not too sure what a star point is, how do I connect it to the metal braid screening?
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not too sure what a star point is, how do I connect it to the metal braid screening?
here is some reading for you.
https://en.wikipedia.org/wiki/Earthing_system
This has been talked about many times on here try a search !! Read some of the build logs etc you don't seem to take advise when offeredQuote:
Originally Posted by ravihotwok
Advise welcome, instructions even better. Searching is great, but is something can be answered in a simple sentence then that saves a lot of time. Will do a search now and see what I can find.
That wiki link explains a lot. Except the best way to go about physically achieving it.
I now understand what a star point is. Can I splice into each of the motor cables just to expose the outer metal braid, then solder/heatshrink a cable to it which can then me linked to a star point in the box?
the screen is just metal that picks up the noise and passes this noise back to ground as current, so as long as you have a good connection to ground that is all you need. so use your initiative and solder a wire onto the screen and connect it to gnd.
how you do it is up to you and depends on how messy you can accept.
Great Gary, I understand that. Im pretty sure I can do that nice and neat and finish off with a bit of heatshrink to keep it all covered up.
Ravi, like this:
Basically you are building a path for any electrical noise that may target your cable and give problems, so it can leave the system.Quote:
Originally Posted by JAZZCNC
Awesome lee, instead of doing it like that I will do it a bit further back as ive got plugs on the end of my cable which connect into the planet control box. But I will put a earth point where the plugs go into the box, so there will only be a short length from the motor cable to the box for earth, should look reasonably neat. Thanks chaps for explaining in laymans terms, helped a lot. Will crack on later tonight and report back with some more pics
G'Day Ravi, as one layman to another, I know it can be tricky getting succinct info on this subject.
Here are a number of references that I have kept on this subject, that I hope may be of some help.
I'm enjoying your thread, keep up the good work!
Andy
Grounding and Earthing
Electric current through a wire creates a magnetic field around it. Current flowing in opposite direction creates an equal and opposite field. Keep the wires close, ideally twisted together, and the magnetic fields cancel out, don't transmit interference, and are resistant to outside magnetic fields for the same reason (rather simplified but the principle is true). Pass wires through separate holes and not only do you lose that "cancellation" effect because the wires are further apart, but you now create a magnetic field between the two wires that can induce (= create) a current in the metal box between them, which is exactly what you don't want to do. I can bang on about differential signalling and common-mode rejection, but the simple model is pretty sound to understand what's happening.
http://www.mycncuk.com/threads/5036-...7665#post87665
Grounding and Earthing often creates a lot of confusion and to some extent depends how old you are. But you don't connect your DC ground to the Star point which is the point where all the screens connect to and then that is connected to the AC earth. The reason for the Star point is to get rid of earth loops (or ground loops if you are old).
Sometimes you have more than one DC power source and again sometimes you have to connect the various DC power -ve together. Hope this helps a bit.
http://www.mycncuk.com/threads/7662-...3631#post83631
But in electrical engineering context words Ground and Earth differ in scope.
Ground is a general term that refers to a reference potential against which all voltages are measured.
Earth is same as ground but used in context of power systems because the ground here is implemented by burying copper conductors deep down into Earth.*
Since Earth has minerals, moisture and it has practically infinite volume, the current flow is only limited by contact resistance between ground/earth conductor and soil. Because of this, on the distribution side, the neutral is connected to earth. On receiving side, fault current from one of the phases can flow into the local earth conductor and make its way to the neutral at distribution side. Apart from being a sink for fault current, the Earth conductor also serves as a return path for instrumentation systems.
http://www.mycncuk.com/threads/7662-...3653#post83653
different disciplines treat the words different such as in electronics PC boards often have a ground plane that is not connected to earth but to DC ground or signal ground in this case ground is not earth.
http://www.mycncuk.com/threads/7662-...3653#post83653
don't forget the chassis ground, signal ground, RF ground - there are loads of grounds but they do not have to be connected to earth :)
http://www.mycncuk.com/threads/7662-...3653#post83653
Grounding is a whole subject in itself! In simple terms, the issue is that wires and connections aren't perfect, and don't have zero resistance. Hence although you might connect things together to form a common ground, there are always tiny differences in voltage across them. This is especially the case when large currents are involved, of if there are multiple paths between the grounded items. And since ground is your reference for everything, then this can cause issues in operation.
http://www.mycncuk.com/threads/10456...8433#post88433