Have you measured these at all?. 50, 100 or harmonics?..
In my recent experience SMPS these days are very "quiet", after all theres been a lot of EMC stuff to cope with for quite sometime now..
Agreed. We had this a while back at a rather rural park location where the CAT 5, best stuff we could find, was crapping out at 90 metres installed Fibre .. excellent stuff that only downside is the splicing of it..
Which is in a way how networks behave..
Yes put it in a duct of some type or the other as it will need adding to, modifying, other requirements will of course arise.
They say that, but is this really a problem?. I'd expect the other sheath to be adequate in this respect but what exactly is it going to be touching, bare mains conductors?.
In the Dado, well sort of, I'm right next to now the CAT 5 cables are in the same duct as 2.5 T&E so I rather suspect the breakdown volts to be rather high;!..
The pont here is that CAT 5 doesn't float, or if it does, its floated by transformers that don't care how high the common mode goes as long as the insulation doesn't break down in them. So it is either more or less tied to earth by a few hundred ohms, which will limit common mode excursion via capacitative transfer, or its so isolated by transformers, it doesn't actually care.
The reason for NOT routing it alongside mains is and always has been a simple safety directive: Essentially you should not route signal cables in the same ducting as mains because the possibility exists that chafing on the same sharp edge will result in exposed wires at the same place.
CAT 5/Ethernet is designed to be as tolerant of interference as is practicable, and to be a good compromise between interference rejection and cost.
No, I haven't. I've had the "fun" of specifying the installation of some of this stuff though. Motor speed controllers in particular can churn out some nasty stuff - usually if you get the earthing to the motor wrong. Although the outputs often have filters, that's not always so for small motors. I realise that the manufacturers are covering their own backsides, but they often have the installer jumping through hoops. :(
A nice big load of SMPS boxes can do wonders for the power factor... lol As you say though, most of them are far better than they used to be.
It's a bit more than shock risk. EN 50174-2 includes a table of minimum separation distances (1), from various types of circuits, for acceptable EMI values. e.g. Fluorescent, Neon, Mercury discharge & HID lamps: 130mm Arc welders: 800mm Frequency induction heating: 1m
There is a safety issue as well, of course, but installation of both the power and data cables is supposed to prevent insulation failure. ;) In a lot of installations power and data cables (even SWA) are not allowed to share the same cable tray or basket, never mind the same trunking. That's for EMI reasons.
Ethernet over cat5 is a current driven interface. there are isolating transformers at each end and no voltages on the cable reach the receiver.
Best use what ethernet is designed for, unscreened cable. If you do run screened cable then you need to watch how the screen is terminated, you do not want to end up with thousands of amps of earth current running down the screen if there is a potential difference at the two ends. One way to avoid it is to only earth one end via a capacitor but you avoid any such problems by using the correct unscreened cable.
Its because it is possible for the cables to chaff and then you can get mains on the cat5.
This wont stop the network working or shock you if you touch the cable. However the terminations/connectors are not designed to stop you or a child contacting whatever voltage is their. Its the same reason you aren't supposed to be able to unplug the lead from a telephone, its to stop kids putting the plug into their mouths and getting a shock while the other end is plugged into the line.
If installed without damage, no movement to cause damage or it never gets a whack to cause damage then things are almost certianly fine but this is the real world...
Not sure why you are bringing a 0 V reference in but OK...
OK. Well apart from the answer being wrong, it should be 4.25 V
Er, no. This is common mode induction so the induced voltage on each wire is the same so your formula should be -1.25 + 3 = 1.75 V
This is a balanced line, preety sure that the signal wires are floating. Balance and isolation being provided by transformers at each end. Common mode voltages on the line aren't a problem until they break down the transformer or arc across the PCB. B-)
I'd be sort of surprised if there is any electronically balanced ethernet kit out there. Transformers provide kV's of isolation, proper balance and are reliable and cheap. Electronics are fragile or needs expensive protection (from a transfomer...)
But the induced voltage is not +/- on the wires it's the same on both wires. There might be protection devices across the wires rated above the differential signal level so if the line becomes badly unbalanced they take the load and the transformer doesn't get saturated. I'd be surprised if there is any protection relative to earth, there doesn't need to be any. And the first near by thunderstorm is likely to zap it any way.
I'd never bothered to investigate, but it seems dennis@home is in fact correct. A ferrite balun seems to be de facto standard at each end Center tapped if you want to use it for power-over-ethernet.
Not so sure its current driven tho. more like low impedance 200 ohm sorta stuff.
Just remembered, the Belden stuff is Datatwist 350. We used it in an environment that was electrically noisy (lots of motors) and it worked where standard Cat5 wouldn't.
It does make you wonder the rather safe environment inside a DADO trunking case, all plastic and not much else to chafe on there. The chances of a couple of wires losing their insulation and touching must be what?..
A damm sight less then a couple of flexible cables coming from sockets on that trunking?..
Thanks to everyone who has responded. Very helpful and I have learned a thing or two!
I haven't decided exactly what to do yet, but I think it will either be a bit of CAT5 cable and to hell with the regs.... :-)
or
and it was John Rumm's comment ...
"If you want to run building to building wifi, then you tend to get far superior results with proper external wireless bridge units, rather than normal wifi kit."
that made me investigate "proper" external wireless bridge units. I came up with this....
Thats what my dad once said they taught him that in the RAF ..
"Rules are for the guidance of wise men and the absolute obeyance of idiots"
;)...
I'm sure it will be fine, but put it in a duct of some sort and leave a drawstring for when you want to expand all this which will be as sure as night follows day....
Yes, just a tad ..
If you need to go radio for any other reason this company who are a recommend supplier on past experience have a boxed kit of two units..
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