void setup()
{
    // Set the pins as outputs
    pinMode(4, OUTPUT);

}

long ms4 = 500;
long Old_Time = 0;
bool status = false;

void loop()
{

    // status (4)
    if (millis() - Old_Time > ms4)
    {

        digitalWrite(4, status);
        status = !status;
        Old_Time = millis();
    }


}