int trigPin = A0;  
int echoPin = A3;
int LED1 = 2;
int LED2 = 3;
int LED3 = 4;
int LED4 = 5;
int LED5 = 6;
int LED6 = 7;
int LED7 = 8;
int LED8 = 9;
int LED9 = 10;
int LED10 = 11;
float Speed = 0.0343;  // Sound speed at cm/us
long duration, distance;

void setup()
{
   pinMode(trigPin, OUTPUT); 
   pinMode(echoPin, INPUT);   
   pinMode(LED1, OUTPUT); 
   pinMode(LED2, OUTPUT); 
   pinMode(LED3, OUTPUT); 
   pinMode(LED4, OUTPUT);
   pinMode(LED5, OUTPUT); 
   pinMode(LED6, OUTPUT); 
   pinMode(LED7, OUTPUT); 
   pinMode(LED8, OUTPUT);
   pinMode(LED9, OUTPUT); 
   pinMode(LED10, OUTPUT);
   digitalWrite (LED1 , LOW);
   digitalWrite (LED2 , LOW);
   digitalWrite (LED3 , LOW);
   digitalWrite (LED4 , LOW);
   digitalWrite (LED5 , LOW);
   digitalWrite (LED6 , LOW);
   digitalWrite (LED7 , LOW);
   digitalWrite (LED8 , LOW);
   digitalWrite (LED9 , LOW);
   digitalWrite (LED10 , LOW);
   
   }
void loop()
 {   
   digitalWrite(trigPin, LOW);        // Make sure that the TRIG is deactivated
   delayMicroseconds(2);              // Make sure that the TRIG is in LOW
   digitalWrite(trigPin, HIGH);       // Activate the output pulse 
   delayMicroseconds(10);             // Wait for 10µs, the pulse remains active during this time
   digitalWrite(trigPin, LOW);        //Stop the pulse and wait for ECHO 

   duration = pulseIn(echoPin, HIGH) ; // pulseIn measures the time  )
   distance = Speed* duration / 2;   //Divide by 2 because we want to have only the “go” time, not the “go and back” time
   
   if ( distance < 40)
   {
       digitalWrite (LED1 , HIGH);       
   }
   else
   {    
       digitalWrite (LED1 , LOW);    
   }

   if ( distance < 80)
   {
     digitalWrite (LED2 , HIGH);      
   }
   else
   {
     digitalWrite (LED2 , LOW);    
   }

   if ( distance < 120)
   {
     digitalWrite (LED3 , HIGH);     
   }
   else
   {
     digitalWrite (LED3 , LOW);    
   } 
   
   if ( distance < 160)
   {
     digitalWrite (LED4 , HIGH);      
   }
   else
   {
     digitalWrite (LED4 , LOW);    
   }
   
   if ( distance < 200)
   {
     digitalWrite (LED5 , HIGH);      
   }
   else
   {
     digitalWrite (LED5 , LOW);   
   }

   if ( distance < 240)
   {
     digitalWrite (LED6 , HIGH);      
   }
   else
   {
     digitalWrite (LED6 , LOW);    
   }

   if ( distance < 280)
   {
     digitalWrite (LED7 , HIGH);      
   }
   else
   {
     digitalWrite (LED7 , LOW);    
   }

   if ( distance < 320)
   {
     digitalWrite (LED8 , HIGH);      
   }
   else
   {
     digitalWrite (LED8 , LOW);    
   }

   if ( distance < 360)
   {
     digitalWrite (LED9 , HIGH);
   }
   else
   {
     digitalWrite (LED9 , LOW);    
   }

   if ( distance < 400)
   {
     digitalWrite (LED10 , HIGH);      
   }
   else
   {
     digitalWrite (LED10 , LOW);     
   }



 }