins the generator. The flexion of the leg turns off the gear so as not to discomfort the person.
Walking involves a change in relative displacement of around ?35 cm between legs. This repeated linear motion could be converted to rotary motion with the help of a pulley and string. Thus, the bio-mechanical work is converted into mechanical form and eventually stored as chemical energy in batteries to store electric energy. The device is clamped on one leg and a hole lets out a string that is attached to the other leg that helps in the conversion of the displacement into rotary motion. Even a slight displacement pulls the string out, thereby rotating the pulley, which turns the central shaft. The shaft is common to the gearbox, the dynamo and the recoil mechanism. So, when the displacement reduces, there is a slack in the string, which is removed by the tension produced by the recoil system. Since the electricity produced is bi-directional and contains spikes, an electronic circuit encompassing a rectifier and a filter converts it into a unidirectional, spike-free wave and stores the energy produced in rechargeable batteries. This stored energy is used as an input supply to mobiles with the help of different adapters.
This new device is motion sensitive, being auto-activated by leg movements and it does not increase the energy spent with walking.
OPERATION:
The mechanism involves three basic stages:
Conversion of mechanical to electrical energy:
People are an excellent source of portable power. An average-sized person stores as much energy in fat as a 1,000-kilogram battery. People recharge their body batteries with food and, lucky for us, there is about as much useful energy in a 35-gram granola bar as in a 3.5-kilogram lithium-ion battery. The device could be used to power computers in remote regions where electricity is scarce.
The repeated linear motion could be converted to rotary motion with the help of a pulley and string. Thus, the bio-mechanical work is converted into mechanical form and eventually stored as chemical energy in batteries to store electric energy. The device is clamped on one leg using a Velcro strap and a hole lets out a Nylon string that is attached to the other leg that helps in the conversion of the displacement into rotary motion. Even a slight displacement pulls the string out, thereby rotating the pulley, which turns the central shaft. The shaft is common to the gearbox, the dynamo and the recoil mechanism. So, when the displacement reduces, there is a slack in the string, which is removed by the tension produced by the recoil system.
A dynamo generally means a generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
Storing the electrical energy:
Since the electricity produced is bi-directional and contains spikes, an electronic circuit encompassing a rectifier and a filter converts it into a unidirectional, spike-free wave and stores the energy produced in rechargeable batteries. This stored energy is used as an input supply to mobiles
Using this energy to charge mobile phones:
Most mobile phone chargers are not really chargers, only adapters that provide a power source for the charging circuitry which is almost always contained within the mobile phone. They are notably diverse, having a wide variety of? DC connector-styles and voltages, most of which are not compatible with other manufacturers' phones or even different models of phones from a single manufacturer.
Timer IC NE555 is used to charge and monitor the voltage level in the battery. Control voltage pin 5 of IC1 is provided with a reference voltage of 5.6V by Zener diode D1. Threshold pin 6 is supplied with a voltage set by P1 and trigger pin 2 is supplied with a voltage set by P2. When the discharged cell phone battery is connected to the circuit, the voltage given to trigger pin 2 of IC1 is below 1/3Vcc and hence the flip-flop in the IC is switched on to take output pin 3 high. When the battery is fully charged, the output terminal voltage increases the voltage at pin 2 of IC1 above the trigger point threshold.
This switches off the flip-flop and the output goes low to terminate the charging process. Threshold pin 6 of IC1 is referenced at 2/3Vcc set by P1. Transistor Q1 is used to enhance the charging current. Value of R3 is critical in providing the required current for charging. With the given value of 39-ohm the charging current is around 180 mA. The circuit can be constructed on a small general-purpose PCB.
For calibration of cut-off voltage level, use a variable DC power source. Connect the output terminals of the circuit to the variable power supply set at 7V. Adjust P1 in the middle position and slowly adjust P2 until LED (D2) goes off, indicating low output. LED should turn on when the voltage of the variable power supply reduces below 5V. Enclose the circuit in a small plastic case and use suitable connector for connecting to the cell phone battery.
ADVANTAGES and FUTURE PROSPECTIVES:
Even if 0.1% of the Indian population uses this device, it can generate 1500 kW/h of energy and can help reduce carbon emission by 2.25 tonnes per day. Thus, Walk-N-Charge promises us a source of energy that is not only clean, portable and inexpensive, but also charges our mobile while you get charged up!
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