# LED Christmas Lights on a dimmer



## CBR372 (Nov 12, 2011)

Hey guys I got a question for all of ya. Im designing a show right now and the set designer wishes to use LED christmas lights in the set. I as the LD don't wish for them to dim, just on or off, but I would like control from the board, and I have no access to a Relay or Constant on dimmer. So my question is will I face any issues plugging directly into a regular dimmer (Either ETC Sensor or Strand CD80 supervisor or more current) Any input would be great, thank you.


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## 65535 (Nov 12, 2011)

The only thing you might need is a dummy load, but for general on off (depending on your console most have some type of full at 1%) christmas lights usually work pretty well.


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## Chris15 (Nov 12, 2011)

Most LED strings I have seen run with a transformer and usually some form of controller...
The transformer is unlikely to be completely happy with "dimmer full" power as a substitute for clean power...


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## BurkeTheJerk (Nov 12, 2011)

My high school's director loves doing this. Not sure about your console, but on my Strand Palette, when patching I set the fixture profile to "non-dim." That way, no matter what value, the console will send 100% to the dimmer.


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## xander (Nov 12, 2011)

As Chris15 said, if there is a transformer (and I don't know of any commercial LED string that doesn't use one) then it's not a good idea. Yes, it'll work. Until it doesn't. And that will hopefully be because you broke the transformer and not the dimmer.


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## derekleffew (Nov 12, 2011)

As we've discussed about a million times, the phase-control SCR dimmer is intended for resistive loads (incandescent lamps) only. IF a device has a transformer, power supply, motor, diode, etc., it probably won't enjoy like being run though a dimmer. Can you "get away" with powering LED xmas strings? Probably. They may even dim smoothly and not erratically or with flicker. The worst that will happen is that the string(s) will never light up again. (IMO, the threat of damage to the dimmer is greatly exaggerated.) But please don't put moving lights or anything expensive that you can't afford to replace on a dimmer. There is no profile or magic setting on the console or in the dimmer's brain that can trump physics.

A ghost load may make the dimming curve smoother (and/or allow it to fade completely out), but probably will not make the device any happier. The phrase "At your own risk" seems applicable. "Do ya feel lucky, punk? Well do ya?"


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## starksk (Nov 12, 2011)

derekleffew said:


> There is no profile or magic setting on the console or in the dimmer's brain that can trump physics.



Amen.

......


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## n1ist (Nov 13, 2011)

In the US, most LED strings (all the residential grade ones I have seen, and most of the commercial ones) simply use a diode (either half-wave or full-wave) and current-limiting resistors. Even the ones with a built-in sequencer use resistive or capacitive dropping. Transformers just cost too much.

Both full-wave and half-wave strings will work on a dimmer; the half-wave ones tend to flicker more. Many of the dimmers for the animated lighting world have 47K snubber resistors (ghost loads) and programmable curves to help even things out. You still can have problems on the low end with leakage current letting the string glow faintly; just a few mA of current is visible.
/mike


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## gafftapegreenia (Nov 13, 2011)

Always try to post this in the LED threads: Doug Fleenor Design - 8 Channel DMX Dimmer



Doug made it specifically for CFL and LED.


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## Morte615 (Nov 13, 2011)

At Cedar Point we use lots of LED Christmas lights! We run them through ETC DDR and Smartpacks to dim these lights. We have no problem with dimming, though we have had to put some snubbers or incandesent loads inline at some trouble spots.

We use commercial grade lights but I have personally used walmrt type lights with a Light-O-Rama board with a snubber and had no issues.


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## MarshallPope (Nov 13, 2011)

For what it is worth, we also use LED Christmas lights on dimmers with no issue. Most of ours are the cheap hardware store type. They turn on and off just fine on the dimmer, but we have had to use a string of incandescent lights as a ghost load for them to dim smoothly.


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## chausman (Nov 13, 2011)

Morte615 said:


> ... we have had to put some snubbers
> ... with a snubber


 
What is a snubber? Would someone like to add that to the wiki? Just click on the red word and start editing.


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## josh88 (Nov 13, 2011)

Matt/ Morte615 is talking about the starlight experience 

PointBuzz - Cedar Point Starlight Experience 
as far as snubbers he may be talking about the GFI's they've got around the system @7:30 I will say it's quite a system they've got spread out through that area of the park.


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## Morte615 (Nov 13, 2011)

josh88 said:


> Matt/ Morte615 is talking about the starlight experience PointBuzz - Cedar Point Starlight Experience as far as snubbers he may be talking about the GFI's they've got around the system @7:30 I will say it's quite a system they've got spread out through that area of the park.


 
Actually what I as talking about are small male plugs that have a resistor placed between the two prongs. Not sure of what size resister but that is pretty easy to find online. Also they use C7 bulbs inline that work the same way, though he C7's are usually plced in the boxes with the dimmable GFCI's to keep them out of sight. These were added after the video was shot so you don't see them there.

I am not on a computer so won't fill out the wiki post yet (I will get to it tomorrow if no one beats me to it) but pretty much a snubber (or dummy load) is an item that is placed inline with the LEDs that draw a small load and make sure that the LEDs turn all the way off and to prevent unwanted flicker.

But Josh is correct on what show I was taking about, I worked this show part time during the summer so became very familer with it!


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## derekleffew (Nov 13, 2011)

josh88 said:


> ... that area of the park.


What!? IMHO, the attraction is totally incongruous with Frontier Trail, which in my day  was lit with gaslamps, IIRC. No really, gaslight. And before a smart aleck asks, NO, it wasn't because the incandescent bulb had not yet been invented.

Other random thoughts:
-----
I wonder which was the Las Vegas-based lighting company?
-----
6m43s: I didn't see the presenter LOTO that Hoffman enclosure before opening it up and sticking his fingers in there. (Although he _might_ have, as there is an edit, between his opening of his Leatherman and the opening of the box.)
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7m57s: Oh great! Did he just pull out a LIVE dimmer "cartridge" ??? Without turning off the module's breakers ??? Again, LOTO may have happened off-camera.
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8m36s: "...and then we have these little colored dots here, which are called SL s..." Good thing there [-]is not[/-] has never been another product from within the Philips conglomeration with a similar name.
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11m59s: I wonder, Does "Park the channel at zero" meet the criteria for Lock-Out/Tag-Out as specified in NFPA 70E?
-----
All snarkiness aside, thanks for posting the video. An interesting glimpse backstage at an "architainment entertraction." I know other parks would NEVER allow such a video to be released.

EDIT: Cross posting to the Show Control Forum, should anyone wish to ask *non-LED* questions of *josh88* and *Morte615*.


Morte615 said:


> ...These were added after the video was shot so you don't see them there. ...


Were these resistors/C7 lamps added after the initial installation to solve an unforeseen problem/issue? To the best of your knowledge, if you know, and you're not on trial here. I only ask because *any* type of change order/alteration/retrofit/field modification can become costly and *might* affect the permitting/ATP process.


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## josh88 (Nov 13, 2011)

Another example of this being a small world we live/work in. Matt you may likely know me as one of the sliders (spiro) from halloweekends.

and derek I know and agree with it not fitting the trail, though it is actually a pretty impressive sight and provided a huge family draw for later in the night in an area that the general public has lost some interest in over the years. 

and yeah I worried about those moments too and knowing how things work I'd like to think he did LOTO, especially if they had cameras on him, the company wouldn't want that on their hands.


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## Morte615 (Nov 13, 2011)

josh88 said:


> Another example of this being a small world we live/work in. Matt you may likely know me as one of the sliders (spiro) from halloweekends.
> 
> and derek I know and agree with it not fitting the trail, though it is actually a pretty impressive sight and provided a huge family draw for later in the night in an area that the general public has lost some interest in over the years.
> 
> and yeah I worried about those moments too and knowing how things work I'd like to think he did LOTO, especially if they had cameras on him, the company wouldn't want that on their hands.


 
LOL yep I actually recognized you from another post on here, and on PointBuzz. I was a Screamster last year in Fear Faire and worked as a fog tech this year in Screamworks.

I know that the system was designed originally to be worked on "live" while the show is going on. So opening the boxes while the show is live is ok, that's what the system was designed for. I'm not really positive but I think those dimmer channels are hot swappable and can be replaced again while live. But if not the breaker for that is right next to the cartridge and him turning it off could have easily have been missed. Though from some sories that I have heard about him Ic ould see him not botherng!


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## DuckJordan (Nov 13, 2011)

While designed to be able to be hot swapped you still have hot three phase rails. So still very likely to hurt or kill if touching the wrong chunk of metal. (this coming from the guy who cleaned an enr dimmers rack while it was still energized. Colortran says you could do it...) 

Sent from my ADR6300 using Tapatalk


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## derekleffew (Nov 13, 2011)

Morte615 said:


> ...I'm not really positive but I think those dimmer channels are hot swappable and can be replaced again while live. But if not the breaker for that is right next to the cartridge and him turning it off could have easily have been missed.


Just in case anyone missed it in the wiki entry Lock-Out/Tag-Out :

> Even something as mundane and seemingly harmless as swapping a dimmer module (a very common troubleshooting procedure) now requires completely powering down the rack.
> 
> starksk said:
> 
> ...




Morte615 said:


> ...I know that the system was designed originally to be worked on "live" while the show is going on. So opening the boxes while the show is live is ok, that's what the system was designed for. ...


I'd love to be shown the safety features that enable this while still maintaining compliance with NEC and 70E. When I was there our primary safety concern was the tinderbox known as the Cedars burning, with occupants trapped inside. Were that to happen while empty, there would have been a celebration! 

Oh, and I never did get the true story of the urban myth about how an Altec-Lansing mixer allegedly "burned down the Frontier Amphitheatre."


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## rphilip (Nov 13, 2011)

derekleffew said:


> I'd love to be shown the safety features that enable this while still maintaining compliance with NEC and 70E.



Is NFPA 70E a "new" standard as applied in situations like this? I'd consider "new" to be up to several years in this case.

Philip


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## shiben (Nov 14, 2011)

rphilip said:


> Is NFPA 70E a "new" standard as applied in situations like this? I'd consider "new" to be up to several years in this case.
> 
> Philip


 
Clicking the link in the wiki suggests that there are multiple revisions, perhaps one per year?


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## shiben (Nov 14, 2011)

derekleffew said:


> What!? IMHO, the attraction is totally incongruous with Frontier Trail, which in my day  was lit with gaslamps, IIRC. No really, gaslight. And before a smart aleck asks, NO, it wasn't because the incandescent bulb had not yet been invented.


 
Well if you had electrical lights why didnt you use them? Did they not have electricity up there while you were there? I know it took a couple dozen years to get all that "national grid" stuff done...


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## derekleffew (Nov 14, 2011)

From History of OSHA, the NEC and NFPA Training :

> The new NFPA standard 70E-Standard for Electrical Safety Requirements for Employee Workplaces was first published in 1979...


Like most NFPA documents, 70E is on a three-year revision cycle. Current Edition: 2012 Next Edition: 2015.


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## CBR372 (Nov 14, 2011)

Thanks for all the wonderful responses guys. One quick question though. i was already planning on putty a dummy load on them, however you use the term "inline" and I was wondering if you could elaborate. What I translate that is have a cable run from the circuit to a twofer with one tail going to the LED's and the second to an incandescent fixture offstage. Am I correct? If not a clarification would be great!


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## shiben (Nov 14, 2011)

derekleffew said:


> From History of OSHA, the NEC and NFPA Training :
> 
> Like most NFPA documents, 70E is on a three-year revision cycle. Current Edition: 2012 Next Edition: 2015.


 
Well that explains why I found a 2009 site and a 2012 site?


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## Morte615 (Nov 14, 2011)

CBR372 said:


> Thanks for all the wonderful responses guys. One quick question though. i was already planning on putty a dummy load on them, however you use the term "inline" and I was wondering if you could elaborate. What I translate that is have a cable run from the circuit to a twofer with one tail going to the LED's and the second to an incandescent fixture offstage. Am I correct? If not a clarification would be great!


 Yep that's it exactly! Also if you are worried about extra light leakage you can use an LED Snubber instead and it will work the same without throwing anymore light. At some point today when I get to a real computer, and not my phone, I will update the wiki and give some instructions on how to build one, or some places that they can be purchased.


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## rphilip (Nov 14, 2011)

*Arc Flash and hot swap dimmer modules*


derekleffew said:


> From History of OSHA, the NEC and NFPA Training :
> 
> Like most NFPA documents, 70E is on a three-year revision cycle. Current Edition: 2012 Next Edition: 2015.


 
Is the particular concern about Arc Flash new in the 2009 or 2012 editions of is this something that was in the code but "ignored" in our industry in the past?

Philip


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## mstaylor (Nov 14, 2011)

*Re: Arc Flash and hot swap dimmer modules*

I am not sure but having seen the results of a panel that flashed, I can atttest to it is nothing to mess with.


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## Morte615 (Nov 14, 2011)

If anyone is interested I finally got to a computer and updated the wiki link for snubber so there is more information there on what this device is and why it is used.


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## shiben (Nov 14, 2011)

*Re: Arc Flash and hot swap dimmer modules*


mstaylor said:


> I am not sure but having seen the results of a panel that flashed, I can atttest to it is nothing to mess with.


 
Are the arc flash suits like the bomb disposal suits, in that they just make you easier to ship home in a box (rather than a lot of them), or do you actually make it thru? Either way it seems like something I dont really want happening to me

And either way, what the dude was doing in the video looks like something that was indeed unsafe but something that I would guess most of us have done at some point or other...


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## FMEng (Nov 14, 2011)

*Re: Arc Flash and hot swap dimmer modules*


shiben said:


> Are the arc flash suits like the bomb disposal suits, in that they just make you easier to ship home in a box (rather than a lot of them), or do you actually make it thru? Either way it seems like something I dont really want happening to me
> 
> And either way, what the dude was doing in the video looks like something that was indeed unsafe but something that I would guess most of us have done at some point or other...



DISCLAIMER: I am not an expert on arc flash.

Arc flash is nothing to screw with. I know a fellow that had a 480 V motor center explode in his face. He spent weeks in a burn ward and is permanently scarred. He wasn't even touching live parts at the time. All he did is open the access door and press the start button. The arc wasn't extinguished until a fuse on the power line feeder opened, taking out power to the whole neighborhood.

The protective clothing amounts to pants, long sleeve shirt, and gloves made up of cloth that doesn't burn or melt for the duration and temperature typical of arc faults. (Fabrics melted onto burned skin make the wounds very difficult to treat.) You can buy shirts and jeans that look like normal ones, but are tested to offer protection. A full-face shield and hard hat is normally worn, too.

Let me put it simply: There is no excuse, N-O-N-E, to work inside a live piece of equipment. No amount of protective clothing makes it really safe.

There is some ongoing discussion as to whether 208 V is a high enough potential to cause an arc flash. Regardless, even 120 V can easily kill you, so it deserves full respect.


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## tjrobb (Nov 15, 2011)

Two things, and yes, I am a member of NFPA. First, the larger suits, class three and four, provide roughly enough protection to limit injuries to a survivable amount of second-degree burns. Second, technically any voltage can arc, but DC is more prone to sustaining an arc. IIRC, 277 volts is the lowest common AC voltage that can create a self-sustaining arc, the lower voltages extinguish themselves on the polarity reversal.


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## church (Nov 17, 2011)

chausman said:


> What is a snubber? Would someone like to add that to the wiki? Just click on the red word and start editing.


 
A snubber is used to control mechanical or electrical vibrations. In dimmers it is part of the dimmer circuit around the TRIAC or SCRs, When the waveform is switched on and off it produces harmonics of the 60Hz. The amplitude and frequecies produced depends upon the phase angle. The problem with the harmonics is they can cause vibration in transformers and inductors wound on metal formers - heard as noise and they can also produce interference with other electronic equipment. The interference may be at harmonic frequencies where the wiring acts as an antenna radiating energy or simply conducted through to other equipment over the supply cables. The snubber acts to filter these harmonics by providing a low impedance path to the return wire. Usually implemented as a resistor, capacitor and inductor network but can be realised using other components. Also limit the transient response which also produces harmonics. The design of an effective snubber circuit requires detailed information re the rest of the circuit design and its operating conditions.

An example of mechanical snubbers include shock absorbers or dampers


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