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LIGHT EMITTING DIODES . Presentation by Evren EKMEKÇİ. A light emitting diode (LED) is essentially a PN junction opto- semiconductor that emits a monochromatic (single color) light when operated in a forward biased direction.
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A light emanating diode (LED) is basically a PN intersection opto-semiconductor that discharges a monochromatic (single shading) light when worked in a forward one-sided bearing. LEDs change over electrical vitality into light vitality. They are often utilized as "pilot" lights in electronic machines to demonstrate whether the circuit is shut or not.

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About LEDs (1/2) The most critical part of a light transmitting diode (LED) is the semi-conductor chip situated in the focal point of the knob as appeared at the privilege. The chip has two districts isolated by an intersection. The p area is ruled by positive electric charges, and the n locale is commanded by negative electric charges. The intersection goes about as an obstruction to the stream of electrons between the p and the n areas. Just when adequate voltage is connected to the semi-conductor chip, can the present stream, and the electrons cross the intersection into the p area.

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How Does A LED Work? (1/2) When adequate voltage is connected to the chip over the leads of the LED, electrons can move effortlessly in stand out course over the intersection between the p and n areas. In the p area there are numerous more positive than negative charges. At the point when a voltage is connected and the present begins to stream, electrons in the n locale have adequate vitality to move over the intersection into the p district .

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How Does A LED Work? (2/2) Each time an electron recombines with a positive charge, electric potential vitality is changed over into electromagnetic vitality . For every recombination of a negative and a positive charge, a quantum of electromagnetic vitality is discharged as a photon of light with a recurrence normal for the semi-conductor material (for the most part a mix of the synthetic components gallium, arsenic and phosphorus)..

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Testing LEDs Never interface a LED straightforwardly to a battery or power supply! It will be crushed in a flash in light of the fact that an excessive amount of current will go through and blaze it out. LEDs must have a resistor in arrangement to restrain the current to a sheltered esteem, for fast testing purposes a 1k resistor is reasonable for most LEDs if your supply voltage is 12V or less. Keep in mind to associate the LED the right path round!

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H ow M uch Energy Does a LED Emit? The vitality ( E ) of the light radiated by a LED is identified with the electric charge ( q ) of an electron and the voltage ( V ) required to light the LED by the expression: E = qV Joules. This expression basically says that the voltage is corresponding to the electric vitality, and is a general explanation which applies to any circuit, and additionally to LED\'s. The consistent q is the electric charge of a solitary electron, - 1.6 x 10 - 19 Coulomb .

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Finding the Energy from the Voltage Suppose you gauged the voltage over the leads of a LED, and you wished to locate the relating vitality required to light the LED. Give us a chance to say that you have a red LED, and the voltage measured between the leads of is 1.71 Volts. So the Energy required to light the LED is E = qV or E = - 1.6 x 10 - 19 (1.71) Joule, since a Coulomb-Volt is a Joule. Duplication of these numbers then gives E = 2.74 x 10 - 19 Joule.

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Applications Sensor Applications Mobile Applications Sign Applications Automative Uses LED Signals Illuminations Indicators

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Sensor Applications Medical Instrumentation Bar Code Readers Color & Money Sensors Encoders Optical Switches Fiber Optic Communication

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Mobile Applications Mobile Phone PDA\'s Digital Cameras Lap Tops General Backlighting

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Sign Applications Full Color Video Monochrome Message Boards Traffic/VMS Transportation - Passenger Information

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Automative Applications Interior Lighting - Instrument Panels & Switches, Courtesy Lighting Exterior Lighting - CHMSL, Rear Stop/Turn/Tail Truck/Bus Lighting - Retrofits, New Turn/Tail/Marker Lights

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Signal Appications Traffic Rail Aviation Tower Lights Runway Lights Emergency/Police Vehicle Lighting LEDs offer colossal advantages over conventional brilliant lights including: Energy reserve funds (up to 85% less influence than glowing) Reduction in support costs Increased perceivability in sunshine and unfavorable climate conditions

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Illumination (1/2) Architectural Lighting Signage (Channel Letters) Machine Vision Retail Displays Emergency Lighting (Exit Signs) Neon Replacement Bulb Replacements Flashlights Outdoor Accent Lighting - Pathway, Marker Lights

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Illumination (2/2) LEDs not just expend far less power than customary types of enlightenment, bringing about decreased vitality costs, yet require less upkeep and repair. Concentrates on have demonstrated that the utilization of LEDs in enlightenment applications can offer: Greater visual advance Reduced vitality costs Increased consideration catch Savings in support and lighting substitutions As white LED innovation keeps on enhancing, the utilization of LEDs for general brightening applications will turn out to be more common in the business.

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Indication Household machines VCR/DVD/Stereo and other sound and video gadgets Toys/Games Instrumentation Security Equipment Switche s

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Driving LEDs Analog LED Drive Circuits Digital LED Drive Circuits

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Analog LED Drive Circuit

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Digital LED Drive Circuits

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Colors of LEDs (1/3) LEDs are produced using gallium-based precious stones that contain one or progressively extra materials, for example, phosphorous to create a particular shading. Diverse LED chip advances transmit light in particular locales of the unmistakable light range and deliver distinctive power levels. LEDs are accessible in red, orange, golden, yellow, green, blue and white. Blue and white LEDs are a great deal more costly than alternate hues. The shade of a LED is controlled by the semiconductor material, not by the shading of the "bundle" (the plastic body). LEDs of all hues are accessible in uncoloured bundles which might be diffused (smooth) or clear (frequently portrayed as \'water clear\'). The hued bundles are additionally accessible as diffused (the standard sort) or straightforward.

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Colors of LEDs (2/3) Tri-shading LEDs The most prominent sort of tri-shading LED has a red and a green LED joined in one bundle with three leads. They are called tri-shading on the grounds that blended red and green light seems, by all accounts, to be yellow and this is delivered when both the red and green LEDs are on. The outline demonstrates the development of a tri - shading LED. Take note of the diverse lengths of the three leads. The inside lead (k) is the basic cathode for both LEDs, the external leads (a1 and a2) are the anodes to the LEDs permitting every one to be lit independently, or both together to give the third shading.

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Colors of LEDs (3/3) Bi-shading LEDs A bi-shading LED has two LEDs wired in \'converse parallel\' (one advances, one in reverse) joined in one bundle with two leads. One and only of the LEDs can be lit at one time and they are less valuable than the tri-shading LEDs portrayed previously.

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Comparison Of Chip Technologies For Wide-Angle, Non-Diffused LEDs

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LED Performance (1/8) Color White light Intensity Eye wellbeing data Visibility Operating Life Voltage/Design Current LED execution depends on a couple of essential attributes:

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LED Performance (2/8) Color Peak wavelength is a component of the LED chip material. Despite the fact that procedure varieties are ±10 NM, the 565 to 600 NM wavelength phantom locale is the place the affectability level of the human eye is most noteworthy. Accordingly, it is less demanding to see shading varieties in yellow and golden LEDs than different hues.

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LED Performance (3/8) White Light When light from all parts of the unmistakable range cover each other, the added substance blend of hues seems white. Notwithstanding, the eye does not require a blend of the considerable number of shades of the range to see white light. Essential hues from the upper, center, and lower parts of the range (red, green, and blue), when joined, show up whit e.

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LED Performance (4/8) Intensity LED light yield shifts with the sort of chip, embodiment, efficienc y of individual wafer parts and different factors. A few LED producers utilize terms, for example, "super-bright," and "ultra-brilliant" to depict LED force. Such phrasing is totally subjective, as there is no industry standard for LED shine.

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LED Performance (5/8) Eye Safety The need to place eye security naming on LED items is reliant upon the item outline and the application. Just a couple of LEDs deliver adequate force to require eye security marking. Be that as it may, for eye security, don\'t gaze into the light emission LED at short proximity

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LED Performance (6/8) Visibility Luminous power (Iv) does not speak to the aggregate light yield from a LED. Both the glowing force and the spatial radiation design (seeing edge) must be considered. On the off chance that two LEDs have the same brilliant force esteem, the light with the bigger survey point will have the higher aggregate light yield.

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LED Performance (7/8) Operating Life Because LEDs are strong state gadgets they are not subject to disastrous disappointment when worked inside plan parameters. DDP® LEDs are intended to work upwards of 100,000 hours at 25°C surrounding temperature. Working life is portrayed by the corruption of LED force after some time. At the point when the LED debases to half of its unique force following 100,000 hours it is toward the end of its valuable life despite the fact that the LED will keep on operating as yield lessens. Dissimilar to standard brilliant globules, DDP® LEDs oppose stun and vibration and can be cycled on and off without extreme debasement.

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