Forgive me if this seems like a basic question but I want to make sure I wire these things up correctly. Currently, I have several LED strips that I am controlling with an Arduino and they are powered by a separate 5v DC power adapter. In that case I have tied in the ground for the DC power adapter to the ground on the Arduino board. The Arduino board itself is then powered by the USB on my computer.
Now, I've decided to upgrade my setup to leverage an ATX power supply. The Arduino will be powered by the 5v stb & ground pins on the 24 pin molex connector and the LED strips will be powered from the 5v & ground pins on the 4 pin molex connectors. The LED strips are programmable via the DIO pins on the Arduino board and I plan to wire the Power On pin from the 24 pin molex connector to one of the Arduino's analog pins so I can use the Arduino to turn the supply fully on to power the strips.
Now my question, sorry for being so long winded. Do I need to run a ground wire between each LED strip back to the Arduino? Since this is all from one supply it will be the same ground so it seems like it would be redundant and not needed. Below is a quick sketch of how I think things should be wired up. If I needed the additional ground wire I was going to run it from each 4-pin molex connector back to the ground pin on the Arduino.
Best Answer
Since you are using the same power supply for both, the Arduino and the LEDs, you do not need to connect the ground pins -- as long as ground is connected internally.
As you have recognized this would be redundant and unnecessary and could even lead to further problems (there would be several ground loops). So I think connecting the Arduino to ground just one time will be fine.