Same power 2 Arduino projects.

I have 2 Arduino Nano projects I would like to work together and I need advice on how and IF it can be done.

I have a game table where I have the whole thing powered by ONE PC power supply.

One 5v lead is powering one Arduino Nano running the scoreboard.

A different 5v lead is powering a SECOND Nano running the sounds.

I have ONE pos and Neg lead coming off the Scoreboard that supplies constant 5v at the end of a game
(the idea was to add a buzzer somewhere down the line)

I'd like that 5v lead (from scoreboard) to signal the second Arduino (sounds board) to play a track off of an DFPlayer mini acting as a switch.

The Question is, Because they are BOTH running off of the same PC power supply could I just hook the positive to a pin on the second Nano and neg to neg on that project?

OR should I use the same 5v lead that powers the First Project, to power the second, and have it hooked up the same way?

I'd ultimately would like the pin state to act as a switch on the sound Nano to play a track.

Thank you.

Can You make it more clear? You tell about powering one controller from Pc supply and You tell about "wires" here and there. Be nore precise!
It is probably okey but check that their GNDs are in order.

Railroader:
Can You make it more clear? You tell about powering one controller from Pc supply and You tell about "wires" here and there. Be nore precise!
It is probably okey but check that their GNDs are in order.

Sure, I have a Pc power supply that I've "hacked". Each of the 12v and 5v wires are powering different aspects of the same Game table (ie: lights, sounds mechanics exct.)

One Pos and Neg wire (5v) from that Power Supply is powering the Scoreboard, the scoreboard is a Nano that runs the Clock and Score, and some LEDs.

Another Nano will be running the Sounds Via. a Dfplayer mini.

I have one set of wires (pos and Neg) coming off the Gnd and A pin on the Scoreboard Nano, that provides 5v at the end of the sketch.

I'd like to have those 2 wires act as a switch on the second Sounds nano.

my question is how to power the second Nano, if it would have to be off of the same 5v Powering the Scoreboard Nano? OR because they are coming off of the SAME PC power supply, are the Ground wires all the same?

Okey. Never mind the kind of pwr supply. Yov’ve got one central supply. That’s okey.
I suggest that You use one GND node near that pwr upply, as well as a +5 node. From those nodes You supply the current consumers. Keep pwr Cables lengt short and awois large circles actiing like antennas for noice.
Still, the code easiest is to use as few controllers as possible. One is the best, no communication difficulties.

Railroader:
Okey. Never mind the kind of pwr supply. Yov've got one central supply. That's okey.
I suggest that You use one GND node near that pwr upply, as well as a +5 node. From those nodes You supply the current consumers. Keep pwr Cables lengt short and awois large circles actiing like antennas for noice.
Still, the code easiest is to use as few controllers as possible. One is the best, no communication difficulties.

Thank you. I'll try that. If I could I would have used one Nano of all of it. But they were built at separate times, and space constraints do not allow for everything to fit in one spot.

Okey. You ask for more and not so easy work involving controller communicatin.
Nevertheless, regarding good electrical pwr supply technics, You are up on the tracks.