const int pin_to =11;
int prev=LOW;
int curr=LOW;


void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(pin_to,INPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
   
   prev=curr;
   curr=digitalRead(pin_to);
   if(prev==LOW && curr==HIGH)
   {
    Serial.println("motion detected");
   }
   if(prev==HIGH && curr==LOW)
   {
    Serial.println("motion stopped");
   }
}