Optocouplers aka Opto-Isolator with an Arduino (or without)

I don’t know why people don’t use optocouplers more often. I look at a quite a few home brew circuits (hackaday.com is a favorite) and I just don’t see them used.  Then again why would someone use them? The best answer for this is in their name, Opto-isolator.  You can use these cheap little ICs […]