When I got my kit, the barrel connector was not soldered to the battery holder. Initially, I ignored that since I was connected to my computer. Now that I am building some projects, I need to use the battery. I looked on the arduino board and on the connector but can not find anything to show me how to solder the barrel to the holder wires.
Please tell me which is the negative and which is positive so I do not destroy the board on my first try.
The center is +. The barrel is -.
Don't worry about getting it backward. There is a protection diode that keeps the current from flowing the other way.