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Stage Pin Connector Safety

Discussion in 'Lighting and Electrics' started by rmarston, Nov 19, 2008.

  1. rmarston

    rmarston Member

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    Connector schemes almost always provide a mechanism for keying that will not allow the connector to be mated with it's counterpart in any way other than the correct way. This is especially important when dealing with hazardous voltage levels - AC line voltage would be one of those. So how do you suppose the stage pin connector scheme ever got UL approval when it is able to be partially mated at 90 degree angles? This would allow connecting a pin in the plug to any receptacle pin that I would choose and essentially have the capability to apply line voltage to any pin on the mating connector. That means I could, if I wanted, connect line voltage to safety ground of the connected device - not to safe. It's obvious that no one would intentionally mate the connectors in this manner, the point is that there is no mechanism to prevent it. Any thoughts.
     
  2. icewolf08

    icewolf08 CBMod CB Mods

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    This is of course provided that we are talking about inline connectors and not panel mount connectors.
     
  3. SteveB

    SteveB Well-Known Member

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    I can see everyone's points about potential safety issues with 2P&G connectors, but I for one, will never bring it up within earshot of anyone connected with the Nat'l Elec. Code.

    Why ?, 'cause the 2P&G, for all of it's potential problems, is still a far superior connector for stage use then an Edison or - gasp, TwistLok. I had TwistLoks. They suck for a lot of reasons, an I will retire before I go back to working in a house with TwistLoks.

    Remember as well that many safety features are designed to protect non-trained civilians, not us trained theater folks. I hope.

    Steve B.
     
  4. STEVETERRY

    STEVETERRY Well-Known Member

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    Whenever a request for increased safety or tighter regulation comes up in a proposal to the NEC, we ask "Is there a record of loss of property or injury of personnel?". That question applies here. I think the answer will be no.

    The pin connector has a long record of safety in entertainment applications. There were tens of thousands of pin plugs in use on both AC and DC power long before the first one achieved a UL listing. That was taken into account when the UL listing was granted.

    ST
     
  5. rmarston

    rmarston Member

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    Ok - so we all like the connector better than any of the alternatives. But how about some upgrades. If the rest of the industry were as unchanged as this, we would still be using reostats. Let's see, how about a locking device - that would save on all that gaff tape to hold the things together. Maybe a shroud around the receptacle side to prevent mis-keying the connection - just a thought. Almost all other industries that want reliable electrical connection use a keyed locking connector system.
     
  6. LightStud

    LightStud Active Member

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    Improve the stage pin connector? Hogwash--it was just "improved" only 35 years ago with the addition of the center pin. About 25 years ago they started becoming ergonomic. A locking device has been tried and failed. If you use Bates brand, see that 3/16" hole in each connector? Put a piece of tieline thru that, or use the hole to screw the connector to something. A shroud would cause compatibility issues, although some 60A and 100A models have them. The 20A-2P&G contains more conductive material than most 50A straight blade devices. Show me another industry where a 20A-125V, 3-pole connector costs about $5. Is the stage lighting industry willing to pay more for additional "features"? I think not.
     
    Last edited: Nov 19, 2008
  7. MNicolai

    MNicolai Well-Known Member Fight Leukemia

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    You're just as capable of reverse engineering the existing 2P&G as anyone else is. Don't take that unkindly, I mean it in all seriousness. There's no reason you can't draft something up, patent it, and pitch it to manufacturers and companies.

    Transferring hand-drawn sketches to Autodesk Inventor would take me a whole 30-45 minutes and I could have a complete rendering ready, followed by waiting 12 hours or so for our rapid prototyper to kick out a 1:1 scale plastic model of the new device, as well as the receptacles to go with it.

    You're on your own for getting the UL listing though.
     
  8. ship

    ship Senior Team Emeritus Premium Member

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    Wow, that’s a deep if not Darwin like question. But a good one to ponder.

    As with my question on the 60 and 100A snap covers that have large holes one could stick a finger into that I’m still interested about the lack of industry attention to, yours is also interesting.

    But as stated, first, it’s a unlikely type of thing and I’m doubtful you could connect other than the hot to neutral/ground sockets in putting pin into a socket the wrong way. Could be wrong but in also wiring up that 60A distro and noting the proximity of interior terminals with the crimped ring terminals attached to them I isolated the ground terminal in making it impossible for an even insulated ring terminal to touch the ground inside the box should for some reason that wire be pulled.

    Still on the unlikely event that I assume only the hot pin can go into another socket - in not testing, that’s where circuit protection and even current standards of GFCI protection get into the effort of saving lives - this in the case that you are touching another say the neutral pin, resistance after a filament doesn’t play a better resistance in you now are the return path for the current. Remember that for current to flow, there has to be supply and return of least resistance. One pin without return path, just as two pins of the same polarity as it were don’t conduct.

    In addition to just plugging in that plug and it has to be in-line (cord) to in-line (cord) as panel mount won’t allow plug in that way, the second part of it is in return path. Have to have a load in need of return path completing the circuit and someone or gear say touching that neutral pin. Plug a unconnected plug hot pin into the neutral and it don’t do anything even if touching the neutral pin. Don’t try that - just know it don’t conduct because there is not a filament or machine completing the circuit.

    Next in completing the circuit, resistance of you or gear in touching that second conducting pin and or what is going on there is a question of the zap. Certainly the NFPA has recognized that due to stuff falling down a wall conducting with a hot pin or shorting, and or the tendency of kids to place a butter knife between wall socket and outlet is important enough to mandate that ground prongs of an Edison now get installed up, and if not and horizontal neutral pins are up.

    In the same way but less percentage, you have a valid point that if some one is doing something stupid as we see in the industry, someone might get shocked before the breaker trips, or the GFCI pops assuming they don’t die.

    Still though I would think the likelihood of someone doing this and than completing the circuit in a low resistance enough way is less in percentage than those that take apart live plugs or even in the industry kill breakers by way of shorting to trip the breaker.

    The stage pin connector - not the proper term for it but the one it became has been around since the 1920's and in many ways was the design concept for most plug types. Its spacing once the ground was added is for the most part safe in this “unless you were to” type way which necessitates both load and touching one of the pins not connected in providing a low resistance path to ground following the resistance of the load.

    Yes, can be done... good thought to be concerned about but I’m not going to loose sleep about someone doing it at this point though it will be at the back of my mind as an interesting Darwin like concept I never thought of.
     
  9. ship

    ship Senior Team Emeritus Premium Member

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    Hmm locking devices... what are you new? Been there towards the end of that effort, never go back. Most or many plugs in addition to being able to gaff also have slots to bolt or tie line them together.

    For the most part with use of properly pin spreader checked pins they shouldn’t come apart if properly supported and not in tension or suspension.

    Did the locking stage pin plugs years ago and while current technology no doubt could do something better than what was innovative years ago, no matter what was come up with would require an entire system and change over to that for male/female to work together or some sort of tension on a pin that would potentially not allow it to become unlocked in need part of why twist locks fell out of favor.

    Details, details.. Agreed with the above, first get the problem in reality, than solve it. Remember a few years ago an older style or current style of Union 60A stage pin plugs that had a protective shield around the female in-line part of them which would prevent this perpendicular connection of a single pin. Problem was they broke left and right and were a constant replacement. Simple solution a ½" shield around the female connector on each stage pin which would be no problem to fabricate and build, this much less mount. Really easy given the slight recess around say a Bates plug to do some form of shielded strap that would prevent wrong plug in’s similar to how the old Union plugs did at least for the 60A. Would anyone invest money into buying it? This also given it would potentially break every time someone dropped a connector, buy replacements? Not likely - whole concept is very remote.
     
  10. LightStud

    LightStud Active Member

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    Would you please cite either the NFPA or NEC document that states this? as the topic arises often on another forum I frequent.

    What then, IS the proper term?
     
  11. MNicolai

    MNicolai Well-Known Member Fight Leukemia

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    @ Charc
    Public school actually. We have a very strong robotics and technical education department, which is why we can afford to have a rapid prototyper, as well as a metal shop, wood shop, Autodesk AutoCAD, Mechanical, Electrical, and Revit on all of our ~50 computers in the department, all updated to Professional 2009. We also have MultiSIM 10.1, UtilBoard, Macromedia Studio 8, Adobe CS3, and a t-shirt printing machine.

    Our Building Trades classes, which are in a series of I, II, and III, actually design and build a house each year. The students design it, and go on-site to visit the contractors and workers and learn about the best methods of insulating the house, determining which materials to use, how to make it as green as possible, etc, etc.

    We also just spent $9 million dollars on a new performing arts center that I get to open in two weeks, and I was able to be the designer/adviser/manager of a $65k renovation of our 125-seat black box theatre this summer. I have to say, I'm really proud of the high school I go to and the administrative, buildings and grounds, and faculty members we have here. You'd have to pay me a lot of money to get me to go anywhere besides Oconomowoc High School.


    ------------------


    The proper term for stage pin connectors are 2P&G, which stands for 2 Pin & Ground. I'll typically use stage pin when I'm talking to people who are caught off guard that we don't use edison, and 2P&G as the more technical term. It's hard to take a moment to comprehend, but there's actually a large number of people who have no idea what an edison connector is.


    ------------------


    They raise a valid point about the topic of locking connectors having been tried before, but don't let that stop you. You could consider using pins of different diameters or shapes to prevent mis-connecting them, or space the pins differently to prevent them from being able to slip around the housing of the connectors @ 90° that they are plugged in to. I'm just throwing ideas out there though. I hate to tell anyone, "Don't fix what's not broken, and don't make attempts to improve products for the sake of improving them."

    Where would we be today if we told all of the inventors from previous decades and centuries not to invent anything because there's no need for it, or it's an impossible product or technology to create?
     
  12. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    I know its 2P&G, but thats a freaking mouthful to say. Stagepin is universal.

    Now, I know what a stage PLUG looks like, but what does a "real" stagepin look like?
     
  13. LightStud

    LightStud Active Member

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    I don't think it gets any more "real" than on pages 40-41 of this 1913 document: G (1914). Note that it mentions UL and NYC compliance.

    [​IMG]
     
  14. MNicolai

    MNicolai Well-Known Member Fight Leukemia

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    I happen to have a three-fer block hanging on my wall. It's made complete by having no ground pin itself, but having holes in it so that you could plug something into that does have a ground pin. It's about as nasty as though ground-lift adapters, which is why it's a wall decoration now and no longer a functional cord.
     
  15. ship

    ship Senior Team Emeritus Premium Member

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    Hmm, interesting counterpoint - note I posted stage pin on Question of the day that your post would balance out in debate over verses that of Fuchs.

    On the threefers... drilled out for ground pin? Never seen that version. Had some without, some with (and still on the market) and some of the without I made grounded though not quite as on-center so well so the plugs didn't get together all the way. That was a bad thing and while I was still learning - and I learned a lot from such things as these cube taps as it were really cube taps.

    Fascinating things these cube taps were both in the corded and male/female/female/female cube (square) tap version they were. Wish I still had one for my wall of shame.
     
  16. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    I own a square, grounded, male/female/female/female three-fer cube tap.

    Other than being of a composite material (tan, maybe fiberglass? not the kliegl black composite) it certainly seems well constructed. How would it be deserving of the Wall of Shame?
     
    Last edited: Nov 20, 2008
  17. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    [​IMG]
    Notice there's no brass visible in the center hole. Drilling for ground used to be a common practice during the "transition period" from 2pin to 3pin.
     
  18. ptero

    ptero Active Member

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    I have two issues with them. The internal connections on mine are made with flat straps (copper) that are put together with a kind of rivet. With age, these loosen and you get flickering now and then. No amount of smackin' em has tightened the rivets to a good level of reliability.

    The other issue is achieving decent tieoff security in the air. I do not like relying on tape and there is no good way to secure these with tie line. I have not tried to drill a hole for this. Quite a bit of the internal area is taken up with the strapping that connects all the pin holes. We have a few of the corded ones and those have a tieline attached to the cable portion. Better, though still a little dodgy for me.

    These sit in a box and are only used if we run out of all other 2 and 3 fers. Then I'll be picky about where they get used. :cool:
     
  19. shiben

    shiben Well-Known Member

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    Electrical Tape is fairly good for applications like this, it will hold it together just as well as tie line, except if you stretch it a bit it works better. We had some of the ones with a hole drilled for ground, but with one major difference: Ours had been fanagled such that it was a termination for a 9 conductor cord. it was retired when it was discovered that it was flickering blue during a dimdown one show.
     
  20. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    I'm pretty sure [user]ship[/user] was referring to the kind with the "drilled out ground hole" meriting Wall O' Shame status, not the "modern" type.

    Interesting, [user]ptero[/user].

    So I just had to open mine up to have a peek:
    [​IMG]

    The one on the left without ground is purely for historical purposes, especially since it has a half stage plug on the other end.:)
     
    Last edited: Dec 19, 2009

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