I'm looking at this 110v to 5v power supply and it has 2 inputs on one side, I assume you can plug either side to either wire coming out of the wall since it is AC.

However, on the other side there are 3 spots to solder in. One negative, one 5v+ and one labeled +.

Does anyone know what the + will be? Would it be the 110v passed through? I don't know why they built it with two +'s.

The part:
http://www.ebay.com/itm/AC-DC-Power...e=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649

 

It's a 5V 700mA single output, smpsu.

 

I assume you can plug either side to either wire coming out of the wall since it is AC.

Yes, if you're sure those two connections are the power supply input.
Use a multimeter to measure the voltage between the negative terminal and the + terminal. What does it measure?

 

From the view of the bottom of the board it looks like the +5V connection is intended for output of a three terminal regulator which is not fitted on this board and so may not be connected to anything, leaving the + and - as the actual power supply output. Best check when it's powered to be sure.

 

I am not 100% sure that hole at the end is for power output. I think it is just a Messy board. Looking at the things on the board on DC side it says +5V I think that is only saying what this supply is able to do. Then I think looking at the PCB layout. They added a - on the one side within a circle and then on the side close to the hole they show another circle with + in it, I think that is only to show why side is Positive and ground. Most times with these they have holes for adding post or something to set them off the mounting surface.

This is only a guess, This guess if from one that I own with many holes at the ends and at the holes there is same type of silk screen however when I tested them holes they were not functional and only was showing what side did what. with other info that was kind of useless.

 

Ok, it seems the consensus is, just test it with a mumultimeter. That makes sense.

I've never seen something like that so I wasn't sure if it was a common technique. I'm not advanced enough to know what can and can't be determined by the community with just a small amount of visual information like the few images of this device.

I guess even master electricians need to test it to be sure.