DIY Motion-Activated LED with Arduino & Ultrasonic Sensor

Step-by-Step Guide to Make a Motion-Activated LED Using Arduino Uno and HC-SR04 Sensor

Materials Needed

• Arduino Uno
• HC-SR04 Ultrasonic Distance Sensor
• LED (any color)
• 470Ω Resistor (for the LED)
• Breadboard and jumper wires

Instructions

Step 1: Wire the Components

Connect the HC-SR04 Distance Sensor:

• VCC to 5V on the Arduino.
• GND to GND on the Arduino.
• Trig to Digital Pin 9 on the Arduino.
• Echo to Digital Pin 10 on the Arduino.

Connect the LED:

• Insert the anode (longer leg) of the LED into Digital Pin 8 on the Arduino through a 470Ω resistor.
• Insert the cathode (shorter leg) of the LED into GND on the Arduino

Step 2: Upload the Code to the Arduino

• Open the Arduino IDE.
• Copy and paste the following code into a new sketch:

// Define pin connections
const int trigPin = 9;
const int echoPin = 10;
const int ledPin = 8;

// Set a distance threshold for detecting movement (in cm)
const int movementThreshold = 20; // Adjust this to your desired distance

void setup() {
  // Initialize pin modes
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);

  // Start Serial Monitor for debugging
  Serial.begin(9600);
  Serial.println("Starting distance sensor...");
}

void loop() {
  // Trigger the sensor to send out a pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure the duration of the pulse
  long duration = pulseIn(echoPin, HIGH);

  // Calculate distance (in cm)
  int distance = duration * 0.034 / 2;

  // Print distance to Serial Monitor for debugging
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // Check if an object is within the threshold distance
  if (distance > 0 && distance <= movementThreshold) {
    Serial.println("Object detected within range. Turning LED on.");
    digitalWrite(ledPin, HIGH); // Turn on the LED
  } else {
    Serial.println("No object detected or out of range. Turning LED off.");
    digitalWrite(ledPin, LOW); // Turn off the LED
  }

  // Delay to avoid overwhelming the sensor
  delay(200);
}