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.