Control/Dimming Dimmer Wiring

[marcusianl]

Our catwalk lights are relatively stationary, but we have a total of 24 outlets up there, corresponding to only 6 dimmers. I'm not positive on the dimmer capacity but we run 4-5 750w lamps on them at a time and they don't trip. Would this mean that I need 24 DD's?

 

[KeeperoftheKeys]

Our catwalk lights are relatively stationary, but we have a total of 24 outlets up there, corresponding to only 6 dimmers. I'm not positive on the dimmer capacity but we run 4-5 750w lamps on them at a time and they don't trip. Would this mean that I need 24 DD's?

ETC say that you can only run 2 (550W 77V HPL) fixtures, one on each side, on a DD, however the rest of their documentation suggests that as long as you don't exceed the maximum drawable current you of the dimmer you could put more fixtures on there.... (though 550W@77V = 7,14A which would mean that a third fixture would @FULL already trip your fuse...)

Whatever the case is even if you get 24 DD you will still only have 12 control channels there as you are splitting the incoming channels.
But having multiple splitters will (as long as you are careful about which side you plug what into) make it easier as far as cabling is concerned....

Have a look at the documentation on the ETC website maybe that will help you....

http://www.etcconnect.com/docs/docs_downloads/datashts/DimmerDoubler_vF.pdf

 

[marcusianl]

According to this the DD's can be ordered in StagePin format, correct? I'd hate to order 24 of them and be stuck with TwistLocks

Nevermind, just read the requirements. All of our fixtures are StagePin, so DD's would be useless.

 

[JD]

So I must have an equal number of fixtures on each side? Must I also run them at the same level (which would seem to negate the DD)? What if a lamp burns out, I now have an unbalanced situation--must I stop the show while I relamp it?

Loads do not have to be equal and can be operated independent of each other. In the DD mode, each half of the SSR is fired appropriately to the channel assigned as compared to the standard mode where both halves of the SSR are fired at the same phase angle after ZVC. The result is that the lamps are actually running DC* as compared to AC. The positive switches are operating as one channel and the negative switches are operating as the second channel. In 60cps AC, there are 120 ZVCs followed by 120 ramps. With DD, 60 are directed to one fixture, and 60 to the other. That is why the lamps are 77 volt as well. The peak voltage (absolute with reference to neutral) remains the same, but with 1/2 of the waveform missing, the RMS becomes lower.

If we pictured this circuit using back to back SCRs, one SCR would be handling one channel, and the other would be handling the other. That is why I say that fully loading a 2k dimmer with the full 2k on channel "A" would be bad. Usually, both SCRs would have the work divided, but in this mode, one SCR is doing all the work while the other is doing nothing. Again, remembering that at its heart, a SSR contains 2 SCRs and an opto-coupler. Again, the dimmer is built so conservative, that probably no harm would come of it.

* = Pulsed DC to be exact, so the arcing associated with DC does not occur.

 

[JD]

Whatever the case is even if you get 24 DD you will still only have 12 control channels there as you are splitting the incoming channels.

Actually, you will get 24 channels of control on the 12 dimmers. There is a software change that is made on the dimmer so that it understands this.

 

[KeeperoftheKeys]

I thought he had 6 incoming dimmer channels so that would give him 12 channels....

 

[MNicolai]

Yes, numbers are being confused. You have only 6 circuits on your FOH catwalk, and therefore will only be able to double to get a total of 12. Beyond that your easiest solution would lie in running DMX data cable up there and operating satellite packs.

 

[marcusianl]

DMX sounds like it might be the best option, seeing as I'm already in a position to run DMX line to our catwalk for the color scanner we're hopefully getting (see New Equipment Thread). If I were already running DMX lines, how many lines would I need to double my controlled channels in the catwalk from 6 to 12 and what type of satellite packs do you recommend for StagePin connectors? Also, how difficult would it be to control satellite packs using an ETC Express? Do they patch in like normal dimmers?

 

[shiben]

You will need to run 1 DMX line to the dimmers and then 1 for your Scroller device, seeing as they have different ends (the dimmers will have female connectors, i believe, and the scroller is a male connector), either with 3 or 5 conductors, depending on what they use. Assuming your new dimmer pack would operate like ours does, there will be a male and female DMX plug on the pack itself, and you can daisy chain them. I would imagine that they would patch like normal units, although I dont have experience with your particular control system.

Do you have any Constant circuits on the catwalk? If you do, you can avoid having to buy Non-Dim or Constant dimming modules for your rack... Our FOH and both over stage bridges have Constant circuits, each one a 20A circuit, every 10' or so, and if you have a similar situation you can have even more channels available. If thats the case, you can get one of these:

Lighting solutions for Theatre, Film & Television Studios and Architectural spaces : ETC

In fact, you could probably use some of the 2x10A ones with the other posted solution, to keep your rig all ETC. However, I would expect that these cost a lot more than the other options.

 

[marcusianl]

We do not have any constant circuits, all our plugs are dimmered. I don't have a problem with running two DMX lines to the catwalk. The way our space is I don't think it would be too difficult. If I can chain them together, will they still be able to be patched as individual units off the single DMX line?

 

[KeeperoftheKeys]

Unless you have multiple DMX universes or a fear that the single cable you are running to the catwalk will be damaged in some way and therefor need a backup you only need to run one DMX cable.

It would be good practise to then put an opto-isolated splitter on the catwalk and have seperate DMX runs for the local dimmers and the "intelligent" lights. Note though that if you intend to buy fixtures that support RDM and want to use that functionality the splitter also needs to support it.

Other than that if you are permanently installing this DMX line you could ask the IT dept to permanently install a CAT5e/6/7 cable...

 

[JChenault]

You will need to run 1 DMX line to the dimmers and then 1 for your Scroller device, seeing as they have different ends (the dimmers will have female connectors, i believe, and the scroller is a male connector),

I don't believe this is correct. In my experience the genders are compatible. IE the 'emitter' of the signal is always a female. The 'receiver' is always a male. (I did see an ETC architectural unit which violated this - but it is not the usual case).

This means that you can run the cables however they make sense to you. There are two DMX outputs on the back of the express. You could run one of these to your FOH catwalk, and then daisy chain all of your new dimmers, scrollers, etc on that cable ( up to 32 devices per cable) - OR - you could run a cable from the last dimmer rack up to the FOH catwalk (Again assuming you do not put more than 32 devices per cable). ( This assumes you do not need more than one universe of addresses which, based on your post, I don't think you need).

Be sure to terminate the end of the DMX cable. As it gets long, you increase the possibility of reflection issues.

You could also get a splitter to turn one DMX cable into several. This is probably overkill in your space at this time. They are moderately spendy and require power to operate.


As for addressing - you will have to decide what DMX addresses you want to map your existing dimmers, your new dimmers, and your scrollers to. When you patch your show, you will assign these dimmer numbers to whatever channel you wish on your console.

 

[JChenault]

Unless you have multiple DMX universes or a fear that the single cable you are running to the catwalk will be damaged in some way and therefor need a backup you only need to run one DMX cable.

It would be good practise to then put an opto-isolated splitter on the catwalk and have seperate DMX runs for the local dimmers and the "intelligent" lights. Note though that if you intend to buy fixtures that support RDM and want to use that functionality the splitter also needs to support it.

I'm curious. Why are you recommending a splitter in this configuration? Is it just to protect from damaged cable, or is there some other reason I am missing.

(And should I consider a splitter in my venue )

 

[MNicolai]

CC20's shouldn't be too expensive. It's a glorified circuit breaker dressed up in an air flow module. Just get three CC20's and replace the dimmer modules you have with those. Then you will have six 20A circuits on your catwalk which you can put probably one or two satellite packs on each depending on their current ratings. You'll probably only be able to find them in 5-15's and pin connectors, so you may need to replace the connectors on your fixtures to accommodate.

With this info goes the usual disclaimer that unless you have a devout understanding of electricity, you should not undertake rewiring everything on your own. It's in your best interest to consult a qualified individual. Even if you do feel competent, it's a liability for the school to allow you as a student to rewire devices without proper training and/or supervision.

 

[KeeperoftheKeys]

I'm curious. Why are you recommending a splitter in this configuration? Is it just to protect from damaged cable, or is there some other reason I am missing.

(And should I consider a splitter in my venue )

It has always been my understanding that it is "best practice" to keep different types of devices on separated DMX lines, or at least to separate movers/intelligent stuff from dimmers.
This is to prevent that a faulty device polluting the DMX signal will affect everything (and to prevent shorts from immediately blowing everything if you have an opto-isolated splitter etc.).

(I believe Adam Bennette's Recommended Practice for DMX512 also mentions this but I don't have it near to me to verify that at the moment)

 

[MNicolai]

It has always been my understanding that it is "best practice" to keep different types of devices on separated DMX lines, or at least to separate movers/intelligent stuff from dimmers.
This is to prevent that a faulty device polluting the DMX signal will affect everything (and to prevent shorts from immediately blowing everything if you have an opto-isolated splitter etc.).

(I believe Adam Bennette's Recommended Practice for DMX512 also mentions this but I don't have it near to me to verify that at the moment)

It's also a good practice to make sure if something spikes the voltage in the DMX lines that the console doesn't become damaged in any regards.

 

[SteveB]

CC20's shouldn't be too expensive. It's a glorified circuit breaker dressed up in an air flow module. Just get three CC20's and replace the dimmer modules you have with those. Then you will have six 20A circuits on your catwalk which you can put probably one or two satellite packs on each depending on their current ratings. You'll probably only be able to find them in 5-15's and pin connectors, so you may need to replace the connectors on your fixtures to accommodate.

My post from yesterday lists the website for the Lex Products Anaconda 6x800w dimmer packs, that do indeed have 2P&G receptacles and that would be my choice for this application.

Steve B.

 

[JD]

During the renovation at our school's theatre this past year we received a new Sensor+ Dimmer rack. However, when wiring our FOH catwalk, they didn't run new Dimmer lines, they just ran new cable through the existing ones, so we only have 6 Dimmers on our catwalk (although we have 18 instruments and 24 outlets). Is there any way to increase the number of controllable dimmers without running more cable? I saw something on ETC's website about a Dimmer Splitter. Would that do the job?

-Marcus

Ummm.. Something we may have all overlooked: If there were 24 outlets up there before the renovation, is it possible that they are already home run to the dimmers? It could be that when the system was upgraded someone was a bit short sighted and tied separate lines together at the rack and only allocated 6 dimmers to the catwalk. If this was the case, reassignment would be easy.

 

[MNicolai]

Very unlikely as it sounds like the previous usage didn't warrant 24 home runs, though possible.


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[marcusianl]

Well the work order supposedly requested all our circuits to be put on individual dimmers (according to my teacher) and the electricians apparantely got lazy or something, and it was already too late to complain when we figured this out. There were 24 circuits up in the catwalk before the renovation, but I didn't have an opportunity to work with the system before the renovation so I don't know if they were each individually controllable. How would I find out if each of the circuits is home run or not?

And as for the CC20's, if I already have stagepin connectors on my instruments and the packs that SteveB recommended have stagepin outlets, wouldn't I just have to swap out the dimmer units on the rack (which I was shown how to do when ETC did their "training session") and attach the dimmer packs to the connectors up in the catwalk? Or do I still need to run DMX cable for control?