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Underwater DMX Lighting Safely


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#1 Ronnee Swenton

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Posted 08 August 2013 - 04:47 PM

Hey all,

 

This is my first time posting here, but I've read the forums for a while and I finally have a problem to solve. Anyway, straight to business.

 

I have a director who wants to shoot underwater in an in-ground pool. My goal is to create a china-lantern type minefield of lights throughout the water hooked up to a DMX controller. AC current is going nowhere near the water for fear of frying the talent. So what kind of options do I have to get this to be 100% safe?

 

My friend is an electrian and suggested that all the lights should be DC battery powered, which I believe is the safest route. My main problem now is how to supply a DMX signal to these lights and be able to dim them. I'll be using sealed plastic spheres (8"-14" diameter).

 

I'll take solutions outside of those parameters. As long as I can achieve dimming control over the spheres I'll be content. Thanks guys.


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#2 Phil Rhodes

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Posted 08 August 2013 - 04:53 PM

There are battery-powered LED lights available that have DMX control. Don't ask me for type numbers; the ones I found were no-name chinese stuff. You will need to be appropriately careful about dimming them, as DMX controlled LEDs are likely to be pulse-width dimmed.

 

P


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#3 Ronnee Swenton

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Posted 08 August 2013 - 05:08 PM

I was considering going that route. The editing will be pretty choppy at this specific section of the video, so PWD might be fitting. I would have to do some tests to be sure.

 

How do you feel about this product?

http://www.alibaba.c...attery.html?s=p


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#4 Ronnee Swenton

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Posted 08 August 2013 - 05:16 PM

Unfortunately I don't have permission to edit posts yet, so I apolgize for a double post.

 

EDIT: I'm just recalling now exactly what this looks like on camera. It's more of a rolling strobe effect than a solid strobe on/off, which I don't think would be aesthetically pleasing.

 

Is it at all possible to find a small battery operated DMX dimmer that could work with standard incandescent globes? I believe running the DMX cables underwater is safe, especially if the ends are sealed off.


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#5 timHealy

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Posted 08 August 2013 - 09:48 PM

Why do the DMX cables have to be underwater at all? If you kept the power supplies up on dry land and run the power to the lights, then the dimmer packs, dimmer board and DMX cables can all be nice and dry on whatever land you are adjacent to. Tungsten lights don't need DMX run to the head. If you were using moving lights then DMX would have to be run to the head. But if you were using moving lights underwater there would be bigger issues.

 

Also I believe all tungsten bulbs can operate on AC or DC voltage. So you could use a run a regular 120 volt 100 watt household bulbs with 120 volt ac or dc. I have never actually done this so it might be wise to check the Harry Box book for a quick look. And one would have to look for a DC dimmer pack, if one exists. The last time a saw a DC dimmer, it was a large ancient thing that looked like it could make really good toast.


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#6 Ronnee Swenton

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Posted 09 August 2013 - 12:26 AM

Thanks for the replies Phil and Tim.

 

Your absolutely right Tim, I'm probably better off just running the power down from a dimmer. My friend who knows much more about electricity than I also enlightened me to the fact that DC or AC, if it's a strong current it doesn't matter which is which, it's gonna sting. He reccomended I hook up multiple dimmers to a few seperate small battery sources and run the power down into the spheres, being sure they're sealed properly of course. His logic is that if an accident does happen, a small battery won't kill anybody like a hot source from a genny or tap-in would. I plan on using 60 watt globes in each sphere. Probably adding up to 360 watts max split between two dimmers.

 

Does this seem like a suitable approach and is there anyway I can manipulate the voltage by choice of battery to make the current safer while still having the juice i need for the globes? I'm also interested if anybody knows of any dmx dimmers that would be more suitable for this installation than what I currently have, which is the DP-415 (http://www.elationli...iles/dp-415.pdf).


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#7 Phil Rhodes

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Posted 09 August 2013 - 06:56 AM

How do you feel about this product?

 

That's the sort of thing I was thinking of, but I've no knowledge of that particular one.

 

 

 

Is it at all possible to find a small battery operated DMX dimmer that could work with standard incandescent globes?

 

Not in my experience. If you wanted to operate mains lighting, you'd have to have mains output from the device anyway, so the safety case is moot at that point.

 

Electrical safety is more or less determined by voltage. Car batteries are 12V, which is harmless unless you short it out and it produces a lot of heat, which can burn you, start fires, etc. Mains is more dangerous electrically and can also start fires, but the higher voltage makes it easier to transmit large total amounts of energy, so you can have bigger mains lights than you can battery.

 

If you must have low voltage lighting, look for solutions to allow you to run Dedolights from car batteries. They're often 100W each.

 

Er, wait, what? You want to put lights in the water? Then you need specialist waterproof lighting, no question, regardless of voltage.

 

P


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#8 Guy Holt

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Posted 10 August 2013 - 05:27 AM

AC current is going nowhere near the water for fear of frying the talent. So what kind of options do I have to get this to be 100% safe?

 

 

You can use AC in and around water with 100% safety if you use GFCI devices – but I am not talking about only the hardware store variety (though you will want to use those too as part of a comprehensive ground fault system.) Large Amperage GFCI devices were, more or less, invented in 1996 for the production of the film "Titanic." Director Jim Cameron wanted the highest level of reality, which meant literally hundreds of people in, around, and under the water, with hundreds of submerged practical lighting units. On top of that there was assembled, what was to date, the largest lighting package ever used on a motion picture production consisting of 5,000 lighting units, requiring 50,000 amps of electrical power, and over 140 miles of distribution cable.

 

Because "Titanic" required a combination of HMIs, incandescent, dimmers and 'specialized' lighting units, "Titanic" Gaffer, John Buckley, and Rigging Gaffer, Mike Amorelli, realized that DC power would not accommodate all of the production's power needs. And, given the scale of "Titanic" traditional methods for handling AC around water (use of distilled water) was insufficient. Realizing "Titanic" required a new approach to working in and around water, they turned to Bill Masten and Rick Prey who operated a company called SMS Inc.

 

Primarily known for their award-winning NiteSun products - portable generator trucks with 120 ft booms for 12k HMIs - these two had already begun work on a protoype of a 208-240V multi-phase device which did not exist at the time. When Rick Prey worked on "The Abyss" in 1988 they used the electrical equipment that was available at the time, and as a Navy trained electrician, it scared him to death, Prey said, because, absent a Class A device, they "had protection, but not personnel protection."

 

After working with the Academy Award winning 100A Shock Block (developed by Stephen J. Kay of the K-Tec Corporation) on several more shows involving water (including "Crimson Tide"), Prey and Masten realized that high amperage multi-phase GFCI devices were technically feasible and were working on a prototype for such a device when approached regarding "Titanic."

 

Recognizing that the magnitude of power needed for "Titanic" (50'000 Amps in all) was beyond the scope of K-Tec's 100A Shock Blocks alone, Prey and Masten began work on developing ground fault protection devices capable of protecting circuits of 400 Amps, which did not exist at that time.

 

Familiar with the Bender Corporation's efforts on the "MagLev Train", a proposed high-speed rail line between Los Angeles and Las Vegas using a Magnetic Levitation Train, Prey and Masten thought that some of the same technology could be applied to their prototype and so they approached Marcel Tremblay at Bender with their schematics. With the help of Bender, SMS built a total of twenty-eight 1200 Amp GFCIs, and a number of 3-Phase 100- and 200 Amp models that were used, along with the 100 Amp 120-volt Shock Blocks from K-Tec, in the production of "Titanic." The proof of concept came when a high wind dragged a piece of heavy duty lighting equipment into the water, the 1200 Amp blocks SMS designed shut down power instantly - saving lives.

 

Using the "Titanic" production as field tests, Bender Corporation worked out further refinements to SMS's basic design for a 1200 Amp device until they had a unit that would meet the requirements for UL listing as a personnel protection device. Shock Block was subsequently acquired by the electrical manufacturing giant Littlefuse which introduced its' own UL listed high voltage multi-phase devices.

 

For more details on how to use GFCI to protect  talent and crew in and around water see a curriculum that I developed on electrical hazard protection for the entertainment industry that is available at www.screenlightandgrip.com/html/481_GFCI_Workshop.html.

 

One important consideration in Ronnee’s case is the source of power. Ronnee, how had you planned to supply power to your dimmer packs?

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip sales and rentals in Boston


Edited by Guy Holt, 10 August 2013 - 05:31 AM.

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#9 Ronnee Swenton

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Posted 10 August 2013 - 08:36 AM

I didn't think gfci's would be safe enough to operate with lights underwater. This definitely simplifies things. Since I plan on using low amps, I was considering either plugging into the location AC or running a puttputt genny originally. Is there a better option in regards to my situation? Thanks for all the help so far Guy(s).

If I did go the battery route, I figured a way to use a car battery and custom LEDs safely, but I would need to order parts, assemble and program LED clusters, and hope it doesn't flicker on camera. I'm much more inclined to go the AC route with the dimmer devices I already own and incandescent globes as long its 100% safe.
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#10 timHealy

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Posted 11 August 2013 - 08:17 PM

If you are only using 60 watt lights bulbs I think you could easily build a waterproof housing that would be camera ready.  And the power cable would have to be weighted down so the things did not float to the surface. if you can't afford hydroflex type prebuilt underwater lighting fixtures you can make your own. many people have. i have a friend who wired a 10k bulb and used some sort of silicon caulking to seal the connections. they put it underwater and slowly turned it on via a dimmer. the water actually keeps the bulb cool. I personally wired up a few 1000 watt par bulbs and a few of those cheapo home depot work lights and caulked the hell out of both of them and used them underwater in a pool with actors and individual 20 amp GFCI's. Of course i tested them without actors and all but one worked. the one that didn't kept tripping the GFCI.

 

So I think you could do the same with your small dimmer pack that you have and 60 watt light bulbs. If you wind up building anything be sure to build it with a ground and check all of your wiring and the outlet you plug into has a ground. use your voltmeter and touch the hot to the ground. if you get 120 volts (in the US) the ground is good to go.


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#11 Guy Holt

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Posted 12 August 2013 - 10:52 AM

... be sure to build it with a ground and check all of your wiring and the outlet you plug into has a ground. use your voltmeter and touch the hot to the ground. if you get 120 volts (in the US) the ground is good to go.

 

 

As Tim points out, AC can be 100% safe around water. James Cameron is crazy enough to put his life at risk, but you can be sure the risk management departments of studios would not put the lives of actors like Leonardo DiCaprio and Kate Winslet at risk if there was any chance they would be injured or killed.

 

 

SB_Titanic_PS3.jpg

 

The erroneous notion that AC can not be not be used safely around water originates from the commonly held belief that "electricity wants to go to the ground." This common fallacy is even found in electrical safety training videos and even books published about electrical wiring. The basis of this belief - called the "Sump Theory of Ground" - is that the earth is some kind of giant drain of electro-magnetic charge to which electrical current is drawn. Nothing could be further from the truth.

 

Electricity wants to return to its source and nowhere else. It is attracted only to the singular magnetic field, in the core of a transformer or the rotors of a generator, from which it was created. The two low impedance conductors that we design into our electrical systems to carry it safely, the neutral and ground conductors, are the preferred rout it takes back to its’ source. Whenever current goes to earth ground, or any other ground loop, it is only because it offers another low impedance alternate path to return to its' source.  If Ronnee were to use a portable generator, place it on a rubber matt to insulate it from earth, ground his fixtures with a grounding wire as Tim suggests, and make sure there are no nicks in his cable that would expose the copper to the water, electricity will not use the water/earth ground as a conductor because it is a much higher impedance circuit. Add a properly designed Interlocking Zone Ground Fault Protection system with GFCIs at the loads and on the main feeder trunk and you have full proof ground fault protection.

 

For GFCIs to work however, you have to make sure the portable generator you use has a bonded neutral (there is a jumper between the neutral of the stator and the grounding system.)  Most of the Honda Inverter generators have Floating Neutrals (the neutral is not bonded to the ground.) What's wrong with a Floating Neutral system? Since the Ground wire and the Neutral wire are not bonded at the generator bus, the Equipment Grounding wire does not offer a path for Fault Current to complete the circuit back to the generator windings. An open circuit, electricity will not go to the grounding wire in the event of a fault. If current won't go to Ground, in a double fault situation, balance can be restored in the distro system before reaching the GFCIs, creating a potential for a lethal shock. In effect, the GFCI will not work even though the GFCI test circuit will indicate it will. GFCI test circuits therefore can be misleading when they are used on Floating Neutral generators. A remedy for un-bonded generators is to use a step-down transformer/distro  to step-down their 240v output to 120 since a transformer/distro bonds the neutral to system ground (see http://www.screenlig...I_Workshop.html for details.)

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip sales and rentals in Boston


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#12 Edward Lawrence Conley III

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Posted 12 August 2013 - 04:33 PM

http://www.hydroflex.com/
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#13 Ronnee Swenton

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Posted 12 August 2013 - 08:36 PM

Thanks for all of the help so far. I'm going to do some tests with the equipment I have now, bulbs sealed in the plastic spheres, hooked up to a grounded dimmer which will be on a gfci and a grounded genny.

 

It will be a while until I can share my results, but I'll let you know how the test goes.

 

Thanks again,

Ronnee


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