Ultrasonic Range Detector Distance Sensor HC-SR04 (2cm - 400cm) 3mm Resolution

Ultrasonic ranging module HC-SR04 provides 2cm - 400cm non-contact measurement function, the ranging accuracy can reach to 3mm. The modules include ultrasonic transmitters, receiver and control circuit. If you are sourcing for an ultrasonic ranging module, the HC-SR04 is a good choose. Its stable performance and high ranging accuracy make it a popular module in electronic market. Compared to the Shap IR ranging module, HC-SR04 is more inexpensive than it. But it has the same ranging accuracy and longer ranging distance.

The basic principle of work:

• Using IO trigger for at least 10us high-level signal,
• The Module automatically sends eight 40 kHz and detect whether there is a pulse signal back.
• IF the signal back, through high level , time of high output IO duration is the time from sending ultrasonic to returning. Test distance = (high level time×velocity of sound (340M/S) /2

Specifications:

• Power supply :5V DC
• Quiescent current : <2mA
• Effectual angle: <15°
• Resolution: 3 mm
• Sensing distance: 0.75in (2cm) to 13ft (4m)
• More precise measurements with ranges up to 6.5ft (2m) away
• Resolution : 0.3 cm

There are 4 pins out of the module : VCC , Trig, Echo, GND. So it's a very easy interface for controller is to use it ranging. The process is: pull the Trig pin to high-level for more than 10us impulse , the module will start ranging ; finish ranging , If you find an object in front , Echo pin will be high level , and based on the different distance,it will take the different duration of high-level. So we can calculate the distance easily :

Distance = ((Duration of high level)*(Sonic :340m/s))/2
 

Arduino Sketch

/*
 HC-SR04 Ping distance sensor:
 VCC to arduino 5v 
 GND to arduino GND
 Echo to Arduino pin 7 
 Trig to Arduino pin 8
 
 This sketch originates from Virtualmix: http://goo.gl/kJ8Gl on 10 Nov 2012.
 */


#define echoPin 7 // Echo Pin
#define trigPin 8 // Trigger Pin
#define LEDPin 13 // Onboard LED

int maximumRange = 200; // Maximum range needed
int minimumRange = 0; // Minimum range needed
long duration, distance; // Duration used to calculate distance

void setup() {
 Serial.begin (9600);
 pinMode(trigPin, OUTPUT);
 pinMode(echoPin, INPUT);
 pinMode(LEDPin, OUTPUT); // Use LED indicator (if required)
}

void loop() {
/* The following trigPin/echoPin cycle is used to determine the
 distance of the nearest object by bouncing soundwaves off of it. */ 
 digitalWrite(trigPin, LOW); 
 delayMicroseconds(2); 

 digitalWrite(trigPin, HIGH);
 delayMicroseconds(10); 
 
 digitalWrite(trigPin, LOW);
 duration = pulseIn(echoPin, HIGH);
 
 //Calculate the distance (in cm) based on the speed of sound.
 distance = duration/58.2;
 
 if (distance >= maximumRange || distance <= minimumRange){
   /* Send a negative number to computer and Turn LED ON to indicate "out of range" */
   Serial.println("-1");
   digitalWrite(LEDPin, HIGH); 
 }
 else {
   /* Send the distance to the computer using Serial protocol, and turn LED OFF to indicate successful reading. */
   Serial.println(distance);
   digitalWrite(LEDPin, LOW); 
 }
 
 //Delay 50ms before next reading.
 delay(50);
}

Datasheet

http://users.ece.utexas.edu/~valvano/Datasheets/HCSR04b.pdf

 

HC-SR04 Arduino Library and example sketches (Arduino Playground)

Simple Arduino and HC-SR04 Example (Instructables)

HC-SR04 Energia Example (from Frank Milburn)