3W LED module lights up twice without motion

[erlank]

I can't find a specific topic covering the following.. I get my 3W LED to light up with the activation of the motion sensor using code provided. What I don't understand is that the LED sometimes light up without ANY movement in front of the motion sensor? It runs smooth from the pc's USB power supply, but once I connect it to a powerbank (the culprit?) it lights up when it shouldn't..

This is dev77cmd's code I copied:

#define SENSOR_PIN 2
#define LED_PIN 3

void setup() {
  pinMode (LED_PIN, OUTPUT);
  pinMode (SENSOR_PIN, INPUT);

}

void loop() {
  int sensorValue = digitalRead (SENSOR_PIN);
  if (sensorValue == HIGH)
  {
    digitalWrite (LED_PIN, HIGH);
    delay(15000);
    digitalWrite (LED_PIN, LOW);
  }
  delay(1000);
}

[marco_c]

How is the sensor wired up? Is the input floating when it is not HIGH?

It may be better if you had pinMode (SENSOR_PIN, INPUT_PULLUP) and then a sensor that made the line LOW when there was something sensed, but that depends on your sensor, which you have not described.

[erlank]

Thanks for the quick response. It's the PIR sensor, 2m-7m range (not the tiny variant). I think the issue was the powerbank. I even connected my two lithium batteries (18650 × 2) I'm using for the 1st time and there is no false alarm anymore. Only last week I learned how a bad powersupply (car battery) can screw with its systems.. the Arduino/sensor "world" seems to be very alike in that way. I should really do an Arduino course, I'm just not sure which one.. I'll check the forums on that topic.

[xfpd]

Looks like data out will be HIGH when active.