Opto 4n35 on Arduino digital input...no signal

Hey guys,

I have some problems to get an signal in my Arduino Mega 2560. The image explains my circuit. I have on the right side of my opto a 5V HIGH/LOW signal which I still get on the other side between opto-pin 5 an 4, but only it is not connect too my Arduino on digital pin 2. When I connect it to may Arduino, my signal HIGH/LOW is between 0v and 0.6V and so i detect only a LOW signal when I make digitalRead(2). Does anybody know why the signal level is falling? I tried a Pull Up resistor 1k, but without effect…

Thanks for all answers

Schem. looks fine for me, only 1 k is too low resistor, should be around 10 k. Anyway, low resistor would drive input to HIGH, not what you observe, are you sure your pin 2 isn't declared as output somewhere? could you post a code?