PIR motion sensor (HC-SR501) false results with NodeMCU

I have a PIR sensor which I use to detect the motion and turn ON and OFF the lights on the basis of it.

I have PIR connected with NodeMCU (ESP8266) based board. I find that sometimes it trigger false positive value. Even when there is no motion. As per my understanding I think any of the following reasons can be there:

1. I have NodeMCU close to it. So may be because NodeMCU heatness triggers it.
2. Some hot air blow near it. But I don’t know. It trigger the false positive even in mid-night.
3. It can be trigger by mosquitoes.
4. I have my other electric wires going from near by.

I am considering these scenarios correct? If yes then how can I prevent from them?

I tried to put it in a box and make it tightly pack. but still its false trigger. I checked even with multiple sensors and have same problem.

Any suggestions to protect this? I also check people put capacitor to smooth it. And put some resistance on Vin.

My Vin of PIR is connected to 5v and OUTPUT pin to D2.

For reference I am having this code for checking.

#define SIGNAL_PIN D2

void setup()
{
  Serial.begin(115200);
  pinMode(SIGNAL_PIN, INPUT_PULLUP);
//  digitalWrite (SIGNAL_PIN, LOW);
}


void loop() {

    static uint32_t lastSeenHigh = millis();
    static bool pirState = false;
    Serial.println(digitalRead(SIGNAL_PIN));

    // If it's active then record that fact along with the time
    if (digitalRead(SIGNAL_PIN) == HIGH) {
        lastSeenHigh = millis();
        pirState = true;
    } else {
        if ((millis() - lastSeenHigh) > 10000) {
            pirState = false;
        }
    }

    if (pirState == true) {
        Serial.println("Pir Is active");
    }
//
    if (pirState == false) {
      Serial.println("PIR sensor inactive");
    }
    delay(1000);
}