Grounding shielded wires

howdy. i got to the wiring portion of my build and i’m using shielded 2 strand wire for the limit switches and i’m wondering where people are grounding the wire and foil? also i see that the instructions call for removal of the foil and bare wire on the shielded stepper motor wires: would it be advantages to ground them as well or will that cause problems.
thanks for your help.

This is something that I’m wondering about too :smile:

  • Is it ok to gather all the shields and grounds and mount them to eg.
    the psu chassis?
  • Should the shields be grounded to the ground connection on the psu?
  • Should the grounds from the AC 230V be grounded together with the
    24V grounds and shields?

Typical newb questions, I know :open_mouth:

You only want to ground them on one end. Then end close to your electronics. You can use the GND pin on the arduino, and run a wire to a “ground bus,” to make things neater. Tie your shields to this ground bus. The negative power to your DC spindle can also be grounded to this bus. Your computer will already share a ground with the arduino. It’s pretty important to make sure you are only grounding GROUNDS ( - ) together.

For the real sticklers out there, I’m fairly certain the 24VDC power supply that comes with the X-Carve kit does not internally ground the DC common. So, if you want your shield to be legitimately ground, I’d recommend splicing a three pin power cable from the wall and running true ground to your DC common and shields.

Yes, especially if using a laptop. I use a regular desktop computer with a full size grounded power supply.

Hmmm, I have a sceptical feeling about combining the AC and DC grounds.
What if there is a ground problem in the AC and suddenly you have AC power going in the grounds? What about lightning through the AC? It will easily burn out the thin cables on the DC side connected to the same ground. Or?

Actually, the two should be exactly the same thing. The 24VDC power supply comes with the output floating, or ungrounded. This means if you stuck a plug into your outlet and tested the 24VDC positive voltage relative to your outlet’s ground pin, you might get 24.28V. But then you might measure the DC common voltage of your supply relative to ground and get 0.28V. Likewise, you might wait five minutes, measure it again, and get 22.7V and -1.3V. In general, this is just sloppy design. I’ve seen occasions in the field where floating power supplies lead to currents between common and ground through components and chips, causing overheating or even fires.

I seriously recommend that everyone connect a large gauge wire between the ground pin on their 24V supply to the DC- pin

This will force the DC -, or common, to be the same voltage as ground. If you don’t, the likelihood that anything will go wrong is pretty minimal. Plenty of people have likely been running their X-Carve like that for a long time. But it’s just one wire. Might as well do it right.

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Another good point! Also, I am just ASSUMING, that because I share a ground with my desktop, that it is in, fact grounding to mains ground. I also use a power conditioner/battery back up that might further impact the grounding situation. But should protect the other electronics from lightnening. But I also have a WIRED ethernet connection.

Too many questions here.

Srednasoft, If your hot AC wire is shorted to ground it will blow a breaker at least or if not will start a fire. There is no danger in combining AC ground and DC ground because there is no such thing as either. Ground is literally that. There is a long conductive stick shoved several feet into the soil under your house that is wired to the ground pin on every outlet in your home, and likely all the plumbing.

EDIT: And to be clear, ground voltage will not be anything but ground voltage whether your 120/240V are shorting into it or not. The whole earth has a pretty large capacitance.

LAST EDIT: One more note, last one, promise: For those of you interested in adding additional voltages to your system, like 12V for LED strips or 5V for another microcontroller or something, all of your DC commons, or DC- should be connected together AND to ground. If you have any questions feel free to ask! :smile:

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Earwigger, the DC common on your laptop isn’t necessarily ground. My senior capstone project involved running an Arduino Uno off of a laptop and found that the DC common was floating relative to ground. I had several other voltage supplies in the system, and my Uno being ungrounded caused me all kinds of headaches until I figured out the problem. Granted, my laptop was like 10 years old, but don’t assume the DC common out of your USB port is ground voltage.

Operative word there: Laptop. I would not trust the laptop ground either.

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thanks guys! i’ll let ya know if i have anymore questions.

Thnx @NathanButler,
So, ground is ground!
I have started to build a controller box for the XC. All the electronics will go inside the box. I will then join the green/yellow ground cable from the controller box wall to the psu and alle other grounds/shields on the DC side together.
Is it correct that on the DC side all of the negative wirings are also grounds?

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Yes, with one minor caveat. You’ll want to connect ground to DC- as close as you can to the supply. Then I would just use DC- for your shields. You really only need to ground your supply. After you’ve done that all of your DC commons and grounds will theoretically be the same voltage, so using commons or grounds for shielding isn’t a big deal.

So when you connect the shielding to the grounds it will go together with th black wire connected to gnd on the psu and the gnd on the stepper controller card.
Is that gnd grounds also the same as the V- on the psu?
And, the gnd and V- should also be connected to AC grounds?

I just tore the interface board apart yesterday, but let me make sure when I get home in an hour or two. The ground wire should only need to be connected to the V- on the 24V supply, and to the Gnd pin on the stepper shield. The AC ground from the wall outlet, yes. That is the only ground you’ve got.

Hehe, sorry for all the lame questions. :open_mouth:

It’s alright, you mentioned you were new to this stuff. Don’t be surprised if you see me begging folks to explain feed rate calculations later this week haha

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This is a drawing I found in another old thread in the forum.
So, no creds to me for that one :smile:


Hmm, but if AC grounds is connected to DC V-, you will have 24V flowing out on the AC grounds cables? Isn’t that a no no? You should not induce power to the grounds cables. Or am I on the wrong planet again?