Arduino + 2PS = only one ground?

I have this simple project:

  1. 12V PS 2A feeding a LED tape
  2. 6V PS 1A feeding an Arduino board with a few LEDs hooked to a couple transistors and a couple LEDs direct (no Arduino controlled)

So basically I have:

  1. Three wires for the controlled LEDs (2 positive and one ground)
  2. Two wires for the direct 6V LEDs (1 positive and one ground)
  3. Two wires for the LED tape (1 positive and one ground)

My problem is that all these wires will come out from the "control box" (where I have the Arduino board and both PS) and pass through a thin pipe that I am fearing that won't be wide enough to accommodate everything. I would like to join all the grounds together then I could eliminate two wires from the harness.

Theoretically I think that it can be done but I am not that smart in electronics (I am concerned with the two different PS). What do you think?

Below a crude layout to give a better idea...

Not only can you connect the grounds, if you're using the Arduino to control the LED tape, you need to connect the grounds.

Is the pipe metal? I'd be tempted to use it as ground if space got really tight.

Hi,
Yes the 3 grounds need to be connected. Th is concept is called "Common Ground Point.

The usual convention is pick one point, connect all grounds to it.

In this case the device with the most current seems to be the 12V power supply.

So I would pick as the “Common Ground Point” the Negative terminal on the 12V supply.

terryking228:
Hi,
Yes the 3 grounds need to be connected. Th is concept is called "Common Ground Point.

The usual convention is pick one point, connect all grounds to it.

In this case the device with the most current seems to be the 12V power supply.

So I would pick as the "Common Ground Point" the Negative terminal on the 12V supply.

That's the worst possible choice then.

The common point should be the Arduino itself - since the 12V supply has high current
its wiring will have the largest IR voltages across it. You don't what those voltages in
the same circuit as sensors and sensitive electronics, just private to the 12V supply and its
LED strip.

One nice little design trick is to draw your circuit and shade the high current wires as
thicker lines. Then keep everything else from sharing any of the "thick" wires.

Thanks for the responses guys!

The pipe is metal (a section of a telescopic car antenna). The Arduino is NOT going to control the LED tape. The strip will be connected directly to the 12V PS and my only reason for add it to the equation is to "eliminate" the extra wire. Now the 6V PS will either feed the Arduino board, a section of LEDs powered directly (no Arduino) and a section of controlled LEDs (Arduino).

Now the 6V PS will either feed the Arduino board,

One of the few voltages that you can’t power an Arduino with. It is too high to feed into the 5V pin and too low to feed into the Vin pin.