Arduino led not blinking
#include &lt;Arduino.h&gt;

void setup()
 {
  pinMode(13, OUTPUT);
 }
void loop()
{
 digitalWrite(13, HIGH);
 delay(1000);
 digitalWrite(13, LOW);
 delay(1000);
}

The problem with your code is that the delay function works in milliseconds and not seconds . 1sec = 1000ms .