Componet Grounding

[Mr.Chips]

I’m building a new console and was wondering/concerned about grounding of the various components.

I’m not electrical savvy but when I thing “ground” I think of connecting things to the green ground wire that runs back to the master breaker box, is this the correct grounding that is thought of in CNC? If not please explain for the items below.

I have Gecko 251’s mounted on a heat sink, should the heat sink be grounded, as above?

Also the shielding on the stepper wires, should that be grounded, as above?

And the metal parts of the machine itself, should that be grounded, as above?

If there are other ground points that I have not mentioned please let me know.

Thanks

Hager

[Al_The_Man]

There have been many previous posts on grounding this is an example.
http://www.ese.upenn.edu/rca/instrum...round/grd.html
The above link requires a little more explanation and I am working on adding a few things to a similar article.
The basic concept is to set up a central ground point which is connected to the service ground.
All P.S. commons that are grounded, cable shields and motor frame grounds should go to this point, if drive heats sinks are connected to chassis, they are usually bonded through the enclosure, otherwise a bonding conductor should be taken to ground point.
Also any metallic part of the machine should also be bonded to the central point.
When using PC based systems, although usually grounded at the power supply point, I always take a separate ground from PS common or where the control exits the PC, in the case of a Desk top PC using the parallel port, this would be port common, this ensures no ground current passes across the MB.
This also helps avoid spurious noise causing false triggering.
Al.

[Mr.Chips]

There have been many previous posts on grounding this is an example.
http://www.ese.upenn.edu/rca/instrum...round/grd.html
The above link requires a little more explanation and I am working on adding a few things to a similar article.
The basic concept is to set up a central ground point which is connected to the service ground.
All P.S. commons that are grounded, cable shields and motor frame grounds should go to this point, if drive heats sinks are connected to chassis, they are usually bonded through the enclosure, otherwise a bonding conductor should be taken to ground point.
Also any metallic part of the machine should also be bonded to the central point.
When using PC based systems, although usually grounded at the power supply point, I always take a separate ground from PS common or where the control exits the PC, in the case of a Desk top PC using the parallel port, this would be port common, this ensures no ground current passes across the MB.
This also helps avoid spurious noise causing false triggering.
Al.

Thanks AL,

Now I have more questions.

My PS lists: See photos.
"N" which I think this is Netural or "-",
"L" I think is Line or "+",
and the "Ground symbol" (green wire earth ground).
Is this correct, did I guess right?

In the "VIIBasic Grounding Practices" section in the link you supplied they show + and - on the PS connections but no ground. and thay show the "-" connected to earth ground. Are the two the same??

So I should establish a common ground point in the control box where all grounds (within the control box and the metal parts of the CNC) are returned to the Green earth ground wire, correct?

"When using PC based systems, although usually grounded at the power supply point, I always take a separate ground from PS common or where the control exits the PC, in the case of a Desk top PC using the parallel port, this would be port common, this ensures no ground current passes across the MB."

I am using a desk top PC, with a parallel cable running to the control box. You mention the parallel port, I know this contains several ground lines, so in this case I do not need to run a ground line to the PC, PS, Is this correct?

Thanks AL

Hager

[Al_The_Man]

The link has to be improved as I say, there is often confusion because common and ground are often interchanged and in some cases are not the same thing.
I prefer to refer to ground when it is actual Earth Ground and a PS -ve to common rather than ground.
Correct on the central ground point.
You can get away without grounding at the port, but keep in mind that if you have any ground current appear on these lines, this current will travel across the MB to get to PS ground.
Coincidentally I had two instances this month of something I have never seen, this was on a ribbon to terminal break out board, a ground had occured on some equipment and the current travelled back to the PC PS burning out the printed trace on the break out board.
This would not have happened if the ground had been bonded separately.
Your PS connections look correct L N and Gnd.
don't forget to take your incoming service ground to the central point.
Al.

[Mr.Chips]

The link has to be improved as I say, there is often confusion because common and ground are often interchanged and in some cases are not the same thing.
I prefer to refer to ground when it is actual Earth Ground and a PS -ve to common rather than ground.
Correct on the central ground point.
You can get away without grounding at the port, but keep in mind that if you have any ground current appear on these lines, this current will travel across the MB to get to PS ground.
Coincidentally I had two instances this month of something I have never seen, this was on a ribbon to terminal break out board, a ground had occured on some equipment and the current travelled back to the PC PS burning out the printed trace on the break out board.
This would not have happened if the ground had been bonded separately.
Your PS connections look correct L N and Gnd.
don't forget to take your incoming service ground to the central point.
Al.

OK AL,
I got it all except "Coincidentally I had two instances this month of something I have never seen, this was on a ribbon to terminal break out board, a ground had occured on some equipment and the current travelled back to the PC PS burning out the printed trace on the break out board. This would not have happened if the ground had been bonded separately."

Too prevent this I should run a ground line from my ground point in the control box to the PC PS case, Correct?

Thanks

Hager

[Al_The_Man]

That is one way, I often run a connection from one of the 4pin HD plugs to ground, this bypasses or shunts the MB GND connections to some degree.
Generally I do not have this problem as I use industrial PC's such as Advantech, these are single board computers that mount in a backplane and they have about six chassis screws that ground the backplane as well as a ground terminal.
Al.

[Mr.Chips]

That is one way, I often run a connection from one of the 4pin HD plugs to ground, this bypasses or shunts the MB GND connections to some degree.
Generally I do not have this problem as I use industrial PC's such as Advantech, these are single board computers that mount in a backplane and they have about six chassis screws that ground the backplane as well as a ground terminal.
Al.

OK, got it.
I'll just tap into the Black (ground) wire on the HD power plug.

Thanks AL

Hager