Working with Sensors

Sensors give your robot the ability to sense the world around it.

Digital vs Analog Sensors

• Digital: Returns ON/OFF (HIGH/LOW) - Example: Push button, IR obstacle sensor
• Analog: Returns range of values (0-1023) - Example: Temperature sensor, potentiometer

Example 1: Push Button

const int buttonPin = 2;
const int ledPin = 13;

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

void loop() {
  int buttonState = digitalRead(buttonPin);

  if (buttonState == HIGH) {
    digitalWrite(ledPin, HIGH);  // Turn LED on
  } else {
    digitalWrite(ledPin, LOW);   // Turn LED off
  }
}
      

Example 2: Ultrasonic Distance Sensor (HC-SR04)

const int trigPin = 9;
const int echoPin = 10;

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
}

void loop() {
  // Send ultrasonic pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure echo time
  long duration = pulseIn(echoPin, HIGH);

  // Calculate distance in cm
  float distance = duration * 0.034 / 2;

  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  delay(500);
}
      

Example 3: Analog Temperature Sensor (LM35)

const int tempPin = A0;

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

void loop() {
  int sensorValue = analogRead(tempPin);

  // Convert to voltage (5V reference)
  float voltage = sensorValue * (5.0 / 1023.0);

  // Convert to Celsius (LM35: 10mV per degree)
  float temperature = voltage * 100;

  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" °C");

  delay(1000);
}