Code for mobility

const int PIN_TO_SENSOR = 2;  // the pin that OUTPUT pin of sensor is connected to  
int pinStateCurrent   = LOW;  // current state of pin
int pinStatePrevious  = LOW;  // previous state of pin

void setup() 
{  Serial.begin(9600);            // initialize serial 
   // set arduino pin to input mode to read value from OUTPUT pin of sensor  
   pinMode(PIN_TO_SENSOR, INPUT); 
}
void loop() 
{

 //Configure an Arduino's pin to the digital input mode
 pinMode(PIN_TO_SENSOR, INPUT);   

 //Read state of sensor's OUTPUT pin 
 pinStateCurrent = digitalRead(PIN_TO_SENSOR);

 //Detect motion start (pin's state change from HIGH to LOW)
 pinStatePrevious = pinStateCurrent; // store old state 
 pinStateCurrent = digitalRead(PIN_TO_SENSOR);   // read new state

 // pin state change: HIGH -> LOW
 if (pinStatePrevious == HIGH && pinStateCurrent == LOW)
 {   
    Serial.println("Motion detected!"); 
    // we can place an alarm to warn human to come near it
 }
 else
 // pin state change: LOW -> HIGH
 if (pinStatePrevious == LOW && pinStateCurrent == HIGH) 
 {   
   Serial.println("Motion stopped!");
   // alarm will stop as human presence is not detected
 }

}