Introduction: The LED: an In-Depth Guide
Last Edited Dec 9 2011
Thanks for all the feedback everybody :D
Sure, we all know a little about this little light, but what is it? What makes it tick? Why are they so efficient? Just what exactly is going on in those little things? These questions, and many more, are about to be answered.
You're free to skip ahead as you feel necessary, but whether you're an electronics newbie, a regular LEDer, or an experienced engineer, chances are you're probably going to learn something new in every step. This guide is a massive collaboration of everything I have learned over the years of using these (Okay, a little over ~2 years, but, hey, I obsess) and as it is an Instructable, I am always ready to listen and improve from ("constructive") criticism. So let's get to it!
Step 1: What Are They?
LEDs, or Light Emitting Diodes, are an electronic lighting device. They are sweeping the world as a cheap, efficient, and overall cool new way of lighting. They're used in just about everything nowadays, and are on the verge of completely replacing regular lightbulbs. LEDs are fascinating little devices that anyone, age 6 to 60, can learn to use.
Step 3: What in the Heck Is in There?
So what's inside an LED, you say? Well, there's lots of things that come together. To put it simply:
*Epoxy Resin - The basic (usually transparent) shell of the LED.
*Metal - Do I need to explain? The shiny, conductive parts.
*Emitting material- A special 'dope' (mixture) of Silicon - an element very, VERY common in nature, not so much in pure amounts, however, as it is extracted by sand - and carbon, also very rich in nature. Different mixtures of silicon and other chemical elements (Gallium, Germanium, Indium, etc.) form the different colors that the diodes emit, sometimes being red, green, blue, Infrared, or Ultraviolet.
The metal is formed into 2 different parts. Both have long, skinny legs. In the inside of the LED at the end of one of the metal prongs is basically a small, flattened metal cup. This is where the silicon-dope mixture sits.
The doped silicon is the part of the LED that is excited by electricity and releases photons.
The second metal part loosely resembles a golf club and it sits right next to the other metal piece. Its purpose is to hold in place a very thin piece of wire, sometimes known as a "cat's whisker" or somewhat more innacurately a "filament" (This is innacurate because this part does not release light, the silicon does) that extends from the "golf club" part and touches the top of the doped material. It is usually made out of gold. Silicon is what is known as a "semiconductor" and provides the LED with its "Diode" aspect - this means that electrons may freely flow through one way, but not the other. (Think of a water check valve, or those springed road spikes)
These parts are all encased in a hardened plastic resin shell, which may or may not give the emitted light its color (see the Clear vs Fogged note in Step 4).
Step 4: What Kinds Are There?
As I said before, LEDs can come in all sorts of shapes and sizes, but there's more to it than that.
The colors of LEDs can be coated with special materials or replaced with a different compound for different color effects. This can be extended to both ends of the visible color spectrum, from Infrared to Ultraviolet.
You probably already know about the different colors of LEDs...
...but these can be altered in two ways.
*Clear LEDs - You can tell a clear LED pretty obviously - The head is completely transparent. While you can't necessarily see straight through it, it's not going to be altering the LED's color. This is sometimes a good thing, but sometimes rather annoying. Since they are transparent, they are typically brighter, and are not suitable for simple status LEDs (IE Green = On, Blinding Red light = Ow) They are NOT always necessarily white LEDs. Unfogged LEDs can emit most any color, but fogged LEDs are sometimes preferred.
These are the LEDs that you can tell what color they are right away. They are "fogged" in the sense that the plastic resin casing filters the light and is by no means clear, rather a slightly transparent color. While these are ideal for status lights as they are a more definite and solid color, they are not helpful for flashlights or regular lighting as they are somewhat dim due to the "filtered" light.
Step 5: How Can I Use Them?
LEDs are being used for all sorts of things. Mood lighting, car internals, replacement light bulb, game console modifications, etc.
But just how do we use them? Like, how could I hook up a battery to an LED to light it up without frying it (which you will, if you do that)
Well, unless you're using very particular kinds of batteries*, you're always going to need to have a resistor connected to an LED. Resistors protect the LED from drawing too much amperage (a factor of electrical power) and frying. You can determine what resistor your specific LED needs by looking at the package and using an online calculator like this or this or this.
You should get used to wiring more than one LED together and be familiar with soldering. This is probably the best video on how to learn to solder.
Ask me any questions you have, even if you don't, please comment! It helps to know that someone out there is reading...
Step 6: So Who Made Them?
Make Presents - The LED
Let me know if you have any questions!