LED blink pattern in Arduino - Mini Project: Build & Apply

LED Blink Pattern

📖 Scenario: You have a small LED connected to your Arduino board. You want to make it blink in a simple pattern to test your setup.

🎯 Goal: Create a program that makes the LED blink on and off repeatedly with a clear pattern.

📋 What You'll Learn

Use the built-in LED on pin 13

Turn the LED on and off with a delay

Use variables to control the delay time

Print messages to the Serial Monitor when the LED turns on and off

💡 Why This Matters

🌍 Real World

Blinking LEDs are used in many devices to show status, alerts, or activity.

💼 Career

Understanding how to control hardware like LEDs is a basic skill for embedded systems and electronics jobs.

1

Setup LED pin

Create a variable called ledPin and set it to 13. In the setup() function, set the ledPin as an output using pinMode. Also, start the serial communication at 9600 baud using Serial.begin(9600).

Arduino

int ledPin = 13;

void setup() {
  // Set ledPin as output
  // Start serial communication at 9600 baud
  // Your code here
}

void loop() {
  // Your code here
}

Hint

Use pinMode(ledPin, OUTPUT); inside setup() to set the LED pin as output.

Use Serial.begin(9600); to start serial communication.

2

Add delay time variable

Create an integer variable called delayTime and set it to 500. This will control how long the LED stays on or off in milliseconds.

Arduino

int ledPin = 13;
int delayTime = 500;  // Your code here

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // Your code here
}

Hint

Declare int delayTime = 500; outside the functions so it can be used everywhere.

3

Write LED blink logic

In the loop() function, turn the LED on using digitalWrite(ledPin, HIGH), print "LED ON" to the Serial Monitor, then wait for delayTime milliseconds using delay(delayTime). Next, turn the LED off using digitalWrite(ledPin, LOW), print "LED OFF" to the Serial Monitor, and wait again for delayTime milliseconds.

Arduino

int ledPin = 13;
int delayTime = 500;

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // Turn LED on
  // Print "LED ON"
  // Wait delayTime
  // Turn LED off
  // Print "LED OFF"
  // Wait delayTime
  // Your code here
}

Hint

Use digitalWrite to turn the LED on and off.

Use Serial.println to print messages.

Use delay(delayTime) to pause.

4

Display the blink pattern

Upload the program and observe the Serial Monitor. The output should show alternating lines of LED ON and LED OFF every 500 milliseconds.

Arduino

int ledPin = 13;
int delayTime = 500;

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  digitalWrite(ledPin, HIGH);
  Serial.println("LED ON");
  delay(delayTime);
  digitalWrite(ledPin, LOW);
  Serial.println("LED OFF");
  delay(delayTime);
}

// Your code here to display output

Hint

Open the Serial Monitor in the Arduino IDE to see the blinking messages.

Practice

1. What does the delay(1000); command do in an Arduino LED blink program?

easy

A. Pauses the program for 1000 milliseconds (1 second)

B. Turns the LED on for 1000 milliseconds

C. Turns the LED off for 1000 milliseconds

D. Sets the LED brightness to 1000

Solution

1. Step 1: Understand the delay function

   The delay() function pauses the program for the given time in milliseconds.

2. Step 2: Interpret the argument 1000

   1000 milliseconds equals 1 second, so the program waits for 1 second before continuing.

3. Final Answer:

   Pauses the program for 1000 milliseconds (1 second) -> Option A

4. Quick Check:

   delay(1000) = 1 second pause [OK]

Hint: delay(ms) pauses program for ms milliseconds [OK]

Common Mistakes:

• Thinking delay turns LED on or off
• Confusing delay time with brightness
• Assuming delay is in seconds

2. Which of the following is the correct syntax to set pin 13 as an output in Arduino?

easy

A. pinMode(OUTPUT, 13);

B. pinMode(13, OUTPUT);

C. digitalWrite(13, OUTPUT);

D. digitalWrite(OUTPUT, 13);

Solution

1. Step 1: Recall pinMode syntax

   The correct syntax is pinMode(pin, mode); where pin is the pin number and mode is INPUT or OUTPUT.

2. Step 2: Match the correct order

   pinMode(13, OUTPUT); uses pinMode(13, OUTPUT); which matches the correct order and parameters.

3. Final Answer:

   pinMode(13, OUTPUT); -> Option B

4. Quick Check:

   pinMode(pin, OUTPUT) sets pin as output [OK]

Hint: pinMode(pin, OUTPUT) sets pin as output [OK]

Common Mistakes:

• Swapping pin and mode parameters
• Using digitalWrite instead of pinMode to set mode
• Missing semicolon at end

3. What will be the output of this Arduino code snippet?

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(500);
  digitalWrite(13, LOW);
  delay(500);
}

medium

A. LED on pin 13 blinks on and off every 0.5 seconds

B. LED on pin 13 stays on continuously

C. LED on pin 13 stays off continuously

D. LED on pin 13 blinks on and off every 1 second

Solution

1. Step 1: Analyze the delay times

   The LED is turned on, then the program waits 500 ms, then turned off, then waits 500 ms again.

2. Step 2: Calculate total blink cycle

   On time + off time = 500 ms + 500 ms = 1000 ms (1 second) per full blink cycle. Each on or off state lasts 0.5 seconds.

3. Final Answer:

   LED on pin 13 blinks on and off every 1 second -> Option D

4. Quick Check:

   delay(500) means 0.5 second blink intervals [OK]

Hint: Sum delays to find blink cycle time [OK]

Common Mistakes:

• Confusing total blink time with single delay
• Ignoring delay after turning LED off
• Assuming delay is in seconds

4. Identify the error in this Arduino code that tries to blink an LED on pin 13:

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(1000)
  digitalWrite(13, LOW);
  delay(1000);
}

medium

A. Missing semicolon after delay(1000)

B. pinMode should be in loop()

C. digitalWrite needs pinMode first

D. delay cannot be used in loop()

Solution

1. Step 1: Check syntax line by line

   Look at each statement for missing semicolons or syntax errors.

2. Step 2: Find missing semicolon

   The line delay(1000) is missing a semicolon at the end, causing a syntax error.

3. Final Answer:

   Missing semicolon after delay(1000) -> Option A

4. Quick Check:

   Every statement must end with ; [OK]

Hint: Check each line ends with semicolon [OK]

Common Mistakes:

• Putting pinMode inside loop instead of setup
• Thinking delay can't be used in loop
• Ignoring missing semicolon errors

5. You want an LED on pin 13 to blink twice quickly, then pause for 2 seconds, and repeat. Which code snippet achieves this pattern?

hard

A. digitalWrite(13, HIGH); delay(200); digitalWrite(13, LOW); delay(200); delay(2000);

B. for(int i=0; i<2; i++) { digitalWrite(13, HIGH); delay(1000); digitalWrite(13, LOW); delay(1000); } delay(2000);

C. for(int i=0; i<2; i++) { digitalWrite(13, HIGH); delay(200); digitalWrite(13, LOW); delay(200); } delay(2000);

D. digitalWrite(13, HIGH); delay(500); digitalWrite(13, LOW); delay(500); delay(2000);

Solution

1. Step 1: Understand the blink pattern

   The LED should blink twice quickly (short on/off), then pause 2 seconds before repeating.

2. Step 2: Analyze each option's timing

   for(int i=0; i<2; i++) { digitalWrite(13, HIGH); delay(200); digitalWrite(13, LOW); delay(200); } delay(2000); blinks twice with 200 ms on and off delays, then pauses 2000 ms. This matches the pattern.

3. Step 3: Check other options

   digitalWrite(13, HIGH); delay(200); digitalWrite(13, LOW); delay(200); delay(2000); blinks once only. for(int i=0; i<2; i++) { digitalWrite(13, HIGH); delay(1000); digitalWrite(13, LOW); delay(1000); } delay(2000); blinks twice but with 1 second delays (too slow). digitalWrite(13, HIGH); delay(500); digitalWrite(13, LOW); delay(500); delay(2000); blinks once with 500 ms delays.

4. Final Answer:

   for(int i=0; i<2; i++) { digitalWrite(13, HIGH); delay(200); digitalWrite(13, LOW); delay(200); } delay(2000); -> Option C

5. Quick Check:

   Loop twice fast blinks + long pause = for(int i=0; i<2; i++) { digitalWrite(13, HIGH); delay(200); digitalWrite(13, LOW); delay(200); } delay(2000); [OK]

Hint: Use loop for repeated quick blinks, then delay for pause [OK]

Common Mistakes:

• Using delay too long for quick blinks
• Not looping for multiple blinks
• Pausing before blinking instead of after