Comments on: DMX Over Ethernet – The Ethernet To DMX Converter

By: Rob Sayer

Rob Sayer — Mon, 16 Mar 2009 14:38:51 +0000

@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.

By: Katfisch

Katfisch — Mon, 16 Mar 2009 14:12:20 +0000

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.

By: Rob Sayer

Rob Sayer — Mon, 16 Mar 2009 09:21:27 +0000

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

By: Katfisch

Katfisch — Sun, 15 Mar 2009 22:49:30 +0000

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