General interfacing advice using optocouplers

Using Arduino General Electronics
6

Hi, thanks for the reply's.

Thanks for the detailed advice Lefty! I will try that :slight_smile: Should I use resistors on the arduino digital pins also? If it is written HIGH via the internal pull ups and I ground the pins, how much current would flow? I know the pins supply about 30mA but how much would it sink?

Apparently the 13V output from the alarm can supply up to 200mA so I plan to run the arduino & ethernet shield from that. Would you simply run 13V into the Vin or step it down first?

Thanks!