RGB LED Strip Circuit with Arduino

This Instructable covers the assembly of a circuit capable of PWM-ing ( pulse width modulating ) a high-power RGB LED strip and programming an Arduino to cycle through a range of colors. In this context, high power  is 9-12 volts. I will discuss how to mount a transistor to a heatsink and assemble the circuit. I will not go into soldering as som
RGB LED Strip Circuit with Arduino - schematic

e of the RGB LED strip comes with leads (and there is no shortage of great tutorials out there). Also, I will use the most plain, non-jargony language possible to explain the circuit because I know how frustrating it can be to learn this stuff. 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. In other words, a component cannot draw more than 40mA of current from each channel. 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). 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). 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. If you want to cut the strip at any point, just be sure to leave connection points on each halve. To understand how the RGB LED strip can be powered with 9-12V, you need to know the difference between circuits in series vs. parallel (this page has a simple explanation with great illustrations, and there is a popular Instructable that covers wiring LEDs...

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