Hi, I am an electrician but this is not my area, so I need help, I'm going to build device that uses electromagnetism to retract usb at restaurants and bars , Im talking minimal voltage for magnet ,my question is if only using usb cable for charging and not data transfer, how much shielding do I need? is typical micro usb cable shielded enough it won't effect? IT will be strictly for charging cellphones at the restaurant tables but when flip switch kills magnet and cable retracts. Following me? I know maybe a little weird but will explain more later, can anyone answer my question?