Control box grounding

[analogman]

I am looking for recommendations for control box grounding. I am using:

Bob Campbells breakout board and relay board
Antek power supply
Gecko G203V

My stepper cables, limit cables and home cables will be shielded.

The only grounding I have right now is:
- AC input grounded to the control box.
- stepper cables are grounded to the control box

What about the other devices? Should they float?

thanks
-

[Al_The_Man]

There are two schools of thought, some opt for attempting complete isolation of all systems, the other method is to tie (bond) all systems together at a common point together with the earth ground conductor.
If you look through past posts here you will find quite a bit on it.
http://www.cnczone.com/forums/showthread.php?t=71923
http://www.cnczone.com/forums/showthread.php?t=79271
http://www.ese.upenn.edu/rca/instrum...round/grd.html
The application of saftey ground should apply regardless of the system used.
Al.

[analogman]

Hey thanks Al - good stuff in those links. So here is what I am going to do:

Obviously AC supply ground is immediately connected to chassis ground of the box.


My CNC machine will be physically & electrically connected to chassis ground. As well as the spindle (router) ground. The controller computer will be connected to the same chassis ground (all to avoid ground loops).


My power supply (Antek) does not have a specific ground other than its metal chassis/heatsink which is connected to the cabinet. I did **NOT** connect either side of the 50VDC output of the power supply to chassis ground.


The steppers or drivers are **not** connected to chassis ground in anyway. The stepper cable shields are connected to chassis ground - and only at the one end.

The breakout board is **not** connected to chassis ground in any way.

The limit/home switches are **not** connected to chassis ground in any way. The shield for the limit home switch cables are connected to chassis ground, only at the one end.


that should do it!

[ad_bfl]

So I have the same exact setup and have a question or two on your appoach before I fry anything expensive or "sensitive" like myself...

When you say AC supply ground is connected to the chasis, do you mean the ac green wire (safety ground) connected to the Antek chassis? If so then I imagine you are connecting all the metal parts of the macchine to the same spot/bus bar, correct?

Or do you mean the actual low side of the AC line (white in the US) connected to the chassis of the Antek, if this is the case, what do you do with the AC safety ground (green wire)?

I looks like your isolating the DC side of the supply from the chassis of the Antek supply and I assume using a star ground approach for the low side of the DC supplies and drivers...

Given that if one wanted to NOT float the DC side, they would connect the DC bus bar to the chassis ground of the linear supply which is connected to the green safety wire of the AC, is that correct?

Al_the_man, any input on this?

Thanks
AD

[Al_The_Man]

First off, the White or Neutral should never be connected to ground at any other point except at the service distribution panel (in N.A. anyway).
However, the service ground conductor should be connected to your machine Star ground point.
If you decide to use isolated DC supplies, the power supply common should not be connected to the Earth ground point in this case.
All metallic parts of the machine should have a bonding conductor back to the star point and the cable shields should be terminated here.
Al.

[ad_bfl]

Al - thanks for the reply

I just wanted to make sure that neutral is NOT connected to anything besides back at the feed transformer off the pole.

Not planning on floating the DC, I have had too many problems in the past lives with floating DC supplies and analog signals, not going to repeat those fun days this time.

Again - thanks

[Al_The_Man]

I have mentioned this before its my policy to always ground all supply commons, it has also cured some flaky trips from some posters here.
Al.

[analogman]

AD, on a 3 conductor wire (black, white and green), green always runs immediately to chassis ground as soon as it enters an enclosure. White is **never** grounded. Consider the white neutral wire just like the black hot for inside an electronic chassis.

[ad_bfl]

Thanks guys

110/220volts scares the C**P out of me, grew up in a family of builders and remember seeing my uncle the electrician blown across a room from being careless.

Thanks again