PAGE 056 OF 150 · WIRING LEDS
Wiring an RGB LED
Three chips share one package and one common lead.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
Pins
A typical 5 mm RGB LED has four legs. The longest leg is the common one, and the other three are red, green and blue.
Resistors
Each colour needs its own resistor, because forward voltages differ. On 5 V at 15 mA: red (Vf about 2 V) needs 200 ohms, so 220 ohms. Green and blue (Vf about 3.2 V) need 120 ohms, so 100 to 150 ohms.
Mixing
Using PWM on each colour gives millions of mixes. Equal red, green and blue approximates white, although the balance usually needs adjusting by eye.
REMEMBER
In series the same current flows through every LED.Try it yourself
Sketch the circuit on paper first, calculate the values, then build it on a solderless breadboard using a low-voltage supply. Measure with a multimeter before you make anything permanent.
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