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Parking Sensor (Ultrasonic + Buzzer)

Beep faster as an object gets closer, like a car parking sensor. Combine an ultrasonic sensor with a buzzer.

Beginner25 min

What you need

Wiring

Arduino Uno
HC-SR04
Piezo buzzer

Hover a pin or a wire to trace the connection.

Code

parking_sensor.ino
// Beep faster as something gets closer (HC-SR04 + buzzer).
const int trigPin = 9, echoPin = 10, buzzer = 8;

long readCm() {
  digitalWrite(trigPin, LOW);  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH); delayMicroseconds(10); digitalWrite(trigPin, LOW);
  return pulseIn(echoPin, HIGH) / 58;
}

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzer, OUTPUT);
}

void loop() {
  long cm = readCm();
  if (cm > 0 && cm < 30) {
    int gap = map(cm, 0, 30, 40, 400); // closer = shorter gap = faster beeps
    tone(buzzer, 1000); delay(gap);
    noTone(buzzer);     delay(gap);
  } else {
    noTone(buzzer);
    delay(50);
  }
}

Steps

  1. Wire the HC-SR04: VCC to 5V, GND to GND, Trig to D9, Echo to D10.
  2. Wire the buzzer: + to D8, − to GND.
  3. Upload, then move your hand toward the sensor — the beeps speed up as you get closer.