![enter image description here][1] [1]: /editor/20170217/58a67692847e3.png When I run simulation I get zero current in the ammeter. The input of the opto is an LED and should act like one. If i put an LED across the Opto input terminals (As shown in diagram) I get the expected current flow. Can anyone tell me what I'm doing wrong with the opto (ignore the output circuit of the opto its not finished yet) to stop it acting like its open circuit?