How to connect Aduino and Ultrasonic Sensor (HC-SR04)

published on 2020-02-17

The following table shows the connections you need to make:

Ultrasonic Sensor HC-SR04	Arduino
VCC	5V
Trig	Pin 11
Echo	Pin 12
GND	GND

Code:

（Upload the following code to Arduino IDE）

Create variables for Trig and echo pins, named trigPin and echoPin. the trig pin is connected to digital pin 11, echo pin is connected to digital pin 12.
```
int trigPin = 11; 
int echoPin = 12;
```
You also need to create two long variables: duration, cm. The variable duration holds the time between the transmission and reception of the signal.
```
long duration, cm,
```
In the setup(), initialize the serial port at a baud rate of 9600, and set the trigger pin as an output and the echo pin as an input.
```
//Serial Port begin
Serial.begin (9600);
//Define inputs and outputs
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
```
In the loop(), trigger the sensor by sending a HIGH pulse of 10 microseconds. But, before that, give a short LOW pulse to ensure you’ll get a clean HIGH pulse:
```
digitalWrite(trigPin, LOW);
delayMicroseconds(5);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
```
Then, you can read the signal from the sensor – a HIGH pulse whose duration is the time in microseconds from the sending of the signal to the reception of its echo to an object.
```
duration = pulseIn(echoPin, HIGH);
```
Finally, you just need to convert the duration to a distance. We can calculate the distance by using the following formula:
```
distance = (traveltime/2) x speed of sound

The speed of sound is: 343m/s = 0.0343 cm/uS = 1/29.1 cm/uS
```
We need to divide the traveltime by 2 because we have to take into account that the wave was sent, hit the object, and then returned back to the sensor.
```
cm = (duration/2) / 29.1;
```
The cm variable will save the distance in centimetres.