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. Redbelly98

    LED light bulbs from Lights Of America

    I recently bought some LED light bulbs, made by Lights Of America, at our local Ace hardware store. Lights of America part number is 2026LED-30k and 2026LED-65k. So here are some of the claims written on the packaging: Uses 1.5W Replaces 40W bulb 90% more efficient than incandescent and...
  2. S

    Engineering Modifying rectifier circuit to include LED indicator

    You bought a charger that does not have a charging satus indicator. Assuming that a regular rectifier circuit configuration (such as this: http://www.physics.udel.edu/~nowak/phys645/AC_circuits_files/image016.jpg ) is used for the charger, modify the rectifier circuit to have LED indicator(s)...
  3. A

    Optics Help With LED Foglights

    well i have been working on this project for a while now. i want to create an led retrofit for my foglights. every idea i have stumbled upon, i have found faults with. my main concern is functionality. i want these to look good AND serve a purpose. for example, i have found pictures of a BMW...
  4. A

    Help! My Flashing LED Circuit Isn't Working

    I just purchased a breadboard and components because I love tinkering with things. It's not for a class or anything more of a hobby, but I just needed some advice on a simple hello world like blinking led circuit. I have gotten down the basics of lighting up leds, and my second project I wanted...
  5. D

    How do I reverse the pattern of a LED ligt?

    I have an ackward question. I've been trying to device a circuit to reverse the pattern of a LED. Let me give you a quick rundown of my situation and my goal. As it stands now. Imagine a an alarm system. When activated a LED is lit 24/7. When a switch is triggered the led will blink...
  6. A

    Current limiting resistor for led on 7408 gate output

    I am building a 2 to 4 decoder with 7408 And gates and need to put LED's on the output as indicators, active high. 2 questions 1. Would I put a current limiting resistor in series with the LED to ground or put the resistor and LED from the gate output to Vcc? 2. The LED draws 30mA at 2V...
  7. O

    LED flashlight, how dangerous are they?

    Ordered this: https://www.amazon.com/dp/B000OGABWM/?tag=pfamazon01-20 Got this warning Warning "Always wear ANSI approved safety goggles when using this product. Before using this product, the user should read the operating instructions to understand everything about this product...
  8. L

    Why do LED throwies last longer than expected with a small 3V watch battery?

    Hello, You've probably already seen sites about "LED throwies" which are little circuits made of An LED A small 3V watch battery A Magnet Some Tape The idea is that you make these and then stick them to different things and the glow and are pretty. Anyway, with that background...
  9. A

    How can I control an LED array for creating patterns and designs?

    Hello all, I recently became interested in building an LED lamp as a gift for a friend. I have a good understanding of technology, but I have only a small understanding of electrical engineering. I have researched and understand how to build an actual LED lamp where I would have all the LEDs...
  10. R

    What resistor values are needed for wiring LED taillights with a SPDT relay?

    Hi. New here. I'm not necessarily a newb at wiring I've used solder before and have wired up other simple wiring diagrams. I'm hoping someone can help me with a task I'm looking at doing. I'd like to wire up a set of LED taillights. 48 red led's in the brake circuit and about 24 in the turn...
  11. J

    Opinion Please: Which of These LED Drive Circuit is Best?

    Your opinion, please. Does one of the two variations of this circuit offer a clear advantage, or is it a wash (see attached)? This indicator circuit turns on the LED below 11V (set by the zener). The LED cathode must be at ground (it is actually part of a tri-color LED with a common cathode)...
  12. H

    Driving an LED through RC circuit(RC time constant)

    Hi, i am trying to design a circuit, where i am trying to light up an LED long enough based on my pulse signal. Here is what i am trying to do. a 10us pulse(every second) --->74HCT04 buffer---> (RC circuit)----> LED. since this is a 10us pulse, i want to make sure to light up the led for...
  13. S

    LED Driver thermal transfer question

    Trying to understand an aspect of LED technology never discussed in the literature. There are many bright LED lamps on the market that incorporate the optics, chips, board, driver and heat sink into a single module. I have a question about the driver. My understanding about how drivers work...
  14. D

    Constraining the path of an infrared LED

    Are there any specific infrared LED's that have a narrow "beam width" when emitting? If not, does anyone know of a way to constrain it? A lens perhaps? I would like to control the beam width over a distance of about 2 ft. I might need to go with a laser emitter... Any suggestions...
  15. N

    Creating a Parallel LED Circuit

    I want to create a little board with 20 LEDs. My only problem is wiring them, I want to make a parallel circuit. I was wondering if I could have a bunch of them in a line and have a thin strip of metal going over all of them. In the end have 2 metal strips one for positive and one for negative...
  16. Z

    Controlling LED Intensity with Light Sensors

    Hi I would like to know if there is a sensor available in the market that would help control the intensity of light given out by a white LED, taking into account the light coming from the surrounding ambient light. As an example I am trying to implement a project in which I would have to control...
  17. F

    Temperature dependence of LED emission bandwidth

    Homework Statement If an LED is used in an optical communications system, explain what would happen to the temporal spread caused by material dispersion in the fibre as the LED is cooledHomework Equations (having trouble using the latex equation editor, sorry) I know that the temporal...
  18. R

    Simple LED Wiring: Step-by-Step Guide with Red and Green LEDs and a Lever Switch

    Alright I need help. I am not electrically inclined so figure this is the best place I could have come. I'll make this as simple as possible. I have: 1 Red 5 mm LED with specs 2.6V - 28mA * 10mcd 1 Green 5mm LED with specs 2.1VDC - 25mA - 6.3mcd 9V battery as source What I need. Need...
  19. M

    Why is the Small LED on my Screwdriver Lighting Up?

    I have a small screwdriver which has a small LED in it. When you stick it into something like an outlet, and hold your finger on the other end, the LED lights up. Today though I held both ends of the screwdriver and the LED lighted up. This confuses me tremendously... Doesn't that indicate...
  20. J

    LED light diffraction, scattering

    I am constructing a 'white line detector' to use on the underside of a robot. The crucial components are an ultrabright red LED and a light-to-voltage converter. My initial idea is to leave the LED as it is, i.e. unshielded. I have to light-to-voltage converter, which is a phototransistor...
  21. T

    12v DYNAMO driving 5v front & 10v rear LED lighting + DIAGRAM

    Hi, I'm wondering how to drive front and rear lights off one dynamo. See diagram for current setup. Lights are hooked up to dynamo in parallel. The LM7805 and LM317 are voltage regulators which drop the voltage from 12v to 5v and 10v respectively. Currently only the headlight works, the...
  22. P

    LED indicator for composite video signal

    Sorry.. I know this is really simple.. I have 3 composite video signals, and switches to select between them. The switches I have are SPCO, so I can't just use another pole for the switch voltage. So, I need a way of detecting the video, and this switching on and LED. At first I...
  23. U

    Infrared LED - Transmitting Multiple Bits

    Hi all, quick question here. As part of a sophomore seminar class, I have this little task to complete. I currently want to send a series of 4 bits through an IR LED that will reach a GaAs photo transistor. What I'm doing is using a shift register to load in the binary value (via a parallel...
  24. N

    AC powered Led Zeppelin electromagnet

    I've posted on here a few times concerning the electrical problems I continue to encounter for my video installations. And yet, here's another one. If anyone remembers, I posted a month back or so concerning the use of an audio signal from a home audio receiver to open and close a small...
  25. S

    How to detremine the lifetime of a LED

    Theoratically a LED can last for 100,000 hours, but how can i prove that this is true? I've found out that the malfunction of a LED is caused by the degradation of the active region in it, but how can i determine when it is going to malfunction?
  26. R

    Poor design led to I-35W bridge collapse?

    This image shows the ground supports of the bridge before the collapse: http://www.wmur.com/2007/0802/13805989_240X180.jpg taken from: Nation's Bridges Face Immediate Inspection. Fifth Victim Found; President Bush To Visit Minneapolis UPDATED: 9:20 am EDT August 3, 2007...
  27. K

    A question related to the LED Dimmer circuit of 05/29/07

    I want to replace a single flashing red LED on my motorcycle alarm with something more ominous to ward away potential hooligans ;) I've searched for flashing & pulsing and ramping LED circuits using Google and came across this forum, so hopefully someone here can help me :) What I would like...
  28. C

    Attaching a LED to the comp power supply

    I bought three LEDs, three 1k ohm resistors, and some wire. When I bought the LEDs, I made the person show me that they worked. He connected the negative end of the LED to the yellow wire, and the positive part to the resistor, which he then connected to the black wire. The LED lit up. As far...
  29. C

    Calculating Planck's constant from LED experiment.

    edit: problem solved. Thankyou berkeman.
  30. ranger

    How can I create a gradual increase in base voltage for an LED dimmer circuit?

    Hey all, I posted this thread just under a year ago, but I never followed up with replies. But I've suddenly become interested in finishing it up. Because I want to power several LEDs (say 5 @ approx. 30mA), I'll use a hefty transistor for Q2 (say TIP31) and a relatively lightweight BC108...
  31. N

    Choosing Resistor for LED Circuits

    I'm hoping this is the right forum for this question, I've never been to this part of PF before. I've taken up some interest in working with LED lights but I'm slightly confused with how to build the circuits for them. I'm told you need to put in a resistor to keep the LED safe from high...
  32. R

    News Nixon led to Clinton and then Bush/Cheney

    If President Nixon had been imprisoned for breaking the law it would have set a precedent that would have deterred Clinton from lying to Congress and Bush and Cheney too.Isn't it about time leaders got locked up for law breaking or else what is the point of the law?
  33. Z

    How does a two-transistors LED flasher (flip-flop) circuit work?

    I don't know when does a capacitors and the transistors switch and turn the other off considering the voltage across them...well, on other words, don't know what makes the LEDs do the flipflop thing...HELP
  34. S

    Testing AC Polarity with LED: Tip & Ring

    We routinely test "continuity" in our phone lines by holding a red/green LED to our "tip" (hot) and "ring" (cold) which lights up bright red if all is well with the AC signal. A bridge rectifier added to the mix let's the "green" shine; reversing the LED wires on + and - will make the...
  35. S

    LED Spectrum Analyzer schematics

    Hi, I am looking to build a basic spectrum analyzer (if that is what you would call it) out of some LED lights for a car stereo. Basically, I want about 8 - 10 bars (for different frequency bands), and I want them to jump up and down to the music, giving it a direct feed off of the car...
  36. E

    LED w/ Built-in FF? Find Out Now!

    Does anyone know if there is such a thing? I need a bar-graph LED with a FF built-in. The only ones I could find on digikey is a regular 10-diode LED, but I need something that would latch or hold that value until the enable changes... I could use a regular one in combination with a D-FF, but...
  37. M

    Find a Cheap uP Starter Kit and Compiler for LED Projects

    Hi, I'm looking for a very cheap uP start kit that I can practice c language and perhaps assembly language on. I want to light up led's and stuff like that. Can anyone direct me to a good url to find one I can purchase. I'm interested in the software (compiler), etc. too. regards...
  38. R

    My LED: Connecting Diodes for Voltage Drop

    Hi, this is my diode: http://img201.imageshack.us/img201/2862/untitledmq1.png Ok, I know Vcathode < Vanode in order for the LED to light up through the current sent through it. Now, my question is, if the three Diodes are connected to 0v, Vanode > Vcathode, therefore the LED will light...
  39. F

    LED Light Array: Why Several Small Ones vs One Large?

    There's a lot of products with LED's these days. However I was wondering why a light made with LED's is done with an array on LEDs instead one large one. Can we not make a large one? Is it possible to make a large LED but it's actually more efficient to have several smaller ones? Any...
  40. N

    LED Lights for Desk: College Student's Guide to Eye Strain Relief

    Hello. Does anyone here use and LED light for their desk? I am a college student and spend a lot of time at my desk reading. I get pretty bad eye strain from reading so much. I am thinking about getting one of these LED lamps. Also, does anyone use any other type of lamp that is better...
  41. ranger

    LED Dimmer Circuit: Questions & Answers

    I was given this circuit and it was supposed to be an LED dimmer circuit that changes its brightness (gradually) when the switch is closed/open. I was told that the darlington pair was supposed to "smooth-out" the changing brightness of the LEDs. But here are my questions about the circuit...
  42. M

    How Do You Design a 4-Way LED Traffic Signal Circuit?

    Hello Genius guys, I am beginner in the field of electronics engineering.Well i am planning to make LED TRAFFIC SIGNAL /i know the wroking of 555 timer ic iknow the working of Multiplexer,Demultiplexer,encoder ,decoder. well can u tell me the circuit diagram of LED TRAFFIC signal 4 way...
  43. P

    The Power of a Single Nail: How it Led to the Loss of a Kingdom

    For want of a nail, the Kingdom was lost!
  44. O

    Revamping My Scooter with 12V LED Neon Sticks & Axle Generator

    I have a scooter, which looks like this one http://img47.imageshack.us/my.php?image=gsra3eng9zq.jpg and i have two 7.2 volt battery packs to run two 12 volt led neon sticks that would sit underneath the deck and light up and look cool :rolleyes: . Well this works, but i think the voltage...
  45. E

    What happens when an LED is connected to a pull-up resistor circuit/switch?

    I am getting ready for my lab tomorrow and one of the questions is this: ok, here's what I think: since current flows from anode to cathode and in first case LED's anode is connected to the pull-up resistor, so there's current through it and it's going to light. In second case, wouldn't it...
  46. K

    Creating Audio-Controlled LED Circuit

    I have held the dream for a long time of LEDs being controlled by an audio signal. You know, when the music gets louder, the LED gets brighter. Not just 'fully on' or 'fully off', but different levels of brightness. However, I don't know how to build this circuit. I think the audio signal...
  47. A

    LED Voltage Drop Fluctuation: Investigating the Cause

    hi i have fixed a simple circuit for lighting up a led.i have included a potentiometer. as the led is white i know that the voltage drop of the led is around 4v.when the potentiometer is at min resistance the voltege drop is actuallu around 3.8v.the problem is that when i turn the potentiometer...
  48. A

    Microphone - transistor switching on a led

    hi i want to use a microphone connected to the base of a transistor.yhe transistor should work as a switch . it should turn on with a sound to the micro phone. does anyone know what voltage the mic can produce?what kind of microphone do i need and what kind of transistor?the circuit is designed...
  49. K

    Can an AC signal light an LED?

    I am wondering this because my car has very nice looking speakers when viewed in the light, however in the car they don't get much light and you hardly even notice. LEDs are cheap lights...so I was wondering if there is any way I can use these, maybe even run them off the sound signal itself...
  50. M

    Display a number, on a single 7 segment LED display

    Can someone please help with the following question. Thanks Develop a program for the Motorola MC68HC11 using the THRSim11 simulator software. The program is to display a number 10 digits long, one digit at a time, on a single 7 segment LED display. Each digit will be ON for 1 second and OFF...
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