Leds Definition and 103 Threads

Hello, I was wondering if anyone know the physical explanation about the following: What happens if I combine two Identical LEDs with the exact same spectral profile (eg 350-450nm with 400nm center wavelength and peak). Assuming the total power of each LED in watts is 300mW. Will...

Hi I am making a project in my spare time and i am getting quite confused with the whole situation. I have 100 LED's that need to be wired up, my first question is what is best to wire them up in, series or parallel? My power source is a 9V alkaline battery and i need to know if a...

Why do LEDs and other light emitting solid state devices have a definite lifespan?

Homework Statement I am trying to prove Planck's constant using LEDs. So far I have measured several LED's wavelengths using a spectrometer and from this their frequency. This will be f in the equation h = E/f. For E I put the LEDs in a forward biased circuit and am trying to use the...

I am building a moving target system for a shooting range. It will have a 40 foot target moving perpendicular to the shooter. I have not had any problem with fabricating the target system, but I want to go above what the customer requires. Hopefully this lead to more work for myself in the...

Why are blue leds so much more expensive than any other colour leds? I could buy a pack of 100 red leds for about $10, and 1 blue led for $4, in Sydney Australia. Does it have anything to do with the frequency of blue light being higher than green, red and yellow?

Well I don't know if this is the right place to do this question. I want to do a project of my class of electronics, and my circuit must contain at lest one intagreated circuit, can somebody give an easy one? It must contain just a integrated circuit and also something with LEDs. I am just a...

Hiya, A co-worker and I were a little bored at work the last week and stumbled our way into playing around with basic circuits. Long story short we have made several simple series and parallel circuit diagrams and we practice working out the math and voltage drops across resistors and what...

So I was wondering how to create a sound activated LED circuit for each of my speakers. I want the red LEDs to light up when the subwoofer is activated and the blue LEDs to light up when the left and right floor speakers are activated. I had a thought about wiring the LEDs parellel to in input...

I have a string of leds hooked up together with the correct resistors in parallel, going out to a TIP31 transistor which then goes to the power cord and to a 3mm jack. This 3mm jack goes into my computer and my leds "dance" to the music, I assume is the change in voltage. Anyways, I have...

I'm a grade 9 student working on s a space design contest. For my project I'm using leds to grow indoor plants. i read that the most efficient leds for growing plant is 660, 615 and 461 nm. does anybody know the luminous efficacy of efficient leds of these types. any suggestions would be helpful...

I have a project in mind that I need help with IR LEDs. I'm not an electricity expert; actually, I have almost no experience in electronics. I had an idea for a project and now I'm just trying to make it work. I will need to power a number of IR LEDs at one time for a continuous period. Is...

Hello everybody, I tried to make a special LED I <3 you gift for my girlfriend and it seems that I failed to take into account the battery discharge curve. I was using 50 red LEDs that I originally measured with my voltmeters LED function at 1.7v. With measuring LED voltage, is it better...

OK, here's what I'm doing: I currently have a single 20 watt halogen puck: [PLAIN]http://www.lightingfx.com/media/images/product_category/ro29.jpg powered through a rectifier from AC. The reason I've done this is because I need the interrupt the AC with a light timer switch. I want...

Okay, this is obscenely easy and that's why I'm confused on it. http://teachwithtech.com/Full-Product-Listing/Vishay-TSAL6400-10-Pack-p21.html What I'm trying to do is power two of those LEDs off of a single triple A battery, if at all possible. I don't know what the specifications mean. I...

Would a gallium arsenide photodiode be sensitive to light from a gallium phopsphide LED?

Hi guys, first post here but I have been looking around a while and this forum has proved to be pretty helpful. I have a question about LEDs. I just did a lab in school where I cooled LEDs by placing them close to liquid nitrogen and also heated them close to hot water and measured their voltage...

I know there are already a number of posts in this general subject area, but they all seem to involve circuits with one or more identical LEDs. I'm trying to come up with circuits containing red (approx 2.5 Vf) and blue (approx 3 Vf) LEDs that will run off a 2AA (3V) battery harness. I'm...

I'm going to go under the assumption that whatever I say is right, even though I know it's probably wrong (it saves me phrasing the entire thing as dozens of questions that way), so... correct me where necessary: If I have a +X volt battery and I connect it up to a circuit with an LED in it...

im trying to wire 100 leds into my playstation using my ps3's 120vac power supply I am new to this so I am not quite sure how to do it but i found a night light wiring diagram and was wondering what i had to do to modify it to fit my needs i attached it to this post i appreciate any help thanks

I'm wiring together 25 rgb leds, each take 3V and I was wondering what would be the most efficient way to wire up as many as possible off one power source using resistors. Which resistors should I use? Series or Parallel? 9V or 12V battery? This is for a small project I'm working on myself...

As the title may suggest, I am in search of a LED that emits radio waves. Yes, radio. I have seen and heard of the wide spectrum of waves LEDs can produce, ranging from ultraviolet to infrared LEDs, but never of anything beyond that, for say, radio waves. Of course, it may sound as stupid as...

Homework Statement hi I've just been doing labs today on data aquisition looking at current voltage characteristics, one thing that i did was look at the forward(working) voltage for a red, green and white LED. Red = 1.5V Green = 1.8V White = 2.6V when i asked the demonstarter why...

OK...I am a total noob when discussing anything electrical...I am more at home in the mechanical side of life. Sorry...lol What my project is...is I would like to replicate a modulating headlight from a motorcycle by using very strong, bright LEDs. I ride a bike and used to use the halegen bulb...

Why don't silicon diodes emit light? Attempt: No idea. However, I do know that gallium arsenide is used as a semiconductor in LEDs.

I am trying to figure out a better way to power 150 leds that need 3.4v and 20mA with a 12v,1A power supply. Right now the best way I can think of is have 3 leds in series and a 100 ohm resistor at the end(50 times). Is their any better way so I can use less resistors

So what has to be right for a metal to release electrons when shot with a light? if you use more than what's needed will it still work? can this be used to power something? what else should i know about it? I want to buy some 5mm LED bulbs to mess around with. from my understanding you can make...

Behaviour of LEDs in presence of magnetic fields?? How do LEDs behave in presence of magnetic field?? Any good books or papers dealing extensively with this?? thanking in advance..

I'm trying to determine the millicandela rating of an LED from a keychain to find equivalent LEDs of different colours. The keychain LED specs are as follows: Luminous Flux value: 4 lumens (from box) Viewing Angle: 30° (I got this value by comparing to LEDs with marked angles) Wavelength...

I am curios about the production process of LEDs, particularly using the method of growing the crystal using CVD. I am not exactly sure where the best place is to start but here goes my first question. The refraction of SiC is as such that the light gets largely reflected back into the...

How far can you push most LEDs beyond their recommended rating before they burn out? I currently have a 25ma, 34k mcd LED that I am planning on putting 50ma through for 10ms durations for 30ms periods. The LED is inside of a aluminum block to help dissipate heat. Do you think and LED like this...

Hi. I have 2 questions about second-order coherence – g2(t): 1) For collision-broadened light according to the literature g2(t)=1+|g1(t)|^2, where g1(t) is the 1st order coherence. Therefore for very low collision rate g1(t) =1 and thus g2(t)=2. However I would expect collision broadened...

Hi everyone, I was wondering if someone could please explain to me the concept of waveguiding, coupling/coupled, and guiding mode. Here is an application of these terms: The photons emitted in the active region of OLEDs are coupled into three types of modes: direct transmission into...

Hello, I have a high power RGB LED with common anode. I want to have 3 of them in series, and put them on 15V power supply. And I want to switch green color on, and red color as well (something like a normal traffic light) Here is the problem: Given that three LEDs are in series, and are...

Hello, I am working on a sound/light installation at the moment and was hoping that someone on here might be able to help me with a question i have. I would like to use the composite output from a DVD player to control the intensity and hue of LED light (or 3 (RGB) if need be). So...

hi everyone, I am new to this forum, hope I am posting a thread in the right place, if not could any MOD please place my thread correctly... thanx guys i need to know how to connect my resistor to a LED i have 12 white leds 5mm that is 3.6v each @ 30mA im using a 12V power supply for...

I'm currently using this circuit, but without the rectifying portion,a audio source from mp3 player instead of a mic, and a 4V LED instead of a bulb. My power source is 12v. However, the voltage across the LED is only around 1-1.5V. How can i increase the voltage across the LED? Here is what i...

I'm trying to feed a voltage to my superbright leds. I am not sure how many voltages they require to work(6v?) I have a 12V dc supply from my computer's power supply unit, which i connect to the potentialmeter(500K, 1M). I then tap the voltage and pass it directly to my LED. However, when I...

Could someone please differentiate this to me? "Why Conventional square LEDs are less efficient than triangular LEDs. If any of you guys could help me out, or point me in the right direction, it would be a great help! Thank you in advance!

I want to build my own under cabinet LED strips for my kitchen. I am looking at wiring 200 Nichia T1 3/4 LEDs to one AC circuit. But I am having problems finding any directions to build the circuit or driver to power a system like this. If I need to buy a premade step down transformer then I...

My physics/electronics teacher told me some thing really interesting and confusing a wile ago and I have been trying to get my head round it. The forward voltage in a LED (voltage needed to drive the current) is proportional to the band gap energy. However Blue LEDs have a higher forward...

Homework Statement an npn transistor is used to drive a constant current I through three ‘white’ LEDs, connected in series. If the required current value is I = 25 mA, and the current-gain of the transistor is β = 300, find the value of the resistor R, giving your answer to 3 significant...

I'm thinking of making a 200 led grow light using red and blue leds(5v). I have little knowlage on electronics. I was wonder if a computer power supply could be used and what other componets would be needed. I'm trying to get this built by late February to start growing my veggies (new project...

Why is it that LEDs do not sharper spectra? I've been considering this recently, and was wondering if it was due to the uncertainty principle (like homogeneous broadening in a laser) or is it due to a fluctuating band gap? I've searched high and low and can't find any explanation for the...

first of all HELLO evry1,i am new here! I have a motorcycle and I want to do something special to it so I decided on putting some LEDs on. I buyed 20 pre-wired LEDs...

I am trying to control a bunch of LEDs to respond to different audio frequencies. I have a microprocessor with A/D converter and know how to use these, but I have no idea how to go about the rest of it. Thanks in advance!

Hey guys, I have a question regarding connecting up 6 * 3mm/5mm super bright mcd Led's in parallel (since they would all have the same forward voltage when wired this way), using a supply voltage of 3V but not sure whether is should be 2*1.5V AAA or 2 * 1.5V AA batteries. The reason i put...

Newbie wiring 20 red LEDs to a 9v battery in parallel...help pls :) hello, i am completely new to the LED world and electronics world. I am wanting to make a little box with LED lights as an aniversary gift. Basically what I need to know is how to wire 20 red LEDs in parallel so that they...

http://physicsweb.org/articles/news/10/5/10/1 Zz.

http://www.cbc.ca/stories/2002/09/04/video_pill020904 sorry if it's not new news , but i just saw it on tv and thought it was very cool..