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. H

    Controling the wavelength of an LED through voltage?

    I was reading some spec sheets for some leds, and it says that, for example, at 1.4V the light is at 650nm and that at 1.7V the light is at 670nm. This is a feature that could be potentially quite useful to me, so I was wondering: is this a common feature of leds? Is it dangerous to change...
  2. J

    Changing the color of an LED bulb

    I recently changed my bulbs in my car's HVAC dash to LEDs. I wanted a blue color and it looks really good and exactly what I wanted. The only problem is that there are three buttons that are lit separately from the new LEDs by green bulbs, which I want to be blue as well, but I cannot simply...
  3. A

    What Bandgap Energy Range is Required for Blue LEDs?

    Homework Statement Blue light corresponds to free space wavelengths of approximately 450 to 495 nm. If we want to use a semiconductor to make a blue LED, what range of energies must the semiconductor's bandgap fall within? Express your answer in units of electron volts(eV). What is an...
  4. L

    Multi LED circuit controlled by photodiode

    Hi, so. I don't know a lot of electronics but this is effectively what I'm trying to create: A photo diode controls the circuit, I assume they give out a current proportional to the intensity of the light it receives. The ciruit, depending on the light intensity will light up different...
  5. H

    Curiousity question into what events might have led to calgary floodin

    RE-POST If you live in Calgary please play close attention to this. Today there was major flooding both here in Calgary and the Philippines. This is a video you need to Watch if you live in Calgary Alberta Canada And there is a Earthquake watch right now for both areas today in the world.These...
  6. S

    Music Post Led Zeppelin Music: For Fans & Lovers

    Here you go. Post your Led Zeppelin music here. https://www.youtube.com/watch?v=KZOAFNri0hM
  7. P

    Looking to make LED strips pulse to bass hits (in my car)

    So basically, I have 4 LED strips (each rated for 12v) that I’d like to make pulse to the bass of the music, such as in this video . There are a lot of misinformed people on YouTube who just hook up their LEDs directly in parallel with the subwoofers, which doesn’t work well at all and will...
  8. C

    LED ARRAY Convergence failed

    im using falstad and my knowledge on circuits is poor or extremely basic.. $ 1 5.0E-6 34.14951009862697 50 5.0 50 162 512 288 816 288 1 2.1024259 1.0 0.0 0.0 162 544 288 896 288 1 2.1024259 1.0 0.0 0.0 162 576 288 960 288 1 2.1024259 1.0 0.0 0.0 w 896 288 816 288 0 g 960 288 960 240 0...
  9. J

    How Do You Program a Sequential LED Light Pattern in MIPS Assembly?

    Hi all, I've only just started MIPS and have been stuck on this introductory lab for a while now. I have 8 LEDs each lit by there corresponding bit being a 1. Hence 0010 0101 at the input would light up LEDS 1, 3 and 6. I need to make LEDs 1-5 light up one at a time and extinguish the...
  10. J

    Multimeter reads different current with LED in series?

    I need help. I was under the impression that LED's in series should have the same current running through them and one's in parallel should have different currents because of the voltage drop variation in the individual LED's. When I put them in parallel, my multimeter shows the voltage across...
  11. S

    LED voltage indicator for 3.7v lithium ion battery

    For my project, the Lithium Ion Polymer Battery - 3.7v 2600mAh powers arduino, transmitter and a few other parts. My whole design works on 3.3v. I'm trying to build a circuit to indicate the status of the battery using LED. When the voltage of the battery is consumed below 3.0v, I want to...
  12. D

    Personal Project. LED Timers

    Hi I have a project in mind and I'd like some help starting it up. Project: I want to create Twisted Fate's Pick a card, for those of you know the popular game, League of Legends. ____________ |L.....L| |....| |....| |...L...| |....| |....| |L.....L|...
  13. T

    LED - Measuring light intensity

    what type of circuit would you draw for this? and how would you actually measure the light intensity of an LED. say you had multiple LEDs and you wanted to compare the light intensity of all of them. how would you do this with with circuit?
  14. V

    Quantum mechanics and an LED lab help

    so i have to do this lab for ib physics and i am a noob at physics and i am having some trouble with the lab that i have to do. Homework Statement the research question is "how does potential difference needed to operate an LED depend on the frequency of the light emitted? it is set up in...
  15. O

    Circuit Analysis: Current and Voltage Ranking

    Homework Statement Consider the circuit at right, consisting of two identical resistors (R1 and R2) and a red LED. The battery is ideal and maintains a constant voltage of +9.0 V (i.e., V1 - V2 = +9.0 V). An ideal voltmeter is connected across the LED and R2. 1. At point a, is the direction...
  16. N

    Power a led with piezoelectricty

    I hae aqiured a piezo disk and LEDS but it will not power them. i do not know if it is the disk or an led. I tried the LED with AA AAA and D batteries but only turned on with 9V they are sea green
  17. R

    LED Case Materials: Epoxy vs. Acrylic and Where to Find Them

    Does anyone have any information on what the clear plastic cases (lens, capsule, w/e) are made of for LEDs? Google says it is some sort of epoxy, but I also read somewhere a while ago that sometimes it is acrylic. Is this true, and can you buy LEDs anywhere that are made of thermoplastic like...
  18. S

    LED Outdoor Lighting Solutions - Bob's Story

    Hi, i recently installed 24 miniture lamp posts around my yard. These lamp posts are using 12 volt push in twist (car backup or brake bulbs). I powered the 24 bulbs with a large 12 volt transformer which is controlled by a switch inside the house. Here in lies the problem not thinking i orderd...
  19. D

    Optic lens to collimate/focus light from a LED.

    Hello. I'm looking for a lens that can collimate (or focus far away >500mm ) a light coming out from a LED. before I give more details is this even possible? Thanks.
  20. J

    LED based solar simulator testing method

    Sir, I'm an undergraduate in 'Electronics'.Intending to develop a solar simulator with LED as the light source. It is understood that the spectral irradiance of sun can not be generated with the LED.So my plan is to light up a number of high power LED arrays of different...
  21. T

    Making a Blinking LED 555 Timer

    Hi guys, I figured I might try making a LED to phase on and off for around 1 second, to be perfectly honest I have NO idea what I'm doing really. But figured that's the best way to learn right :P. So I'm using a Timer 556 and connected it in a way that kind of made sense from the 555 IC timer...
  22. A

    Doubting Ohm's Law: LED & 220Ω Resistor

    As the title states I am really doubting Ohm's law. This is why: On a breadboard I placed a white LED and a 220Ω resistor with the 9v battery all in series. The total current flowing through the circuit shouldn't be more than 41mA by V=IR, but my multimeter points between the range of...
  23. S

    Power on/off bi-color led circuit?

    In a robotics project and need an indicator to show the operator when the safety circuit is open or closed. Got it done in software but need a physical idiot light. Thinking a bright red/green bi-color led. Have 24 vdc constant supply and a pin that sinks to ground (100mA max) just while the...
  24. M

    Help designing analog filter designs for an audio activated 8x8x8 LED cube

    I am working on designing a music visualization system using LEDs. I would like to create an analog design that uses op amps to filter, amplify, and add DC bias to an audio signal so it can be read into the A/D of a 5V microprocessor. The input signal is a +/- 1.5V volt audio signal coming from...
  25. sophiecentaur

    Domestic LED lamps: reliability

    I have bought just four mains voltage LED lamps, in my life. Three of them have failed. One has failed after only a very few months and is being replaced by the supplier. They claim that these expensive items are supposed to last for tens of thousands of hours. Has anyone else had this problem...
  26. J

    Collimating incoherent light emitted by a LED

    Hello, What would be the best method to "collimate" light from a LED with an emitting area of 12mm^2 and a maximum divergence angle of 80° with minimal loss of light intensity? I want to collimate it into a beam of approximately 5-10mm. I have an aspheric condenser lense at hand with...
  27. Y

    Making a poster with 5mm 2 pin LED lights.

    Hey, I want to make a get better poster with led light sticking out of the poster. I found the following LEDs: http://www.play-zone.ch/de/bauteile/led/led-sortiment-mit-180-leds-oem.html . I have very little experience with wiring circuits (did AP physics a while back) and I'm not sure if this...
  28. B

    What color of LED light to use for display of minerals? Cool or warm?

    I'm going to display my rock and mineral collection in glass door cabinets in the living room. I've found some LED under-the-counter lights, 21 small LED lights per 2-ft string. I plan to use one of the strings for each shelf. They come in two "colors", warm and cool. Sorry, they don't...
  29. P

    Calculating radiant power of LED over its whole spectrum

    Hello OK so I'm very new to electronics and I really need some clarification/guidance. I am using this integrating sphere which is basically just a glorified photodiode. I am going to be measuring the output photocurrent using the responsivity curve of the photodiode. The sphere also has...
  30. L

    Understanding LED Light Pipes: How They Work and Their Composition

    I have a basic question about light pipes - How exactly does it work? Is it like Fiber optic cable (total internal reflection)? or does it leak since the light pipe is fully made of glass.
  31. M

    Why is a current limiting resistor necessary in an LED circuit?

    Let's say that I have an LED where If=20mA and Vf(typ)=2v. I want to power it directly with a 2v lead acid battery. According to most answers to this question I have read this will either not work (with the outcome unspecified), will destroy the LED, or is just a bad idea because of how an ideal...
  32. C

    Increase in Wavelength of an LED Immersed in Liquid Nitrogen

    Hi, I've been working on an experiment where I dip LEDs into liquid nitrogen and note the color change. All online sources I've seen predict that the wavelength of the light emitted by the LED will decrease upon immersion. What I've been observing, however, is a sudden decrease in...
  33. S

    What is the Music Behind BBC's Clip on LED's 50-Year Anniversary?

    Recently BBC made a photo clip on LED with audio from the inventor Prof Nick Holonyak himself. "LED at 50" http://www.bbc.co.uk/news/technology-19886534 It's really inspiring. Does anybody knows the music played behind?
  34. N

    Voltage required in an LED circuit

    I am currently working on making two LED eyes for a costume which needs a top row of 2x LEDs, middle row of 6x LEDs and a bottom row of 2x LEDs. I am currently trying to figure out how many volts are needed for the circuit in order to light it (at which point I can see what resistor is needed...
  35. P

    How Much Power Should an LED Emit to Be Visible from 5 Meters?

    Homework Statement In ideal conditions human eye can feel something if 100 photons with wavelengh of 5500A fall directly tu human eye in one seconds time.LED(lambda=5500A) is placed 5m away from human eye. Homework Equations Calculate the power of LED to achieve that the human eye can...
  36. J

    110V wiring question (what to use, to provide minimal power to LED driver)

    :smile: Okay folks... Not sure where to turn to at this moment (I'm stuck, and need some help!)... however, I am working this from two angles as I also have the China manufacturer (of my LED pendant lighting) trying to figure this out too. I'll start with; I'm not an elect.engineer and will...
  37. T

    Troll physics: Solar cell and LED in series

    So today my brother and I were playing with a mini solar cell that I just got, watching the voltage change with a multimeter, and seeing how even an LED would produce about .5 V in the cell, when he posed a question: If you were to take a solar cell (i.e. photodiode) capable of producing...
  38. C

    Resistor values of LED, LCD, Processors

    I have a generator which after being regulated, outputs 70mA through 3V. (I should say the amps go through the voltage right?) In some circuits I may be using diodes. Some advice me that the voltage drop is 0,7. Others say it's dynamic, that I should divide the driving voltage over the...
  39. N

    Designing a NOT-gate Circuit with LED Output

    Hi I am trying to design something similar to a NOT-gate (very simple), and I have been following this figure: http://en.wikibooks.org/wiki/File:Electronics_TTLNOT.PNG. My question is the following: Say that I instead of grounding the lower branch want to send a current through it to e.g. a...
  40. A

    [ASK]What IC can display A-F to 7-segment LED

    guys, you just created a circuit a BCD 4bits Full adder but in my case i just need a 3bits-3bits addition so that i set the A4 to 0 by default... i used 7483 for 4bits full adder and connect it to a 7447 BCD to 7-segment A4A3A2A1 + B43B2B1 A4 & B4 are set to 0 so 7 is the maximum...
  41. M

    Different LED displays (Assembly)

    Homework Statement Create a Menu to run a program for LED sequences using procedure calls or macros as follows: [1] Blinking LED [2] Two at a time [3] Alternate [4] Rotate Right [5] Rotate Left . The program will display „1‟ for LED “ON” and „0‟ for LED “OFF”. Use delay, message output and...
  42. S

    Calculating Efficiency of LED Without Plastic Dome

    Greetings everyone, I need to calculate the efficiency of an LED without a plastic dome, thus total internal reflection is a limiting factor in this case. The book asks me to show that TIR at the interface with air reduces the emission efficiency by the factor 1-cosθ where θ is the critic...
  43. M

    555 w/ 4017 7-segment LED Question

    I have a 555 and a 4017. My question is that there seems to be a bunch of 7-segment LED controllers for BCD outputting decade counters but I don't see (or know what to Google) for a non-binary coded decimal output. The 4017 outputs single digital pulses on a given terminal which indicates...
  44. J

    Led Lights Burn With Power Off

    I have Led lights in the house ceiling fixtures running on household AC when the are switched off they still give a small amount of light am I paying for this current or is this current that would have been lost anyway? John
  45. B

    Powering PV(solar) panel with LED lights

    I have seen some questions and responses in this regards in this forum. I am not very convinced, so I shoot the question again. Is it possible to feed PV cells with LED lighting? With LED's coloured lighting is easier, and getting a frequency in the range rated for a panel is easier. But...
  46. I

    Fading In/Out LEDs with Mic and Amplifier

    I would like to start this thread in simple terms, at least initially, just to get an idea of what is required for the following project and then get more in detail when necessary. We are working on a project where we are using a simple mic an amplifier, controller and a few LEDs. the Idea is...
  47. J

    Total Current Draw Of LED And Resistor Combined

    I am using a 3.3 volt led rated 25 ma powered with 12 volts and have 1000 ohm resistor in between. Ohms law says amps = ohms / volts so 12 / 1000 = 12 ma so is this all the LED and resistor combined will draw? As I know the led can only handle 25 ma, but if the led where using this much current...
  48. D

    Learn How to Calculate 12V DC LED Forward Current for SMD Chip 3528

    We are using smd chip led 3528 which prescribe 20 miliamp standard forward current. I want to know basic calculation like those bulb. How do i find forward current? 12 volt dc light, 48 pc smd chip, 16 parallel connection 3 series (as each chip volt is 3.5 to 4) Now we found that 3.14 watt is...
  49. N

    How to turn on & off an LED continously for 1 second?

    Please help me the simplest possible way to turn on & off an LED continously for 1 second. Please don't suggest me to get it done by micro-controller, help me achieve my goal by the most possible and easiest way.
  50. A

    Basic LED circuit, 9v battery, what resistors to use?

    Hi all, I am a new guy to the forum, glad to meet you all. iv been doing a little rc project and now need to wire up some lights. iv never done circuit work before but I am willing to gain knowledge on how to. the main problem is that no matter how much i read or calculate, i cannot work out...
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