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DMX Over Ethernet – The Ethernet To DMX Converter

DMX over Ethernet has been around in stage lighting control for quite a while. The concept of sending DMX512 universes over a network, using Cat5 cable or Wireless, has some advantages but an ethernet to DMX converter has not been cheap. As a new low cost ethernet to DMX gateway enters the market, On Stage Lighting looks at the use of DMX over a network.

Enttec, the makers of the Open USB DMX and the USB DMX Pro, has added another piece of hardware to it’s expanding lighting control range. The Enttec Open DMX Ethernet (ODE) is a cheap ethernet to DMX converter/gateway (or vice versa) that supports ArtNet and ESP, two common protocols used to distribute DMX data on a network. Featuring both 5 pin DMX Input and Output, 10/100 network connection and set up using a PC interface, at 200 Euros, the ODE is an inexpensive way to enter the world of ethernet lighting control. So what’s this DMX network thingy all about?

What is DMX Over Ethernet?

DMX512, the serial stage lighting protocol, has many limitations and control capacity is one of them. The 512 channel limit per DMX universe/cable seemed huge when all we wanted to do was control single dimmer channels. As time passes, intelligent lighting needs more channels of control per fixture and that leads to the need for multiple DMX universes.
DMX Over Ethernet enables the sending of multiple DMX universes of control data via a network using CAT5 cable, just like a computer network does. This also means that modern complex stage lighting systems can talk to each other, each part as a “node” on that network.
Sending DMX Over Ethernet also allows the possibility of using a WiFi system to have your lighting control “wireless”.

What is DMX Over Ethernet used for?

A DMX network using DOE, at it’s simplest, is used to transmit many DMX universes from a lighting control console, down a single CAT5 cable, to the stage. An ethernet to DMX converter is used, via DMX buffers/Splitters to send data off to different parts of the lighting rig. It certainly beats running four or more standard DMX XLR cables over the same distance.

The real benefit of DMX over ethernet centres around the lighting control equipment itself. More consoles, visualisers, media server and other complex parts of a large lighting system can use the two way nature and bandwidth of a network to communicate in a way that the “old” DMX 512, one-way serial protocol just can’t do.

If we can send lighting control signals via a network, why bother with DMX at all?

DMX512 control is limited but simple and robust. Being a “standard” also means that there is a legacy of stage lighting equipment that uses DMX and that doesn’t look set to change any time soon. A real advantage of using DMX is that you can “daisy chain” lighting fixtures together in a control chain. DMX Cable goes to Fixture 1, out and along to Fixture 2 then 3 etc.

Some lighting equipment manufacturers have built RJ45 sockets alongside the conventional DMX connectors, which gives us the option of using the first fixture in the chain as a ethernet to DMX converter. Not sure how comfortable I am with the concept of the whole system relying on a hot, dusty, moving light that is 8m from the ground.

Ethernet networks are like a spider with many legs. Each cable connection has to come from a network hub(*see comments) switch and this could lead to an excess of control cabling. Because each lighting fixture is a “node” on the network, more control complexity creeps in – instead of just “listening” for an instruction, each node must communicate with the switch correctly. This could lead to all kinds of trouble, just think about the last time you tried to set up a network of a few PC’s and magnify that by 100 – then take it on tour!

Why not get rid of the cables and control all intelligent lights using a WiFi network?

If you think that administrating a DMX over ethernet cable network sounds painful, imagine trying to get a wireless network of 100 fixtures together – With all the nodes surrounded by steel roofwork, truss and bits of drape. The possibility of making sure that the network was a closed loop, without interference from other wireless sources, seems like a mammoth.

Also, as we have not invented a wireless way to get power to moving lights, the benefit of wireless lighting control systems is minimal. WiFi or radio DMX systems are the answer to a specific logistical problem.

So, not much point in getting this DMX Over Ethernet stuff, then?

DMX over Ethernet has its advantages as mentioned above. Wisely integrating the network with existing DMX control equipment has now become affordable. Ethernet is also set to play a part in the future of stage lighting control, mainly due to fast progress in the lighting media and control sector.

Get yourself a PC based Stage Lighting control, a cheap WiFi access point and an Ethernet to DMX converter and you could have your first wireless stage lighting control system.

10 Responses to DMX Over Ethernet – The Ethernet To DMX Converter

  1. Katfisch March 15, 2009 at 10:49 pm #

    Just thought you might like to know . . . Ethernet Hubs are no longer available. You can only buy Ethernet Switches.

    Also . . . if the folks making the Ethernet to DMX Converter were to also install an Ethernet Switch inside the Converter (it would be 1 channel and therefore real cheap to do and still real fast) then you can daisy chain them. A great example of such a system that is used in commercial and industrial applications is a network called EtherCAT. You can connect it in star, daisy-chain, and any combination thereof. It’s also blazingly fast – it can communicate with 100 industrial servo drives in 100 microseconds, 30,000 inputs/outputs in less than 50 microseconds, etc. Notice that’s microseconds – not milliseconds! It’s also safety rated and so you can handle any machinery that requires Emergency Stops over the same network.
    It also uses standard Network Interface Cards, standard CAT5 cable, standard (or special) connectors, etc. If you don’t like CAT5, fiber optic cable is also available (imagine having to run only one cable between the console and the stage that is virtually bullet-proof).
    There’s also a large number of servo, stepper, and dc-motor drives available plus hundreds of input and output cards (even exotic types like oscilloscope) available.
    It’s really cool.
    So then, if they can do it, why can’t DMX?
    For a good description of EtherCAT, see http://www.ethercat.org/pdf/ethercat_e.pdf

  2. Rob Sayer March 16, 2009 at 9:21 am #

    Hi Katfisch, have updated the article (it was first published when hubs were still around).

    Interesting to hear about EtherCAT, the stage lighting world has as many artists (like me) as technologists and it can be hard to keep up with things “outside”. Enttec are well known for their work in lighting systems control and I expect that development in this area continues. Let us know if you hear of anything.
    Cheers

  3. Katfisch March 16, 2009 at 2:12 pm #

    Thank you, Rob. I re-read the article and believe the point I was trying to make was still missed. No doubt, that was my fault.
    If the DMX network is replaced with Ethernet (CAT5 and/or Fiber) and the Ethernet to DMX converters had the daisy-chain feature (i.e., add the Ethernet Switch inside the converter), then the cabling is greatly reduced but the controllability is greatly increased . . . when chosen. The new network provides for incredible opportunities to do some really sweet stuff. For example, if one Universe went “down”, all the others would still continue running. If machinery were added, the same network controls the machine.
    Ethernet is easier than DMX in that there are no DIP switches, resistors, etc. and it’s not limited to 512, 1024, 2048, or whatever. You also don’t have to concern yourself with how many addresses a device needs. Just plug and go.
    Regular Ethernet will work fine in this arrangment. EtherCAT is not required. However, if you want to mix lighting controls with machinery (i.e., Jaws, King Kong, etc.) then having everything on one network (including all the safety issues) would be a real asset. If you need redundancy (i.e., to automatically handle a cable break and keep the “show” running) then EtherCAT is the way to go.

    EtherCAT is an open standard and there are schematics, etc. available at http://www.ethercat.org.

    By the way, the section of the article regarding the use of WIFI is interesting and true. The problem with WIFI is that its too slow due to saturation or 2.4Ghz interference. The right way to do it is to use a 900MHz Radio Modem. While it can handle distances of up to about 40 miles, its most important feature is being able to communicate through walls, pipes, building steel, and the like. The provided link is for just such a Radio Modem unit. http://www.industrialethernet.com/aw900i.html There are also numerous other suppliers of such equipment (i.e. Phoenix Contact, Weidmuller, Banner, etc.) but their prices are quite a bit higher.

    The reason I’m getting into Lighting Controls is because my customer, Cabbage Patch Dolls, wants to add a stage, product displays, etc. to their manufacturing business. As I recall, a number of New York department stores do similar with their window displays – especially at Christmas. Having each window be a Universe would make developing and controlling the window features much easier. If a window went “down” at least the rest of the windows would keep running.

    One last thing, with regard to software . . . if the various manufacturers of PC Lighting Control systems used a real-time kernel for operating the “system” and used Windows for the development and basic display, then a Windows crash would not affect the rest of the system – the “show” would go on. Just restart windows and keep going.

    For those who are afraid to use a PC as their primary control because of virus, etc. the simple solution is to never let that PC touch the web and screen every disc/memory stick for bad stuff before connecting with that PC. It’s SOP for industrial.

    All the above is SOP for the industrial world. With all the new complexities being added to the theater world, maybe the features of the industrial should be looked at more closely. A good web site for what’s possible with industrial and PC-based control, check out http://www.beckhoff.com

    My apologies for being so long winded.

  4. Rob Sayer March 16, 2009 at 2:38 pm #

    @Katfisch, I only updated the article regarding switches vs hub terminology. The point of the cheap ethernet to DMX converter is that it provides a simple way of sending DMX over ethernet. DMX might be legacy but it’s what we’ve got a lot of. While modern lighting control systems have endless real networking capabilities (many of them proprietory at the moment) and people fling terms like ACN around every now and again, the reality is that many venues/shows would love to even have a DMX system.

    Thanks for your valuable information.

  5. Jake February 10, 2011 at 12:34 am #

    I’m in the lighting crew at my school and I have a question. We are running an ETC system (ETC Express 48/96) in our AUD. We don’t own any moving lights. How could we go about getting our lighting system broadcast via Ethernet so we could control it wireless on a laptop.

  6. Abel Zyl Zimmerman January 6, 2012 at 4:20 pm #

    In response to Jake:

    I am running an Ipad based console, that only outputs wifi/dmx. I place my router and ethernet-dmx convertor up in the grid. Then i get to run around the theater… This usually means, when i am working alone, that i am backstage fixing the kicked over light and running cues at the same time!

    If the ETC comes with remote control software, and you have it hardwired to your dmx system. All you should need is an ethernet/artnet connection to the ETC console. And a dedicated wireless router connected to the ethernet. The laptop will transmit to the router, the router will communinicate via ethernet/artnet to the console.

    I will look up that ETC, because i use one sometimes… But i think it has an ethernet port.

    Abel

  7. Abel Zyl Zimmerman January 6, 2012 at 4:24 pm #

    The Etc does have an ethernet port. I havent used it remotely via a laptop… Better check to make sure there is a PC remote utility. Good luck!

  8. Crockers January 24, 2012 at 3:12 pm #

    I found the article helpful cheers, especially for someone brought up solely on the humble but much revered par can

  9. Corey October 22, 2016 at 1:46 pm #

    Very interesting article. I have a question regarding DMX to Ethernet. The company i am working for is considering purchasing a lighting visualization program.. We have and Avolites Pearl 2010, which i would love to be able to do some pre programming via Capture Atlas. Being aware that the Pearl 2010 does not send out Artnet, what I wanted to know is if i purchase a DMX to Ethernet converter, will I be able to control Capture via the Pearl.

  10. Rob Sayer October 22, 2016 at 3:00 pm #

    Short answer, yes. Classic Pearl also supported CITP but the hardware setup is a little old skool.

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