Designing a Built-in Computer Desk, EMI shieldin...

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Designing a Built-in Computer Desk, EMI shielding questions
   
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网上论坛：comp.dcom.cabling
日期：2003-05-11 21:45:52 PST

Folks, I'm designing a computer workstation that will be built in, and
never moved.  As such, I want to include in the design a good amount
of power (I have a lot of components to plug in).

I am going to have a cabling trough that will run below desktop level
at the back of the workstation, which will be the spine down all of
the cables will run.  I want to place a couple of long powerbars in
this trough.  There will be a lot of standard voltage hardware to be
plugged in here (two monitors, two loaded PCs, scanner, two printers,
A/V component system) as well as *bunch* (about 11) of "wall warts"
(transformer blocks) to be plugged in as well.

What will be the effect of all these power cords on other computer
cabling that is also to be routed in this trough?  Specifically:
- CAT5 UTP Ethernet
- RG6 Coax
- telephone wire
- Analog audio and video cabling
- S-video cable
- VGA extension cables
- parallel printer cable
- USB extension cable
- Firewire cable
- RS232 serial cable
(yes, I've got a lot of stuff!)

If the answer is "Yes, expect problems", then I need to shield the
power from the data in some way.

A basic question of EM physics: does it "bend" around corners?  That
is, do I have to completely enclose a source of EMI in order to
prevent it from affecting its surroundings?  Or would a "wall"
suffice: could I simply separate two troughs (1 power, 1 "the rest")
with a metal strip so there is no line-of-sight bewteen them?  If so,
what kind/thickness of metal will do the job?

If a separation of distance is all that is required between the power
trough and "the rest" trough running side by side, how far apart
should they be?  Inches?  A foot?  More?  :-(

Thanks in advance for any light you can shed on this for me.

-----------------------------------------------------------------------------------
Darren Best
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寄件者：Justin Time (a_user2000@yahoo.com)
主旨：Re: Designing a Built-in Computer Desk, EMI shielding questions
   
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网上论坛：comp.dcom.cabling
日期：2003-05-12 09:42:22 PST

darren@sweetums.ca (Darren Best) wrote in message news:<71f7ce7.0305112045.14993165@posting.google.com>...
> Folks, I'm designing a computer workstation that will be built in, and
> never moved.  As such, I want to include in the design a good amount
> of power (I have a lot of components to plug in).
>

The first issue you are going to have to deal with is physical space.
Once you start to build something in, you find you forgot to plan for
the space new equipment will occupy.

> I am going to have a cabling trough that will run below desktop level
> at the back of the workstation, which will be the spine down all of
> the cables will run.  I want to place a couple of long powerbars in
> this trough.  There will be a lot of standard voltage hardware to be
> plugged in here (two monitors, two loaded PCs, scanner, two printers,
> A/V component system) as well as *bunch* (about 11) of "wall warts"
> (transformer blocks) to be plugged in as well.

Are you planning on building this computer center into new
construction or is it an existing house that you are remodeling?  It
appears you will need at least 2 15A circuits, on separate breakers
and preferably "dedicated and isolated".  There is no mention of a UPS
to power your equipment in case of power failure or for protection
against surges and sags.

The cabling standards state your data cables should be separated from
any power, and the recommendation is they run at right angles to any
power.  Use of grounded metallic pathway for your power circuits is
also recommended.  This will effectively eliminate the bulk of any
interference from power lines, but does not guarantee to be the cure
for all the problems you could encounter.

Running power and phone or data cables in the same pathway also has
other restrictions from a safety standpoint that have to be addressed.
From your e-mail return address you are in Canada.  You will need to
be certain your design - if you are doing this yourself - meets
Canadian electrical and safety laws and regulations.

----------------------------------------------------------------------------
线索内的第 3 条留言
寄件者：SpitsOnSpammers (spammerspitter@aol.com.invalid)
主旨：Re: Designing a Built-in Computer Desk, EMI shielding questions
   
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网上论坛：comp.dcom.cabling
日期：2003-05-12 11:36:33 PST

a_user2000@yahoo.com <Justin Time> wrote:
>The cabling standards state your data cables should be separated from
>any power, and the recommendation is they run at right angles to any
>power.

Shouldn't that read "...they run at right angles to any power LINES ONLY WHERE
THEY HAVE TO CROSS POWER LINES. FOR PARALLEL RUNS OF DATA AND POWER LINES,
PLACING THEM AT LEAST 12 INCHES APART IS SUFFICIENT"?


Note that this posting account rejects all email.  Posting to this newsgroup is
the only way to reach me.  Email address harvesters can harvest away and be
damned.

----------------------------------------------------------------------------------------------------
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寄件者：Darren Best (darren@sweetums.ca)
主旨：Re: Designing a Built-in Computer Desk, EMI shielding questions

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网上论坛：comp.dcom.cabling
日期：2003-05-12 18:02:02 PST

a_user2000@yahoo.com (Justin Time) wrote in message news:<2207e6fa.0305120842.34043226@posting.google.com>...

> The first issue you are going to have to deal with is physical space.
> Once you start to build something in, you find you forgot to plan for
> the space new equipment will occupy.

I've tried to be as thorough as possible.  The "stuff" in my list is
actually only about 75% purchased so far: I'll be expanding as I go
on.

> Are you planning on building this computer center into new
> construction or is it an existing house that you are remodeling?  It
> appears you will need at least 2 15A circuits, on separate breakers
> and preferably "dedicated and isolated".  There is no mention of a UPS
> to power your equipment in case of power failure or for protection
> against surges and sags.

It is an existing house, and I am building a rather large wall unit
(which includes the workstation).  Yes, I am planning on pulling two
new circuits for the workstation.

I have a power conditioner for the PC.  A UPS is possible for the
future.

> The cabling standards state your data cables should be separated from
> any power, and the recommendation is they run at right angles to any
> power.  Use of grounded metallic pathway for your power circuits is
> also recommended.  This will effectively eliminate the bulk of any
> interference from power lines, but does not guarantee to be the cure
> for all the problems you could encounter.

Like I said, I was thinking that I could (if I need to) separate the
trough into two for the two purposes.  You're saying that I need some
kind of "complete" surrounding for the power cords (not just a metal
vertical barrier)?

Look, there's very little that is different between this and a
standard computer desk (as it pertains to cabling interference
issues).  Is there any experience with computer users having troubles
with their data cables because they've got a bunch of power cables
lying around with them (over a distance of 4-6 feet)?

> Running power and phone or data cables in the same pathway also has
> other restrictions from a safety standpoint that have to be addressed.
>  From your e-mail return address you are in Canada.  You will need to
> be certain your design - if you are doing this yourself - meets
> Canadian electrical and safety laws and regulations.

A given.

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