Terminators and Twofers

[Shawncfer]

I know these are completely different things. But I need to make both and I wanted to make sure I understand how to do it.

Terminators:
I need a 3pin and a 5pin DMX terminatior

3 pin - Buy a male XLR adapter and attatch a 100ohm resistor to pins 1 and 2 right? I mean one resistor for each?

5 pin - Same concept but Im not sure which pins to attatch the resistor to. So...help?

Twofers:

V style twofer. Get two Female Stagepins (Btw Im using stage pin in my theatre) and one male stagepin. I run 12/2 SJOOW cabe from each female into the male and put two black in the hot screw, two white in the nuetral, and two green in the ground. Right?

Y Stlye twofer. This one I have two female and one male stage pin. I run 12/2 SJOOW cable to a 4" square deep box and attatch the cables together with wire nuts right? Obviously the three hots, three nuetrals, and three grounds.

Now What I dont know, when I buy the 12/2 SJOOW cable, does it come with a ground in there already? And do I have to buy some sort of jacket, or is there already a jacket around the wires? And the deep box, do I have to wrap it in something (if that makes sense) or is it fine just being metal like that?

Thanks

 

[Footer]

Pins 2 and 3 for the terminator on both 3 and 5 pin. 120 ohm resistor or 100 ohm can be used and both have been debated which are better.

sent from my HTC Incredible

 

[gcpsoundlight]

With the terminators -

You need to place the resistor ACROSS pins 2&3, thereby finishing the line. Also, in the 5 pin version, put one betweeen pins 4&5, as some theatres run 2 universes down one cable.

Either of the twofers would work, but be carefull.

 

[xander]

3 pin - Buy a male XLR adapter and attatch a 100ohm resistor to pins 1 and 2 right? I mean one resistor for each?

I am not sure if you mean one resistor for each the 3-pin and the 5-pin, or if you are saying attached one resistor to each pin 2 and pin 3. If you are suggesting the latter, then, no. You attach the resistor across the two pins; solder one lead of the resistor to pin 2 and the other lead to pin 3.

Now What I dont know, when I buy the 12/2 SJOOW cable, does it come with a ground in there already? And do I have to buy some sort of jacket, or is there already a jacket around the wires? And the deep box, do I have to wrap it in something (if that makes sense) or is it fine just being metal like that?

First of all, 12/2 cable will not have a ground, so to speak, because it is 2 conductor cable. That's what the 2 in "12/2" means. So, because of that, you need to be using 12/3 SO (or SJO, or derivitive, like SJOOW) cable. This will contain 3 conductors; one for hot, one for neutral, and one for ground. As for your Y-type two-fer, I have never heard of constructing a two-fer like that. I would go with your first version or buy molded "rubber chicken" two-fers.

-Tim

 

[mrb]

DO NOT make a twofer using a junction box. Not code, and not an accepted practice (also wire nuts have no business being installed in anything portable).

If you make the V type twofer, dont use stagepins where you stick the wire in the hole. Use the type that take a crimp terminal.

 

[dcollins]

Definately use 12/3 cable, not 12/2.

Also, I'm pretty sure, but not certain, that SJOOW is not good for theater. SOOW is the preferred, and SJOOW is a 'junior' version, if I had the choice I'd use SOOW exclusively. Other acceptable options are SO and SOW. There is also a temperature rating, either 60, 75, or 90 degrees C, not sure which are or are not considered acceptable.

Also, anything with a T in it, such as SJTW, is no good.

As always with electrical work, check cables for continuity and shorts with a multimeter before use, and have your work checked by a competent electrician.

 

[dramatech]

As has been discussed many times in this forum and also on the lightnetwork, SJOOW cable is acceptable in the theatre for drops from battens, breakouts from Soca and twofers. There is a limit to the length, but the matter has been posted before. Use the search engine, and I am sure that the final and definitive word on the matter will be a post by Steve Terry.

 

[Shawncfer]

So let me see if I understand this right. For Terminators I need to put ONE Resistor across both pins 2 and 3.

For the Twofer, Dont do the Y stlye but instead the V stlye. Use SO cable. BUT SJ cable is ACCEPTALE as long as its not over so many feet. So can I just use SO cable so i don't have to worry about the size?

 

[derekleffew]

The Y-style is fine, as long as you use a pre-made cable assembly manufactured for the purpose.

Note you can buy just the cable assembly, and supply and wire your own connectors.

http://www.norcostco.com/ysplicebluntend.aspx

In twofers, SJ cable is limited to 3.3' (1m).

You're not going to be able to fit two pieces of 12/3 SO cable into the strain relief of the connector, so NO, you can't "just use SO cable...".

RE: Terminators, there's information and even a picture at Terminator, DMX. There's a link to step-by-step instructions at DMX Termination.

 

[Shawncfer]

Okay, So I need JUST SJ cable? or can it be SJOOW or SJwhateverelse?

 

[derekleffew]

SJandwhateverletterstheytackon, except avoid the letter T, indicating plastic insulation, which tends to melt in proximity to hot lighting fixtures. The local home improvement stores probably have SJOOW, for $0.75-$1.10 per foot.

 

[Footer]

So let me see if I understand this right. For Terminators I need to put ONE Resistor across both pins 2 and 3.

Yup, thats it. Pin 1, 4, and 5 stay empty. Not really much to it.

 

[JD]

One odd thing about cable types: When you buy Romex cable for house wiring, 12/2 comes with 3 conductors. Kind of a legacy thing back to the days before grounding (prior to 1955) So, 12/2 became 12/2 with ground. Then all the cable was manufactured with grounds so the "with ground" was dropped. The result, 12/2 Romex has three conductors, and 12/3 Romex has four, but 12/2 portable cable has two! You are not the first person to assume that 12/2 portable cable comes with a ground!

 

[erosing]

One odd thing about cable types: When you buy Romex cable for house wiring, 12/2 comes with 3 conductors. Kind of a legacy thing back to the days before grounding (prior to 1955) So, 12/2 became 12/2 with ground. Then all the cable was manufactured with grounds so the "with ground" was dropped. The result, 12/2 Romex has three conductors, and 12/3 Romex has four, but 12/2 portable cable has two! You are not the first person to assume that 12/2 portable cable comes with a ground!

I did it the opposite way the first time I needed to pick up Romex, knowing 12/3 such as SOOW had 3 conductors, i bought 12/3 Romex thinking it would have 3 conductors, didn't notice until it was already cut.

Sent from my iPhone using Tapatalk

 

[zmb]

That has surprised me too when helping my dad around the house.

 

[Grog12]

First off SJ whatever is only acceptable overhead. See Ship's post in this thread for just about every answer to questions on cable you could have. [MENTION=6350]Shawncfer[/MENTION] I highly recomend following Derek's advice and buying the prebuilts even if you wire them yourself. While both options you put in your original post are something you could do, its not something you want to do.

 

[SteveB]

First off SJ whatever is only acceptable overhead.

Actually, that's not seemingly the case. Here's the quote from Steve Terry from this recent thread:

http://www.controlbooth.com/forums/lighting/21000-whats-difference-2.html

"--6.0 m (20') max length for SJ (junior hard service or hard usage) and derivatives in breakout assemblies. Must be protected from physical damage by being supported over its entire length by a pipe, truss, tower, scaffold, or other substantial support structure. There is no minimum height off the ground specified. Must connect a single multi-pole connector containing two or more circuits and multiple 2-pole, 3-wire connectors. Must be protected by an overcurrent protective device of not over 20A. Section 520.68(A)(4)"

The point here is that on-deck usage is OK as long as the cable is protected in some manner by being used in and attached to a structure - I.E. not laying across the deck under matting or some other non-structural system.

Note on this thread there is other information that we (as stage electricians) need to pay attention to regarding use of SJ cable in adapters and two-fers as well.

SB

 

[Grog12]

Fair enough SteveB, I should have elaborated a little more in my blanket "overhead" statement. (man I've got to stop posting before the coffee kicks in)

 

[SteveB]

Fair enough SteveB,

Imagine how I felt when ST commented - "Just for the 413th time (no attitude here ), v-style twofers using type SJ or its derivatives are allowed under NEC article 520."

To paraphrase the old TV commercial from the 60's (When EF Hutton speaks), When ST speaks......

SB

 

[SteveB]

As follow up to the issue of home built manufacture of two-fers, I had a conversation today with a rep at Lex Products (as well as one yesterday with one of my suppliers), both of whom confirmed that the use of a male plug as the splice point for 2 separate cables, to create a V style two-fer, violates the UL rating of the plug. Which is why key manufacturers are no longer making V style with SJOOW cable and in the case of Lex, only molded Y types.

Which brings up the issue that while the NEC allows SJOOW cable to be used in a two-fer, such use kills (in some cases, depending on plug design) the UL rating of the plug. Bates Connectors (Marinco group) specifically makes a 20 amp, 2P&G male plug, UL listed for twofer use, but quite possibly, other plugs of 2P&G, Edison and locking types might well not be appropriate for twofer use. Thus I suspect that the UL issue might be with the type of strain relief to the cable, not the terminal design per say.

Others might have better info.

SB