using ATX12V PSU for arduino/stepper/LED array

Other Hardware General Electronics
1

Hello,

I've made some posts about this before, I'm making a 3D zoetrope/strobescope sculpture using an arduino and a stepper. I'm getting very close now! The problem is, is that there is a little bit of drift on my objects being animated. I have the program strobing 15 times per rotation because there are 15 objects to animate. The problem is that the objects don't stay still, but drift a little to the left. I feel like maybe it's because I'm not powering the project correctly and the stepper slows down just a little and speeds back up each rotation.
So
I want to swap out the 12V 5A wall wort that I'm using and use an ATX PSU I have laying around.
It's 12V 8A, or 14A. I was going to use a few different outputs to power the arduino, the motor and the LED array separately. So my question is, is that can I damage anything giving so much amperage? I remember reading somewhere that steppers have a maximum current rating or something. Is there any way to find out what mine is? I can't find the datasheet anywhere for it but I know it's a 1.8degree stepper at 200 pulses per rotation. A pretty standard little stepper that someone who worked at MakerBot gave me awhile ago. I think they used them in the old replicators. Could I damage the Arduino if I use one of the 5V outputs? It says the 5V ones are 20A.
Thanks so much for any input!

2

I don't know how many times I have had to say this:

The current rating of a power supply is the ABSOLUTE MAXIMUM that it CAN supply.

The device attached to it demands X amount of current. The supply gives X amount IF IT CAN. If the device asks too much, the power supply may fail.

Just because a power supply is rated at 20A doesn't mean that it will force 20A down the throat of anything attached to it. If that were the case, then the computer you'd taken it from would have gone up in flames as soon as you turned it on.