Control/Dimming Net3 Bandwidth?

[Chris15]

Paging the good folks from ETC or others in the know?

We're mulling adding a couple of nodes to our ION to get around a failed, inaccessible, DMX line but we'd need to run down a bandwidth constrained link to make this work.

My gut is we are talking, for a single universe, of the DMX max data rate of 250kbps plus some level of overhead, even if that's 100%, we're still only at 500 kbps or 0.5Mbps.

Am I in the right ballparks? Could not seem to easily find this info published...

 

[SteveB]

Outside of running a replacement DMX line, the alternative is a standard Ethernet distribution system - I.E. Cat 5/6 cable from console to central Cat 5/6 patchbay, network switch with Power over Ethernet capability, then more Cat5/6 cabling to ports where the nodes will live. AND a node(s) to get DMX to the dimmers, unless they are Sensor CEM+ or later, in which case new Cat5/6 cabling.

As this Cat5/6 and switch system is inherently at 10/100 mps speed, the DMX speed becomes irrelevant. As well, the ETC Net2 and 3 (sACN) systems are inherently at 32 and above universe capability (might be 64).

You do NOT want to do this as a WiFi link between console and devices, as BTW or any kind of WiFi for mission critical data (console to anything else). WiFi is only generally reliable for the RRFU device and/or iRFR/aRFR appa and OSC apps.

And you have options for nodes as the Ion talks sACN, so can look beyond the ETC stuff.

 

[Rob]

we're still only at 500 kbps or 0.5Mbps. Am I in the right ballparks?

Yes - one, two, three or four universes of DMX on even a 10-base-T network has plenty of room. You can investigate gateways like our Pathports or others. Or a wireless solution like City's Show Baby. But if you can't get to the damaged DMX cable and you are running Cat5 (and you have both ends of the Cat5 - not going through a switch) why not just use the Cat5 to transport the RS485 DMX? This table shows the ANSI E1.27-2 standard DMX pinout when using Category 5 (or higher) wire. ANSI E1.27-2 is the second part of a two-part standard for DMX512 cabling, and is for permanently installed cables.

 

[RC4Wireless]

Shameless plug, perhaps...

An added advantage of wireless is that you instantly get DMX distribution to all kinds of places you didn't have it before. This can be very handy from time to time. Rather than using a 2.4GHz solution, which is prone to interference from WiFi, Bluetooth, and various other consumer technology, check out our RC4Magic-900 Wireless DMX System. It operates in the 902-928Mhz band with 4 times the range of any 2.4GHz solution. We debuted it at Super Bowl XLIX last year, and recently retrofitted Michael Jackson 1 in Las Vegas with 4 simultaneous universes of 900MHz wireless DMX.

James David Smith, Product Designer
RC4 Wireless

 

[Malabaristo]

Am I in the right ballparks? Could not seem to easily find this info published...

It's not generally published, because it's usually not the determining factor for whether something will work. What's the nature of this "bandwidth constrained link" you plan to use? As Rob mentioned, the bandwidth requirements of a single universe of DMX are pretty trivially small, but things like latency and packet loss can have very significant effects on performance. Those two things are the main reason Wi-Fi is not a good solution for sACN or other DMX over Ethernet protocols.

 

[Rob]

For more information on bandwidth usage and why sACN is preferred over other eDMX protocols, check out this video series on IGMP.

 

[Chris15]

So this is where it can get a little frustrating for people who ask questions here on CB, I asked a fairly specific question about bandwidth, not about how to solve my problem, and I'm getting responses extolling various wireless DMX products. It really is much better for everyone if we concentrate on the questions being asked and try and wrap them up before we digress into alternate solutions. And I know I'm also guilty of it, but just a gentle reminder to all...

So the situation I find myself in is that a <insert unprintable decriptors here> decided to install the cable by cable tieing it off to the structure above an architectural ceiling that is riveted in, where every panel is unique, and basically getting it off to get access is prohibitively expensive.
We have been using W-DMX as a temporary solution but have not had good experiences. The generation of gear we have is now a few years old, but it causes painful interference into our 2G4 wireless comms and does nasty things to the enterprise WiFi network which our Network Operations guys don't like. The 900 MHz range may be an option - has it been through RCM testing for sale in Australia?

Anything critical over WiFi will happen over my dead body.
They didn't run data to the positions - that would have been helpful, but hey they didn't bother putting mains power on the floor at initial fitout either... doh!
But we do have easy access to the hard power lines that feed up to the positions, and so we're mulling the use of powerline carriers to get ethernet up there and drop a node at each position.
Initial sums are still way in front of getting a contractor in to do anything with the ceiling.

But I want to be fairly sure that the engineering on paper adds up before we even think about it, there are enough things that don't behave how they are meant to without trying to make something that was never going to work function...

 

[SteveB]

Well, Chris the saying is "free advice is worth exactly that"

Rather then getting annoyed at the bunch of us who took some time to offer reasonable replies to an odd question, in terms of the extent of what you were attempting as well as your current level of knowledge, perhaps next time you want a more precise answer, maybe add into the OP what you put into paragraph 2 of your follow on.

On the face of it, it appeared as a question from a novice wanting to bypass a failed DMX line and wants to move to networking.

Recall as well that CB was founded somewhat to answer precisely the type of question you asked, from folks who typically have far less knowledge then you appear to have, thus the habit is to educate.

And the question remains as to why bother worrying about the bandwidth of DMX when you would be potentially moving to Ethernet anyway. And if I recall from my days of using the old X10 control systems, which send data at the zero crossing of the A.C. sinewave, it's really slow and I could see all kinds of issues attempting either DMX or sACN over mains, but I defer to others more knowledgable.

 

[icewolf08]

The amount of data for a single universe over sACN is actually pretty tiny. In fact, it is barely more data than a standard DMX frame. Actually, it really isn't more than a list of DMX values and some header information. The sACN data is only updated about 3 times per second except when values are changing, in which case it updates as values change.

I would want to test with ethernet over powerline adapters before putting them in service. I doubt that many perform nearly as well as they advertise, and most are designed for home use. In a theatre or performance venue, there is probably a lot more interference and oddity in the power lines than in a home, which would likely impair performance. This is likely a situation where testing would be more useful than paper specs. It may even be a case where wireless solutions are more reliable. It is a case of it should work in theory, but unless someone has actually done it, I don't think anyone knows, and may differ from one venue to the next.

 

[RC4Wireless]

We have been using W-DMX as a temporary solution but have not had good experiences. The generation of gear we have is now a few years old, but it causes painful interference into our 2G4 wireless comms and does nasty things to the enterprise WiFi network which our Network Operations guys don't like. The 900 MHz range may be an option - has it been through RCM testing for sale in Australia?

Yes, RC4Magic-900 is certified for use in Australia (and USA, Canada, Brazil, and Singapore). Australian authorities have allocated enough 900MHz spectrum to support multiple universes simultaneously.

RC4 Wireless turned 25 this year. I guess that makes me a pioneer. One of my behind-the-scenes mantras has always been, "I don't have a problem with competition, that's how the world works. But if you're going to be in the wireless business please do it well. Because any bad experience leaves people distrusting all wireless." Unfortunately, there is some crap out there.

RC4Magic-900 (900MHz) and RC4Magic Series 3 (2.4Ghz) systems are available for no-charge evaluation (refundable deposit required in most cases). I'm confident that you and your Network Op guys would be very pleased.

James Smith
RC4 Wireless
www.theatrewireless.com