A brief introduction to the ins and outs of LEDs.

Everyone loves things that blink, flash or light up, and LEDs are a quick and simple way to make that happen. From a simple "power on" indicator to fully animated billboards, the applications for LEDs are seemingly endless. They're also the ideal starting point for physical computing -- a basic blink sketch functions serves the same purpose as "Hello World." If you're just getting into electronics or want to up your LED game, we have some great LED resources, like our Guide to Light-Emitting Diodes, tons of project and design ideas for LEDs, and the video below.

Whether you're looking to beautify your home this winter with some simple luminaries, or you want to make a full album art display to enhance the visuals of your party playlist, LEDs will help you light up your life!

If you don't want to do all of the math to figure out what resistors your circuit needs, (but seriously, you should also learn to do all of the math,) there's a really handy website I've found that will allow you to input your source voltage, LED forward voltage, LED forward current, and the number of LEDs you're using. It will then return not only the resistor values it recommends, but it will even give you a wiring diagram, schematic, or ASCII representation of your desired circuit. You can find that site here http://led.linear1.org/led.wiz.

## Interested in learning more about LEDs?

See our LED page for everything you need to know to start using these components in your project.

• Member #134773 / about 5 years ago / 1

Rob,

Just a reminder: At about 13 minutes, you promised a "link below"... I don't see it...

BTW, you're making me feel old... when I first got into electronics, LEDs were one of those things that were "laboratory oddities" you'd read about occasionally in electronics magazines. You'd either use an incandescant bulb, or a neon bulb (such as an NE-2). I recall one of my first projects where I put an NE-2 in as a power-on indicator. First time I turned it on, I got this bright flash, and the NE-2's leads had vaporized! Investigating further, I discovered the need for a series ("ballast") resistor.

• ROB-24601 / about 5 years ago * / 1

Thanks for catching that! We had it in the YouTube description, but it slipped my mind here. If you refresh the page, you should see it now. And for the record, I too have blown through my fair share of neons and incandescents.

• Member #134773 / about 5 years ago / 1

I don't have time at the moment to track it down, and don't have it in my current cell phone, but I recall having downloaded an App on an iPod, so likely there are ones for smart phones.

In general, the vast majority of LEDs (especially those likely to be encountered by hobbyists) can handle 20mA, and will work nicely at 10 to 15 mA. If you're supply votage is 5V, a resistor of 330 ohms is usually good, and 220 ohms is generally safe. Some of the colors, such as blue, purple, or UV may have trouble lighting up at all on 3.3V micros, though there are more advanced ways of getting around this.

BTW, one of the "tricks" (though I haven't personally used it extemsively) of powering an LED directly from a coin cell (without a resistor) works is that the internal resistance of the coin cell acts as a "limiting resistor".

• jma89 / about 5 years ago / 1

The ElectroDroid app on Android has a lot of calculators, LED resistor values being one of them. (Can't speak to the equivalent for iOS devices though.)