How to Attach 9v Battery Snap to a DC Power Plug?

Hey, I am trying to attach a 9v battery snap to a 2.1 DC power plug, I got these from my nearest electronics store.

However, in order for it to work with my Arduino in need to make the connection center positive, not center negative but I do not know where I have to solder the positive/negative leads on the battery snap to either the bigger pin or smaller pin show in the picture, any help would be much appreciated.

If not sure, use a meter & buzz it out. Handiest, least expensive tool you can have for elecrtronics.

but i don't have a multimeter, nor do i have the money to get one

vdemons: but i don't have a multimeter, nor do i have the money to get one

How about an LED, a resistor, a battery, and a couple of pieces of wire? There's more than one way to skin this particular feline.

If I were to guess, I'd say the longer lead with the hook thingy (on top in the picture) is the (-) or ground terminal. Best to be certain though, wouldn't want you to fry your Arduino...

I'd recommend saving your pennies and picking up a cheap VOM - you can find them for well under $20 (and significantly less if you look around). If you have a dollar store nearby they can be a good source for cheap ones, as can auto parts stores. The parts store near my house seems to always have cheap little AC/DC/Ohmmeters "clearanced" for $5 or so. As CrossRoads mentioned, it's probably the handiest tool you can own for electronics.

The upper (bigger) connection goes to the outer sleeve and the lower (smaller) connection goes to the center pin.


Edit: The 'hook thingy' is designed to be crimped around the shield of a coaxial cable.

A 9 V battery snap is color code. Red is Positive, Black is Negative. Red will be going to the center of the barrel ( the smaller ) connection. The Black is going to the larger connection ( outside of the barrel ) Solder carefully and you are done. Don't forget to insert the plastic barrel ( the battery snap wire ) before you solder the wire. You don't want to "paint" yourself in the corner.