You've heard about LEDs. Chances are you've already tinkered with them. But there are so much details you probably don't know about. Sadly the resources available are often incomplete or just unpractical. This guide takes you all the way from a beginner level to adept skills!
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This is chapter 1 of a short series. Use the table of contents below to browse the content I've already published.
In this chapter we'll focus on how to choose the right LED for your project. Along the way you'll learn a few nifty things that'll come in handy later on.
Chapters:
LEDs are everywhere, and not without reason. Compared to traditional light sources they are highly efficient, resulting in less power consumption and less heat for the same brightness. They are available in all sizes, whether it be a tiny package suitable for mobile devices or in large clusters to illuminate rooms. Instead of fading on and off like lightbulbs they can be switched instantly, making them suitable for displays and precise brightness control. Powered correctly, they can last for decades without replacing.
All those benefits come at the cost of increased complexity of the circuit. The term "LED" is short for "Light Emitting Diode" and as all semiconductor based components they show highly non-linear characteristics. This means you can not treat an LED like an ordinary lightbulb and connect it straight to a power supply!
The good news: The circuit required is not that complicated either.
The circuit you will build must be tailored to the LED it is supposed to drive, so it is wise to pick first which LED is best suited for your project.
LEDs come in a huge variety of styles. We'll take a look at the most common features:
Mounting Types
There are three common way in which LEDs can be mounted:
THT components might be what you are most familiar with: Their pins go through holes in a PCB and are soldered on the other side.
SMD parts are soldered directly to the surface of a PCB. With this method they can be made much smaller than THT parts and are perfect for tiny projects, such as wearables. On the flipside they are more difficult to solder.
Some LEDs, especially power LEDs are mounted on an aluminum or ceramic substrate to improve the cooling. They are meant to be mounted with either screws or a thermal adhesive.
Optics
The LED chip itself produces a wide beam of light (about 120°). To make it suitable for spotlights a clear dome is placed right above the chip to act as a lens. Some LEDs, so called diffused LEDs, don't have any beam at all, they evenly scatter the light in all directions. This is very useful for indication LEDs as the light is visible from any direction.
Multi-Color/ RGB LEDs
You may have seen LEDs with multiple chips for different colors into one case. With such LEDs you can not only select the color you want, but also mix the light to get any color in between! We'll come back to this in "Chapter 3: Switching & Dimming".
Often it is not possible to have two dedicated pins for each LED chip, in such case either the anodes or cathodes are connected internally to only one common pin.
LED Matrix
Similar to Multi-Color LEDs these contain multiple LEDs in one package, but usually all the same color. They are also available as both, common anode and common cathode configurations. They can be used to display text or numbers and are readable from quite afar. However the high LED count usually requires a micro-controller and multiplexing. In "Chapter 4: Matrix & Multiplexing" we'll dig deeper into this.
7 Segment Display
While numbers can be displayed with a simple LED matrix, a seven segment display provides a much more elegant solution with way less LEDs you need to control. Alphanumeric displays are based on the same idea, but with a total of 14 or 16 segments they can show in addition all uppercase English letters. Electrically this kind of display is identical to the common LED matrix.
Integrated circuit
No matter the light effect you want, with some effort everything is possible. For the most common effects, such as blinking or color cycling, you don't even need to invest that much time. Some LEDs come equipped with a tiny circuit to do just that.
A very special LED is the WS/ WSB, sold as "Neopixel" by Adafruit. The chip inside takes serial data from a micro-controller (such as an arduino) and controls the RGB LED to match that!
No matter which LED you decide to get, check the datasheet briefly, so you don't miss anything important.
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