6. RGB LED

This lesson uses: Arduino UNO R3 board, TinkerBlock TK02 RGB LED module, jumper wires (or breadboard). Control three RGB LED channels; learn multi-channel digital output and #define. Outcome: red on 1 s → green on 1 s → blue on 1 s → all off 1 s, repeat (optional: serial prints current color).

1. Wiring

Connect TK02 RGB LED to Arduino (three colors to D3, D5, D6; in code use 3, 5, 6 for these pins):

• GND → Arduino GND
• RED → Arduino D3
• GREEN → Arduino D5
• BLUE → Arduino D6
• NC — leave unconnected

2. New sketch

1. Arduino IDE: File → New (or Ctrl/Cmd + N) to create a blank sketch
2. Confirm board and port are selected (same as Lesson 01)
3. Type the code below into the default setup() and loop() yourself

3. Program structure

Same as last lesson: two fixed blocks setup() and loop().

• setup(): Tell the board “pins 3, 5, 6 are for the RGB LED”; start serial (optional, to print state); runs once.
• loop(): Keep repeating “red on → green on → blue on → all off → repeat”.

Type the code below and the LED will go red, then green, then blue, then off, in a loop.

4. Code to write

Type the code below line by line into setup() and loop() (do not copy-paste; typing it yourself helps you remember):

// RGB LED: red(D3), green(D5), blue(D6), one color at a time then all off
#define RED_PIN 3
#define GREEN_PIN 5
#define BLUE_PIN 6

void setup() {
  pinMode(RED_PIN, OUTPUT);     // red / green / blue all outputs
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);
  Serial.begin(9600);
  Serial.println("RGB LED started");
}

void loop() {
  digitalWrite(RED_PIN, HIGH);   // red only
  digitalWrite(GREEN_PIN, LOW);
  digitalWrite(BLUE_PIN, LOW);
  Serial.println("Red");
  delay(1000);
  digitalWrite(RED_PIN, LOW);
  digitalWrite(GREEN_PIN, HIGH);  // green only
  digitalWrite(BLUE_PIN, LOW);
  Serial.println("Green");
  delay(1000);
  digitalWrite(RED_PIN, LOW);
  digitalWrite(GREEN_PIN, LOW);
  digitalWrite(BLUE_PIN, HIGH);  // blue only
  Serial.println("Blue");
  delay(1000);
  digitalWrite(RED_PIN, LOW);     // all off
  digitalWrite(GREEN_PIN, LOW);
  digitalWrite(BLUE_PIN, LOW);
  Serial.println("Off");
  delay(1000);
}

Program notes

Overall idea: Three pins for three LED channels; only one HIGH at a time, others LOW, then delay(1000); cycle red → green → blue → all off. Same idea as the traffic light; use #define for the three pins so the code is easy to read and change.

5. Hands-on

1. After entering the code, click Verify (✓) to compile
2. Click Upload (→) to upload to the board
3. Watch TK02 RGB LED: red 1 s → green 1 s → blue 1 s → all off 1 s, then repeat
4. (Optional) Open serial monitor (Tools → Serial Monitor, 9600 baud) and watch the printed state
5. Try it yourself: turn on two colors at once (e.g. digitalWrite(RED_PIN, HIGH) and digitalWrite(GREEN_PIN, HIGH)) and see what mixed color you get

Expected result:

Proceed to Lesson 07.

6. Common issues

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