Ethernet

[dirkenstein]

Woops, looks like everybody's beaten me to a response on this one. I'll post anyway. Why not. The electrons are all recycled....

 

As to using fibre, I personally would find the idea immensely scary for non-permanent installs.

The bend radius limitations on all conventional fibre cable I've encountered are such that unless somebody can convince me that the mil-grade stuff stands up to the kind of abuse you can subject a DMX cable to (I.e I can bend it back on itself, tape it down, and step on it. In boots.) I would be very wary of it.

 

What would be lovely is some sort of working power-over ethernet. Just one cable to each fixture. It wourln't even need to be that high bandwitdth, just low latency. If such a beast could survice in the dimmer-hash EMI environment of most theatres.

Ethernet has its problems over straight DMX:

 

It has a tenth of the range,

Not really a practical limitation for most venues. I can't personally think of any DMX installations that would have needed to use anything near the full 2000ft cable length for an unbuffered run. I also can't imagine many venue electricians or LDs that would be comfortable with actually needing even half of that for a free run. I don't know exactly where the lmits are (4000ft for RS485 at 100Kbits, so DMX can't really be more than half that). But I wouldn't like to go anywhere near them.

uses 4 of 8 pins (making it impractical to run down mic looms),

And your mic looms are twisted pair certified at 110 ohms, are they? I know that, in practice, such things as running DMX over mic cable may very well work 99% of the time. I also know, from experience, that 1% of the time the DMX gremlins will bite you on the nose at you at the worst possible time if you do this, or split cables, fail to terminate, or engage in any number of unnatural DMX practices. Save yourself the ulcer meds and reduce suicide by blunt instrument known as Director risk and do it right the first time.

To extend the cable you need either an adapter or booster, the connectors and cable is fragile,

Ethernet hubs and repeaters are so cheap that the cost of needing some sort of signal boost over 100m is rather less than the cost of equivalent DMX repeaters over any longer distances...

Agreed, RJ45s aren't exactly the most robust connector in the universe. Ethercons, anyone? Cheap cat5 installation cable is admittedly too fragile for touring use. The flexible patch stuff is definitely better. And Gepco make a touring grade cat5 cable. Not cheap, but neither is good starquad, generally.

Ethernet cable is blue and do you really want blue lines flying around from mover to mover, then either hiding them or letting the audience see and have to live with it?,

We have some bubblegum pink cat 6 in our lab. Try hiding that. I also have some black. I'm sorry it's not matte NPL ultrablack, but we can't have everything.

Ethernet cables are crimped, and anyone who's done some crimping will know that they are a b**** to crimp correctly,

Yep, that's why you test them afterwards. Hand-crimping is one of these truly peculiar things. It either produces the best or the worst possible connections. Practise helps a bit. So does using the 50 quid ratchet crimpers rather than Maplins 10 pound special. Which does work, but has, by my experience, a rather higher reject rate.

And what about addressing dimmers or movers, setting an IP thats twelve digits long on an up/down button setup, per fixture?

I suspect any sensible system of Ethernet to fixtures or distributed dimming will use some for of DCHP-like autoconfiguration.

Or, as somebody suggested- you patch the unique MAC address on your desk and configure nothing on the fixture itself.

In any case, ethernet is not currently well suited for running to lighting bars because of the star rather than daisy-chain arrangement of cables. What it is good for is running permanent high-capacity links between various locations in a venue, for instance between light box and dimmer room.

And for that, any sensible installation will use private wiring and static configuration. Given that I have seen broadcast storms and similar faults take out whole corporate networks on single (>1000 desk) sites, I wouldn't really want to be mixing my packets with the venue's anyway.

The benifits are: booster/splitters cost much less (since they are ethernet switches/hubs), they carry more information, is interfacable with computers and ready made cables are only as far as the local computer store.

Indeed. Ubiquity is very helpful. But I suspect we both agree that the standard cables we can pick up anywhere might not stand up to theatrical-grade abuse. The other advantage is that many new PC-based desks (Congo and MagicQ spring to mind) all support outputs on Ethernet 'out of the box'.

But have you ever needed more than one universe on a desk with one DMX universe output? Have you needed more than four DMX universes? if not, stick with DMX XLR's or make up XLR to RJ45 (or RJ11) adapters using different pairs of wires for each universe.

I help out in am-dram, and our LDs lighting plots have come closer than you might expect to filling a single universe (300 odd channels. 10-channel movers are rather channel hungry). We have split the rig onto two universes to shorten cable runs before. Admittedly on a two-universe desk.

We also regularly use a DMX splitter/repeater to avoid the 'one long chain' topology with the associated failure behaviour.

And we definitely intend to use cat5 for some permanent-install DMX runs in future.

It's cheaper than most DMX cable, and generally just as good (see ESTA articles).

We don't really need the capacity of Ethernet at the moment, and can't justify the expense of obtaining convertors. Nor are we likely to have a desk that's going to use it anytime soon.

Just out of curiousity, Who has ever needed more than 512 channels for either all the dimmers or all the movers?

There have been some interesting descriptions of truly big rigs in L&SI. Brit Awards. 64 universes I think? Something that looked like a very tidy explosion in a spaghetti factory by the DMX splitter and repeater racks... A bit out of my league. But ethernet for show control is going to get rapidly popular when it saves you that much cable patching. It is a real problem for really big shows. for the likes of me, it's just a cheaper cable source. For now. What current standards for this stuff won't do is solve and DMX-specific problems overnight. Just consider Artnet's sillier limitations and that everything else is pretty proprietary (or just plain doesn't exist yet) and you'll realize there's no point in worrying about Ethernet somehow replacing humble DMX all that quickly. But it would be foolish of technicians not to be prepared for the amount of ethernet they are going to encounter now and in the near future, which is enough to need to know about ethernet and IP networking in general, now.

[Cuelist]

The limitation has more to do with the type of cable used and the connectors.

 

Bog standard CAT 5/6 cables with RJ-45 connectors will not give you much range but using special cabling with large area, additional shielding and high performance connectors, you can go up to 500'/150m without packet losses. That's the what PRG uses in their ACS400 system.

 

Office style Ethernet cabling was never intended for the show environment.

 

 

Mats Karlsson

Product Manager

Barco NV

[Bean]

Well I stand corrected, Ethernet doesn't have as many problems as I thought,

However for what I'm doin at the moment I'm going to stick with DMX, Or Ethernet to DMX breakout boxes. I've never used all 512 channels exept at that big gig with the two stages 200m apart with me in the middle. Even then I was at 300 channels a universe.

So I guess what I want to say is Ethernet is good in it's place, DMX is more practical in some situations.

 

Bean

[dbuckley]

As to using fibre, I personally would find the idea immensely scary for non-permanent installs. The bend radius limitations on all conventional fibre cable I've encountered are such that unless somebody can convince me that the mil-grade stuff stands up to the kind of abuse you can subject a DMX cable to (I.e I can bend it back on itself, tape it down, and step on it. In boots.) I would be very wary of it.

Talk to a noize boy with a Digico D5 system; thats all fibre stagebox to desk, and the fibre "cables" get treated about the same as any other cable. There are tough fibre cables available.

[bruce]

As to using fibre, I personally would find the idea immensely scary for non-permanent installs.

The bend radius limitations on all conventional fibre cable I've encountered are such that unless somebody can convince me that the mil-grade stuff stands up to the kind of abuse you can subject a DMX cable to (I.e I can bend it back on itself, tape it down, and step on it. In boots.) I would be very wary of it.

I guess you're thinking about fibre patch cables when writing this, rather than ruggedised/install/milspec cables..

 

The fibre itself is very small - 125 micron outer diameter - but it's surprisingly robust. It's jacketed and buffered, then generally kevlar armoured. The ends are delicate, but the cable itself is tough. Stepping on it in boots is not a problem, and if you can bend the heavier stuff back on itself in a tighter loop than the minimum bend radius, then you've probably got muscles like Popeye :D.

 

In an installation environment, the only time I've seen cable accidentally damaged (as opposed to ends) is by fire, rats, or a close encounter with a Stihl saw... I've also known a cable splice to break when a piledriver was being operated 3 feet away - but the fibre was unjacketed at that point. If it hadn't previously been spliced, it would have survived.

 

Think about how the telcos install this stuff. It's going into ducts under the street, which are generally full of water, s**t and rats, and they haul this stuff from manhole to manhole in 2km lengths. It's got to be strong and robust to survive that.

What would be lovely is some sort of working power-over ethernet. Just one cable to each fixture. It wourln't even need to be that high bandwitdth, just low latency. If such a beast could survice in the dimmer-hash EMI environment of most theatres.

Not sure what you mean here? power-over-ethernet is standardised, and available today. However, it's limited to (from memory) a max of 15W per device, often less, so I'm not sure what the applictaion would be. Ethernet-over-power - now that's perhaps a more interesting area....

[booboo]

Think about how the telcos install this stuff. It's going into ducts under the street, which are generally full of water, s**t and rats, and they haul this stuff from manhole to manhole in 2km lengths. It's got to be strong and robust to survive that.

 

Had the chance to watch BT install the fibre lines into our new building a few months ago. They seem to have it pretty sussed. They ran an empty 200m length of (inflexible, large & rugged) 2 channel plastic ducting into the building from the local BT box. They then hooked a compressor to that end of it and blew the fibres all the way into our 1st floor comms room where the BT guy spliced and patched it into the NTE with bright orange patch cables that were strengthened with Kevlar. The guy told me he's done runs of over a mile like that.

 

The process seemed pretty quick and painless, unlike the intense stress of actually getting them in to do the job before we moved in.

[bruce]

That's known as (surprise surprise) "blown fibre". The telcos - especially BT - use it a lot for internal runs, and for "last mile" stuff - ie the connection into the building. It's been around for years, but it's still not particularly common outwith BT.

[dbuckley]

... but it's still not particularly common outwith BT.

Could be something to do with "blown fiber" being a BT trademark... They came up with it.

[maeterlinck]

What would be lovely is some sort of working power-over ethernet. Just one cable to each fixture.

 

Well as said PoE (Power over Ethernet) does exist. However, it's not generally recommended, I believe, and is only recomended for long runs where getting power to the end point would be difficult.

I think you're thinking of something more like EoP (Ethernet over Power). Again this exists. But it appears to be limitted to the cheapy realms of maplin type shops, although I think d-link make/made one. Would be interested to know how it measures up to regular Cat5 in a real world situation. Any one?

[Andrew C]

One limitation of EoP will be the need for three "transmitters" one for each phase. In many cases this will mean that you need to run a cable to a suitable 3Ø board and connecting to it in some way, rather than just plugging your PC/desk/whatever to the nearest mains socket. That aside, I like the idea! I could save a whole lot of work running cables, particularly in difficult buildings.

[Modge]

Thinking of how noisy theatre power can become, with dimmer's and strobes and the like on there I worry as to exactly how well the stupidly high frequency square wave that is Ethernet would fare. Granted we have TCP and other vaguely robust protocols for a reason, but all things network generally don't enjoy loosing connectivity regularly e.g. whenever you fire up the atomics (or large strobe of your choosing...). If when ever you did anything like this the noise drowned out the signal all the devices suddernly loosing contact with the desk would not be good. I don't know exactly what the maplins type system uses in the way of filtering out this noise, but it had best be good. http://www.theregister.co.uk/2005/08/30/powerline_broadband/

is the best I could find from el reg (where I'm sure there's a decent article about this)

 

Edited For spelling

[musht]

Looks like got a heck of a lot more reading to do do on DMX over ethernet and WiFi, and picking up Mr Howell`s book isn`t the complete answer...

 

Any reccomendations on ethernet for dummies, light on the maths please?

 

One limitation of EoP will be the need for three "transmitters" one for each phase. In many cases this will mean that you need to run a cable to a suitable 3Ø board and connecting to it in some way, rather than just plugging your PC/desk/whatever to the nearest mains socket.

 

At Plasa last year Avo had a prototype DMX over Power setup, 72 way rack getting its DMX from its power supply, engineer said he actually had one built into a ceeform plug, XLR 5 - 16A connector , but left that at home as felt might be a bit disturbing for some.

 

X-10, consumer mains signalling, is better established in U.S. but was actually developed in Glenrothes, by Pico Technologies in the late 70`s, X-10 was project code name , X-11 was the Accutrak a programmable vinyl turntable. Calluna who developed the miniature hard drive also came from Glenrothes, Strand Kircaldy was about 10 miles away.Remember if it wasn`t for us Scots you wouldn`t have telephone, televison, anisthetic etc ad nauseum ;-)

 

Phase jumping in X-10 is done by having an optical jumper back at distro board linking phases. You can , afair, plug in any phase and signal will appear on any other phase.

 

http://www.x10.com

 

X-10 isn`t super robust or intended for data really, more recent is Homeplug

 

http://www.homeplug.org

 

This isn`t foolproof though, as a friend discovered with a recent installation. 6 computers to server, fine when its one to one but contention issues rendered it useless when several machines tried to access server at once. Might work better as a DMX model, one transmitter many receivers but this may fall apart again with RDM and all the devices trying to talk back again.

[dirkenstein]

What would be lovely is some sort of working power-over ethernet. Just one cable to each fixture.

 

Well as said PoE (Power over Ethernet) does exist. However, it's not generally recommended, I believe, and is only recommended for long runs where getting power to the end point would be difficult.

I think you're thinking of something more like EoP (Ethernet over Power). Again this exists. But it appears to be limited to the cheapy realms of maplin type shops, although I think d-link make/made one. Would be interested to know how it measures up to regular Cat5 in a real world situation. Any one?

 

Yup- meant power-line networking, rather than PoE. Don't worry, I'm not wiring a 125A ceeform to RJ45 adaptor just yet.... I was aware that X-10, homeplug, and similar standards existed. I merely considered that all of that technology was consumer-oriented and virtually anything like that would fail to work reliably in a theatre environment given the potential EMI level from dimmers. I know around 10 years ago in Germany it was possible to able to buy 3-phase coupling transformer for home use to allow power-line FM baby monitors to work in larger houses that were split across 3-phase supplies. Interesting to hear from later posters that companies are actually demonstrating this kind of thing. I was thinking mainly of its use for movers and for distributed dimming, really. I will have to visit AVO at PLASA to find out if they've done more on it.

 

As to fibre. I was aware that the Kevlar sheathed/Kevlar former stuff is rather robust for installs. Never having held any of it in my hands I couldn't say how flexible it was. The last time I witnessed a fibre install it certainly seemed to be the termination, rather then the pulling, that was delicate and laborious work. My experience is really with patch cables and the like. One thing I didn't realise that it was possible to get fibre cable that was both flexible enough for temporary/patch use, and robust enough to survive being kinked and stepped on. The fact that there are digital snake cables is something that lurked only in the back of my mind, and their use of fibre is something I wasn't aware of.

[bruce]

Well as said PoE (Power over Ethernet) does exist. However, it's not generally recommended, I believe, and is only recomended for long runs where getting power to the end point would be difficult.

 

Today, the main applications of PoE are for wireless base stations and for IP phones - applications where you need a low voltage supply and a network connection. Also things like surveillance cameras. If you don't have PoE, you need a wall-wart adaptor, and installing a 13A socket can be more expensive than getting the network installed.. As IP telephony becomes more commonplace, PoE will become equally common.

 

It has interesting implications for network infrastructure people. The PoE spec says that each port must be able to deliver 15W, although most devices make compromises here. But lets assume there are no compromises. So that 48-port switch, which used to draw about 50W, now needs 770W - that's 50+(48*15). Add in some overheads, and we're talking about a kilowatt....

 

Now lets assume we've got half a dozen of these in a wiring closet. At present, that's a load of 300W. You can easily add a small UPS, and drive the lot from a 13A socket. With fully specced PoE, worst case, it's over 6kW. So now we've got to think about 3 phase supplies and external cooling ..... The UPS and aircon guys are about to make lots of money....

[maeterlinck]

Just been having a look at http://www.poweroverethernet.com/ hadn't realised how common it had become. Although stands to reason given VoIP phones etc.

 

Are current telephone switchers UPSed? The only one I've had dealings with wasn't I'm pretty sure. If the power for the building went so did it. Why do VoIP phones need to be different? Plus I've never seen the need to UPS the workstation network switches. If the power fails so are all the workstations, unless everyone happens to have laptops. :D