Proximity Sensor and LED Circuit

Proximity Sensor and LED Circuit

Proximity Sensor Activated LED

We started learning robotics during the summer to prepare for the robotics electives I'm taking next year. We created a circuit where an LED activates once a proximity sensor detects nearby objects within 6 inches. Here's how it works:

  1. The process begins with the proximity sensor emitting ultrasonic sound waves. This emission is triggered by setting the Trig Pin HIGH for 10µs (microseconds).

  2. The sensor then measures received ultrasonic waves on the Echo Pin. From the measurement, we can calculate the time it takes for the sound waves to travel out from the emitter, bounce off a target, and return to the sensor. From the time delay, we can then calculate the distance to the target using this formula (in inches):

  1. At room temperature, the speed of sound is approximately 343 m/s, which converts to 0.0343 centimeters per microsecond, or 0.0135 inches per microsecond.

  2. The calculated distance is printed to the serial monitor and compared to a predefined threshold of 6 inches.

  3. If the distance is 6 inches or less, the LED activates. If the distance is greater than 6 inches, the LED remains off.

Diagram

Proximity Sensor Diagram

Arduino Sketch

// Define the pins for the ultrasonic sensor and the LED
const int trigPin = 9;   // Trigger pin of the ultrasonic sensor
const int echoPin = 10;  // Echo pin of the ultrasonic sensor
const int ledPin = 13;   // LED connected to digital pin 13

// Define constants for calculating distance
// Speed of sound in air at 20°C is approximately 343 meters per second.
// This translates to 0.0343 cm per microsecond, or 0.0135 inches per microsecond.
const float SPEED_OF_SOUND_IN_INCHES_PER_MICROSECOND = 0.0135;

// Define the distance threshold in inches
const float DISTANCE_THRESHOLD_INCHES = 6.0;

void setup() {
  // Initialize serial communication for debugging (optional, but highly recommended)
  Serial.begin(9600);

  // Set the trigger pin as an OUTPUT
  pinMode(trigPin, OUTPUT);
  // Set the echo pin as an INPUT
  pinMode(echoPin, INPUT);
  // Set the LED pin as an OUTPUT
  pinMode(ledPin, OUTPUT);

  // Ensure the trigPin is low initially
  digitalWrite(trigPin, LOW);
}

void loop() {
  // --- Step 1: Clear the trigPin by setting it LOW for a short period ---
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2); // Wait for 2 microseconds

  // --- Step 2: Set the trigPin HIGH for 10 microseconds to send a pulse ---
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10); // Keep it HIGH for 10 microseconds
  digitalWrite(trigPin, LOW); // Set it LOW again

  // --- Step 3: Measure the duration of the pulse on the echoPin ---
  // pulseIn() reads a pulse (HIGH or LOW) on a pin. It waits for the pin to go to the specified state,
  // starts timing, then waits for the pin to go to the other state, and stops timing.
  // It returns the length of the pulse in microseconds.
  long duration = pulseIn(echoPin, HIGH);

  // --- Step 4: Calculate the distance based on the duration ---
  // The duration is the time for the sound to travel to the object AND back.
  // So, we divide the duration by 2 to get the one-way travel time.
  // Then, multiply by the speed of sound to get the distance.
  float distanceInches = (duration / 2.0) * SPEED_OF_SOUND_IN_INCHES_PER_MICROSECOND;

  // --- Step 5: Print the distance to the Serial Monitor (for debugging) ---
  Serial.print("Distance: ");
  Serial.print(distanceInches);
  Serial.println(" inches");

  // --- Step 6: Control the LED based on the distance threshold ---
  if (distanceInches < DISTANCE_THRESHOLD_INCHES) {
    digitalWrite(ledPin, HIGH); // Turn LED ON if object is closer than 6 inches
    Serial.println("Object detected! LED ON.");
  } else {
    digitalWrite(ledPin, LOW);  // Turn LED OFF if object is farther than 6 inches
    Serial.println("No object detected. LED OFF.");
  }

  // Add a small delay between readings to stabilize the sensor and avoid erratic behavior
  delay(100); // Wait for 100 milliseconds before the next reading
}