Video
Circuit Diagram
Source Code
1// ─────────────────────────────────────────
2// BlueGrays · bluegrays.com
3// HC-SR04 Mesafe Olcme (Serial Ekran)
4// ─────────────────────────────────────────
5// TR: HC-SR04 ultrasonik sensorle mesafeyi olcer ve 3-100 cm arasindaki
6// sonuclari 0.5 sn'de bir Serial Monitor'e cm olarak yazar.
7// EN: Measures distance with the HC-SR04 ultrasonic sensor and prints results
8// between 3 and 100 cm to the Serial Monitor in cm every 0.5 s.
9//
10// Pinler / Pins:
11// D7 -> HC-SR04 Trig
12// D6 -> HC-SR04 Echo
13// HC-SR04 VCC 5V'a, GND GND'ye / HC-SR04 VCC to 5V, GND to GND
14
15int echoPin = 6; // Yanki girisi / Echo input
16int trigPin = 7; // Tetik cikisi / Trigger output
17int maxDistance = 100; // Gosterilen en buyuk mesafe (cm) / Largest distance shown (cm)
18int minDistance = 3; // Gosterilen en kucuk mesafe (cm) / Smallest distance shown (cm)
19
20void setup() {
21 pinMode(trigPin, OUTPUT);
22 pinMode(echoPin, INPUT);
23 Serial.begin(9600);
24}
25
26void loop() {
27 // 10 us tetik darbesi ses dalgasini gonderir / A 10 us trigger pulse sends the sound burst
28 digitalWrite(trigPin, HIGH);
29 delayMicroseconds(10);
30 digitalWrite(trigPin, LOW);
31
32 // TR: Echo'nun HIGH kalma suresi (us) gidis-donus suresidir. Ses 0.034 cm/us
33 // hizla gider; yol ikiye bolunerek mesafe bulunur
34 // EN: How long Echo stays HIGH (us) is the round-trip time. Sound travels at
35 // 0.034 cm/us; halving the path gives the distance
36 unsigned long duration = pulseIn(echoPin, HIGH);
37 double totalPath = (double)duration * 0.034;
38 int distance = totalPath / 2;
39
40 // Yalniz gecerli aralikta yaz / Print only inside the valid range
41 if (distance > minDistance && distance < maxDistance) {
42 Serial.print("Distance: ");
43 Serial.print(distance);
44 Serial.println("cm");
45 }
46
47 delay(500); // 0.5 sn bekle / Wait 0.5 s
48}
49FAQ
How does the HC-SR04 measure distance?▾
The sensor emits a 40 kHz sound wave and measures the time it takes for the echo to return. Sound travels through the air at a speed of approximately 343 m/s; the distance is converted to centimeters using the formula: distance = time × 0.0343 / 2 (dividing by 2 accounts for the round trip).
What are the shortest and longest distances it can measure?▾
In practice, it measures distances ranging from approximately 2 cm to 400 cm. Measurements may be inaccurate or read as 0 when the distance is less than 2 cm, or when measuring very far distances or on sound-absorbing surfaces (such as fabric or foam).
Sometimes the readings are 0 or very large—why is that?▾
If no echo is received, `pulseIn` will time out. Make sure the sensor is facing a flat, hard surface, wait at least 60 ms between measurements, and filter out erroneous readings in your code.
Can I use it with the ESP32?▾
The HC-SR04 operates at 5 V, and its ECHO pin outputs 5 V. Since the ESP32 operates on 3.3 V logic, you should either add a voltage divider (e.g., 1 kΩ + 2 kΩ) to the ECHO line or use the 3.3 V-compatible HC-SR04P model.