IR sensor for obstacle detection in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this IR sensor reading code?

Consider this Arduino code snippet that reads an IR sensor value and prints if an obstacle is detected.

const int irSensorPin = A0;
int sensorValue = 0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  sensorValue = analogRead(irSensorPin);
  if (sensorValue > 500) {
    Serial.println("Obstacle detected");
  } else {
    Serial.println("No obstacle");
  }
  delay(1000);
}

Assuming the sensor reads 600, what will be printed?

Arduino

const int irSensorPin = A0;
int sensorValue = 600;

void setup() {
  Serial.begin(9600);
}

void loop() {
  // sensorValue = analogRead(irSensorPin); // Simulated as 600
  if (sensorValue > 500) {
    Serial.println("Obstacle detected");
  } else {
    Serial.println("No obstacle");
  }
  delay(1000);
}

A Error: sensorValue undefined

B No obstacle

C 600

D Obstacle detected

💡 Hint

Check the condition comparing sensorValue to 500.

The code prints "Obstacle detected" because the sensor value 600 is greater than 500.

🧠 Conceptual

intermediate

Which component is essential for IR obstacle detection?

Which of the following components is essential to detect obstacles using an IR sensor on Arduino?

A Ultrasonic transmitter

B Infrared LED and photodiode

C Temperature sensor

D Light bulb

💡 Hint

Think about what emits and detects infrared light.

An IR sensor uses an infrared LED to emit light and a photodiode to detect reflected IR light from obstacles.

🔧 Debug

advanced

Why does this IR sensor code not detect obstacles correctly?

Look at this Arduino code snippet:

const int irPin = A0;
int val = 0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  val = analogRead(irPin);
  if (val = 700) {
    Serial.println("Obstacle detected");
  } else {
    Serial.println("No obstacle");
  }
  delay(500);
}

Why does it always print "Obstacle detected" regardless of sensor value?

Arduino

const int irPin = A0;
int val = 0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  val = analogRead(irPin);
  if (val = 700) {
    Serial.println("Obstacle detected");
  } else {
    Serial.println("No obstacle");
  }
  delay(500);
}

A The condition uses assignment (=) instead of comparison (==)

B The sensor pin is not initialized

C Serial.begin is missing

D Delay is too short

💡 Hint

Check the if statement condition carefully.

The if condition uses = which assigns 700 to val and always evaluates true, so it always prints "Obstacle detected".

📝 Syntax

advanced

Which option fixes the syntax error in this IR sensor code?

Find the option that fixes the syntax error in this Arduino code:

void loop() {
  int sensorVal = analogRead(A0)
  if sensorVal > 400 {
    Serial.println("Obstacle");
  }
}

A Change analogRead to digitalRead

B Remove the if statement entirely

C Add semicolon after analogRead line and parentheses around if condition

D Add curly braces after analogRead

💡 Hint

Check missing punctuation and if statement syntax.

In Arduino C++, statements need semicolons and if conditions require parentheses.

🚀 Application

expert

How many times will "Obstacle detected" print in this loop?

Given this Arduino code snippet:

const int irPin = A0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  for (int i = 0; i < 5; i++) {
    int val = analogRead(irPin);
    if (val > 600) {
      Serial.println("Obstacle detected");
    }
  }
  delay(1000);
}

If the sensor reads 650 every time, how many times will "Obstacle detected" print each loop() call?

A 5 times

B 1 time

C 0 times

D Infinite times

💡 Hint

Look at the for loop and condition inside it.

The for loop runs 5 times, and each time the sensor value is 650 > 600, so it prints 5 times.