I bet it won't make much difference whether you select 5v or 7v. But I'd rather under volt something than over volt. So I'd see if it works at 5v. It's probabl

I bet it won't make much difference whether you select 5v or 7v. But I'd rather under volt something than over volt. So I'd see if it works at 5v. It's probably unlikely but an over voltage could result in some component going through its breakdown voltage level (although I think 7v rather than 6v makes this unlikely). And from Ohm's law (V=IR) current and voltage are proportional and so more volts and you'll get more current and that could burn something up.