Using the Earth Ground... Questions

Using Arduino Project Guidance
1

I have (2) 5VDC @ 1A switched floating ground (groundless) power supplies.

PSU #1 drives the Arduino via the round plug

PSU #2 drives a PC case fan (DC motor for all practical purposes)

I will be reading (3) analog voltages from external sensors. These sensors are using shielded cables to each (CAT7 cable).

Can I bring the Arduino ground, shield drains on the cables, and machine chassis to earth ground of my wall outlet to lower voltage fluctuation and increase stability?

I would imagine this would optimize the analog reads...

Ideas?

Thanks,
Beefey

2

Not exactly your question, but this explains how you decide what and where to ground things in your Arduino DC circuits.

PROTECTIVE EARTH/GROUND is different, but should verified by qualified electrician to keep your users alive.

Arduino DC Grounding and power supplies.

3

Can I bring the Arduino ground, shield drains on the cables, and machine chassis to earth ground of my wall outlet

Yes if you want.

to lower voltage fluctuation and increase stability?

It won't do that for you.

4

lastchancename:
Not exactly your question, but this explains how you decide what and where to ground things in your Arduino DC circuits.

PROTECTIVE EARTH/GROUND is different, but should verified by qualified electrician to keep your users alive.

Arduino DC Grounding and power supplies.

I read this thread... I am only tying the arduino and the cord shields to earth ground (the round pin on the 120V plug) through a separate cable.

The fan is being driven through a relay so I'm not too worried about any grounding there.

Will my laptop USB ground mess with that earth ground?

5

Will my laptop USB ground mess with that earth ground?

Unlikely, and may cause serious issues.

The laptop internals may be floating above ground (not necessarily any perceptible voltage to touch, but enough to fry your gear) if you tie the negative DC supply rail to ground.
The laptops USB outer shield could be tied either to DC 0V or Earth, you can’t depend on it.

You can buy USB opto-isolators for this type of problem, but it may be worth finding someone that understands earth currents to review your work before putting it in the wild.

Controlling external mains from any electronic devices should be with relays or similar, or inputs that provide total electrical isolation - both for people and equipment.

The Worst case is electrocuting someone with ‘apparently’ low voltages.