![]() ![]() Perhaps the greatest take-away is the power limitation of the Arduino. One more thing, these strips are "common anode," meaning the LEDs share a positive terminal ( read about anode vs. Not all RGB LED strip is powered in the 9-12V range, such as Adafruit's digitally addressable RGB LED strip). Be sure to look at your product's datasheet to prevent frying your components. ![]() For example, since an average RGB LED requires 3.3 V and 60mA (at full brightness each color channel draws 20mA, so R-G-B all on at same time is 20 x 3 = 60mA), each strip of 3 RGB LEDs will require approximately 9.9V ( the strip I'm using from Jameco can be powered between 9-12V. Basically, when active components are connected in series, their supply voltages are added together. parallel (this page has a simple explanation with great illustrations, and there is a popular Instructable that covers wiring LEDs in series & parallel). To understand how the RGB LED strip can be powered with 9-12V, you need to know the difference between circuits in series vs. If you want to cut the strip at any point, just be sure to leave connection points on each halve. Without getting too technical, its worth knowing that individual strips are made up of 3 LEDs in series which can be cut with clippers at any junction. To accommodate a load that requires more current than 40mA at 5V, we will use our microcontroller to control a transistor, which will provide a component with power from an external source (the battery). To refer to the water analogy of electronics, the "pump pressure" is 5V, and the amount of water is the number of electrons (measured in Amps, or in our case, a much smaller amount - milliamps, mA). ![]() ![]() In other words, a component cannot draw more than 40mA of current from each channel. If you are new to Arduino and are wondering why more than a few LEDs or other components like motors won't activate when functions are called in the code, its because each output has a current limit of 40mA. Adafruit produces one variety called NeoPixels and they have an excellent guide. individually controllable LEDs), so I added an additional section for these as well (circuit and code). Update 2015: A lot of people seem to be interested in digitally-addressable LEDs (opposed to LEDs in "series", in other words the ones that blink together vs. You will need: - A Microcontroller - Breadboard or PCB - RGB LED strip - Battery (9-12v) - 3 NPN transistors (I'm using TIP 120s) - LM7805 Voltage regulator (optional, but recommended) - (4) 4-40 screws (length, up to you) - (4) 4-40 nuts - (4) nylon washers - 22g hookup wire I will discuss how to mount a transistor to a heatsink & assemble the circuit but won't get into soldering as some RGB LED strips come with leads (and there is no shortage of great tutorials out there). * Adafruit Arduino - Lesson 3.This Instructable covers the assembly of a circuit capable of PWM-ing ( pulse width modulating) a 9-12v RGB LED strip and programming an Arduino to cycle through a range of colors. The following sketch code changes the color of the LED, running through a series of colors. Here is a photograph of the final breadboard arrangement with the Arduino Leo: We do the same thing here, except now, instead of a single wire connecting to a single resistor ahead of a single LED, we have three wires connecting to three resistors ahead of three legs of our single RGB LED. With our Hello World Arduino Micro project we already encountered resistors ahead of an LED. The following is a diagram of the breadboard layout for our simple Hello World program. This is a simple circuit to turn on the LED and cycle through different colors. For example, to make purple, you'd turn on the red and blue LEDs and turn off the green LED. Like a pixel on a computer screen, you can control the output of all three lights to create different colors. The RGB LED has three different colors of LED inside of it. ![]()
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