BOB\Driver crashing? on CNC Plasma table.

[gr8fun]

Thanks Guys.
I'm more of a mechanical chap than electronics...

The wiring and circuitry has always been my toughest part of this project. So, before you tell me I have deserved this...
my earthing and shielding is, ..well lets just say.... "inadequate"

My power lines are (more by luck than judgement) away from the signal wires but the earthing is only through what gets provided via the 3 pin plugs used - nothing more than that occurred to me - sorry.

To improve my position, what is the proper way to earth a system like this and how best should I shield things?
Many thanks for your help - sorry I set myself up for this, then dropped it on you...

[EddyCurrent]

Have a read here maybe, there's some small diagrams showing correct and incorrect earthing.

http://www.randyray.com/tmc/rf_shielding.htm

[JAZZCNC]

Well I think you have been very lucky to get it working anything like stable if you haven't got sheilded wires and correct form of grounding.

It's not difficult really and it's more attention to detail than anything with a few correct procedures.

Earthing is all done thru the Mains earth but what you don't want is individual earth wires going to several earth points on the machine. You need ONE point which connects directly to the MAINS earth. This then acts like a STAR Earth point for all other earths Ie: shield wires to connect too. This then avoids any earth loops which flip drives etc brains out.!

ALL Signal wires and Motor wires should use Shielded cable which the shield wire then goes to the STAR point.

It's that simple really but makes a big difference regards noise handling.

One more thing to note is that you shouldn't confuse DC Negative with AC Earth. All DC Negatives should be taken to the DC supply Negative and not to mains EARTH.
Also the PC or it's case should NOT be Earthed to the STAR point. The PC will have take it's Earth from the mains directly so treat it as separate and best put on another separate Plug.

[gr8fun]

One more thing to note is that you shouldn't confuse DC Negative with AC Earth. All DC Negatives should be taken to the DC supply Negative and not to mains EARTH.

Thank guys.
Grounding rod, clamp, cable and connector are ordered. Looking into shielded wires now...

WRT the quote above JAZZCNC, I must admit, the thought had crossed my mind... but fortunately, I had taken it no further - so thank you for assuming I was a real noobie - you hit the nail on right on the head! ;-)

ATB
Danny

[JAZZCNC]

Thank guys.
Grounding rod, clamp, cable and connector are ordered. Looking into shielded wires now...

You should not have to do this and I'm not sure it's a good idea even, given lightening strikes etc, in regards insurance and safety.
Unless your mains has No Earth, which I doubt, then I'd just go with making a better job of the shielding etc.

Regards the DC Negative AC Earth comment then wasn't meaning or thinking your a Numpty but rather it's a very common misunderstanding and cause of confussion for folks not electricly minded.!

[gr8fun]

Hi JAZZCNC

I think I should be doing something, even if it s to earth all the bits (table, water bath, garage doors etc.) to the same star earthing point as currently nothing is earthed unless it is plugged in (and I'd hazard a guess some of my kit does not have earth connected! - I inherited much of it from my grandfather)
So I plan to link it all up and connect it to the mains earth (the rod arrived, but I've not decided on a location for it yet - if i can use the mains earth that will save me a job.)

Moving on to the shielded cable, I've just got my head around mains wiring, but signal cables are a totally different ball game I'm sure.
What should I be looking for? I need 4 core shielded, but how "big" or "small"? Is bigger better or detrimental?

I'll be taking the opportunity to relocate the PC and drivers etc. further away from the table so this is all a good thing :-)
Thanks for your help everyone.

Dan

[JAZZCNC]

What should I be looking for? I need 4 core shielded, but how "big" or "small"? Is bigger better or detrimental?

1.5mm/2 for steppers and for signals to drives, limits etc then 0.75 or0.5mm/2 will be enough. You could also use shielded Cat5 cable which as 8 wires in twisted pairs which is good to use in the control box to cut down on wire runs.

I'll be taking the opportunity to relocate the PC and drivers etc. further away from the table so this is all a good thing :-)

Don't go crazy on the length keep it to the minimum you need.! . . . Long wires mean longer more receptive/conductive antenna.!!

[gr8fun]

Don't go crazy on the length keep it to the minimum you need.! . . . Long wires mean longer more receptive/conductive antenna.!!

I was planning on relocating the control box and PC next to the table rather than under it. so perhaps a couple of meters difference..
Thanks for you guidance, much appreciated.

Dan

[irving2008]

1.5mm/2 for steppers and for signals to drives, limits etc then 0.75 or0.5mm/2 will be enough. You could also use shielded Cat5 cable which as 8 wires in twisted pairs which is good to use in the control box to cut down on wire runs.

Use CY cable. Never use CAT5 cable for anything that moves regularly unless it's flexible patch cable. Normal CAT5 cable will work harden and fracture.