int led1 = 6;
int led2 = 7;
int led3 = 8;
int led4 = 9;
int led5 = 10;
int led6 = 11;
int led7 = 12;
int led8 = 13;
#define ECHO_PIN 2
#define TRIG_PIN 3
float buzzer = 5;
void setup() {
Serial.begin(115200);
pinMode(TRIG_PIN, OUTPUT);
pinMode(ECHO_PIN, INPUT);
pinMode(led1, OUTPUT);
}
float readDistanceCM() {
digitalWrite(TRIG_PIN, LOW);
delayMicroseconds(2);
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);
int duration = pulseIn(ECHO_PIN, HIGH);
return duration * 0.034 / 2;
}
void loop() {
Serial.print("Measured distance: ");
Serial.println(readDistanceCM());
if (readDistanceCM() < 50) {
digitalWrite(buzzer, HIGH);
delay(50);
} else {
digitalWrite(buzzer, LOW);
delay(50);
}
if (readDistanceCM() <= 40 && 
readDistanceCM() > 35) {
  digitalWrite(led1, HIGH);
digitalWrite(led2, HIGH);
digitalWrite(led3, HIGH);
digitalWrite(led4, HIGH);
digitalWrite(led5, HIGH);
digitalWrite(led6, HIGH);
digitalWrite(led7, HIGH);
digitalWrite(led8, HIGH);
}
if (readDistanceCM() <= 35 && 
readDistanceCM() > 30) {
digitalWrite(led1, LOW);
digitalWrite(led2, HIGH);
digitalWrite(led3, HIGH);
digitalWrite(led4, HIGH);
digitalWrite(led5, HIGH);
digitalWrite(led6, HIGH);
digitalWrite(led7, HIGH);
digitalWrite(led8, HIGH);
}
if (readDistanceCM() <= 30 && 
readDistanceCM() > 25) {
digitalWrite(led1, LOW);
digitalWrite(led2, LOW);
digitalWrite(led3, HIGH);
digitalWrite(led4, HIGH);
digitalWrite(led5, HIGH);
digitalWrite(led6, HIGH);
digitalWrite(led7, HIGH);
digitalWrite(led8, HIGH);
}
if (readDistanceCM() <= 25 && 
readDistanceCM() > 20) {
digitalWrite(led1, LOW);
digitalWrite(led2, LOW);
digitalWrite(led3, LOW);
digitalWrite(led4, HIGH);
digitalWrite(led5, HIGH);
digitalWrite(led6, HIGH);
digitalWrite(led7, HIGH);
digitalWrite(led8, HIGH);
}
if (readDistanceCM() <= 20 && 
readDistanceCM() > 15) {
digitalWrite(led1, LOW);
digitalWrite(led2, LOW);
digitalWrite(led3, LOW);
digitalWrite(led4, LOW);
digitalWrite(led5, HIGH);
digitalWrite(led6, HIGH);
digitalWrite(led7, HIGH);
digitalWrite(led8, HIGH);
}
if (readDistanceCM() <= 15 && 
readDistanceCM() > 10) {
digitalWrite(led1, LOW);
digitalWrite(led2, LOW);
digitalWrite(led3, LOW);
digitalWrite(led4, LOW);
digitalWrite(led5, LOW);
digitalWrite(led6, HIGH);
digitalWrite(led7, HIGH);
digitalWrite(led8, HIGH);
}
if (readDistanceCM() <= 10&& 
readDistanceCM() > 5) {
digitalWrite(led1, LOW);
digitalWrite(led2, LOW);
digitalWrite(led3, LOW);
digitalWrite(led4, LOW);
digitalWrite(led5, LOW);
digitalWrite(led6, LOW);
digitalWrite(led7, HIGH);
digitalWrite(led8, HIGH);
}
if (readDistanceCM() <= 5 && 
readDistanceCM() >= 
0) {
digitalWrite(led1, LOW);
digitalWrite(led2, LOW);
digitalWrite(led3, LOW);
digitalWrite(led4, LOW);
digitalWrite(led5, LOW);
digitalWrite(led6, LOW);
digitalWrite(led7, LOW);
digitalWrite(led8, HIGH);
}
delay(100);
}