Small lighting system, DMX over ethernet ideas

[gafftaper]

Hey all,
I'm designing a small lighting system for a small local venue. It doesn't get very heavy use and doesn't have a huge budget so we are going to go with four portable dimmer packs, a smart fade, and a dozen S4 Jrs. I'm having double the power outlets installed at the battens so renters can add four additional dimmer packs of their own to expand the house system. They also should be able to rent their own more complex console if they want.

My question is how to distribute control cost effectively. I'm thinking the cheapest way, (and a somewhat future proof way) is to build a small ethernet network. One line from the control console location to a hub located in the ceiling, then branch lines out to the dimmer locations. That's cheap. Then at the ends I'll install 5 pin XLR plugs instead of RJ45 jacks (as has been discussed here in the past). Cheaper than a true DMX run, cheaper than dmx over ethernet the way the factories do it with nodes, and more universally adaptable than going with a specific manufacturer's network control protocol at this point. Down the road if they decide they need to go ACN they can simply pull the 5 pin XLR plugs and replace them with RJ45 jacks and the system is good to go.

Seems like an easy and cheap solution. What do you think? Am I missing anything? Anyone have a better idea? Is Cat 5e the cable to choose for the job?

 

[jxgriffi]

One line from the control console location to a hub located in the ceiling, then branch lines out to the dimmer locations. That's cheap. Then at the ends I'll install 5 pin XLR plugs instead of RJ45 jacks (as has been discussed here in the past).

You can't just put in an Ethernet hub for a DMX network. It will not work. You need to put an Opto splitter in the central room and distribute that way if you are just running DMX signal over the Ethernet wiring. In the central room, I would install RJ45 jacks and build the RJ45 to DMX adaptors. Put in the Opto Isolator and send the signal back out. This way, if you ever end up doing nodes, you don't have to redo the wall ports back to RJ45.

If you are using a "TRUE" DMX over Ethernet protocol, then the hub will work as it transmits as a network (Artnet, sACN, etc.)

 

[PadawanGeek]

To add to what jxgriffi said, if you want to run an ethernet hub or wifi, you need to be using somthing like Artnet. In the end, doing straight DMX would be cheaper, but with Artnet, you need to buy nodes like this one from Enttec. They also have make some nice DMX splitters like the RDS4.

The cheapest way to wire up data would be to do a normal DMX daisy chain, I'm not sure why you would need to have multiple runs or artnet nodes in a venue that small. At the most you might need two runs, one for the lights over the audience, and one over the stage, which you could split with something cheap like this.

 

[starksk]

... My question is how to distribute control cost effectively. I'm thinking the cheapest way, (and a somewhat future proof way) is to build a small ethernet network. One line from the control console location to a hub located in the ceiling, then branch lines out to the dimmer locations. That's cheap. Then at the ends I'll install 5 pin XLR plugs instead of RJ45 jacks (as has been discussed here in the past). Cheaper than a true DMX run, cheaper than dmx over ethernet the way the factories do it with nodes, and more universally adaptable than going with a specific manufacturer's network control protocol at this point. Down the road if they decide they need to go ACN they can simply pull the 5 pin XLR plugs and replace them with RJ45 jacks and the system is good to go.

Seems like an easy and cheap solution. What do you think? Am I missing anything? Anyone have a better idea? Is Cat 5e the cable to choose for the job?

jxgriffi is right that a modern switch will not likely work to transmit/repeat DMX over an ethernet backbone. (At least not without a good deal of configuration.) A true hub might work as it is designed to repeat all signals to all ports, but they are getting harder to find.

If you are going to run Cat5e, stick to Cat5e standards for termination at both ends, then add your adapters. That means keeping your wire runs under 300' and terminating each end with a female connector. I would suggest using a patch panel in the control rack and an Opto-splitter instead of a switch/hub. Use XLR to RJ45 Adapters as your patch cables from the patch panel to the opto.

At the output wall plate, I would suggest using a biscuit-box: (original image) to terminate the other end of the run in the back box. You can build your adapter into the face plate.

Then, when you want to switch to a true network, you can replace the opto-splitter with a network switch, replace your adapters with true patch cables, and replace the faceplate with a pass-thru connector to a patch cable in the back box.

Be sure to test all conductors of every run with a network tester so when the time to switch over comes, you don't have to worry about broken or mis-terminated conductors.

Whichever direction that you end up going, LABEL EVERYTHING!!!

A note on your high-voltage extra outlets that I am sure you have already considered, but don't forget to include a circuit breaker at the input patch point for each circuit to protect the wire in the wall.

 

[mstaylor]

It sounds like you are overcomplicating the system with no advantage I can see. If all you are running is four dimmers I would run standard DMX cable and either daisy chain or run to an inexpensive opto and run two lines. If renters want to add packs they can just extend or break into the chain.
Running extra power is always a good idea.

 

[gafftaper]

jxgriffi is right that a modern switch will not likely work to transmit/repeat DMX over an ethernet backbone. (At least not without a good deal of configuration.) A true hub might work as it is designed to repeat all signals to all ports, but they are getting harder to find.

Yes I understand I'm cheating a lot, this isn't a great idea for long distances, and it definitely isn't DMX compliant. But since you can use cat 5 instead of dmx cable, why can't you use a hub in the middle of that cat5 run? It's just a dumb box repeating everything it hears on all ports.

I realize I fully into that CB classic territory, "You can run DMX over a barbed wire fence but it isn't a good idea" with this idea. So I should probably just forget it and tell them they need to cough up a few hundred bucks more to do it a more conventional way. But it seems like it should work.

mstaylor, the Advantage is cash. I'm looking at a couple hundered feet of DMX cable vs. Cat 5/5e to do this daisy chain. I can save some cable by adding an opto, but that adds more money.

I guess the simple and cheap solution that we know will work is to just drop the Hub and daisy chain with Cat5 cable and XLR plugs.

 

[mstaylor]

Gotcha, in that case I will back out because I don't have enough experience in that area to help. I will be interested in the answer.

 

[n1ist]

Ethernet gear (hubs, switches, repeaters, wifi, etc.) will NOT work with straight DMX. The wire might be the same, but the pinout, signals, and data format are totally different.

I agree with jxgriffi. In your case, I would run a separate cat5 cable from each dimmer location and spare location back to a central patch panel, and would terminate everything with RJ45 jacks. Then I would make up some patch cords with RJ45 on one end and XLRs on the other (use the standard DMX-over-RJ45 pinout) and put an optosplitter by the patch panel. Later on, you can replace the optosplitter with an ethernet switch and the XLR patchcords with normal patch cords if you want to change over to Ethernet.

As for power, take a close look at your dimmers. Many of the shoebox dimmers can't handle more than 10A or 15A combined, even if they are rated for 600W per channel. Also, some will want two separate 15A circuits to feed them, while ithers want one 20A circuit. I would at least run one 20A circuit to each location; two 15A may be better.
/mike

 

[gafftaper]

So essentially you are saying that the hub would be dumb and repeat what it hears but if it isn't listening for DMX it worn't work. I guess that makes sense. I'll just go with the daisy chain instead. I was trying to find a creative solution, I'll stick with tried and true.

Don't worry about power. Data distribution confuses me, power doesn't. I've got 16 seperate 15A circuits being distributed in pairs around the space, each with their own breaker. I'm buying four dimmers and leaving four extra pairs of outlets for rentals and future expansion.

 

[icewolf08]

Odds are that a plain old Ethernet hub would not work for you. Even though they are inherently "dumb" devices, they are still designed to work with a specific type of data signal. While all data being sent down a cable is transmitted as changes in voltage, the way that it is read, the voltages used and all that kind of thing are not the same.

An Ethernet hub is not like a DMX opto-splitter. An opto splitter is probably more "dumb" than a hum in that all it is doing is taking the raw voltage input, converting it to pulses of light and then back to raw voltage. It is also a uni-directional device. A splitter is also designed to output the correct voltage patterns for DMX signal.

A hub actually does some processing and interpretation of the information coming in. While the hub may re-broadcast all the data to all the connected devices, it has to know where data is coming in from. The hub is not equipped with signal processing equipment for DMX transmission. It is therefore unlikely that it is capable of processing the DMX data and outputting the correct voltages down the line.

I have to imagine that if using a standard networking hub would work for DMX distribution then we would see a lot more of them used for that purpose in theatres, seeing as the technology is much less expensive. If it worked, people would do it even if you were not supposed to (like using microphone cable or XLR-3 connectors).

 

[n1ist]

I guarantee 100% that no active ethernet devices (hubs, switches, routers, etc.) will work with DMX. Even though you can use the same wire, and even the same connectors/patch panels, the voltages, signalling format, and data format are entirely different.

Artnet and similar DMX-over-TCPIP systems are different; they use Ethernet as the underlying transport layer, so they would use regular network gear.

/mike

 

[Anvilx]

Lex sells RJ45 to DMX adapters. Data Products™ Cables & Adaptors: DMX to Ethernet Wiring Adapters | Lex Products

 

[derekleffew]

Lex sells RJ45 to DMX adapters.

As does Production Advantage, in a possibly more-friendly style.

CPoint XLRJ45-5F DMX Adapter, RJ45 Female to 5-pin XLR Female

 

[RonaldBeal]

Why ethernet equipment will not work

Here are some basics on why ethernet gear will not work for straight DMX:
1. DMX is +- 5volts, Ethernet is +- 2.5v (for 10B-T) or +-1v (for 100B-T)
2. DMX runs at 250 KBPS, Ethernet runs at 10MBS or higher
3. DMX can be run 1200 feet, Ethernet 330 feet.
Lots of other differences, but that is why an ethernet switch or hub will not work, (and may even be damaged) by sending raw DMX into it.

 

[g15]

although i'm 150% sure that this won't work, i'm SO tempted to go find a hub and try this....just don't have any DMX gear to risk blowing out...

 

[LuxMax]

Like everyone has said, DMX data over cat5 and ethernet data over cat5 are electrically different! You will damage any hub or switch if you put DMX signal down a cat5 line.
Take it from us, it will not work, no matter how hard you try.
To get DMX into a ethernet data format, you need hardware to transform DMX into artnet packets THEN you can distribute via normal networking switchgear.

 

[JD]

Hubs themselves are not as dumb as they appear. They try to sync to data speeds of 10m / 100m / or 1ghz (newer.) Most actually try to do a bit of routing as well, looking for common calls and answers on certain ports. When they find patterns, they stop "bothering" the other ports with those calls. (If you ever watch a hub that has been in place for awhile, you will see that all the lights no longer blink together.)

DMX on the other hand is a banshee scream. The transmitter blares a loud message, like a public address system, never expecting to hear a reply. The hub would see nothing but a lot of noise that is way outside any recognized protocol and fail to recognize anything that looked like data that needed to be relayed.

Not sure if anything would get damaged or not, but sure it will not work.