I have a 5v 12A power supply. With the image attached, I am getting no lights on the led light strip. When I plug in the 5v cord from the led strip directly to the arduino the light strip turns on.
Is there something simple I am missing with the power supply? Pretty new to this.
Thanks!
PLEASE tell me that the black and white are NOT carrying mains power?
AJLElectronics:
PLEASE tell me that the black and white are NOT carrying mains power?
If I understand correctly, I think it is. The white and black cord from the PSU is plugged into a wall outlet.
That needs to be dealt with before you do anything else, it is not just dangerous, it is lethal. Tidy up the connections and then fit the insulating strip that is normally supplied with those PSUs. If you have no insulator, your first project must be to put the PSU in a suitable plastic or earthed metal case and strain relieve the incoming mains supply cable. It also needs a low value fuse in line with the mains and low Voltage sides.
Then we can help with your query.
AJLElectronics:
That needs to be dealt with before you do anything else, it is not just dangerous, it is lethal. Tidy up the connections and then fit the insulating strip that is normally supplied with those PSUs. If you have no insulator, your first project must be to put the PSU in a suitable plastic or earthed metal case and strain relieve the incoming mains supply cable. It also needs a low value fuse in line with the mains and low Voltage sides.Then we can help with your query.
Thank you! I'll start working on that.
Terminal 3 is Earth ground ! ! !
It appears term 6 is + and terminal 5 is Common (Arduino GND/0V).
Confirm the voltage between terminal 6 and 5 with a DVM.
Fix the poor connections on the Hot and Neutral power input wires.
I count seven screws on the back of the power supply. What are they? If two of them are for voltage sensing, not having them connected is going to become a problem. Documentation, or model and manufacturer, or a link or something, please.
By the way, the picture is a bit difficult to view but it appears that your Arduino's more negative power connection is connected to earth ground rather than the more negative OUTPUT power connection of the power supply. This would be incorrect or at least incomplete.
I count seven screws on the back of the power supply. What are they? If two of them are for voltage sensing, not having them connected is going to become a problem.
Obviously I can't be sure about that particular PSU but based on a similar one I have I would expect 2 of the 4 right hand screws to be 0V out and the other 2 to be +5V out. Which ones exactly are which I'm not going to guess, but I'd expect it to be marked.
The 3 on the left are mains in, including safety earth.
Thank you for all of the responses! Switching the ground over to the - did solve the problem, the led's are working as expected now.
Expand!
OK, a number of things from the previous discussion.
First and most important - safety!
I see that your power cord has a green wire. I presume it has a three pin plug. Having removed the plug from the wall socket, you need to start again with the terminations by cutting the black and white back to the same length as the green, then remove the sheath for about 2½ inches so all three wires are available, strip the ends ¼ inch, twist the strands together so they stay together and "tin" just the end with solder. Then connect the live and neutral to the first two screws and the ground (green or green /yellow) to the third which is marked with the "earth" symbol.
Now you have a safe power supply (as long as you do not touch the terminals! 
).
You may have been confused by the general reference to "ground" or "GND" in Arduino projects. This refers to the negative reference, but is not always going to be actual ground - it may or may not be connected. The power supply however deliberately does not connect the negative to ground but its "earth" is the connection to the metal case and you do want that to be connected to your mains ground to prevent it picking up any spurious voltage from its internal parts. In fact, should a part somehow short out to the case, you want that to blow a fuse instead of making the case "live".
vaj4088:
If two of them are for voltage sensing, not having them connected is going to become a problem.
No, they will not be for voltage sensing in this case (not that heavy a current supply), but for parallel connection to distribute the quite heavy current rating of the power supply. Clearly the terminals are in order: "L", "N", "earth", "-", "-", "+", "+".
With only a few inches between power supply Arduino and LED strip, you would not need the 1 mF capacitor directly across 5 V and ground at the LED strip, but with longer leads you do. Since the Arduino is (presently) separately powered, you should have a 470 Ohm resistor in series with the data line at the LED strip.