### Project 27 HC-SR04 Ultrasonic Sensor

![](media/image-20251125121657531.png)

**1.Introduction**
The HC-SR04 Ultrasonic Sensor is a very affordable proximity/distance sensor that has been used mainly for object avoidance in various robotics projects. It essentially gives your Arduino eyes / spacial awareness and can prevent your robot from crashing or falling off a table. It has also been used in turret applications, water level sensing, and even as a parking sensor. This simple project will use the HC-SR04 sensor with an Arduino and a Processing sketch to provide a neat little interactive display on your computer screen.

**2.Specification**

- Working Voltage: DC 5V
- Working Current: 15mA
- Working Frequency: 40Hz
- Max Range: 4m
- Min Range: 2cm
- Measuring Angle: 15 degree
- Trigger Input Signal: 10µS TTL pulse
- Echo Output Signal Input TTL lever signal and the range in proportion
- Size: 46*20.4mm
- Weight: 9g

**3.Connection Diagram**

![](media/image-20251126092257518.png)

**4.Sample Code**

- VCC to arduino 5v

- GND to arduino GND
- Echo to Arduino pin 7
- Trig to Arduino pin 8

```c
#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);
}
```