IR sensor for obstacle detection in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read the IR sensor value.

Arduino

int sensorValue = analogRead([1]);

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

A13

BA0

C5

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using a digital pin number instead of an analog pin.

Forgetting to use analogRead for analog sensors.

The IR sensor is connected to analog pin A0, so we use analogRead(A0) to get its value.

2fill in blank

medium

Complete the code to set the IR sensor pin as input in setup().

Arduino

pinMode([1], INPUT);

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

AA0

B13

C7

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the wrong pin as input.

Using digital pins instead of the analog pin connected to the sensor.

The IR sensor is connected to analog pin A0, which should be set as input using pinMode(A0, INPUT);.

3fill in blank

hard

Fix the error in the if statement to detect obstacle when sensor value is less than threshold.

Arduino

if (sensorValue [1] threshold) {
  Serial.println("Obstacle detected");
}

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

A<

B==

C>

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using greater than operator which triggers detection incorrectly.

Using equality operator which rarely matches exactly.

When the IR sensor detects an obstacle, the sensor value is usually less than the threshold, so the condition should be sensorValue < threshold.

4fill in blank

hard

Fill both blanks to complete the code that reads sensor and prints "No obstacle" when value is above threshold.

Arduino

sensorValue = analogRead([1]);
if (sensorValue [2] threshold) {
  Serial.println("No obstacle");
}

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

AA0

B<

C>

D13

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong pin number.

Using less than operator which means obstacle detected.

The sensor is read from analog pin A0, and when the value is greater than the threshold, it means no obstacle is detected.

5fill in blank

hard

Fill all three blanks to create a dictionary-like structure that maps sensor states to messages.

Arduino

const char* messages[] = {"[1]", "[2]"};
int sensorValue = analogRead(A0);
Serial.println(sensorValue [3] threshold ? messages[0] : messages[1]);

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

AObstacle detected

BNo obstacle

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the messages order.

Using wrong comparison operator.

The messages array holds the two messages. The condition uses < to check if sensorValue is below threshold, printing "Obstacle detected" if true, otherwise "No obstacle".

Practice

1. What does an IR sensor detect in an obstacle detection system?

easy

A. Visible light intensity

B. Magnetic fields around objects

C. Sound waves bouncing off objects

D. Reflected infrared light from nearby objects

Solution

1. Step 1: Understand IR sensor function

   IR sensors emit infrared light and detect the light reflected back from objects.

2. Step 2: Identify what is detected

   The sensor measures reflected infrared light, not visible light, sound, or magnetic fields.

3. Final Answer:

   Reflected infrared light from nearby objects -> Option D

4. Quick Check:

   IR sensor = reflected infrared light [OK]

Hint: IR sensors detect reflected infrared light, not visible or sound [OK]

Common Mistakes:

• Confusing IR sensor with light or sound sensors
• Thinking it detects visible light
• Assuming it detects magnetic fields

2. Which Arduino code snippet correctly reads an analog IR sensor value from pin A0?

easy

A. int sensorValue = analogRead(A0);

B. int sensorValue = digitalRead(A0);

C. int sensorValue = analogWrite(A0);

D. int sensorValue = digitalWrite(A0);

Solution

1. Step 1: Identify correct function for analog reading

   analogRead(pin) reads analog sensor values from specified pin.

2. Step 2: Check pin and function usage

   Pin A0 is analog input; analogRead(A0) is correct syntax.

3. Final Answer:

   int sensorValue = analogRead(A0); -> Option A

4. Quick Check:

   Use analogRead for analog sensors [OK]

Hint: Use analogRead() for analog sensor pins like A0 [OK]

Common Mistakes:

• Using digitalRead() for analog sensors
• Using analogWrite() which is for output
• Using digitalWrite() which is for digital output

3. What will be printed if the IR sensor value is 350 and the threshold is 300 in this code?

int sensorValue = 350;
int threshold = 300;
if(sensorValue > threshold) {
  Serial.println("No obstacle");
} else {
  Serial.println("Obstacle detected");
}

medium

A. Error

B. No obstacle

C. 350

D. Obstacle detected

Solution

1. Step 1: Compare sensorValue with threshold

   350 is greater than 300, so condition sensorValue > threshold is true.

2. Step 2: Determine printed output

   Since condition is true, code prints "No obstacle".

3. Final Answer:

   No obstacle -> Option B

4. Quick Check:

   350 > 300 = true, prints "No obstacle" [OK]

Hint: Check if sensor value is above threshold for output [OK]

Common Mistakes:

• Confusing greater than with less than
• Expecting sensor value to print
• Thinking else block runs when condition is true

4. Identify the error in this Arduino code for obstacle detection:

int sensorPin = A0;
int threshold = 400;
void setup() {
  Serial.begin(9600);
}
void loop() {
  int sensorValue = digitalRead(sensorPin);
  if(sensorValue < threshold) {
    Serial.println("Obstacle detected");
  }
  delay(100);
}

medium

A. Using digitalRead instead of analogRead for analog sensor

B. Missing Serial.begin in setup()

C. Incorrect delay value

D. Threshold comparison operator is wrong

Solution

1. Step 1: Check sensor reading function

   IR sensor outputs analog values, so analogRead() must be used, not digitalRead().

2. Step 2: Verify other code parts

   Serial.begin is present, delay is reasonable, comparison operator is correct.

3. Final Answer:

   Using digitalRead instead of analogRead for analog sensor -> Option A

4. Quick Check:

   Analog sensor needs analogRead() [OK]

Hint: Use analogRead() for analog sensors, not digitalRead() [OK]

Common Mistakes:

• Using digitalRead for analog sensor pins
• Forgetting Serial.begin() (not the case here)
• Misusing delay() values

5. You want to detect obstacles only when the IR sensor value is between 200 and 400. Which code snippet correctly implements this?

hard

A. if(sensorValue < 200 && sensorValue > 400) { Serial.println("Obstacle detected"); }

B. if(sensorValue >= 200 || sensorValue <= 400) { Serial.println("Obstacle detected"); }

C. if(sensorValue > 200 && sensorValue < 400) { Serial.println("Obstacle detected"); }

D. if(sensorValue == 200 && sensorValue == 400) { Serial.println("Obstacle detected"); }

Solution

1. Step 1: Understand range condition

   To detect values between 200 and 400, sensorValue must be greater than 200 AND less than 400.

2. Step 2: Analyze each option

   if(sensorValue < 200 && sensorValue > 400) { Serial.println("Obstacle detected"); }: impossible condition (< 200 && > 400); if(sensorValue >= 200 || sensorValue <= 400) { Serial.println("Obstacle detected"); } uses || which allows all values; if(sensorValue > 200 && sensorValue < 400) { Serial.println("Obstacle detected"); }: > 200 && < 400 correct; if(sensorValue == 200 && sensorValue == 400) { Serial.println("Obstacle detected"); } checks equality to both values simultaneously, impossible.

3. Final Answer:

   if(sensorValue > 200 && sensorValue < 400) { Serial.println("Obstacle detected"); } -> Option C

4. Quick Check:

   Use AND (&&) for range checks [OK]

Hint: Use && to check sensor value within a range [OK]

Common Mistakes:

• Using || instead of && for range
• Checking impossible conditions
• Using equality instead of range