...light from a light-emitting diode (LED) and then measuring the amount of light either transmitted or reflected to a photodiode. Each cardiac cycle appears as a peak, as seen in the figure 1. The PPG consists of a pulsatile AC which is generally riding on a large DC component. This AC component is obtained due to the variation in the light absorbed by the pulsing arterial blood. The DC component is obtained due to no variation in the light absorbed by the surrounding tissues and skin. Fig 1: A PPG signal PPGs are used to measure oxygen saturation since they are easy to obtain, simple and economically convenient. Principle of pulse oximeter: A pulse oximeter relies on the principle that the light absorbances of oxygenated haemoglobin and deoxygenated haemoglobin at two wavelengths is different. Hence pulse oximeter employs an optical sensor (which consists of a red LED a, an IR LED and a photodiode) to measure the percentage oxygen in blood. The Oxygenated haemoglobin absorbs more infrared light and allows more red light to pass through. Deoxygenated (or reduced) haemoglobin absorbs more red light and allows more infrared light to pass through. Hence red light is in the 600-750 nm wavelength light band. Infrared light is in the 850-1000 nm wavelength light band. Hb shows maximum absorption at 660nm and HbO2 shows maximum absorption at 940nm. This is shown in figure 2. The transmitted light or reflected light intensity detected at the photodiode varies with the pulsing of the blood...
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...sensing —an IR LED emits infrared light and an IR photodiode generates a photocurrent which varies with the amount of incident light. Both emitter and detector have a center wavelength of devices are especially designed for proximity sensing —an IR LED emits infrared light and an IR photodiode generates a photocurrent which varies with the amount of incident light. Both emitter and detector have a center wavelength of devices are especially designed for proximity sensing —an IR LED emits infrared light and an IR photodiode generates a photocurrent which varies with the amount of incident light. Both emitter and detector have a center wavelength of devices are especially designed for proximity sensing —an IR LED emits infrared light and an IR photodiode generates a photocurrent which varies with the amount of incident light. Both emitter and detector have a center wavelength of devices are especially designed for proximity sensing —an IR LED emits infrared light and an IR photodiode generates a photocurrent which varies with the amount of incident light. Both emitter and detector have a center wavelength of vv devices are especially designed for proximity sensing —an IR LED emits infrared light and an IR photodiode generates a photocurrent which varies with the amount of incident light. Both emitter and detector have a center wavelength of v devices are especially designed for proximity sensing —an IR LED emits infrared light and an IR photodiode generates a...
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...PROF WONG 12NOV2014 LIGHT SOURCES AND COMPONENTS – Definitions Forward biased LED-is a positive voltage that is applied to the P region and negative voltage to the N region, causing current to flow through the LED. Incoherent light- out of phase photons that emitted from the junction with the PM and regions meet and are not in phase nor are they launched in the same direction. Laser-the term laser is actually an acronym that stands for light amplification by stimulated emissions of radiation. Output pattern- the output pattern or NA of the ways the light source relates to the energy coupled into the core of the optical fiber. Output power-the output power of the light sources used in fiber optic Communication Systems varies dramatically depending on the application. Modulation speed- Is the main factor that can limit the performance and fiber-optic Communications System. Core Diameter mismatch-this occurs when there is a difference in the core diameters of the two optical fibers. A loss may occur when the Core Diameter of the transmitting optical fiber is greater than the Core Diameter to receiving optical fiber. Current- Is the flow of electrons in the conductor. PIN photodiode- A light-sensitive diode that conducts current in one direction only. PIN photodiodes have a fast response time. Avalanche photodiode (APD) - is a semiconductor-based photo detector (photodiode) which is operated with a relatively high reverse voltage. APD is a highly sensitive...
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...Unit 9. Exercise 1 1. Forward Biased LED – Semiconductor diode with a positive voltage applied to the p-region and a negative voltage to the n-region. 2. Incoherent Light – Light in which the electric and magnetic fields of photons are completely random in orientation. Incoherent light is typically emitted from light bulbs and LEDs. 3. Laser – Acronym for light amplification by stimulated emission of radiation. The laser produces a coherent source of light with a narrow beam and a narrow spectral bandwidth (about 2cm). Lasers in fiber optics are usually solid-state semiconductor types. Lasers are used to provide the high-powered, tightly controlled light wavelengths necessary for high-speed, long-distance optical fiber transmissions. 4. Output Pattern – LED and laser semiconductors used in fiber-optic light sources are packaged to couple as much light as possible into the core of the optical fiber. The output pattern or NA of the light source directly relates to the energy coupled into the core of the optical fiber. 5. Output Power – This power of light sources used in fiber-optic communication systems varies dramatically depending on the application. LEDs are typically designed to support transmission distances of up to 2km while laser light achieves distances in excess of 80km. Laser optical power output levels can exceed LED optical output power levels by more than 20dB. 6. Modulation Speed – One factor that can limit the performance/bandwidth of a fiber-optic...
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...Forward Biased LED- When the LED is forward biased (a positive voltage is applied to the p region and a negative voltage to the n region), current flows through the LED. 2. Incoherent Light- Photons emitted from the junction where the p and n regions meet are not in phase, nor are they launched in the same direction. These are out of phase photons 3. Laser- Acronym for light amplification by stimulated emission of radiation. It produces a coherent source of light with a narrow beam and a narrow spectral bandwidth. Used to provide the high-powered, tightly controlled light wavelengths necessary for high-speed, long-distance optical fiber transmissions. 4. Output Pattern- The output pattern or NA of the light source directly relates to the energy coupled into the core of the optical fiber. The output pattern of a laser light source is very narrow, allowing a majority of the light energy to be coupled into the core of a single-mode or multimode optical fiber. 5. Output Power- Optical output power levels are normally expressed as the amount of light coupled into a one meter optical fiber. Laser output power varies depending on the application. 6. Modulation Speed- Light Emitting Transistors are responsible for the modulation speed. Modulation speed of 4.3 gigahertz was reached in 2009. 7. Core Diameter Mismatch- When 2 different cores are 2 different circumferences. 8. Current- The flow of electrons in a conductor. 9. PIN Photodiode- works like a PN...
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...Montie Ramsarran August 11th, 2014 NT1310 Mr. Amos Unit 9 Exercise 1 Light Source and Components-Definitions 1. Forward Biased LED: A bias voltage that is applied to a pn-junction in the direction that causes a large current flow; used in some semiconductor diode circuits. 2. Incoherent Light: Light in which the electric and magnetic fields of photons are completely random in orientation. Incoherent light is typically emitted from light bulbs and LEDs. 3. Laser: Acronym for light amplification by stimulated emission of radiation. The laser produces a coherent source of light with a narrow beam and a narrow spectral bandwidth (about 2cm). Lasers in fiber optics are usually solid-state semiconductor types. Lasers are used to provide the high-powered, tightly controlled light wave lengths necessary for high-speed, long-distance optical fiber transmissions. 4. Output Pattern: A setting that selects the output pattern for comparison outputs. This enables outputs for changes in levels rather than just upper/lower limit comparisons to set value. It can be set according to the control applications. Note: The settings must be as follows for correct zone outputs. 5. Output Power: The useful signal or power delivered by a circuit or device. 6. Modulation Speed: (1) Coding of information onto the carrier frequency. Types of modulation include amplitude modulation (AM), frequency modulation (FM), and phase modulation...
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...MAJOR PROJECT LASER TORCH BASED VOICE TRANSMITTER AND RECEIVER CHAPTER -1 INTRODUCTION 1.1 ABOUT PROJECT LASER TORCH-BASED VOICE TRANSMITTER AND RECEIVER Using this circuit you can communicate with your neighbors wirelessly. Instead of RF signals, light from a laser torch is used as the carrier in the circuit. The laser torch can transmit light up to a distance of about 500 meters. The phototransistor of the receiver must be accurately oriented towards the laser beam from the torch. If there is any obstruction in the path of the laser beam, no sound will be heard from the receiver. The transmitter circuit comprises condenser microphone transistor amplifier BC548 (T1) followed by an opamp stage built around µA741 (IC1). The gain of the op-amp can be controlled with the help of 1-mega-ohm pot meter VR1. The AF output from IC1 is coupled to the base of transistor BD139 (T2), which, in turn, modulates the laser beam. The transmitter uses 9V power supply. However, the 3-volt laser torch (after removal of its battery) can be directly connected to the circuit—with the body of the torch connected to the emitter of BD139 and the spring-loaded lead protruding from inside the torch to circuit ground. The receiver circuit uses an npn phototransistor as the light sensor that is followed by a two-stage transistor preamplifier and LM386-based audio power amplifier. The receiver does not need any complicated alignment. Just keep the phototransistor oriented towards the remote transmitter’s...
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...valuable suggestions. This constant, sincere inspirations and liberal co-operation in all respects are really unforgettable experience for us. We have been very much benefited from his technical advice and support during the period of our work on this summer project. CONTENTS Certificate Acknowledgement Introduction Overview Brief about Components used Designing and working Applications References INTRODUCTION Digital Displays are such devices which provide output in the form of visual or tactile form. They provide visual information according to the electrical input provided either by the emitting light or by the modulating light available during the process of reflection or transmission. Some examples of them are LCD, LED, plasma display, cathode ray tube etc. It has found application in almost all fields , one such application is ‘Digital Voting Machine’, which is going to be discussed below. Our digital display is only capable of displaying digits and uses a seven segment display. Digital voting machine is the advanced form of voting machine which is used till date in elections to cast votes in India. It is a combination of electrical, electronics and mechanical equipments. More about digital voting machine is as discussed in other sections. OVERVIEW Our project gives a basic overview of the working of voting machines. The voting machines consist of two main parts : • Balloting unit : the voter casts vote through this unit. • Control unit : used...
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...Summary: Half Duplex Data Communication between Two computers using LASER is a senior project design for EE 411 course. After going through a hard time I represent this project which involves C/C++ programming in addition with two electronic circuits to send data between two computers using the parallel port. At the beginning of this report, I will present background about the project in chapter one. Then, in chapter two I will give brief information about each component that I used. Moreover, in Chapter three will be about the circuit Construction. After that, I will present information about C programming and the Codes that I used in chapter four. The next chapter will be about implementation and testing the circuit to show the results. The last chapter is conclusion. Acknowledgments: First of all, I would like to thank my advisor Dr. Mohammad Ousman for his guidance in the project and helping me to understand the importance procedure of the project. He was great working with me on the project to get useful information as possible. His suggestions and ideas were very helpful to me to complete my project. Furthermore, I would to thank the lab engineer Mr. Azeddine Hamroouni for his support and guidance in this project. Finally, I would like to thank the University of Hail especially electrical engineering department. The electrical department is helped me in my life and build a good knowledge for me. . ...
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...* Forward Biased LED is a voltage applied to a circuit or device in the direction that produces the larger current. * Incoherent Light is light in which the electric and magnetic fields of photons are completely random in orientation. * Output Pattern or NA of the light source directly relates to the energy coupled into the core of the optical fiber. * Output Power is a typical LED light source used in fiber-optic communications is * 10dB or more below the lowest power laser light source. * Modulation Speed is the speed of the light source in fiber optics. * Core diameter mismatch occurs when there is a difference in the core diameters of the two optical fibers. * Current is the flow of electrons in a conductor. * Avalanche photodiode is a specialized diode designed to use the avalanche multiplication of photocurrent. * Responsivity is the measure of how well a photodiode converts a wavelength or range of wavelengths of optical energy into electrical current. * Optical subassembly is the portion of a fiber-optic receiver that guides light from the optical fiber to the photodiode. * Dynamic range is the difference between the maximum and minimum optical input power that an optical receiver can accept. * Operating wavelength is the wavelength at which a fiber-optic receiver is designed to operate. * Fiber-optic coupler is a component used in fiber optic systems with one or more input fibers and one or several output fibers. * Optomechanical...
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...Modeling and Designing of a New Indoor Free Space Visible Light Communication System∗ Z. Wu, J. Chau, and T.D.C. Little Department of Electrical and Computer Engineering Boston University, Boston, Massachusetts tdcl@bu.edu August 1, 2011 MCL Technical Report No. 08-01-2011 Abstract–Recent developments in solid-state light-emitting diode (LED) materials and devices is driving a resurgence into the use of free-space optics (FSO) for wireless broadband communication. This technology uses the visible spectrum provided by “white” LEDs that are becoming ubiquitous in lighting and has some desirable properties competitive with existing radio frequency (RF) communications. By leveraging the low-cost nature of LEDs and lighting units there are many opportunities to exploit this medium for widespread optical communication deployment. The optical medium, however, has particular characteristics, including directionality and susceptibility to noise sources in the visible spectrum that must be managed. In this paper we present a new indoor FSO system, also known as a visible light communication (VLC) system that addresses achieving satisfactory data rates through diffuse link while supporting mobility under line of sight (LOS) constraints. The system model is presented with theoretical performance analysis indicating a promising rate for indoor scenarios. The new VLC prototype that can deliver in excess of 1 Mbps while providing both illumination and communication at several meters is also...
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...1. Forward biased LED-a semiconductor device that emits a narrow spectrum of light. 2. Incoherent Light- light in which the electric and magnetic fields of photons are completely random in orientation 3. Laser- acronym for light amplification by stimulated emission of radiation 4. Output pattern-the pattern of light produced in fiber optic that translate in the data 5. Output power – the amount of light produced by a fiber optic device 6. Modulation speed- the speed of which data is transferred over light 7. Core diameter mismatch- occurs when there is a difference in the core diameter of two optic fibers. 8. Current- the flow of electrons in a conductor 9. PIN photodiode- alight sensitive diode that conducts current in one direction only 10. Avalanche photodiode- is a highly sensitive semiconductor electronic device that exploits the photoelectric effect to convert light to electricity. 11. Responsivity-the ratio of a detector output to input usually measured in unit of amperes per watt 12. Optical subassembly- the portion of a fiber optic receiver that guides light from the optical fiber to the photodiode 13. Dynamic range- the difference between the maximum and minimum optical input power that an optical receiver can accept 14. Operating wavelength- the wavelength at which a fiber optic receiver is designed to operate 15. Fiber optic couple- a device that connect two piece of fiber for the purpose of extent...
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...* DISPENSER * IR LEDS * SENSOR * INDICATOR * LAVATORIES * PHOTOTRANSISTOR * INFRARED * GALLIUM * ARSENIDE * PHOTORESISTOR(LDR) * RELAY * TELEGRAPH CIRCUIT * PROTECTIVE RELAY * IC BURNER DISPENSER One that dispenses or gives out, especially a machine or container that allows the contents to be removed and used in convenient or prescribed amounts. IR LEDS An IR LED, also known as IR transmitter, is a special purpose LED that transmits infrared rays in the range of 760 nm wavelength. Such LEDs are usually made of gallium arsenide or aluminium gallium arsenide. They, along with IR receivers, are commonly used as sensors. The appearance is same as a common LED. Since the human eye cannot see the infrared radiations, it is not possible for a person to identify whether the IR LED is working or not, unlike a common LED. To overcome this problem, the camera on a cellphone can be used. The camera can show us the IR rays being emanated from the IR LED in a circuit. SENSOR A sensor (also called detector) is a converter that measures a physical quantity and converts it into a signal which can be read by an observer or by an (today mostly electronic) instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube. A thermocouple converts temperature to an output voltage which can be read by a voltmeter. For accuracy...
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...Wire Symbols | | Electrical Wire | Conductor of electrical current | | Connected Wires | Connected crossing | | Not Connected Wires | Wires are not connected | Switch Symbols and Relay Symbols | | SPST Toggle Switch | Disconnects current when open | | SPDT Toggle Switch | Selects between two connections | | Pushbutton Switch (N.O) | Momentary switch - normally open | | Pushbutton Switch (N.C) | Momentary switch - normally closed | | DIP Switch | DIP switch is used for onboard configuration | | SPST Relay | Relay open / close connection by an electromagnet | | SPDT Relay | | | Jumper | Close connection by jumper insertion on pins. | | Solder Bridge | Solder to close connection | Ground Symbols | | Earth Ground | Used for zero potential reference and electrical shock protection. | | Chassis Ground | Connected to the chassis of the circuit | | Digital / Common Ground | | Resistor Symbols | | Resistor (IEEE) | Resistor reduces the current flow. | | Resistor (IEC) | | | Potentiometer (IEEE) | Adjustable resistor - has 3 terminals. | | Potentiometer (IEC) | | | Variable Resistor / Rheostat(IEEE) | Adjustable resistor - has 2 terminals. | | Variable Resistor / Rheostat(IEC) | | | Trimmer Resistor | Preset resistor | | Thermistor | Thermal resistor - change resistance when temperature changes | | Photoresistor / Light dependent resistor (LDR) | Photo-resistor - change resistance with light intensity change...
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...Learn Making sense out of complex Pro A/V and Broadcast technologies. edu Guide An educational resource published by Communications Specialties, Inc.. Introduction to Fiber Optics The equipment, tools and cabling that comprise a fiber optic link, how they work and their advantages over traditional copper. commspecial.com edu Guide Communications Specialties, Inc. is committed to increased education and knowledge in the Pro A/V and Broadcast industries. We hope that you enjoy reading – and learning! – with our eduGuide series of educational resources. For additional information on these and other industry related technologies, please visit us at commspecial.com today! ©2009 Communications Specialties, Inc. All Rights Reserved. Specifications, claims or other product information contained in this document are subject to change without notice. This document may not be reproduced, in whole or in part, without the express written consent of Communications Specialties, Inc., Fiberlink, Pure Digital Fiberlink, the starburst logo, Scan Do and Deuce are registered trademarks of Communications Specialties, Inc. CSI and the triangle designs are trademarks of Communications Specialties, Inc. October 8, 2009 Table of Contents A Brief Introduction ............................................................................................................ 2 Advantages of Fiber Optic Systems ......................................................................
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