I was wondering what your recommendations about the ground reference and where it should be.
One of my projects uses a power supply that supplies 24 volts dc via V+ and V-. I have dc-dc converters, temperature sensors, and load cell electronics.
Is it better to power all the electronics from the power supply and reference the ground of the arduino board to the V- of the power supply? I am trying to avoid the possibility of ground loops.
I do not plan on powering the Arduino board with the power supply but I would need to share common ground if I want to get readings from my sensor electronics to my Arduino board.
I think you are missing the point. The data signals and the POWER for your devices should not share the same conductor! The data conductor ground and the power ground must be connected at a single point. When they share the same conductor, any current changes in the power conductor also becomes a voltage change in the data signals and may be interpreted as stray data signals.
I have a rough flow diagram of my connections I proposed. The data lines are not sharing the same conductor as my power lines. The data lines go to the MCU "Arduino board" but I also connect the ground of the MCU to the V- of the power supply.
The "PSU" should be galvanically isolated from line ground, as if it is on a separate AC circuit from the USB 5V you could run into household AC ground loop problems.
I kept the 24-12 convertor because we had a sensor that needed a 12v input power. Currently it is not in use but I might switch back to using it.
The 5V USB is coming from my laptop. I am using the Serial monitor therefore I am powering the MCU with my laptop via the USB cord. Unless I cut off the 5V line from my USB and just use it for Serial, then I could perhaps pull the 12v from the dc-dc converter to power the MCU.
Would the Star Grounding method be implemented if I use terminal blocks? Have one row of red terminal blocks for V+ and another row of black terminal blocks for V- ? All the grounds would be coming to the same point.
The important point about star grounding is to make sure that sensor grounds do not carry any ground return current from motors and other noisy or high power components.
If all ground connections separately converge on a single point, then you don't need to worry about that possibility.
