Arduino Based Distance Measurement using Ultrasonic Sensor

Ultrasonic sensors are great tools to measure distance without actual contact and used at several places like water level measurement, distance measurement, etc. This is an efficient way to measure small distances precisely. In this project, we have used an Ultrasonic Sensor to determine the distance of an obstacle from the sensor. The basic principle of ultrasonic distance measurement is based on ECHO. When sound waves are transmitted in the environment then waves return back to the origin as ECHO after striking on the obstacle. So we only need to calculate the traveling time of both sounds means outgoing time and returning time to origin after striking on the obstacle. As the speed of the sound is known to us, after some calculation we can calculate the distance.  

Components Used

1. Arduino Pro Mini
2. Ultrasonic sensor Module
3. 16x2 LCD
4. Scale
5. Breadboard
6. 9-volt battery
7. Connecting wires

Ultrasonic Sensor Module

Ultrasonic sensor HC-SR04 is used here to measure distance in the range of 2cm-400cm with an accuracy of 3mm. The sensor module consists of an ultrasonic transmitter, receiver, and control circuit. The working principle of the ultrasonic sensor is as follows:

1. A high-level signal is sent for 10us using Trigger.
2. The module sends eight 40 kHz signals automatically and then detects whether a pulse is received or not.
3. If the signal is received, then it is through the high level. The time of high duration is the time gap between sending and receiving the signal.

Distance= (Time x Speed of Sound in Air (340 m/s))/2

Timing Diagram

The module works on the natural phenomenon of the ECHO of sound. A pulse is sent for about 10us to trigger the module. After which the module automatically sends 8 cycles of 40 kHz ultrasound signal and checks its echo. The signal after striking with an obstacle returns back and is captured by the receiver. Thus the distance of the obstacle from the sensor is simply calculated by the formula given as

            Distance= (time x speed)/2.

Here we have divided the product of speed and time by 2 because the time is the total time it took to reach the obstacle and return back. Thus the time to reach an obstacle is just half the total time taken.

Circuit Diagram and Explanation

In-circuit connections Ultrasonic sensor module’s “trigger” and “echo” pins are directly connected to pin 18(A4) and 19(A5) of Arduino. A 16x2 LCD is connected with arduino in 4-bit mode. Control pin RS, RW, and En are directly connected to Arduino pin 2, GND, and 3. And data pin D4-D7 is connected to 4, 5, 6, and 7 of Arduino.

First of all, we need to trigger the ultrasonic sensor module to transmit a signal by using Arduino and then wait to receive ECHO. Arduino reads the time between triggering and Received ECHO. We know that the speed of sound is around 340m/s. so we can calculate the distance by using the given formula:

Distance= (travel time/2) * speed of sound

Where speed of sound around 340m per second.

A 16x2 LCD is used for displaying distance.

Program Description

In code we read time by using pulseIn(pin). And then perform calculations and displayed result on 16x2 LCD by using appropriate functions.

Code: 

#include <LiquidCrystal.h>

#define trigger 18
#define echo 19

LiquidCrystal lcd(2,3,4,5,6,7);

float time=0,distance=0;

void setup()
{
 lcd.begin(16,2);
 pinMode(trigger,OUTPUT);
 pinMode(echo,INPUT);
 lcd.print(" Ultra sonic");
 lcd.setCursor(0,1);
 lcd.print("Distance Meter");
 delay(2000);
 lcd.clear();
 lcd.print(" Circuit Digest");
 delay(2000);
}

void loop()
{
 lcd.clear();
 digitalWrite(trigger,LOW);
 delayMicroseconds(2);
 digitalWrite(trigger,HIGH);
 delayMicroseconds(10);
 digitalWrite(trigger,LOW);
 delayMicroseconds(2);
 time=pulseIn(echo,HIGH);
 distance=time*340/20000;
 lcd.clear();
 lcd.print("Distance:");
 lcd.print(distance);
 lcd.print("cm");
 lcd.setCursor(0,1);
 lcd.print("Distance:");
 lcd.print(distance/100);
 lcd.print("m");
 delay(1000);
}