[sdiy] grounding sheilded wire?

[Jim Patchell]

    Larry...

    Here is what I use (or will on my next project, to be started in just a
couple of weeks).  I purchased a roll of "microphone cable".  This is two
conductor shielded cable.  But, I have a different set of requirements from you,
most likely.

    I require the conductors to be 24ga, because I use crimp on terminals where
they come off my PC boards (I hate to hard wire to circuit cards as this makes
working on them very difficult).  I am so dedicated to crimp on terminals I
actually spent my hard earned money to by a good crimping tool (and it was worth
every cent I spent on it, even though it put a big dent in my credit card).  I
use one wire for hot, the other for the ground return, and the shield is
connected to the panel.  This seems to work for me.

    Anyway, I don't remember the model number of the wire (I got it from
Digikey), but it is sort of thin, about 1/8", and it is flexible.  I don't think
it had a drain wire though, well, you can't have everything.  1000 feet cost me
about $120.

    I am going home at lunch, so, I will get the part number then and post it so
you can at least consider it.

    -Jim

Larry wrote:

> Okay, I'm new and I admit it.  So my, probably heard it a thousand times
> before, question is: What type of shielded wire should I get?
>
> I now know to connect the shield at the PCB, and cover the unconnected
> shield at the front panel to prevent accidents.  But what kind of cable
> should I buy?  (I presume RG-59 is NOT a good choice.)
>
> Actually, what is a good choice of cable for patching when using:
> Banana Plugs?
> 1/8" Jacks?
> 1/4" Jacks?
>
> Thanks to everyone for all the interesting discussions on circuits in the
> list recently.  I might finally learn to understand all this analog stuff
> at last...  (Thick as my head is, things do, eventually, soak in.)
>
> Larry Troth
>
> At 09:35 PM 10/1/01 -0400, you wrote:
> >Its still a good idea to ground the shield at one end... even for the
> >"tip only" type plugs. This will minimize capacative coupling between
> >the wires.  Terminate the shield at the PCB end... and leave the jacks
> >connected only by the center conductor. I like a little piece of heat shrink
> >tubing at this end to make things pretty.
> >
> >H^) hary
> >
> >Dave Krooshof wrote:
> >
> > > >But I wonder
> > > >how I am supposed to ground the sheild, do I just connect one end to
> > ground
> > > >and leave the other end floating?
> > > Ideally, each module of your synth is grounded in only one way.
> > > This means that if you connect the shield of your wire to
> > > ground on both ends, that your likely to have more then one
> > > ground lead, simply because you'll probably connect more then one
> > > lead to a module, and you might have chosen to connect it to ground
> > > internally as well.
> > >
> > > What you can do, is to make a central ground somewhere in the
> > > middle of your box. Then you connect each module's ground to that.
> > > (like a star) The female connectors of your modules are grounded
> > > to the modules ground.
> > >
> > > Then your wires. In a jack plug, I'd connect the shield to one connector.
> > > I'd leave it unconnected on the other side. This way, you won't
> > > connect two "beams" of the "star". I might be wrong, but a banana plug
> > > doesn't have a ground ring, does it? What I call a banana plug is a
> > > one-tip-only thing.
> > >
> > > I do not know is shielding is of much use then. It might even work as
> > > a small capacity... Do you happen to have any hum/hf problems
> > > that make you want to shield?
> > >
> > > >is it ok to just have wires
> > > >tapping ground with loose (ie not connected to anything) ends?
> > > >or does it need to go in some sort of continuous loop?
> > > Synths differ from "guitars with effects" in the fact that
> > > guitarist tend to patch modules in a line...
> > > guitar-->fuzz-->wah-->flanger-->chorus-->amp.
> > > They connect the shielding to earth in the amp, so everything
> > > inline is grounded.
> > >
> > > ...and synthesizer players tend to build networks, in which their
> > > modules can be connected in more then 2 ways. If you'd choose
> > > to ground all shieldings of your wires on both ends, you'd make
> > > loops in the grounding. Ground-loops are a problem because they
> > > behave like a dynamo: The alternating magnetic fields of
> > > electricity in your house will generate some current flowing
> > > in your groundloop (a simple coil). Hummmmmmm....
> > >
> > > Dave
> > >
> > > BTW in the studio-control room, I can patch the mixerconsole
> > > to either the studio, the theater, or the dance theatre. I
> > > measured their grounds... 4 volt AC. I decided to connect a led.
> > > I glowed! In the building are 3 rods in the ground to ground
> > > the building. The Amsterdam soil is a battery...