As I understand it, a non-contact voltage tester works by creating a capacitive connection from a power line to ground, via the detection circuit and the operator's hand/body. This connection passes a tiny amount of current which the detection circuit can pick up.
I'd like to use my Arduino to detect the presence of mains voltage (120v) in a wire without actually connecting to the conductor (for safety and isolation reasons). Because there may not be any current in the wire, current transformers/hall effect sensors would not work.
Is it possible to use a similar approach to the non-contact voltage testers to detect the voltage? I couldn't find any schematics online for commercial testers to see and understand how they work.