What is Led: Definition and 457 Discussions

LEd (formerly LaTeX Editor) is a TeX and LaTeX editing software working under Microsoft Windows. It is a freeware product.
LEd offers a project manager, powerful editor, integrated spellchecker and thesaurus, built-in DVI viewer, descriptive hints for LaTeX commands, code complete mechanism, word wrapping, code folding, multilingual environment, and more. Nevertheless, LaTeX Editor is a small program.

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  1. Toma

    LED alternatively powered by different voltages

    Hello this is my first post here and I am not very good at electric circuits, so I'm not familiar with the jargon either, I'll describe the practical use of the circuit I'm trying to make, basically I have a LED underneath the pedals in my car which will be permanently connected to something...
  2. Kara386

    I Why does LED band gap decrease as temperature increases?

    I've tried to summarise the explanation my professor gave. Is it correct or have I misunderstood? It's a highly simplified view of things anyway, but here goes: Taking the simplest 1D case, there are two possibiities for an electron in the lattice: it may be scattered and move back the way it...
  3. Kara386

    Why does LED shunt resistance decrease with increasing T?

    I'm not entirely clear what shunt resistance is, it's fairly hard to find things on google which refer to it in the context of LEDs. So we did an experiment in which we measured the IV characteristics of InAs at different temperatures, and observed the gradients of these graphs (apparently those...
  4. B

    High Voltage LED Solution for 4.2A Circuit

    I have a circuit and it has a cap that has around 680V and the high current that is pull it 4.22A. I need to add an LED to let me know when the Cap is drain. The problem I am having is that since the voltage and current are so high, I can't use a Hall effect sensor . I can't find one rated for...
  5. M

    I Calculating LED Efficiency with Radiant Power and Temperature

    i wonder if it is possible to get the efficiency of an LED just by knowing the radiant power an the outside temperatur. i also know the temperatur of the emmited light. well they say the LED has an efficiency >1 because it takes heat from the out side and turns it into rays. so these two things...
  6. Matt2623478600

    Can I Use AC to Power DC LED Light Bars for Stage Production?

    I need guidance in the explanation of utilizing LED light bars for a different function then designed. I do stage production, sound and lights for concerts and would like to adapt these LED light bars to "blind" to crowd. My issue is that each light bar operates 12-30 Volts DC @ 300 Watts. In...
  7. T

    LED Characteristic Homework: Find Current & Voltage in Circuit

    Homework Statement I have a LED Given: u-i-characteristic curve -> thus the wavelengh It's Part of a curcuit. Also (After the LED) There is a resistance of R (known) An a capacitor, (known) Homework Equations If i have a Voltage of U, how can i find the current Running through the LED and...
  8. A

    Op Amp LM358 LED flasher oscillator

    I have tried many times testing some Op Amp LED flashing circuits on a breadboard from the internet. So far, none of them works. The photo above is one of my attempt using a Ti IC chip LM358. I have double checked my wiring and swap the 100k with 10k and 56k resistors. what is the problem...
  9. J

    LED Light Wavelengths: What to Know for Photolysis Prevention

    I work in a factory where we package pharmaceuticals. There are quiet a few products that are light sensitive to a certain wavelength. The lights in the older buildings are fluorescent and were have defined wavelength specification. The wavelength determined the color light/filters set in the...
  10. Metals

    I Blue lights (LEDs) consume more power than red (and green)?

    Referring to LEDs as I'm not aware of any other "colour-producing" light, does blue light use more energy than red light? Planck's formula (E=hf) leads me to believe that blue light would drain a battery quicker than red, due to its higher frequency. Surely a device emitting blue light would...
  11. otaKu

    I A software for simulating palsmonics based LED designs

    So I'm not exactly sure if this is the correct place to post this thread but I was looking for a software to model LED structures incorporating plasmonics nanolayers or nanostructures. I've read publications where people have performed FDTD simulations on similar structures but they don't...
  12. Planobilly

    Need ideas for a LED Pilot light for a tube amp

    Hi, Is there any reason I should not use the 5VAC or the 6.3VAC taps on the power transformer and design a rectifier circuit to power a LED? Thanks, Billy Be back in a bit
  13. J

    Lighting up a 5mm LED using a homemade battery

    Homework Statement I'm currently doing a mini project as an assignment in my engineering course. I tried replicating the coin battery, where I stack a piece of cardboard soaked in black vinegar (couldn't find white vinegar), a piece of aluminium foil, then a 20 sen coin (Malaysian...
  14. T

    Question about Non-Linear LED Loading

    I often create LED arrays, and have encountered a common issue where, as the LED load is increased, the total current requirement is not a linear factor as each branch (LED strip) is added to the circuit. It is common to have many branches of LED strips on a 12VDC 60W power supply. Power...
  15. M

    Factors that influence the spectral linewidth of an LED

    So I'm doing up a physics report but i got stuck on this question :( Q: Explain the factors that influence the spectral linewidth of the emission spectrum. i'm guessing that it has something to do with the types of elements used in doping the semiconductor? but i don't know how the theory part...
  16. SmritiB

    Detecting Current Flow in a Circuit with LEDs

    I am desgning a circuit(network), where i need to show the path traversed by the greater part of the current at each node, consecutively. using an ammeter (or voltmeter) in every branch (around 20) makes it too tedious. Will LEDs do the required work? But they would light up at all locations...
  17. P

    How to shut off Led on buck converter

    I am using a buck converter with a battery pack, for a usb charger. The issue is, is that the buck converter I have ( http://www.ebay.com/itm/DC-Converter-Step-Down-Buck-Module-7V-24V-to-5V-3A-5V-usb-output-power-adapt-/261030150117?hash=item3cc69bffe5:g:Q3UAAMXQTT9R0Qos ) has a led on it, which...
  18. E

    I Diffusion of carriers in a double heterostructure

    Hello! Double heterostructures are used in LEDs and lasers to provide both the confinement of the charge carriers and the confinement of the generated light. This image is a comparison between a homojunction and a heterojunction. As regards the unbiased junctions, when the n region and the p...
  19. Hassan Raafat

    LEDs: Connect 3 LEDs Without Microcontroller

    Is there is a way to connect three LEDs so that there are three cases where one LED only is working in every case of the three without using micro controller ?
  20. Lotic7

    I Determine emission spectrum of an LED

    I recently purchased some 660nm LEDs. They look kind of orange not deep red. What is the easiest and cheapest way to determine the emission spectrum. Eventually I wanted to try to use the 660nm LEDs to grow some plants.
  21. Marcin H

    Calculating Current in a Series Circuit with an LED

    Homework Statement Homework Equations V=IR The Attempt at a Solution I'm not sure if this is right, but I did this problem by finding the current in the 300ohm resistor by doing I=5V/300ohms = .0166A and since they are in series they have the same current. I don't think that is right...
  22. W

    Why is the band offset of an LED equal to the band gap?

    I am doing an experiment where we have to use the threshold voltage of LEDs to determine Planck's constant given the following relation $$ eV_0 = E_g = \frac{hc}{\lambda} $$ where ## V_0 ## is the threshold voltage, ## \lambda ## is the wavelength of emitted light and ## E_g ## is the band...
  23. T

    Engineering Question about this simple LED circuit with potentiometer

    Homework Statement This isn't really a homework question, but I was fiddling around on the virtual electronics lab at 123D circuits to familiarize myself with the various electrical components used in making circuits and just to familiarize myself with building electronics in general since I'm...
  24. D

    What is the formula for calculating the optical output power of an LED?

    Hi, i was doing a science project on LEDs, and i needed to calculate optical output power versus input electrical power to find relative wall plug efficiency. This is the only good formula i found Optical output power of LED (watts) =Nlinearfactor × Voltage drop across resistor (volts) Pout = N...
  25. P

    Diffraction of red LED light picture with spots

    I would like to know what the dots are. This reminds me of X-ray diffraction, but I am imaging a sphere of liquid on the end of a microcapillary nozzle (2um inner diameter glass nozzle with sputtered gold outer coating on nozzle). I am taking a picture of a small glass nozzle with a metal...
  26. M

    Project sharp shadows from LED

    Using a high-power LED light (the surface mount kind, about 4x4mm with 120 degree viewing angle) I'd like to project shadows of a fine metal mesh onto a wall. I have tried various lens arrangements and found that placing a pinhole in front of the LED makes the sharpest shadows. This makes...
  27. J

    How to Repair a 5W LED Bulb (A15) | Step-by-Step Guide

    I am trying to repair a A15 LED Bulb rated 5 WATT 46 MA 120 Volt. It runs on 30 Volt DC it has 5 cells inside one is not working so based on this information each cell needs 6 volts so the remaining 4 good cells will burn with 24 volts which I applied and my ammeter says 90 MA I know not how...
  28. A

    Help designing a music visualizer for a 12x12 LED screen

    I am working in a group for designing a LED interactive Screen. My part of the project is the design of the music visualization system. I am new in this area, but I know I need to use some op-amps to filter the input signal from the mp3 player. Could anyone give me any suggestions on how to...
  29. S

    How many batteries are needed to light up this led button?

    Hello everyone, I am currently involved in a project where I'm building a pipboy 3000 from scratch. I'm close to finishing it and I wanted to take the extra step and make some functional/interactive buttons on it. I've been searching for led button switches to use for some of the buttons for...
  30. K

    Why orange color is visible with blue LED?

    I am making a DIY spectophotometer. What you see in this photo is flask of methyl orange solution in water with blue led in the back in a black box. As you can see the surrounding is blue because the box reflect blue light, however the light coming through the flask is orange. I don't...
  31. I

    Infrared LED array for heating?

    We have LED arrays for visible lighting. What problems exist for using infrared LED arrays as a heat source for humans, like those in a residential settings? Does effectiveness vary much by wavelength and skin color, clothing worn, etc? Thanks. :-)
  32. H

    F = (1/4)(n2/n1)2[1-{(n1-n2)/(n1+n2)}2] ?

    Hi，I was wondering if someone could tell me the name of this equation, where does the equation come from? “If light is isotropically generated in a medium then the fraction transmitted to the outside world is given by: F = (1/4)(n2/n1)2[1-{(n1-n2)/(n1+n2)}2]” Thank you so much :)
  33. P

    How to Calculate Light Emitted from an LED Screen: A Guide

    Hi, I have a question how to calculate the light emitted from a LED screen. The LED display is rated at 5000 nits. Total size of the display is 64sqm. (8m x 8m touching the floor) I would like to calculate the total light emitted, the light on the floor in front 1m away and the light on the...
  34. C

    Heat generation of phosphor layer in white LED

    In a package of a phosphor converted white LED (blue LED + Yellow phosphor), two heat generation mechanisms exist. 1. Joule heating at junction temperature of blue LED 2. Heat generation of the yellow phosphor layer due to stokes shift and blue light absorption. Now I have questions. 1. Where...
  35. J

    4000w LED Chip Array Driven Directly by Mains

    Hi folks. I'm currently designing a 4000w LED chip array in which I plan on using 3x 1500w 12v switch mode power supply's. A DC-DC converter will convert the 12v to 35v powering two chips. This totals to 20 step up converters and 3 switch mode power supplies to drive the proposed 40 100w chips...
  36. J

    Where does the energy in LED come from?

    I know that the electrons in the N-type are in the conduction energy level, while the holes in the P-type are in the valence energy level, so when they recombine light is emitted. What I don't understand is where that energy comes from. The electrons in a copper wire can freely flow from the...
  37. Semiavas

    Class 2 battery charger as a LED power supply?

    Hello, I'm planning to light up a tile chess board with 64 LEDs (blue and white) set between the tile squares, and I was wondering if this Class 2 Battery charger output: 12VDC 900mA, would work to power 16 parallel sets of 4 LEDs + 1 ohm 1/8W resistor and a SPST toggle switch? The current...
  38. Salvador

    What Is the Best Wiring Method for My Custom LED Cube Lamp?

    Ok, so please folks could you advise me which way would be better. I've given a job to build a LED light.the light is a cube shaped lamp which i built myself and put all the diodes in , and now I have to think which way of wiring them would be the best.basically I have 98 red colored 3w led's...
  39. E

    LEDs, LED Drivers, Thermal Management

    I'm trying to wrap my head around thermal management of LEDs and LED driver circuits. http://blogs.indium.com/blog/amanda-hartnett/controlling-junction-temperature-of-leds-with-thermal-management-materials A concern has been expressed that a lighting supplier needs to demonstrate (not sure...
  40. D

    Can I Create a Visible Light Pattern Using a Combination of Laser Beam and LED?

    I want to create a visible pattern of light from 1-5 feet away. The pattern would have a bright dot in the middle (ala sniper sight) visible in bright light at 5 feet. The cheap toy pointers seem to work just fine. It would also have a filled circular pattern around the dot, 8" in diameter at 4'...
  41. P

    Bright light from white light connected 240ac through 1k

    I have connected 4 White LEDs with 240ac main through 1K resistor in series. The brightness of the output is not satisfactory. What can i resolve this issue? Thanks
  42. Drakkith

    LED Bulb that Stays Lit Despite Power Outtage

    Random question, folks. A friend of mine lost power in his house this past evening, yet his front porch light, an LED bulb, is still shining bright. Any idea why this might be? Do they sell bulbs with some sort of backup battery built in? Edit: Apparently the light on one of his power strips...
  43. J

    What to optimize in LED array?

    I'm making an array of 11 3.3V LEDs, and I've got multiple various setups possible depending on source voltage (batteries supplying either 6V, 9V, or 12V) and whether I decide to put a bunch of the LEDs in a combination of series/parallel or all in parallel. I need to maximize battery life, so...
  44. S

    Exploring 488nm LED Options for Fluorescence Activated Cell Sorters

    Why can't I find any LED's at 488nm? I am trying to find a cheaper light source than the traditional argon ion laser for a possible fluorescence activated cell sorter. See link below for schematic. Does anybody know a good retail site for lights in this spectrum I can't find good results with...
  45. G

    IR LED irradiance, radiant exposure and radiance

    Hi! I'm trying to design a device to detect eye blinking while a person is sleeping. I have tried to use TCRT5000 sensor (http://www.vishay.com/docs/83760/tcrt5000.pdf) in the prototype and it works like charm ! However, since the TCRT5000 sensor has an IR emmitter I have some safety...
  46. Superposed_Cat

    Microcontroller, LED, DC motor problems

    Hey all, me and my friend are attempting to control a 5v dc motor and make a LED blink simultaneously using a H-Bridge Motor Driver 1A - SN754410 and ATMEGA328 micro-controller(16mhz, 8bit). The issue is is that when my H-Bridge activates the motor using input from the micro-controller then the...
  47. V

    Total radiant flux measurement of an LED with an optometer

    Measuring the total radiant flux with an optometer of SFH 4550 LED from osram I'm getting ~70mW, If I place 5mm long rubber hose around the led (top 2,5mm of the led is free), the power is reduced to 50-40mW. This does not make sens to me, the led has a half angle of ±3° and emits nothing to...
  48. G

    NEWB - LED Tail light wiring diagram

    Hello. So I have a pair of LED tail lights that are operated by 2 modules. One is for Dimming, Braking and strobe function, and the other is for Turn signal blinking. One tail light is wired to the other through a wire harness and then the wires for dimming and brake function come out the other...
  49. E

    Please recommend a high-performance CPU cooler with red LED

    Could someone please recommend a high-performance aluminum aftermarket CPU air cooler that has a red LED light?
  50. V

    Radiant intensity, LED specifications

    Hi all, I have a problem of understanding the concept of radiant intensity, in particularly I’m interested in LED characteristics and confused with specification in LED datasheet. For example in the datasheeat for the VSMY2850 LED from Vishay it is stated that typical radiant intensity is 100...
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