I'm having a hard time understanding how an optocoupler works. I made a circuit based on example 15 if the Arduino projects book. Instead of trying to hack a button, I'm trying to just light an LED on either side of the optocoupler. I'm misunderstanding how this should work because the LED I'm trying to light doesn't light.
My youtube video shows my circuit. You can see the blue LED which runs from pin 2 of the optocoupler into ground lights up, but the red LED (which works, I verified) which runs from pins 4 to pin 5 of the optocoupler does not. I was under the impression that if I emitted high from the arduino to the pin 1 of the optocoupler through a 220 resistor (mine is 270 actually) and provided a path to ground that the optocoupler would be switched on and I would get current and ground from the pins on the other side.
Any suggestions - what am I missing?