Circuit with two Ultrasonic Sensors.

Other Hardware Sensors
8

First

const int trigger=5;
const int echo=6;
const int motorPin=7;
long int duration, distanceInches, distanceCm;
int LimitCm = 100;

void setup()
{
pinMode(motorPin, OUTPUT);
}
void loop()
{
pinMode (trigger, OUTPUT);
pinMode (echo, INPUT);
digitalWrite(trigger, LOW);
delayMicroseconds (2);
digitalWrite(trigger,HIGH);
delayMicroseconds(5);
digitalWrite(trigger,LOW);

pinMode(echo, INPUT);
duration = pulseIn(echo,HIGH);

distanceInches=microsecondsToInches(duration);
distanceCm=microsecondsToCentimeters(duration);

checkLimit();
delay (100);
}
void checkLimit()
{
if(distanceCm < LimitCm)
{
digitalWrite(motorPin,HIGH);
}
else
{
digitalWrite(motorPin,LOW);
}
}
long microsecondsToInches (long microseconds)
{
return microseconds /74/2;
}
long microsecondsToCentimeters(long microseconds)
{
return microseconds /29/2;
}

Second

const int trigger=5;
const int echo=6;
const int LedPin=7;
const int speaker=8;
const int LedAlert=4;
long int duration, distanceInches, distanceCm;
int LimitCm = 100;

void setup()
{
pinMode(LedPin, OUTPUT);
pinMode(LedAlert, OUTPUT);
pinMode(speaker, OUTPUT);
}
void loop()
{
digitalWrite(LedPin, HIGH);
pinMode (trigger, OUTPUT);
pinMode (echo, INPUT);
digitalWrite(trigger, LOW);
delayMicroseconds (2);
digitalWrite(trigger,HIGH);
delayMicroseconds(5);
digitalWrite(trigger,LOW);

pinMode(echo, INPUT);
duration = pulseIn(echo,HIGH);

distanceInches=microsecondsToInches(duration);
distanceCm=microsecondsToCentimeters(duration);

checkLimit();
delay (100);
}
void checkLimit()
{
if(distanceCm < LimitCm)
{
digitalWrite(LedAlert,HIGH);
delayMicroseconds(2);
digitalWrite(speaker,HIGH);
delayMicroseconds(5);

}
else
{
digitalWrite(LedAlert,LOW);
delayMicroseconds(2);
digitalWrite(speaker,LOW);
delayMicroseconds(5);

}
}
long microsecondsToInches (long microseconds)
{
return microseconds /74/2;
}
long microsecondsToCentimeters(long microseconds)
{
return microseconds /29/2;
}