Those are good questions
It came from a place called mikrocontroller.net as a Unipolar Photovoltaic Amplifier. It contained an Op Amp on the output but i was already getting levels i liked from the opto isolator and i havent included it yet.
This is what i am NOW running...
I fixed the diagram
The output of the IL300 is connected to the 5V and GND of the Joystick port. I Assumed maybe wrongly that it would work like a potentiometer for an analogue joystick.
The other GND and 5V are entirely independent of the STE
The Signal i am watching is between pin 9 and 5
EJP is Enhanced Joystick Port
My scope is between pin 9 and the point between R4 and Pin 5 so that i can still monitor if pin5 is connected or not
If i do not connect Pin 5 i get the to two traces
If i DO connect pin 5 i get the bottom two
The 741 seems to to have something to do with the IL300, apparently the matched photo diodes at 3/4 and 5/6 keep it stable, feeding back from the 3/4 photodiode ... i would imagine its a little sensitive because its a linear coupler instead of a simple on/off thing.
I should put the other opamp in shouldnt i? Instead of the cap?