The LED: an In-Depth Guide





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 2:

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.

Colored LEDs
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.

*Fogged LEDs
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?

I'm not one who likes to quote large chunks of text, or copy it down from a video, and this video does a great job of showing you and telling you a lot about LEDs. This guy's a little...odd...but it's all good.

Make Presents - The LED

Let me know if you have any questions!



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    23 Discussions

    Great information,

    what would i need to make and how would i make a strobe light bar with 46 LEDS?


    This issue has been addressed, and the article has been revised. The article is also now under the Attribution license.

    devans0 is right, this is put together very well. I'm really just starting out dabbling in programming and creating my own electronics and I found it very helpful. Thanks!

    1 reply

    Thank you so much. Comments like these have really made writing this worth my time, and I'm glad to see I've helped someone who is in my position from a few years back :D

    Hey there! Amazing info, and I have been wanting to learn how to build my own l.e.d fixture for my Salt Water Aquarium! I would LOVE to get any feed back on...Either a great place to purchase L.E.D's for a good price that could be used for this application, or possibly a website ( or if you can help in anyway I would appreciate that to the fullest ) to where you can learn about the different fixtures o build! Thank you again, and God Bless,

    1 reply

    Hi! I couldn't tell you where you could buy LEDs in person, but the place I buy from online is called DealExtreme. They're run out of Hong Kong, but they're trustworthy and they take PayPal. Expect a 2.5 week shipping time, depending on where you live.

    As for fixtures, I've never built my own but I'm sure google would bring up a few results. Try searching "DIY LED fixture", but be aware that you'll have to solder them together. If you want a great video of how to solder properly, search YouTube for"How and why to solder correctly".

    Hope this helps!

    dam good information , well done ,, i am planning on building my led cube soon (any one know where i can buy inexpensive 5mm leds) thx ... keep up the good work.

    1 reply

    I made a simular guide to this.
    Anyway dealextreme has very cheap LEDs.
    about $1.25 for a pack of 10. And they are bright

    This is awesome stuff... Thank you. It will help me to get started on things.

    Enjoyed the read...Have one question, can the power source be AC when using LED's or does it have to be converted to DC...Everything I've read deals with DC...I know there are AC LED applications, for example the pic of the replacement light above, but is it getting converted to DC somewhere in the mix?  Thanks.

    1 reply

    LED's can also be used with AC 220 or 110 volts.
    See my Instructable "LED Chandelier" and "Spiral LED Chandelier" ( with AC Transformers)
    LED's can also run of  AC with capacitors and resistance.

     This is an unusually complete DIY.  I was weak on solder skills and the circuit calculator really sped up my RV light project.  Thanks!

    Thanks for the simple explanation. We see them everywhere, and some burn 24/7. Good insight.

    Hey, uh, Coodude, I was wondering about the "published" status of this 'ible:

    The ible itself says it was published on Aug 7, 2009. Here:

    At the same time your, "you" page doesn't list it under your ibles. Here:

    Is this another glitch in the matrix? I mean another instance of the Instructables software/moderation screwing up again? Just wondering. BTW, I'm not anyone who has the power to fix these things, and I'm not sure who here does.

    When the silicone gets "excited", electrons build up on an energy level of the silicone atoms that cannot sustain a high number of electrons. The electrons then try to drop to a lower energy level in the silicone, but instead drop to an energy level in the "golf club" - usually a metal with a similar energy level layout. In doing so, the electrons give off energy (as light) so they fit into the lower energy level.

    I bought my first one in, oh about 1975 or so... They have recently taken off as a area lighting device, but, they have been used by off grid'ers for years as well.

    2 replies

    In case you didn't notice, this 'ible isn't published yet, but thanks for the info. How did you find this, anyway?

    Didn't do anything special, was just browsing through instructables and it came up with other LED articles.