The HY-SRF05 is a popular ultrasonic distance sensor that works great with the ESP8266. In this guide I will show you exactly how to wire it up and read distance values in real time.
What you need
- ESP8266 (NodeMCU or any variant)
- HY-SRF05 ultrasonic sensor
- Jumper wires
Wiring
The sensor has five pins: VCC, GND, TRIG, ECHO, and OUT. For this setup we only use TRIG and ECHO — that is all you need to measure distance.
- VCC → 5V
- GND → GND
- TRIG → D1
- ECHO → D2
The sensor performs better at 5V, so power it from the 5V pin rather than 3.3V.
How it works
The sketch sends a short pulse on TRIG, then listens on ECHO for the return signal. The time between send and receive lets us calculate distance using the speed of sound (0.0343 cm per microsecond).
The code
Full source: github.com/viktoriabuilds/esp8266-ultrasonic-sensor
#define TRIG_PIN D1
#define ECHO_PIN D2
long duration;
float distance;
void setup() {
Serial.begin(115200);
pinMode(TRIG_PIN, OUTPUT);
pinMode(ECHO_PIN, INPUT);
}
void loop() {
digitalWrite(TRIG_PIN, LOW);
delayMicroseconds(2);
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);
duration = pulseIn(ECHO_PIN, HIGH);
distance = duration * 0.0343 / 2;
Serial.print("Distance: ");
Serial.print(distance);
Serial.println(" cm");
delay(500);
}Upload the sketch and open the Serial Monitor at 115200 baud. You will see live distance readings printed every half second.
Common uses
- Obstacle detection in robots
- Distance measurement for automation
- Object detection for IoT projects