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6/30/2015 LightemittingDiodes(LEDs)learn.sparkfun.com

https://learn.sparkfun.com/tutorials/lightemittingdiodesleds?_ga=1.43468261.1900427809.1434378181 1/13

LightemittingDiodes(LEDs)

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CONTRIBUTORS: NPOOLE

FAVORITE 3

TheBasics

LEDsareallaroundus:Inourphones,ourcarsandevenourhomes.Anytimesomethingelectronic

lightsup,there’sagoodchancethatanLEDisbehindit.Theycomeinahugevarietyofsizes,

shapes,andcolors,butnomatterwhattheylookliketheyhaveonethingincommon:they’rethe

baconofelectronics.They’rewidelypurportedtomakeanyprojectbetterandthey’reoftenaddedto

unlikelythings(toeveryone’sdelight).

Unlikebacon,however,they’renogoodonceyou’vecookedthem.Thisguidewillhelpyouavoidany

accidentalLEDbarbecues!Firstthingsfirst,though.WhatexactlyisthisLEDthingeveryone’stalking

about?

LEDs(that’s“elleedees”)areaparticulartypeofdiodethatconvertelectricalenergyintolight.In

fact,LEDstandsfor“LightEmittingDiode.”(Itdoeswhatitsaysonthetin!)Andthisisreflectedinthe

similaritybetweenthediodeandLEDschematicsymbols:

Inshort,LEDsareliketinylightbulbs.However,LEDsrequirealotlesspowertolightupby

comparison.They’realsomoreenergyefficient,sotheydon’ttendtogethotlikeconventional

lightbulbsdo(unlessyou’rereallypumpingpowerintothem).Thismakesthemidealformobile

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Summary of content (13 pages)

PAGE 1
6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com   Lightemitting Diodes (LEDs) CONTRIBUTORS:  FAVORITE NPOOLE Your A Log In Regist 3 The Basics LEDs are all around us: In our phones, our cars and even our homes. Any time something electronic lights up, there’s a good chance that an LED is behind it. They come in a huge variety of sizes, shapes, and colors, but no matter what they look like they have one thing in common: they’re the bacon of electronics.
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6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com devices and other lowpower applications. Don’t count them out of the highpower game, though. Highintensity LEDs have found their way into accent lighting, spotlights and even automotive headlights! Are you getting the craving yet? The craving to put LEDs on everything? Good, stick with us and we’ll show you how! Suggested Reading Here are some other topics that will be discussed in this tutorial.
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6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com The positive side of the LED is called the “anode” and is marked by having a longer “lead,” or leg. The other, negative side of the LED is called the “cathode.” Current flows from the anode to the cathode and never the opposite direction. A reversed LED can keep an entire circuit from operating properly by blocking current flow. So don’t freak out if adding an LED breaks your circuit. Try flipping it around.
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6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com It’s also not a math tutorial, so we’ll give you a few rules of thumb for getting LEDs up and running. As you’ve probably put together from the info in the last section, you’ll need a battery, a resistor and an LED. We’re using a battery as our power source, because they’re easy to find and they can’t supply a dangerous amount of current.
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6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com Another way to light up an LED is to just connect it to a coin cell battery! Since the coin cell can’t source enough current to damage the LED, you can connect them directly together! Just push a CR2032 coin cell between the leads of the LED. The long leg of the LED should be touching the side of the battery marked with a “+”. Now you can wrap some tape around the whole thing, add a magnet, and stick it to stuff! Yay for throwies! https://learn.
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/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com Of course, if you’re not getting great results with the trial and error approach, you can always get out your calculator and math it up. Don’t worry, it’s not hard to calculate the best resistor value for your circuit. But before you can figure out the optimal resistor value, you’ll need to find the optimal current for your LED.
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6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com as long as you keep the LED within its suggested voltage and current ratings. LED Voltage Let’s see what other kinds of tables they’ve put in here… Ah! This is a useful little table! The first row tells us what the forward voltage drop across the LED will be. Forward voltage is a term that will come up a lot when working with LEDs. This number will help you decide how much voltage your circuit will need to supply to the LED.
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6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com intensity. This LED has a pretty tight viewing angle. You can see that looking straight down at the LED is when it’s at its brightest, because at 0 degrees the blue lines intersect with the outermost circle. To get the 50% viewing angle, the angle at which the light is half as intense, follow the 50% circle around the graph until it intersects the blue line, then follow the nearest spoke out to read the angle.
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6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com RGB (RedGreenBlue) LEDs are actually three LEDs in one! But that doesn’t mean it can only make three colors. Because red, green, and blue are the additive primary colors, you can control the intensity of each to create every color of the rainbow. Most RGB LEDs have four pins: one for each color and a common pin. On some, the common pin is the anode, and on others, it’s the cathode. Some LEDs are smarter than others.
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6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com HighPower LEDs, from manufacturers like Luxeon and CREE, are crazy bright. Generally, an LED is considered HighPower if it can dissipate 1 Watt or more of power. These are the fancy LEDs that you find in really nice flashlights. Arrays of them can even be built for spotlights and automobile headlights. Because there’s so much power being pumped through the LED, these often require heatsinks.
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6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com other, releasing energy in the process. In most diodes that energy leaves as heat, but in LEDs that energy is dissipated as light! The wavelength of light, and therefore the color, depends on the type of semiconductor material used to make the diode. That’s because the energy band structure of semiconductors differs between materials, so photons are emitted with differing frequencies.
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6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com Forward Voltage Drop Oh, I also promised that we’d talk about the concept of Forward Voltage Drop. Remember when we were looking at the datasheet and I mentioned that the Forward Voltage of all of your LEDs added together can’t exceed your system voltage? This is because every component in your circuit has to share the voltage, and the amount of voltage that every part uses together will always equal the amount that’s available.
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6/30/2015 Lightemitting Diodes (LEDs) learn.sparkfun.com Yeah… it’s not spectacular. https://learn.sparkfun.com/tutorials/lightemittingdiodesleds?_ga=1.43468261.1900427809.