1. Arduino Uno microcontroller

2. Ultrasonic sensor HC-SR04

3. Red (2), yellow (2) and blue (2) LEDs

4. 74HC595 shift register 

5. Active buzzer 

6. 2.6kohm resistors (7)

7. Jumper wires 

#include "SR04.h"

int latch = 3;
int clock = 4;
int data = 2;

int buzzer = 8;

int trig = 11;
int echo = 10;
SR04 sr04 = SR04(echo, trig); //calling the library for ultrasonic sensor as a variable "sr04" 

int dist; 
void setup() {
  pinMode(latch, OUTPUT);
  pinMode(clock, OUTPUT);
  pinMode(data, OUTPUT);
  pinMode(buzzer, OUTPUT);
  
  Serial.begin(9600);
  delay(1000);
}

void update(byte light) {
  digitalWrite(latch, LOW);
  shiftOut(data, clock, LSBFIRST, light);
  digitalWrite(latch, HIGH);
}

void loop() {
  dist = sr04.Distance(); //function from library
  if (dist >= 30) {
    byte lights = B1100001;
    update(lights);
    digitalWrite(buzzer,LOW);
    Serial.print(dist);
    Serial.println("cm");
    delay(100);
  }
  else if (dist <= 29 && dist >=8) {
    byte lights = B0011000;
    update(lights);
    digitalWrite(buzzer,LOW);
    Serial.print(dist);
    Serial.println("cm");
    delay(100);
  }
  else if (dist <=7 && dist >=4) {
    byte lights = B0000110;
    update(lights);
    digitalWrite(buzzer,LOW);
    Serial.print(dist);
    Serial.println("cm");
    delay(100);
  }
  else {
    byte lights = B0000110;
    update(lights);
    delay(100);
    lights = B0000000;
    update(lights);
    digitalWrite(buzzer,HIGH);
    Serial.print(dist);
    Serial.println("cm");
    delay(100);
  }
}