All About LEDs

Choosing Your LED

LEDs come in many different colors, packages, brightnesses and technologies. With so many options, you’ll have many things to consider as you plan your project and choose the best LED for your needs.

Size and Shape

How big do you want your LEDs to be? Are you using them in a breadboard, soldering them by hand, or designing a PCB? Individual through-hole LEDs are great for prototyping and can be incorporated into just about any project. Small, surface-mount SMD LEDs work great if you want to design and populate your own PCB.

Color

Do you want a single, solid color, or is the variable RGB more your speed? You can have colored, diffused, or clear plastic housings. There are even unique options like infared and ultraviolet LEDs for special projects.

Number

How many LEDs do you want? Do you want a single LED as a power indicator light, or are you looking to create a wall-sized display? Single LEDs can be incorporated into just about any project, but strips or panels will be easier to set up for large displays. More LEDs will also require more power to light them all at once.

Brightness and Power

The brighter the LED, the more current it requires. If your power supply (or the space for it) is limited, your LED's brightness will also be limited. High-current LEDs will require specially designed driver boards or MOSFETs for control, in addition to any microcontroller you may use. Another option to take control of the brightness is to use Pulse Width Modulation (PWM), which requires a microcontroller.

Control (Addressable LEDs)

While individual LEDs can be turned on and off with just a switch, addressable LED types such as WS2812 and APA102 let you control many individual LEDs, but will require more complex code than turning on and off a simple LED. The APA102 LEDs are very similar to WS2812s with a few caveats: APA102s can be controlled with a standard SPI interface, and they have an extremely high PWM frequency. We recommend using FastLED (an Arduino library) for controlling your LEDs.

Just a few of the sizes and shapes that LEDs come in.

Choosing Your Controller

The next step after deciding what kind of LEDs you'd like to use is to consider how you want to control them. There are a few options, depending on how complex your arrangement is.

No Controller

You want an LED for a power indicator, a night light or a joule thief. The light comes on and stays on so long as power is connected to it. For this setup, you don’t need any sort of controller other than your power switch.

An example of a simple circuit using a non-addressable LED strip and barrel jack adapter.

Minimal Controller

Want things to blink, but don’t want to write a program? Consider a 555 timer.

Microcontrollers

This category covers a broad range of options. The best choice will depend on what kind of LEDs you are using, the kind of patterns you want and how many LEDs you are trying to control.

Even a minimal microcontroller will be able to control non-adressable LEDs. Turning on one LED per pin is the simplest way, but you will be limited by the number of pins on your microcontroller. If you want to control the brightness of your discrete LED, those pins will also need to be PWM-capable (Pulse-Width Modulation).

Dealing with Addressable LEDs will have many considerations. As mentioned above, using a library such as FastLED makes your coding much easier. When using a library, you'll need to make sure that the microcontroller you want to use is compatible with library you'd like to use.

One of the main considerations when picking a microcontroller for controlling a number of LEDs is how fast they can transmit data. APA102 LEDs, for instance, can transmit data very quickly, so you should use a microcontroller fast enough to take advantage of this. Another thing to consider when you start getting into higher LED counts is the amount of RAM taken up by the LED frame. Each LED takes up 3 bytes of space in RAM, which doesn't sound like a lot, but if you're controlling 5,000 LEDs, you might need something with a bit more RAM than your traditional SparkFun RedBoard Qwiic. The below chart outlines the quantities of LEDs where you may start running into memory issues. Keep in mind that these are very generous estimates and will decrease depending on what other global variables are declared.

Like what you see here? See how it's done with the LuMini Ring Hookup Guide.

As mentioned before, more LEDs or brighter LEDs means more current. To find the total current, check out the LED’s datasheet and find the listing for Forward Current. If you’re using an RGB LED, the current may be listed per color. You’ll need the total current per LED, or total power in watts. Multiply by the total number of LEDs to figure out the total current you’ll need, and multiply that by the voltage to get the total power in watts. Find a power supply to match. Make sure the power supply matches both the watts (or volts) and the amps current. If you choose a power supply that cannot supply the current needed for your LEDs, you may brown out your power supply and get weak or inconsistent results from your LEDs.

In a best-case scenario, you'll have access to a benchtop power supply. It's a good idea to test your installation on a benchtop power supply to truly know how much power you will need before choosing your supply.

If you power LEDs through your microcontroller and try to draw too much current through your microcontroller’s pin, you may damage it. To determine what will be safe for your microcontroller to provide directly, find the maximum current output per pin, usually found in the datasheet or the product’s tutorials. Also consider the total current that the board can provide across all pins, which will be found in the same places. If the total current of the LEDs attached to one pin will draw more current than the maximum current per pin, or if the total current of the LEDs and other devices across all the pins will exceed the total current output for the microcontroller, then a driver board will be a good choice to isolate the LED needs and prevent them from being pulled through the microcontroller. For more advanced users, you can use a transistor as a switch for the LEDs that will be connected directly to the power supply.