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+AD4-   Simply put, I need to know when something has been unplugged 
+AD4- from a AC socket.  I don't care about how much current its 
+AD4- drawing (I do...but I dont need to know), because in some cases 
+AD4- it might be a 100mA wall wart and in other cases a 100W power 
+AD4- supply.
you can always put a shunt resistor in and then compare the voltage accross it with a threshold. If we assume its a 20A outlet and that we can tollerate a maximum of 0.5V of volt drop that means we need to use a resistor of 0.025+A6k-. That means at 100ma we have a voltage of 0.00125V accross the resistor. To detect this i'd amplify (use an inverting amplifier design since the input is low voltage but also low impedance) and evelope detect it with an op-amp circuit powered by a transformerless (resistor/capacitor) power supply with its +ACI-ground+ACI- at mains live then feed to an opto-isolator to transfer it to the rest of your system.






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