Magician:
No problem, if it is 5V output you can connect it directly to Vin, instead of power connector jack.
That is just plain wrong. External power connector and Vin pin must have at least 7vdc to power the on-board +5vdc regulator correctly.
Magician, I've noticed you frequently give out advice and answers that are just not even close to correct. Perhaps if you read and study more you might gain the knowledge to give more accurate advice.
Maybe you don't understand the questions being asked correctly? Not meant to offend you, but it's just that most of your responses to posts are just kind of off the wall. Why is that?
Lefty