Serial.begin(9600) // initialize serial communications at 9600 bps That way, you can have a balance between the brightness of the internal LEDs. But if you have access to the datasheet of the RGB LED that you're using, check the forward voltages of internal LEDs and from that, you can calculate the right resistance of the resistors that you're going to use.

Note: In this example, we just used the same resistance value for the RGB LED series resistors. The cathode pin of the RGB LED is connected to the GND pin of the Arduino Uno. The D10 pin controls the intensity of the green LED and D11 controls the intensity of the blue LED. As you can see in the image above, the D9 pin controls the intensity of the red LED of the RGB LED. The ADC of the Arduino Uno reads the analog voltage across the wiper terminal of the potentiometers/trimmers and based on that voltage, the Arduino Uno adjusts the duty cycle of the PWM signals generated at the PWM pins D9, D10, and D11.

Basically, what happens here is that we have 3 potentiometers/trimmers connected to the A0, A1, and A2 ADC channels of the Arduino Uno.

They're all connected through the jumper wires that we have. We have here a common cathode RGB LED, an Arduino Uno board, 3 potentiometers/trimmers, and 3 resistors.

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