What are you interfacing to? On consoles I have no idea where you can get 5v or even if you can. Unless its an xbox, those have 5v I believe. If its a PC you can easy get 5volts from a power connector, a keyboard port, or USB. If your connecting to a console you could try to find an old PC power supply and get your 5 volts from that. Another option would to get a 5v transformer.