endryha:
I want to trigger LED when voltage is HIGH and this is exactly what I already tried, but connecting LED with series resistor like this reduces input voltage to driver input pin from 5V to 3V because of the series resistor, so I feel that this is not the best way to approach.Or you trying to say that it doesn't matter that I have voltage drop? Sorry I still confused about this...
If your output signal drop to 3 volts, there are 2 possibilities. Either you are using too low a resistance or no at all, and the LED "shunts" the voltage heavily, which will eventually break your Arduino.
Otherwise, you have the resistor placed incorrectly. Look at my drawing attached.
// Per.
