RGB LED
A common-cathode RGB LED in one 5 mm package: four legs, three separate LED dice under one lens.
The long leg is the shared cathode; the other three are the anodes of a red, a green and a blue LED. There is no chip and no protocol. It is three LEDs that happen to share a leg, and every one of them still wants its own resistor.
Pins
| Pin | What it does |
|---|---|
R |
Red anode (or cathode, on a common-anode part). |
G |
Green. |
B |
Blue. |
C |
The shared leg. |
Properties
common: cathode (the usual wiring, anodes driven high) or anode (the common leg
to the rail, anodes pulled low).
What the model gets right
The three dice really are three separate diodes, each conducting on its own between its anode and the shared node, so driving all three adds their currents at the common leg exactly as it does on the bench, and each die has its own forward drop rather than one shared number. That is what makes a single resistor in the shared leg give each color a different current depending on which others are lit. The probe reports the perceived color using the same 8 ms brightness averaging the LED uses, so a PWM-mixed color reads as the color your eye would actually see.
What it does not model
No dice-to-dice spread. The three drops come from the catalog's shared per-color table, which since September 17, 2026 has the red die at 1.8 V and the green and blue InGaN ones at 3.0, so the spread is the real one a wiring diagram shows three resistors for. Every RGB LED on the canvas has exactly those three dice, where a real bag of them varies by a couple of tenths of a volt a die.
The effect is the right size now: on equal 220 ohm resistors from a 5 V rail the red die runs at 14.9 mA and the green and blue ones at 9.8, which is the pink white the diagram warns about.
Each die is the same Shockley diode the plain LED is, with the same caveats: one curve per color, no dice-to-dice variation, no color binning, no junction capacitance and no temperature.
Common mistakes
Using one resistor for all three colors instead of three. The classic wiring diagram exists for a reason: without three separate resistors, mixing colors shifts hue as one channel's brightness changes.
See it in action
Keypad lock lights an RGB LED to show locked, unlocking or open. Open it at /templates.