tinkercad LU-5-R SPDT relay + 4N35 optical switch

void setup()

{

  DDRD = 0b00000100; //pin 2 as output

}

void loop()

{

  PORTD ^= 0b00000100; //toggle pin 2

  delay(1000);

}

reference:

https://www.youtube.com/watch?v=dmvvZPVOGro