That DMX has a mind of its own.

MircleWorker

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Mar 1, 2006
Location
Grand Rapids, MI , USA
heere is a fun one for you all.

a week ago I had a concert with 4 MAC650s with conventionals, controlling them through a Colortran innovator 600. DMX ran trough a spillter then to the fixtures with a total run of approx. 300'. The fixtures were unresponsive and kept moving on their own. I was getting control sometimes but then it would not respond and they fixtures would do there own thing again.

I put a GAM check in line to see if I was getting any wierd signals, didn't see any. What it did do was cleaned up the signal to the Macs.

This was the first time in four years that I have used Automated lights through my console, and used my DMX splitter.
 

Van

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zac850

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300 feet is about the far end of a DMX run. Try to put the console closer to the lights (use less cable) and see if the problem persists.
Unless your splitter was in the middle of the run, the data signal may just be having to much resistance.

In that, are you using mic cables or the true DMX cables, the signal in the mic cables will diminish much faster then the signal in the DMX cable.


Also, Mac 650? Martin has a 600 and a 700 and a 750, no 650 that I see.... typo? or have I just not heard of this fixture?
 

MircleWorker

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Location
Grand Rapids, MI , USA
Thanks, For the replies, Sorry for not getting back. I'm currently working on our Musical, Beauty and the Beast.

I had a GAM Command Not a GAM DMX checker

This is all a separate Universe from the conventional

From the console to wall The DMX is 512 5-pin w/twisted lines, True DMX Cable, No Mic cables. From there it is hard wired through conduit to the rack about 175' to the racks give or take 25'. Then, it runs through two Colortran DMX Splitters then wired through conduit to different locations through theater. The second DMX splitter is terminated, not the first. I think one of the outs of the the first splitter runs to the second one.

I have to fixtures mounted on a batten, Daisey chained with the DMX coming from one of my outs at the SMP, another 75' to a 100'.

That is where I had the GAM command in the line. it was set to read the DMX line coming in.

But, I didn't have a Terminator on the last Mac. I thought that they were self terminated.
 

Van

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But, I didn't have a Terminator on the last Mac. I thought that they were self terminated.

They can be if you select it. < if I remember correctly> thgey usually have a small slide switch for term / open. If Not be sure to terminiate the throughput.
 

disc2slick

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Feb 11, 2004
Location
Key West, FL
It may not apply to your set-up, (and correct me if I'm wrong), but don't things get a little wonky sometimes if your rack and your fixtures are not o the same phase? Or are on the same phase. Something to do with phases?

-Dan
 

Van

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You always want your board pluged into the same phase as your moving lights. Thats why most distros have an convenience outlet.


JH
a. Where do you get that idea ?
b. Why would it matter ?
c. Why is your distro close enough to your board to plug into the convenience outlet ?
d. How do you know what phase the convenience outlet is on without opening the distro ? Are you licensed to do that ?
e. If your moving lights are 220v <typically they are> that means there are two phases per fixture. Which phase do you choose to plug into ?
f. If you are using more than 3 moving lights how do you adequately balance the load on the panel between all 3 phases and get your board on the same phase as all your moving fixtures.
g. Your'e not just guessing are you ?
 

len

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a. Where do you get that idea ?
b. Why would it matter ?
c. Why is your distro close enough to your board to plug into the convenience outlet ?
I have been told that as well, but never knew why. As for getting power off the distro, we have several lighting snakes. They are either 4 universe snakes with a head (similar to a sound snake) and the head acts as a splitter also (custom made) and we also have some 2 universe ethercon snakes. Ethercon has adaptors at both ends for either 3 or 5 pin connections. Both have an a/c line to run back to the console. Also, we keep a splitter in the dimmer or distro rack to save wiring time. So it is possible to get a/c from the same leg back to the console, but again it doesn't make sense to me as to why because there have been plenty of times when I have not done so.
 

disc2slick

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I got the idea of keeping the MLs and the console on the same phase from a conversation I had with one of the guys I worked with in a rental shop over the summer. My guess is that it has to do with the same reason you want your Amps and sound board on the same phase (is that right? I dunno...sound guys?). I imagine just as a ground loop can cause an annoying hum in speakers it manifests itself as misbahving lights in MLs.
 

Grog12

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I got the idea of keeping the MLs and the console on the same phase from a conversation I had with one of the guys I worked with in a rental shop over the summer. My guess is that it has to do with the same reason you want your Amps and sound board on the same phase (is that right? I dunno...sound guys?). I imagine just as a ground loop can cause an annoying hum in speakers it manifests itself as misbahving lights in MLs.
Yeah....let me give you a good reason not too...especially if you're using a generator.

Once upon a time I was helping set up a concert and the shop sent out a person along with the equipment rental. The venue didn't have a distro so they rented a generator to power the package. The guy from the shop plugged the board...into the generator as well. When he hit the audience blinders it drained the generator to the point where it over compensated and boom dead board (also a good reason for a surge protector on boards.)
This is two and a half ours before the show starts.
The shop is a 2 hour round trip away and no one is at the shop.

He made it back with another board...which he insisted on plugging into the generator...despite our numerous protests.

Yes halfway through the show he blew the second board....running rock and roll on dimmer test switches sucks :(
 

len

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Oct 23, 2004
Location
Chicagoland
The guy from the shop plugged the board...into the generator as well. When he hit the audience blinders it drained the generator to the point where it over compensated and boom dead board (also a good reason for a surge protector on boards.)
I understand your point, but chances are something bad would have happened regardless. If hitting the moles caused the genie to max out, it's likely that either the genie was inadequate or the rig was wired wrong, etc. And if there were moving lights on that rig, some or all of them could have been damaged beyond immediate repair as well, which I'm assuming wasn't the case since you didn't mention them and you managed to get thru by using the test buttons.
 

SHARYNF

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Sep 3, 2006
Having the mixing board on mains power and the rest of the audio rig on a generator is not recommended, since they would have two different grounding systems. The problem was very likely due to the gen being underrated. The draw for audio systems is typically quite low below what is rated on the unit, but the draw from lights is instant and typically right to the max so, undersizing is a major problem

Sharyn
 

SHARYNF

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Sep 3, 2006
a. Where do you get that idea ?
b. Why would it matter ?
c. Why is your distro close enough to your board to plug into the convenience outlet ?
d. How do you know what phase the convenience outlet is on without opening the distro ? Are you licensed to do that ?
e. If your moving lights are 220v <typically they are> that means there are two phases per fixture. Which phase do you choose to plug into ?
f. If you are using more than 3 moving lights how do you adequately balance the load on the panel between all 3 phases and get your board on the same phase as all your moving fixtures.
g. Your'e not just guessing are you ?
This area is pretty interesting, and there are a variety of practices.
Because of how three phase power works, and how the distro in connected in and what service the building has it can be a bit complex.

On the audio side of things it usually IS recommended to keep things all on the same phase, so the hot neutral and ground are all the same for the equipment. It probably has more to do with equipment that has possible problems, for instance consumer gear that is only two wired, double insulated, and old tube guitar amps etc, but while it is not a hard and fast rule, it DOES in a number of instances reduce ground loop noise.

IN general, and this is an over simplification, I have found that having equipment that is either audio, or digital signaling (like DMX) works best if they all share the same GROUND. So the argument re knowing the same phase is valid, but most of the problems can come if your board is on one system say an outlet in the house, and your lights, dimmers and moving L are on another system with a different path to ground. The reason is that some buildings use the conduit as the ground, don't have a continuous independant wire etc, and all of this can cause variations on the ground. In addition sometimes the xlr connectors are incorrectly wired where the shield is connected to the case of the connector, the connector comes in contact with something that creates another ground. Basically grounds work best if there is ONLY one point in the system where there is an actual ground, vs multiple partial grounds.

This is also why in most concert setups, you will find that good practice is to run power from the distro back to FOH or lighting positon.

Most distro's should have the outlets color coded to determine the phase they are on, In the US it is black red and blue, and different countries it is different colors.

Another potential area of problems is the whole issue of 220/240/208 volts here in the US
If you are connected to a three phase wye service, than if you connect an instrument using two of the hot legs from two of the phases, you will only get 208 volts. If your instrument was rated at 220, you will probably not get the same level of output. If your system was wired up Delta, then you CAN get the full 220, but it is trickier to have a distro connected in. (this is why most large houses have a pre wired disconnnect wired in to the system to avoid problems and work with the design. The problems tend to arise when you show up with your own distro, and the electrician connects it into the nearest panel for you. IF everything is running on your distro, fine, but if part of the system is already installed, and your system needs to interface is where things can get a bit more difficult

Sharyn
 

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