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Download The first battery-powered flashlights were designed around 1899
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ECE 3710 Application Notes Name: Sean Metcalf GTID: 902610511 Major: ME Project Name: Linear Induction Flashlight Source of circuit/application: http://en.wikipedia.org/wiki/Flashlight ; www. Shake-flashlights.com/ ; hypderphysics.phy-astr.gsu.edu/hbase/electric/farlaw.htmsl I. Introduction of application : The first battery-powered flashlights were designed around 1899 with the new invention of the dry cell battery and miniaturized incandescent light bulbs. Flashlights today use primarily incandescent light bulbs or light-emitting diodes and operate by disposable or rechargeable batteries. In this application, a LED is used because it is more efficient than an incandescent bulb. White LEDs produce approximately 100 lumens/watt, where as small incandescent bulbs produce 8-10 lumens/watt. LED flashlight tends to have a longer battery life and more robust in comparison to incandescent bulbs. Technology involved with the design of flashlights has evolved into mechanically powered flashlights operate by electricity generated by a form of physical work. Therefore, batteries don’t need replacement or recharging from an electrical source. There are many ways to generate voltage for a flashlight through mechanical work: squeezing a handle, winding a crank shaft, or shaking. The energy stored by mechanical work can be stored in a flashlight through a spring, flywheel, or capacitor. This application consists of a mechanically powered flashlight that generates voltage through shaking and stores it in a capacitor. II. Diagram of circuit: Figure #1) Displays diagram of circuit for linear induction flashlight with basic components Figure #2) Displays diagram of a source transformation. The magnet passing through the inductor or coils of wire with velocity (V) generates voltage, and can be symbolized as a voltage source ( ). Diagram of Application: Figure #3) Displays application of the previous circuit diagram in the linear induction flashlight: Components: 1. Magnet- permanently magnetized magnet 2. Wire Coil – copper wire coiled N times 3. Full-Wave Rectifier- consists of four diodes 4. Capacitor- used like a battery to store charge 5. LED- light source 6. Resistive load- used to pull current through LED 7. Deflector/Lens- reflects and focuses light source 8. Switch- controls currents through LED ( “ON” or “OFF”) III. Explanation 1. How does the circuit operate? The flashlight basic design and operation is conceptualized through linear circuits. There’s a voltage source generated by an electromagnet, which is essentially an inductor. The alternating voltage source is passed through a full-wave rectifier, which consists of a diodes, resistor, and capacitor. This converts the alternating current waveform into something that closer resembles a direct current waveform. This is useful for storage in a battery, which is a larger capacitor in this case, that will power the light source or light emitting diode (LED). a.) Indicate what are the inputs and outputs Inputs: , voltage source produced by electromagnet Outputs: ; b.) Relationship between the output and input (e.g. Transfer function) c. )Explain what the circuit does and how it works. When the flashlight is shaken, the magnet moves back and forth through the coil of wires. This produces an electromagnetic force (EMF), and generates an alternating voltage waveform. This isn’t particularly useful in this application, so we need a voltage and current waveform that resembles something more direct, in order to store it. Thus, the waveform is passed through a full-wave rectifier and stored in a capacitor, while the switch is “open”. When the switch is “closed”, the charge stored in the capacitor discharges through the diode and resistive load. Assuming there’s enough charge stored in the capacitor to generate a voltage greater than the forward voltage of the diode. In this particular case, there is a light emitting diode, so light is emitted when the diode in “on”. Figure #4) Displays voltage and loop in which the current follow, when the switch is “open”. The EMF generates voltage, which stores charge in the capacitor or “battery”. There’s a voltage across the capacitor associated with the voltage source. Figure #5) Displays the circuit, when the switch is “closed”. At this point, the user has stopped shaking the flashlight and generating voltage. Thus, the charge stored in the capacitor is discharged through the resistive load. This pulls current through the diode and turns it “on”, emitting light. Assuming, , for real life diodes: 2. How the circuit interfaces with the application that you chose The linear induction flashlight is powered mechanically through the use of an electromagnet. The user shakes the flashlight, which contains a permanently magnetized magnet that passes through a coil of wires many times. Faraday’s law states that a voltage is generated by changing the magnetic field. In this case, it is generated by the magnet moving toward and away from the wire coil, which produces an EMF. Lenz’s law states that an EMF is produced by change in a magnetic flux, and the polarity induced by the EMF produces a magnetic field that opposes the charge that produces it. Equation for voltage generated by a change in the magnetic field (Lenz’s Law): N- number of turns for the wire coil BA- magnetic flux T- rate of change in time i.e.) Determine the change of rate in time for (turn “on” voltage for LED), 100 turns of wire, and magnetic flux of 5 Tesla. (Approximately the time it will take the user to shake and generate the given voltage, under ideal conditions) Figure #6) Displays the concept of Lenz’s Law. A magnet is move toward the coiled wired with a velocity (V). There’s a difference in potential from the two ends of the coiled wire through a resistive load ( ) that generates a voltage. This is caused by change in the magnetic flux (BA). IV. Conclusion The linear induction or “shake flashlight” eliminates the problem of used or “dead” batteries that can no longer be used to power a flashlight. Not only does this flashlight potentially save operation costs over time, but it also contributes to a lower environmental impact. Disposal of batteries can be an expensive process, and potentially harmful to the environment if disposed improperly. A flashlight that doesn’t require batteries eliminates the factor of battery disposal. The components that are used in this design of a linear induction flashlight are relatively inexpensive and readily available. This is a great practical application of linear circuits that can be built and assembled at home.