Remote-Controlled PC Power button PCB question

[stig124]

Hello,

I finally "made" (I'm in the middle of the making actually) a remote controlled PC power button using :

- An Arduino Uno (soon be replaced with a Nano)
- A Raspi 3 for network connection purposes
- and a basic 5V relay

It works but it needs a PCB and enclosure to stay permanently in my setup (the relay is lying upside down actually on the bottom of my PC Case  )

So I made the appropriate schematic and board in Eagle

My question actually is :

How a PC power button work is by shorting a pin with a standby voltage (I believe it's 3.3V) with a recieving one.
As I want it only to be on for around 200ms at each request I hooked the PWR+ on my Motherboard to the common pin (pin 1 of the relay) and the pin 5 (NC) of the relay to the PWR- of my Motherboard but I'm facing a dilemma here, the NO pin (pin 4 on the SCH, and on the top left hand of the relay in the PCB) of the relay will obviously be 99% of the time with the standby voltage at it's pin, which is floating actually (I know it's very dangerous in my case, but as it is temporary I take the risk).

Though I can't find a way to ground it in my case, the only way I found to ground it to the GND of the Arduino but I don't know if it's a good idea as the current is produced by the motherboard, not the Arduino (And I can't ground it to the motherboard as all the gnd pin are taken)

If someone could give me advices that would be awsome