Re: [Emc-users] Allowable length of db25 interconnect cabling --> ribbon cable

2016-12-25 Thread Chris Albertson 
Comments re. below

1) "Everyone" already puts grounds between every signal in ribbon
cable.   All the limits you read are already assuming you have done
that.   So still about 30 inches max.

>> Differential signal is the best but I do not how big difference will be 
>> against
>> ground in one of the pins instead. For signal   conversion I think RS-422
>> transciver/receiver is the choice, they are also readily available in 
>> different speeds.
>>  Ethernet  cable is twisted pair and readily available.

Ethernet is not only differential  it is galvanically isolated, a
transformer is used at each end

The difference in performance is dramatic.  A single ended (ground
reference) signal can go about 10 meters and maybe up to 2 MHz,   As
we see with Ethernet a differential baseband signal goes up to 100
meters at 1Ghz.  That is 500X faster and 10X farther.  All modern
interfaces are differential, USB, Ethernet, Thunderbolt, SATA and so
on.

But differential will not help in this case.  The OP has parallel
printer port data to move.   My suggestion is to just don't do that.
Use a very short parallel cable, just a few inches and make the high
voltage motor cables as long as needed.   Yes this costs more because
those cables need to use thicker gauge conductors.   12 Ga, or even
larger duplex wire is easy to find.



On Sun, Dec 25, 2016 at 3:04 AM, Nicklas Karlsson
 wrote:
>> > ...
>>
>> You are right, ribbon cables are not very good at carrying signals over
>> long cables. They will pick up too much noise if not shielded and suffer
>> often from significant cross-talk if too long.
>
> A trick is to put ground in half of them, either odd or even. Then of course 
> they get twice as expensive.
>
>> The "standard" old-school printer cables (the round ones) are often
>> shielded and twisted pair, which are actually quite good.
>
> Twisted pair is the best.
>
>>
>>
>> > For over 30 feet use some kind of differential signaling or fiber.
>>
>> Differential signaling or fiber is of course better, but very much more
>> expensive. You will also need to convert the signals on each end.
>
> Differential signal is the best but I do not how big difference will be 
> against ground in one of the pins instead. For signal conversion I think 
> RS-422 transciver/receiver is the choice, they are also readily available in 
> different speeds. Ethernet cable is twisted pair and readily available.
>
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Chris Albertson
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Re: [Emc-users] Allowable length of db25 interconnect cabling --> ribbon cable

2016-12-25 Thread Gene Heskett 
On Sunday 25 December 2016 06:04:51 Nicklas Karlsson wrote:

> > > ...
> >
> > You are right, ribbon cables are not very good at carrying signals
> > over long cables. They will pick up too much noise if not shielded
> > and suffer often from significant cross-talk if too long.
>
> A trick is to put ground in half of them, either odd or even. Then of
> course they get twice as expensive.
>
> > The "standard" old-school printer cables (the round ones) are often
> > shielded and twisted pair, which are actually quite good.
>
> Twisted pair is the best.
>
> > > For over 30 feet use some kind of differential signaling or fiber.
> >
> > Differential signaling or fiber is of course better, but very much
> > more expensive. You will also need to convert the signals on each
> > end.
>
> Differential signal is the best but I do not how big difference will
> be against ground in one of the pins instead. For signal conversion I
> think RS-422 transciver/receiver is the choice, they are also readily
> available in different speeds. Ethernet cable is twisted pair and
> readily available.
>
In this case, we are talking about a data rate (baud) in the 32 MHz 
range. I have some 422 adaptors, intending to play with them at some 
point, but have doubts they can run that fast as they are usb driven 
from the computer.

> --
> Developer Access Program for Intel Xeon Phi Processors
> Access to Intel Xeon Phi processor-based developer platforms.
> With one year of Intel Parallel Studio XE.
> Training and support from Colfax.
> Order your platform today.http://sdm.link/intel
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Cheers, Gene Heskett
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Allowable length of db25 interconnect cabling --> ribbon cable

2016-12-25 Thread Nicklas Karlsson 
> > ...
> 
> You are right, ribbon cables are not very good at carrying signals over
> long cables. They will pick up too much noise if not shielded and suffer
> often from significant cross-talk if too long.

A trick is to put ground in half of them, either odd or even. Then of course 
they get twice as expensive.

> The "standard" old-school printer cables (the round ones) are often
> shielded and twisted pair, which are actually quite good.

Twisted pair is the best.

> 
> 
> > For over 30 feet use some kind of differential signaling or fiber.
> 
> Differential signaling or fiber is of course better, but very much more
> expensive. You will also need to convert the signals on each end.

Differential signal is the best but I do not how big difference will be against 
ground in one of the pins instead. For signal conversion I think RS-422 
transciver/receiver is the choice, they are also readily available in different 
speeds. Ethernet cable is twisted pair and readily available.

--
Developer Access Program for Intel Xeon Phi Processors
Access to Intel Xeon Phi processor-based developer platforms.
With one year of Intel Parallel Studio XE.
Training and support from Colfax.
Order your platform today.http://sdm.link/intel
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