IR sensor for obstacle detection in Arduino - Step-by-Step Execution

Concept Flow - IR sensor for obstacle detection

Start

↓

Read IR sensor value

↓

Is value < threshold?

No→No obstacle detected

Yes↓

Obstacle detected

↓

Take action (e.g., LED ON)

↓

Repeat reading

The IR sensor reads distance values continuously. If the value is below a set threshold, it means an obstacle is close, triggering an action.

Execution Sample

Arduino

const int irPin = A0;
const int ledPin = 13;
int sensorValue;

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

void loop() {
  sensorValue = analogRead(irPin);
  if(sensorValue < 300) {
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(ledPin, LOW);
  }
  delay(100);
}

This code reads the IR sensor value and turns on an LED if an obstacle is detected (sensor value below 300).

Execution Table

Step	Action	sensorValue	Condition (sensorValue < 300)	LED State
1	Read sensor value	250	True	ON
2	Read sensor value	320	False	OFF
3	Read sensor value	280	True	ON
4	Read sensor value	350	False	OFF
5	Read sensor value	290	True	ON
Exit	Loop continues indefinitely	-	-	-

💡 The loop runs forever, continuously checking sensor values and updating LED state.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	Final
sensorValue	undefined	250	320	280	350	290	last read value
LED State	OFF	ON	OFF	ON	OFF	ON	depends on last sensorValue

Key Moments - 3 Insights

Why does the LED turn ON when sensorValue is less than 300?

Because the code checks if sensorValue < 300 to detect an obstacle close by. When true, it turns the LED ON as shown in execution_table rows 1, 3, and 5.

What happens if the sensorValue is exactly 300?

The condition sensorValue < 300 is false if sensorValue is 300, so the LED stays OFF. This is shown in execution_table row 2 where 320 is false, similarly 300 would be false.

Why is there a delay(100) in the loop?

The delay slows down the loop so readings happen every 100 milliseconds, preventing too fast changes and giving time to see LED changes clearly.

Visual Quiz - 3 Questions

Look at the execution_table, what is the LED state when sensorValue is 320?

A ON

B Blinking

C OFF

D No change

💡 Hint

Check execution_table row 2 where sensorValue is 320 and LED state is OFF.

At which step does the sensorValue first cause the LED to turn ON?

A Step 2

B Step 1

C Step 4

D Step 5

💡 Hint

Look at execution_table row 1 where sensorValue is 250 and LED turns ON.

If the threshold changed from 300 to 280, what would happen at step 3 where sensorValue is 280?

A LED would be OFF

B LED would be ON

C LED would blink

D No change

💡 Hint

Since condition is sensorValue < threshold, if threshold is 280, 280 < 280 is false, so LED OFF.

Concept Snapshot

IR sensor reads analog values to detect obstacles.
If value is below a threshold, obstacle is near.
Use if condition to check sensorValue < threshold.
Turn LED ON when obstacle detected, OFF otherwise.
Loop reads sensor repeatedly with delay for stability.

Full Transcript

This Arduino program uses an IR sensor connected to analog pin A0 to detect obstacles. The sensor value is read continuously inside the loop. If the sensor value is less than 300, it means an obstacle is close, so the program turns on an LED connected to pin 13. Otherwise, the LED is turned off. The loop repeats every 100 milliseconds to update the LED state based on the latest sensor reading. This simple logic helps detect obstacles using the IR sensor and gives visual feedback with the LED.