A very long DMX run.

[madorangepanda]

Hello,

 

I've become involved in a project which will require controlling some fixtures (via DMX) on the other side of a valley from the main event. They do need to be controlled from the main event to keep in sync.

 

It is possible to run cable, but having walked it today the run is ~5km across farmland to which we have access.

 

There is also good line of sight should this yield an easier solution.

 

We are currently thinking of running in CAT5 and placing DMX repeaters run from batteries/inverters in peli cases along the length.

 

It is a one night event so hiring kit is preferential to buying.

 

Any ideas/comments as to a better (cheaper) solution?

[pritch]

Artnet? Maybe using a point-to-point microwave link, if you can manage to hire one in?

[JackPott]

Whirlwind do a laser modem which you could carry Artnet over. I've never used it personally, and I don't how easy they are to hire, but given you have line of sight its an option. The website blurb (http://whirlwindusa.com/catalog/digital-audio-networking/e-beam-laser/ebeam) mentions a figure of 900ft, that would be really disappointing if that's its maximum range.

[kitlane]

Whirlwind do a laser modem which you could carry Artnet over. I've never used it personally, and I don't how easy they are to hire, but given you have line of sight its an option. The website blurb (http://whirlwindusa.com/catalog/digital-audio-networking/e-beam-laser/ebeam) mentions a figure of 900ft, that would be really disappointing if that's its maximum range.

 

You're talking about Free Space Optical Communication. The terrestrial limit is about 2 miles, depending on atmospheric conditions. Works great in space, though!

[J Pearce]

Will artnet run over a VPN? Then the remote connection could be a 3G modem, though do a site survey for coverage first!!

[scjb]

Is it a predefined show or a busker? Just wondering if you could stick a second desk out at the remote location and then sync the systems together. Timecode (especially if the second desk permits freewheeling) may be a more resilient data stream?

[Absti]

I think an Artnet connection with a fiber optic cable would be a possibilety for you.
otherwise like scjb said, 2 consols, 2 times the same show and start both over a Timecode Signal
To run the signal over a VPN connection is not a good idea (no really safe connection an a very long delay)

sorry for my bad english

[dbuckley]

Timecode a good idea if it'll work for you; requires no more than a motorola handy talky at the receive end, and ideally a base station rated for continuous transmit at the sending end, but easily and cheaply hireable.

[madorangepanda]

The show will be busked, so unfortunately timecode is not an option. (I really do wish it was however)

 

I think the direct distance between the sites is greater than 2 miles. Will try and work out the actual distance.

[Smiffy]

Who are your Console Manufacturer of choice ?

 

You'll find that most of them love a project like this as it's good for some free marketing in the Magazines. If it's Avo, then they have been involved in numerous long-range wireless Data things in the past, and I'm sure that they would be able to point you in the right direction.

 

I think that in this situation, I would be considering a wireless microwave link. Especially if you have clear 'line of sight' between FOH and the Location that you want to place the remote fixtures.

 

Cheers

 

 

Smiffy

[pritch]

Then the remote connection could be a 3G modem, though do a site survey for coverage first!!

 

I'd hate to use a mobile data connection for this sort of thing; in theory, the bandwidth is plenty high enough, however you may well find that things will work perfectly during fit-up, but once you've got the public in the area, your data link will become unusable, especially if there's something going on that they find appealing enough to get out their 3G phones, and make video calls to their mates.

 

On a more general reliability question, what happens if your link goes down? Is it so critical that you need a redundant link? Or, assuming you've got someone on the far side looking after the gear, would they be able to run a cut-down version of what's needed from a laptop or backup console, taking cues over radio?

[Sully]

I think that in this situation, I would be considering a wireless microwave link. Especially if you have clear 'line of sight' between FOH and the Location that you want to place the remote fixtures.

 

I'll keep mostly to the Ethernet side of stuff

 

Telco grade microwave kit over that sort of distance is more or less bombproof, we had a 3 mile link across north London using such units running 24/7 over 6 years and had only one failure in that time, it tends to be licensed as well so interference issues are extremely unlikely bordering on miniscule.

 

Some of the higher end "Unlicensed" 5.8Ghz band Ethernet kit such as the Motorola PtP series is also very very solid and is available for hire from certain suppliers such as http://www.csuk.co.uk/ and http://www.co-channel.co.uk/

3 miles isn't a particularly long link for such kit, we had some of these on trial recently (over a somewhat shorter distance) and I couldn't fault them. With the transmit power dialed down they were still performing and there were no drop-outs whatsoever over the trial period.

 

The installers will normally come in and install and align the kit above which doesn't take too long so you'd need no expertise on the wireless bit of it.

 

If your budget doesn't quite stretch to the above there are cheaper 5.8 Ghz bridging kits such as http://www.wifigear.co.uk/cctv-wireless-ki...t-to-point-kits. With that of course you may have to install and align it yourself or pay a bit extra for someone to come and do it for you. I've no personal experience with these particular kits but 3 miles would be well within their design spec. The 5.8 Ghz band has a number of non-overlapping channels and is relatively unused, in a rural setting I'd be astonished if there were any interference issues.

 

If it were me I'd consider any of the above preferable to a 5 mile relay of cable interspersed with batteries carrying data. Edit: or 3G All of the above are Ethernet based, I've left aside the requirement of converting the DMX to something like Artnet and back again and what it requires in terms of link characteristics.

 

David.

[Tomo]

Do *not* even consider 3G - the latency is quite ridiculous, often in the range of several seconds.

 

With the majority of networked lighting control, the absolute bandwidth is almost irrelevant.

What matters is the latency, or the time between "Snap to black" on the console and the actual dimmers/fixtures doing it.

 

When ETC were lighting the Burj Khalifa from a hotel balcony a mile away, we used a microwave link to send the control data over - it had a pretty tiny bandwidth, but the latency was very small.

 

For this kind of event, there's basically three options, in order of decreasing complexity and expense.

 

A) Radio, microwave or laser link between console and dimmers & fixtures.

Look into wireless DMX first, see if there is a version with the required range when coupled with a suitably directional antenna.

 

- Note that this does raise regulatory issues, so you will need to check with the relevant authorities (OFCOM and possibly the CAA in the UK).

 

B) Hard-wired optical link using Cat5 to Fibre media convertors that will drive a suitably-long fibre link.

Then send the network protocol of choice down it - prior to and during the event, keep a heartbeat going over the link so you know that it's still working!

 

C) Multiple operators and consoles.

Put an operator with a console at the remote location with a pair of good radio handsets, and work together.

 

Personally, I would go with option C - the remote location does not have to be 'controlled' by the main event, only 'synchronised'.

Rehearse it at base, maybe using visualisation, and you'll be surprised how good people are.

 

Finally, if it is important that the remote location works, then you will also need an operator and console at that location anyway so that you have a backup, and to do the pre-programming, setup and test while the 'big' link is being assembled.

[Matthew Robinson]

Electricity travels at about the speed of light - 3x10⁸ ms^-1. Speed = distance / time, therefore time = distance / speed. Therefore, time_delay = 5x10³ / 3x10⁸ = 1.6x10^-5s (1/60 000 of a second). So, delay shouldn't be a problem. However, the latency of the repeaters- if you have a lot of them one after the other- may be a completely different issue!

[son of lx dad]

There is/was an entertainment industry company that specialize in this sort of thing. They are called dAFT dATA (capitalization is correct). Unfortunately there website is just a picture of a sheep at the moment.

The company was run by a chap called Chris Crockford, a proper expert in the field who does shows such as the London Eye at New Year Eve. I believe he also has been involved with the wireless links to McLaren F1 cars.

Hopefully someone here has a number for him, or I know that Stage Electrics use him for the London Eye, so you could try contacting the SLX Production Dept for a contact for him.