STP16CP05 with Arduino wiring help.

why do they say forward voltage ie 3.5V? Thats just confusing.
Thanks again Rob

Because a diode will not start to conduct until the applied voltage is the correct polarity and exceeds it's forward voltage drop rating. Then, even if you raise the applied voltage, the volt drop stays constant across the diode. Different diodes, especial LEDs, have different forward voltage drop ratings.

Lefty