Problem with PIR HC-SR505 and relay

Other Hardware Sensors
1

Hello,
first I want to apologize if my english is not very good,
but anyway, let's talk about this PIR problem :

I'm using an arduino with more than a PIR and a relay, but It is obvious that that is what the problem is;
to illustrate the problem let's use this situation with just the PIR and the relay :

Connections :

  • PIR: (HC-SR505)
  • ---> 5V

  • ---> Gnd
    out ---> D6

  • Relay : (SRD-05VDC-SL-C)

  • ---> 5V
  • ---> Gnd
    S ---> D5
//relay pin:
const int relay= 5;


//PIR pin:
const int ir=6;


// count down variables:
  int c=-1; // We define the relay as open
  int timedelay = 100;


void setup() {
  
//relay pin:
pinMode(relay,OUTPUT);

//PIR pin:
pinMode(ir,INPUT);
digitalWrite(ir,LOW);


//Console 
Serial.begin(9600);
}

void loop() {
int pirVal = digitalRead(ir);
Serial.println(pirVal);

  
if(pirVal==HIGH) {
  
if(c == -1){digitalWrite(relay,HIGH);}  //the relay was open, so we close it
c=timedelay; //while there are mouvements, we reset the countdown to the chosen delay
}

else { // here: pirval==LOW

if(c>0){c--;}
if(c==0) { // if time is up 
  Serial.println("time's up");
  digitalWrite(relay,LOW); // we open the relay
  Serial.println(pirVal); //1*
  delay(10);
  Serial.println(pirVal);//2*
  c=-1; // We define the relay as open
}
}

 delay(100);// a test every 100ms
}

The purpose of all of this is to activate the relay if there is mouvement, and desactivate the relay after a chosen delay (here 10s) without mouvement.

But here the problem comes: about 10ms after the desactivation of the relay, I have a unwanted signal from the pin OUT of the PIR:

at 1*,pirVal= 0
at 2*,pirVal= 1

without no mouvement in front of the PIR !

To calm down after this brief signal, the PIR needs about 7-8 seconds,
So when the loop restart, the program re-activate the relay, and it never stop to desactivate and re-activate the relay every 17-18 seconds..

Can someone help me ?