Earthing cable which will be happy in the cable chain, flexable.. I am earthing the frame, gantry etc...

I think you dont need to pull a wire to the gantry, it is sufficient to bolt a wire somewhere to the table. metal conductivity will do the rest.

Danilo, you definitely need to pull ground/earth wires to all the moving parts.

I used auto audio cable. It is very flexible and about a # 10 wire. It's zip wire so it's easy to separate into a single.

Thanks for replys, I need to earth my gantry,car etc... also i am using plastic vee rollers at the moment. So its a must for me.

Adam, you will have to walk into a couple of shops and see what they have. Automotive supply shops (auto-electricians) could be very helpful - their wires are more flexible than most.

Lugs on sheilding
 

Can anyone describe the best way of attaching a lug to the sheilding braid.

Everytime I attempt this, the wire just disintergrates.

Is there a knack in trimming the sheilding.

Thanks for everyones help in advance.

Peter

I used crimped on lugs.

Pete, the basic approach is to separate the braid from the rest of the wires, and then squeeze / twist the braid into a solid bunch onto which you can crimp a connector.

Three possibilities for you:

1) Fast and sloppy: cut a vertical slit in the braid along the wire for a few inches. Shake the loose bits out, twist the remains together.

2) Elegant: Use something pointy to elongate one of the diamond holes in the weave a few inches from the end. Carefully pull all the internal wires out though this hole.

3) Fallback: Use something pointy to unweave the braid starting at the end and working backwards bit by bit.

The other technique sometimes applied is if you are coming into a connector with a clamp-on metal strain relief. Then you clamp a solid wire under the clamp with the braid, and use it to complete the wiring.

Thanks
 

Thanks Brad

I have done 1,2 & 3 and 2 & 3 win they are not hard to do if you raid the wifes sewing box.

Any thanks again

Peter

Im thinking about the Ground loops and my conclusion is "irremediable"

this is my ground schematic.

Attachment 11565

http://www.mechmate.com/forums/attac...4&d=1268042455


Between the Screen and the PC we have one irremediable ground connection via VGA port. pins 5 to 10 are ground.
Between the PC and the PMDX we have one irremediable ground connection via Parallel port, pins 18 to 25 are ground.
Between the PMDX and the Drivers we have one irremediable ground connection. In PMDX are COM ouputs, in Driver PUL- and DIR-.
Between the driver and Control Box chasis, screws.
And the Chasis is connected to the 220V Ground.

I tested all with the continuity meter.

Im thinking only one solution, and is cut the Grounds cables between Screen and 220V and between PC and 220V.

Any sugestions?

Hmmm. I'm thinking I wouldn't want to cut the grounds in an industrial environment, particularly at 220V.

I don't think that the potential ground loop with the screen matters.

If your drivers are Geckos, there's optoisolation on the inputs, so ground loop effects are likely to be mitigated.

I don't see your motor power supply on your diagram. My suggestion would be to make the motor power supply have the reference ground post for the entire system, and have that be the point that ties to the supply ground (along with the feed to the power supply). Use that as a star wiring point to ground all portions of the table, all the drivers, all the cable shields, and all the motors.

Don't worry about the PMDX, the computer, or the screen. If you don't have optoisolation for your drivers for some reason, consider adding an optoisolation board on the parallel port (like the PMDX-103) should you have problems. Then you can definitely ignore any potential ground loops on the computer side of things.

I agree with Brad, I do would like to add.

If they are Gecko's you should have 3 inputs. A common, a step and a direction, don't confuse that common with a GND, common is not a GND.
Since the inputs are isolated (in case of a gecko for example) you just connect these 3 wires with the GND, a step and a direction pin on your PMDX, Don't connect the GND of the PMDX with a GND of the drivers! Again, if the drivers are opto-isolated.

I would also suggest like Brad to add a opto-isolation board in case your drivers are not opto-isolated, but I would put it between the PMDX and the driver, that decision is up to you...

Yes, the drivers are optoisolated.

But my test with the continuity meter was wrong... i put positive continuity meter in the driver COM and the negative continuity meter in the Box chasis and obviously we have continuity by the long way. now i can see the ground is in the driver chasis from the box chasis and the ground is in the common from the pc ground. (one optoisolated loop ground).

Thanks.

I have read this thread looking for a concensus on how to deal with the shields in the large pushbutton box. This box contains cables that originate in the main control box that have their shields grounded in the control box.

There are other cables that originate in this pushbutton box and go to the y-car and far end of the gantry. What is the preferred option for dealing with these shields?

Please advise?

Clayton

I connected all shields together in my control box and left them all unattached on the machine. All runs fine.

Al

Hi Alan,

Tying all shields together in the pushbutton box has been done but ...

It was suggested that this was not a best practice (Mike Richards and Gerald in posts 59 and 60). Shielding and grounding are different as they serve different purposes. Since the shield is there to prevent interference and not necessarily for safety, can I simply connect the shields that originate in the pushbutton box to a nearby ground point on the machine?

Clayton

I like to see grounds terminated at one end. This will transfer stray frequencies to ground at the supply end and not the machine end. Tying at both ends or the middle may induce stray unwanted frequencies causing funny unwanted things to happen.


Al