mrDickson:
i see..
No, you very probably don't see. You have already said the code works when connected to the computer. Is that true or not? If it is true, you might start over by giving a concise summay of the reasons why you consider the code is suss. Failing that, you might plug Arduino back into the computer and report on the result. If it does work, again, you might have found some motivation for reading reply#3, amongst others, again. What have you done to change the situation? You have changed the power supply. Is the power suss? Very likely. Does your description of the wiring make any difference to that suspicion? Not really, as your verification of the adequacy of the connections is non-existent..
In the meantime, what happens when you connect the 5v,3A, to 5v and GND, any lights? Have you actually checked the voltages, or are you just guessing? In view of the code working, and 3A very likely to be adequate, a slack-arsed connection is a reasonable bet. I recognise that you appear to have cut yourself off from visual indication, a temporary LED activity light might help - or even repeating to LCD, but a $5 digital volt meter is a good thing to have right now.