AJ-SR04M Waterproof Ultrasonic Ranging Module

• Operating voltage 5VDC 5mA - 30mA
• Acoustic emission frequency 40 kHz
• Farthest distance: 4.5m 
• Blind: 25cm
• Module size: 41mm x 28.5mm 
• Resolution: about 0.5cm 
• Angle: less than 50 degrees 
• Working temperature: -10 ~ 70 ℃ 
• Storage temperature: -20 ~ 80 ℃

• Vcc -> 5v
• Gnd -> Gnd
• Trig -> 13
• Echo -> 12

const int pingPin = 13;
int inPin = 12;


void setup() {
Serial.begin(9600);
}

void loop()
{
long duration, cm;

pinMode(pingPin, OUTPUT);


digitalWrite(pingPin, LOW);
delayMicroseconds(2);
digitalWrite(pingPin, HIGH);
delayMicroseconds(5);
digitalWrite(pingPin, LOW);
pinMode(inPin, INPUT);
duration = pulseIn(inPin, HIGH);

cm = microsecondsToCentimeters(duration);

Serial.print(cm);
Serial.print("cm");
Serial.println();
delay(100);
}

long microsecondsToCentimeters(long microseconds)
{
// The speed of sound is 340 m/s or 29 microseconds per centimeter.
// The ping travels out and back, so to find the distance of the
// object we take half of the distance travelled.
return microseconds / 29 / 2;
}