LED blink pattern in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the LED pin as output in the setup function.

Arduino

void setup() {
  pinMode(13, [1]);
}

void loop() {
  // LED blink code here
}

Drag options to blanks, or click blank then click option'

AINPUT_PULLUP

BINPUT

COUTPUT

DHIGH

Attempts:

3 left

💡 Hint

Common Mistakes

Using INPUT instead of OUTPUT will not allow the LED to turn on.

Using HIGH as a mode is incorrect.

The pinMode function sets the pin mode. To blink an LED, the pin must be set as OUTPUT.

2fill in blank

medium

Complete the code to turn the LED on inside the loop function.

Arduino

void loop() {
  digitalWrite(13, [1]);
  delay(1000);
}

Drag options to blanks, or click blank then click option'

AHIGH

BOUTPUT

CLOW

DINPUT

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOW will turn the LED off instead of on.

Using pin modes like OUTPUT or INPUT in digitalWrite is incorrect.

To turn the LED on, the pin must be set to HIGH using digitalWrite.

3fill in blank

hard

Fix the error in the delay time to make the LED blink every half second.

Arduino

void loop() {
  digitalWrite(13, HIGH);
  delay([1]);
  digitalWrite(13, LOW);
  delay(500);
}

Drag options to blanks, or click blank then click option'

A500

B250

C50

D1000

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1000 will make the LED blink every second, not half second.

Using 250 or 50 will make the blink too fast.

The delay time is in milliseconds. To blink every half second, use 500 ms.

4fill in blank

hard

Fill both blanks to create a blink pattern where the LED is on for 300 ms and off for 700 ms.

Arduino

void loop() {
  digitalWrite(13, [1]);
  delay([2]);
  digitalWrite(13, LOW);
  delay(700);
}

Drag options to blanks, or click blank then click option'

AHIGH

BLOW

C300

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOW to turn the LED on will keep it off.

Using 500 ms delay will not match the required on time.

The LED should be turned on with HIGH and stay on for 300 milliseconds.

5fill in blank

hard

Fill all three blanks to create a pattern where the LED blinks twice quickly (200 ms on, 200 ms off) then stays off for 1000 ms.

Arduino

void loop() {
  digitalWrite(13, [1]);
  delay([2]);
  digitalWrite(13, LOW);
  delay([3]);
  digitalWrite(13, [1]);
  delay([2]);
  digitalWrite(13, LOW);
  delay(1000);
}

Drag options to blanks, or click blank then click option'

AHIGH

B200

DLOW

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOW to turn the LED on will keep it off.

Using wrong delay times will change the blink speed.

The LED is turned on with HIGH for 200 ms, then off for 200 ms, repeated twice, then off for 1000 ms.

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