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Author Topic: Very Basic Uplighting Rig Question  (Read 804 times)

johnlich

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Very Basic Uplighting Rig Question
« on: May 19, 2017, 09:25:08 am »

First and foremost, please forgive me if this is in the wrong forum, or if this posting creates a duplicate post. (If so, please advise!)

Disclaimer: I know my following words will haunt/ irritate some people, but I sincerely would like some honest opinions.

I have created a very modest DMX PAR LED uplighting system that will range anywhere from 3 to 18 light fixtures. The brain of the system is a Chauvet Obey 3 which has a single DMX Out port on the back and then runs to my first fixture. The cable I have used for this purpose is CAT 5E Ethernet cable. Very simply put, it is currently run within all of my baseboard within a large banquet room. Now I know I have two options: 1. Create a daisy chain in which there is 1 set of 3 wires for IN and 1 set of 3 wires for OUT. or 2. Utilize a passive Y-Split in which I only utilize the 3 wires for IN and let the wire itself maintain the chain.

Now it should be noted that I would never even contemplate utilizing a rig such as this for lights >$50. But the lights used in this rig are basic 18 LED DMX 512 lights that range from $20-35. The power for each light comes from an AC outlet and the only purpose of the DMX cabling is to send a signal of RGB.

https://www.amazon.com/gp/product/B00EADCPDS/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

Would option 2 be sufficient for this purpose? Also, I have read that DMX terminators are no longer needed with modern light fixtures. Should I install one at the end of the chain/ wire?

Thanks. I look forward to feedback!

-John


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Mark Cadwallader

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Re: Very Basic Uplighting Rig Question
« Reply #1 on: May 19, 2017, 10:08:04 am »

DMX signal is not intended to be wyed. An isolated optical splitter is the recommend route to go for creating multiple lines. Terminators are still recommended, to the best of my knowledge. Finally, you should check the specs of your cable to determine whether it is consistent with DMX-512 requirements.

That said, if you want to try your idea, go ahead. You won't hurt your lights or control surface.  I don't think that I would spend the time to make a wiring harness as you are contemplating, but it's your time and labor. If it doesn't work as desired, you can use standard methods to run the signal. I personally would do it the standard/recommended way the first time, but maybe that's just me.
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Scott Hofmann

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Re: Very Basic Uplighting Rig Question
« Reply #2 on: May 19, 2017, 10:14:24 am »

I would think that with the inexpensive fixtures you have that the DMX cabling setup would possibly be more important than with more expensive fixtures.

Cat5e cable is often spec'd and compliant for DMX use, but in a protected environment, which yours may not be. However for a budget-conscious situation such as yours, I think it's a good choice, but recommend stranded Cat5e, as repeated flexing of solid conductor cable will become a reliability issue.

I would not "Y" DMX connections under any circumstance.
Yes, they are essentially Y'd inside the fixtures, but these are very short "stubs".

Either daisy-chain properly or get a cheap DMX splitter.
I'm also trying to envision how you would "Y" within a long cable and have any flexibility in the placement of fixtures at different venues, as a daisy-chain system would be much more flexible; the use of a splitter even more so.

Your information on no longer needing DMX termination is incorrect. I would be interested in the source of your information. You would only need one terminator in a daisy-chain and just a few more if you use a splitter. It is such a minimal expense to do it properly.
My honest opinion!
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Scott Hofmann

Steve Garris

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Re: Very Basic Uplighting Rig Question
« Reply #3 on: May 20, 2017, 03:51:30 pm »

I'm not as dmx knowledgeable as most here, but I've tried different things and can suggest the following:

Use dmx cables. I purchase them from MCM electronics for dirt cheap. It's the really thin wire type, much easier to conceal if that is important.

If not, use wireless dmx transmitters & receivers. These will work much like a splitter, but do not need any cables. I have the battery powered units on my rig, and they last for about 5 hours. When the battery runs out, the lights go dark, but you can plug a small charger in and they'll work. I run a big rock show lighting rig with pre-wired tree's of 4 and 5 lights, so I only need (3) receivers.
https://goo.gl/X24KwZ

Regarding terminals, yes they are technically still required, but FWIW I never use them and haven't had any problems at all. I've got several of them in a drawer collecting dust. But if you do have any dmx weird behavior, then a terminator is the first thing you should try.

I have a couple of those lights you have. While they work ok they have an extremely narrow beam. You might have better results if you placed a diffuser on the front of them. If you want much brighter lights from China, I recommend these:
https://goo.gl/KYGhtK




This is the light show I run using the Chinese led's and Donner wireless. My current board is a Magic 260 but I'm moving to Luminair (iPad control):


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johnlich

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Re: Very Basic Uplighting Rig Question
« Reply #4 on: May 23, 2017, 03:14:26 am »

DMX signal is not intended to be wyed. An isolated optical splitter is the recommend route to go for creating multiple lines. Terminators are still recommended, to the best of my knowledge. Finally, you should check the specs of your cable to determine whether it is consistent with DMX-512 requirements.

That said, if you want to try your idea, go ahead. You won't hurt your lights or control surface.  I don't think that I would spend the time to make a wiring harness as you are contemplating, but it's your time and labor. If it doesn't work as desired, you can use standard methods to run the signal. I personally would do it the standard/recommended way the first time, but maybe that's just me.
Thanks for the feedback! Reading over my own post, I see that I worded it in a way that would make my setup seem a bit extra risky.

When I say make a passive y split, it is not for a long length by any means. In essence, I have one key length of Ethernet cable run around the room under the baseboards, and then have a series of openings in which I can access and tap into the cable. My "y's" are simply pulling the wires out of those accessible openings without having to rip apart my wiring each time. Because there are 8 wires within cat5e cable, I utilize 6 of them in the form of 3 in and 3 out. So I still am using the daisy chain method.

I was just curious if anyone has found success in having a single wire run and then just having a series of outputs spliced in, as opposed to be having to fully break the connection to create both the in and out for each unit.

I'm also proud to say that after successfully completing my set up, my 3 modest par lights worked flawlessly for their first wedding. (6 hours and running thus far!)

Also, I should note that this was a system I inherited and since the Room's construction is complete, this is not a mobile set up but rather a permanent one. I don't worry about the wires breaking or failing as they will not be moved.




Sent from my iPhone using Tapatalk
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Jeff Lelko

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Re: Very Basic Uplighting Rig Question
« Reply #5 on: May 24, 2017, 05:05:33 pm »

I was just curious if anyone has found success in having a single wire run and then just having a series of outputs spliced in, as opposed to be having to fully break the connection to create both the in and out for each unit.

No, the advice you've gotten so far is valid - DMX is not meant to be passively branched regardless of the length.  While you can argue that the fixtures do essentially the same thing internally, you're just asking for problems by inserting junctions in your cables.  It might work for a while but I wouldn't trust it.  The reasoning has to do with the signal reflecting from one leg and corrupting the data in the other.  If you're curious about the technical details, here's some info from a well-respected source (link).  Hope this helps, and congrats on your first wedding!
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Jerome Malsack

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Re: Very Basic Uplighting Rig Question
« Reply #6 on: May 27, 2017, 05:08:24 pm »

mcm also has a splitter that I have tried and works.  http://www.mcmelectronics.com/product/STELLAR-LABS-DMX-SPLIT8-/555-20220
It has one optical isolator from the main signal to the outputs.  Not the best, but for the price and being mostly metal it is workable.
 
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Scott Hofmann

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Re: Very Basic Uplighting Rig Question
« Reply #7 on: June 01, 2017, 09:52:37 am »

"My "y's" are simply pulling the wires out of those accessible openings without having to rip apart my wiring each time. Because there are 8 wires within cat5e cable, I utilize 6 of them in the form of 3 in and 3 out. So I still am using the daisy chain method."

I re-read your post and am trying to figure out what you actually meant by using the Cat5e cable "in the form of 3 in and 3 out".
If you mean that you are using one wire for Pin 1, one wire for Pin 2, and a third wire for Pin 3, then it is possible whoever rigged this up in the first place did not have an understanding of properly using Cat5e for DMX. One wire of a twisted pair should go to Pins 2 and 3, and both wires of another twisted pair to Pin 1. Therefore, all 8 conductors should have been used. Admittedly it will still work, but not so reliably if the Pin 2 and 3 wires are not from the same pair, as this is what gives the signal better noise immunity.
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Scott Hofmann
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