The Ultrasonic sensor just detects the same distance int tPin = 11;
int ePin = 12;
long duration, inches, cm;

void setup()
{
    Serial.begin(9600);
    pinMode(tPin, OUTPUT);
    pinMode(ePin, INPUT);
    pinMode(2, OUTPUT);
}

void loop()
{
    digitalWrite(tPin, LOW);
    delayMicroseconds(5);
    digitalWrite(tPin, HIGH);
    delayMicroseconds(10);
    digitalWrite(tPin, LOW);
    duration = pulseIn(ePin, HIGH);
    cm = (duration / 2) / 29.1;
    inches = (duration / 2) / 74;
    Serial.print(inches);
    Serial.print("in, ");
    Serial.print(cm);
    Serial.print("cm");
    Serial.println();
    delay(100);

    if (inches &lt;= 10) {
        digitalWrite(2, HIGH);
        delay(50);
        digitalWrite(2, LOW);
        delay(50);
    }
    else {
        digitalWrite(2, HIGH);
        delay(500);
        digitalWrite(2, LOW);
        delay(500);
    }
}


The serial print displays the same distance that it first detects. How can I fix this?
First of all you need to make cm, inches and duration float to be more precise. Second, you need to make the delay 2 and 10 microseconds between triggers. Overall, if I'm not wrong you can use the code below without changing your circuit.

int tPin = 11;
int ePin = 12;
float duration, inches, cm; //floating numbers to make the result more precise

void setup()
{
    Serial.begin(9600);
    pinMode(tPin, OUTPUT);
    pinMode(ePin, INPUT);
    pinMode(2, OUTPUT);
}

void loop()
{
    digitalWrite(tPin, LOW);
    delayMicroseconds(2);         //Delay 2 microseconds
    digitalWrite(tPin, HIGH);
    delayMicroseconds(10);        //Delay 10 microseconds
    digitalWrite(tPin, LOW);
    duration = pulseIn(ePin, HIGH);
    cm = duration / 58.2;          //Instead of duration/2/28.1
    inches = cm / 2.54;            //You can use cm that was created before for conversion
    Serial.print(inches);
    Serial.print("in, ");
    Serial.print(cm);
    Serial.print("cm");
    Serial.println();
    delay(100);

    if (inches &lt;= 10) {
        digitalWrite(2, HIGH);
        delay(50);
        digitalWrite(2, LOW);
        delay(50);
    }
    else {
        digitalWrite(2, HIGH);
        delay(500);
        digitalWrite(2, LOW);
        delay(500);
    }
}