Bundled cables?

[timelord]

Gooday to all, I,m currently assembling my pier and was planning to route some cables through the main tube to alleviate some of the cable management problems.
The cables I,m planning to route through the pier are 12volt dc, guideport cable,and a usb port cable, they will pass through the concrete base of my pier via a 50mm pvc pipe installed during construction.
My question is has anyone had any problems regarding interference with their cables in close proximity ie 50mm? Should I individually conduit the cables?
Any suggestions or previous experience greatly appreciated.
Al.

[leon]

Hi Al, I personally wouldn't mix power cables, with other cables, by all means run then through the pier, but power ones in one conduit, and USB and such in an other conduit.

Although it may not cause you and problems now, it may somewhere up the track.

Leon

[ballaratdragons]

Never bunch power cables and computer cables together. The power cables cause interference. I keep my underground control cables about 2 feet away from the underground power cable.

As far as with the pier, Leons suggestion is a good one :thumbsup:

[dugnsuz]

Agree - even though I don't have a permanent setup, last session I got a dark band throughout my entire exposure set which I think was down to power cables being tangled up with USB cables.
see the noise exaggerated pic below!!!:eyepop:
All the best
Doug:thumbsup:

[Glenhuon]

The guys have it right there, never put power and data cables in the same conduit. If I remember correctly its actually a regulation for telephone cables.
I had problems with this monitor for a while and eventually discovered that the power cable was lying alongside the data one, caused some weird shadows on the screen.

[montewilson]

I have all my wires bundled into a single loom of about 30mm thickness but I have chokes on all the signal lines and no noise problems. You can get clip on chokes from Jaycar.

[Lee]

Monte - do you only need one choke per signal cable? Does it matter where on the cable???
I now have 3x 12V, 1 USB, 1 firewire, 1 autoguiding cable in my cable conduit now.... was starting to wonder if some graininess in my images might be some interference (I'm sure it isn't - but can't be too safe!)
cheers

[montewilson]

I have one where the STV signal/vision cable enters the STV box and one where the STL USB cable enters the computer. I don't think I have any on the power cables themselves.

Have you tried to find where the source of the noise is by elimination? You could try running some of the power sources from a battery (which of course is noiseless) and see when or if the noise dissapears.

Also the noise may be inherent in the camera itself (ie it has a problem) but lets hope it's much more simple than that.

[Tamtarn]

Great information Guys. Something to be aware of.

Am I right in assuming that USB leads can be bunched together.

David

[ballaratdragons]

Yes David, you can run all sorts of data cables together.

[gary]

Hi,

Keep in mind that USB itself has two lines devoted to carrying power and
ground through the cable.

Also keep in mind that USB uses differential signaling, so *in theory* common
mode noise gets cancelled out. Furthermore, high speed USB cables have
a braided shield to help with both radiation and assist with immunity.

*In practice*, for reasons I won't go into here, common mode noise problems
can still occur on USB cables.

What is really important is that the designer of the PC and the USB peripheral
have incorporated best design practice in their designs. For example,
the USB lines should have had appropriate protection filtering at the PCB
level at either end and the metal shields terminated correctly to the appropriate
'dirty' ground points.

With the high signaling speeds of modern digital systems including USB
inter-connects, PCB traces and cables become antennae which can both transmit
and receive RF radiation. This poses challenges for the designers of such systems.

Though noise from AC systems can be an issue, don't think for one moment
that powering the system from a battery will necessarily eliminate any problems.

Again, the culprit can actually be the high speed data traces on the PCB itself
being transmitted back out along the power lines that came into the unit.
Again, this is where best design practice can make all the difference and
on a properly designed peripheral, conduction of noise back through the
power lines should have been designed to be within regulatory limits - but
it may not have been. In other words, one bad apple can spoil the basket.
Only buy peripherals that carry a C-Tick marking (or CE). That doesn't
mean they won't cause a problem, but you are at least assured they were
probably tested.

Best Regards

Gary

[Dennis]

Thanks for the write up Gary - it's nice to get some education and insight into these issues and you have explained it well to this layperson.:thumbsup:

Cheers

Dennis