Arduino Uno R3

Mix color with an RGB LED

Control the red, green, and blue channels independently, then mix repeatable colors with PWM values.

CSTA 2026 mapping candidatesNot reviewed by CSTA

MS-PRO-VD-16ProgrammingMS-PRO-TR-19Programming

Students will

Identify the shared and individual RGB LED leads
Protect each color channel with its own resistor
Use three PWM values to create and document mixed colors

Evidence of success

Each channel lights independently through its own resistor
Three recorded PWM recipes produce distinguishable colors
The student can explain why common-anode hardware requires inverted output values

Hardware

Arduino Uno R3
Starter Kit RGB LED
Three 220 Ω resistors
Breadboard and jumper wires
Transparent color gels for comparison

Prerequisites

Build a protected LED output
Identify PWM-capable pins
Read the exact RGB LED lead arrangement

Before class

Verify the actual RGB LED pin order and whether its common lead is cathode or anode
Prepare a known-good three-resistor circuit
Explain that this sketch assumes a common-cathode LED and must be inverted for common-anode hardware

Reviewed connection map

Three protected color channels

D9 / D10 / D11PWM-capable red, green, and blue outputs

3 × 220 ΩOne resistor for each color channel

RGB LEDVerify channel order and common-lead type

GND or 5VCommon lead depends on the verified LED type

Connect each color lead through its own resistor to the matching program pin.
Connect the common lead only after verifying whether the supplied LED is common-cathode or common-anode.

Build and test

01Identify the RGB LED common lead and the red, green, and blue channel leads
02With power disconnected, connect each color channel through its own 220 Ω resistor to D9, D10, and D11
03Connect the verified common cathode to GND; stop and adapt the circuit and sketch if the actual part is common anode
04Test red, green, and blue independently before mixing them
05Record three PWM recipes and compare the emitted colors with the kit gels

Read before uploading

Annotated Arduino sketch

const int RED_PIN = 9;
const int GREEN_PIN = 10;
const int BLUE_PIN = 11;

void setColor(int red, int green, int blue) {
  analogWrite(RED_PIN, constrain(red, 0, 255));
  analogWrite(GREEN_PIN, constrain(green, 0, 255));
  analogWrite(BLUE_PIN, constrain(blue, 0, 255));
}

void setup() {
  pinMode(RED_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);
}

void loop() {
  setColor(255, 0, 0);
  delay(800);
  setColor(0, 255, 0);
  delay(800);
  setColor(0, 0, 255);
  delay(800);
  setColor(120, 30, 180);
  delay(800);
}

Optional engineering record

Record evidence from this lesson

Choose the prompts that help students explain predictions, evidence, debugging, and transfer. Saving creates a new entry in this browser’s Rudi notebook.

Record your thinking — optional4 prompts

Use these prompts if they help students capture evidence, decisions, or questions. You do not need to complete every prompt or create an entry at every step.

Predict: Before you begin, what do you expect to observe when you identify the shared and individual RGB LED leads?Evidence: What evidence best demonstrates this result: Each channel lights independently through its own resistor?Debug: If you encounter “One color never appears,” what will you check first, and why?Transfer: Where could you reuse the skill from “Mix color with an RGB LED” in another classroom project?

Nothing is saved until you choose this button.

Troubleshooting

One color never appears

Disconnect power and verify that channel's lead, resistor, breadboard row, and matching PWM pin.

Colors are inverted or the LED will not turn fully off

Verify whether the actual LED is common cathode or common anode and adapt both the shared connection and PWM values.

2026 middle school standards

Potential CSTA connections

Not reviewed by CSTA

These are evidence-based crosswalk candidates for curriculum review—not a claim of official alignment.

MS-PRO-VD-16

Use variables of multiple data types to store, access, and manipulate data within a program.

Students manipulate three integer channel values to create and compare color outputs.

Lesson evidence: Three documented PWM recipes

MS-PRO-TR-19

Use systematic strategies to test, refine, and document changes to a computing technology to meet the intended purpose.

Students isolate variables, compare observed behavior with the intended purpose, and document a revision.

Lesson evidence: Independent-channel and mixed-color test

View the official 2026 CSTA standardsStandard text: Computer Science Teachers Association (2026), CC BY-NC-SA 4.0.

Supporting concepts

ohms-law · power-and-signals · sketch-foundations

Sources and review

Arduino Uno R3 documentation Arduino Projects Book · CC BY-NC-SA 3.0 Arduino Fade example

Starting point, not verified curriculum. Review the actual hardware, circuit, code, power requirements, and classroom conditions.

After teaching this lesson