/diy/ - Do It Yourself

>>1504838
voltage divider thing > adc
pic related looks pretty good

If you just want to sense whether it's live instead of measuring its amplitude, then either rectifying it and dividing it down and/or some form of capacitive sensing to isolate the ardy should do the trick. Watch that you don't get any nasty ground loops, but that your arduino's ground is properly referenced relative to the mains. I'd recommend using the earth lug for this if you have the luxury (i.e. aren't pushing any current through it), but otherwise the neutral pin should work fine.