Cue Light System: What do you think?

[Lambda]

Well, some people have been asking me about a cue light system for a while. So I've planned one out.
We currently have a three-wire cord running from the control booth to stage-right wing, so I thought I'd just use this instead of pulling new cable. I can control four lights this way.
For the base station, I was thinking a simple interface with silent rocker switches (not momentary) for each light, and an indicator wired in series that will warn of a broken circuit.
The light units themselves is where I have some doubt, I think I'm over-thinking them. They'd be small boxes with large LEDs in them, that would connect to the line with some sort of robust three-pin plug. There would be two of these per unit, allowing them to be daisy-chained in parallel like DMX devices. Each unit would have switches allowing its "address" to be set.

Questions I have:
What type of connector should I use for the light units? I don't want to use XLR, since the working voltage will be 6 volts AC at times, I'd hate for someone to accidentally connect it to some audio equipment. I don't want to use telephone or cat5 because they cables should have the ability to be connected end-to-end like XLR cable can.

Do you think I'm over-thinking the light units, what with the addressing and all? Would it be better just to give up some versatility and have each unit hardwired to be a certain number?

Do you think I'm under-thinking the light units, should I have a brightness control for the LED?

Is there anything drastically wrong that I'm overlooking here?

And overall, what do you think of it? Is it worth building?

 

[chausman]

I'f there is three wires, shouldn't that only be able to control one light?

 

[Lambda]

I'f there is three wires, shouldn't that only be able to control one light?

No. An LED will only light when current is applied in correct polarity. So if you have one 'hot' wire and a ground, with two LEDs connected between the hot and ground with polarity opposite, if you apply a positive voltage, one lights. Apply a negative voltage, the other lights. Apply an alternating current, and they both appear to be lit at the same time (although in reality they flicker).
I'm using half-wave rectified AC for each LED. When both the lights on one wire are switched on, the result is a sine wave and they both light.
So, with two LED's per wire and one ground, three wires can control 4 lights, and they can all be on at the same time if needed.
Once you have the ground wire, each additional control wire can control two additional LEDs.

 

[Chris15]

Yes I think you're over thinking it all

Use XLR, it's just easier...

How are you planning this control regime to work?
Are you planning 1 common and 2 wires of half wave switched AC?

So you answered my question while I was posting...
You realise you can switch other loads that way using relays, just by throwing a diode in between the control line and relay? (in one direction for one, the reverse direction for the other)

 

[Lambda]

Yes I think you're over thinking it all

Use XLR, it's just easier...

How are you planning this control regime to work?
Are you planning 1 common and 2 wires of half wave switched AC?

Yes, half-wave switched AC. About the XLR, you don't think that someone might conect the system to a mic-level input? That's my main concern here, inexperienced high-school students will be using this. And what really concerns me is that one of the current freshmen will be in charge of sound in 4 years.

EDIT:

You realise you can switch other loads that way using relays, just by throwing a diode in between the control line and relay? (in one direction for one, the reverse direction for the other)

Hadn't occurred to me, I've never needed to do that. I'll remember that though.

 

[Chris15]

Use an XLR4 or XLR6 or XLR7 - they are all far less frequently encountered.
It does mean you'll need dedicated cables though.

That said, we've been running comms on 3 pin alongside audio for years and that's 30V DC.
The incidents are in my experience rare...

 

[derekleffew]

...What type of connector should I use for the light units? I don't want to use XLR, since the working voltage will be 6 volts AC at times, I'd hate for someone to accidentally connect it to some audio equipment. I don't want to use telephone or cat5 because they cables should have the ability to be connected end-to-end like XLR cable can. ...

All valid points. I'm guessing your criteria also include: small, fairly readily available, inexpensive but sturdy, easy to terminate, rarely found for any other purpose, both genders in both line and panel mount.
XLR4 meets many, but not all, of those. Likewise, NEMA ML-2. Or one of the bajillion offerings from Molex or Cinch-Jones. Do you have a Fry's Electronics or equivalent nearby (just wander the aisles), or are you limited to The Shack and mail-order?

Against your objections, I think I'd still use XLR3, but LABEL VERY CLEARLY, paint a unique color, keep the parts locked up when not in use, etc.

Have you seen these threads?
http://www.controlbooth.com/forums/stage-management-facility-operations/2996-cue-lights.html
http://www.controlbooth.com/forums/stage-management-facility-operations/6740-led-cue-light.html
http://www.controlbooth.com/forums/lighting-electrics/25808-cue-light-systems.html
http://www.controlbooth.com/forums/...26484-cue-light-system-what-do-you-think.html
There may be un-mined gold in them thar threads; then again may only be pyrite. Mama always says, "ControlBooth is like a box of chock-lats; you never know what you're gonna git."

 

[tyler.martin]

I was going to mention Cinch-Jones connectors. I used a bunch from old Slide Projector pickle cables for a stage marker LED system.

 

[Lambda]

All valid points. I'm guessing your criteria also include: small, fairly readily available, inexpensive but sturdy, easy to terminate, rarely found for any other purpose, both genders in both line and panel mount.
XLR4 meets many, but not all, of those. Likewise, NEMA ML-2. Or one of the bajillion offerings from Molex or Cinch-Jones. Do you have a Fry's Electronics or equivalent nearby (just wander the aisles), or are you limited to The Shack and mail-order?

Against your objections, I think I'd still use XLR3, but LABEL VERY CLEARLY, paint a unique color, keep the parts locked up when not in use, etc....

I think the ML-2 is really overkill for 6 volts and a handful of miliamps. I've looked through Molex and cinch-jones, but didn't find what I really had in mind.
This is what I had in mind. But I can't seem to find an in-line jack or panel-mount male connector for it.

I don't really have an electronics store nearby, I'm limited to mail-order (or radioshack, but their stuff is too expensive unless I really need it today).
XLR3 does seem to be the best choice, but believe me, as soon as I leave next year, despite any labeling or painting, people will still be grabbing for them when mic cable is scarce. Or they'll be using mic cable for the cue lights when it's handy.
I suppose the chance of things going wrong is small, but I keep invisioning somebody connecting the cue light system directly to a power amp, and the horrid KBZZZZZZZ- followed shortly by the stench of burnt electronics.
4-pin XLR might still be an option. I'll have one unused pin, though. It's also the same cable as we use in our intercom, which is used much less frequently than XLR3, so less chance of someone connecting it where it shouldn't be.

 

[Lambda]

I was going to mention Cinch-Jones connectors. I used a bunch from old Slide Projector pickle cables for a stage marker LED system.

Oops, I missed your post. What do you mean by a slide projector pickle cable? I haven't heard that term.

 

[derekleffew]

tyler.martin inspired me, as I thought the Kodak pickle was a 5pin DIN, but different than MIDI.

Lambda, What about a 3 or 4pin DIN?

 

[emac]

Is there anyway to post pictures and schematics when you are done???? I have been trying to get something like this together for a long time and that would help me a ton.

 

[Chris15]

I've always thought of DIN as a "back of the rack" connector rather than an on the deck connector.
They rapidly pale in comparison to an XLR in terms of ability to be dropped, stepped on, etc. and survive...

 

[shiben]

I think the ML-2 is really overkill for 6 volts and a handful of miliamps. I've looked through Molex and cinch-jones, but didn't find what I really had in mind.
This is what I had in mind. But I can't seem to find an in-line jack or panel-mount male connector for it.

I don't really have an electronics store nearby, I'm limited to mail-order (or radioshack, but their stuff is too expensive unless I really need it today).
XLR3 does seem to be the best choice, but believe me, as soon as I leave next year, despite any labeling or painting, people will still be grabbing for them when mic cable is scarce. Or they'll be using mic cable for the cue lights when it's handy.
I suppose the chance of things going wrong is small, but I keep invisioning somebody connecting the cue light system directly to a power amp, and the horrid KBZZZZZZZ- followed shortly by the stench of burnt electronics.
4-pin XLR might still be an option. I'll have one unused pin, though. It's also the same cable as we use in our intercom, which is used much less frequently than XLR3, so less chance of someone connecting it where it shouldn't be.

I am confused why you cant just use an XLR cable for this project in the first place. I used to have a huge bunch of projector dousers that you hooked up to a 9V battery and switchbox via an XLR/mic cable, and Comms uses them all the time with way more voltage than you will be. Wouldnt the only thing you need to label well be the outlet where you hook your cue lights to? I guess Im just wondering why you cant use mic cables. If they run out of them, you clearly have a problem anyhow, right? Saves you from having to buy too much new stuff as well.

 

[Lambda]

Is there anyway to post pictures and schematics when you are done???? I have been trying to get something like this together for a long time and that would help me a ton.

I will post final schematics if it ever gets built. There's a chance it won't get approved by the department, and if it does, it will likely take a while.

I am confused why you cant just use an XLR cable for this project in the first place. I used to have a huge bunch of projector dousers that you hooked up to a 9V battery and switchbox via an XLR/mic cable, and Comms uses them all the time with way more voltage than you will be. Wouldnt the only thing you need to label well be the outlet where you hook your cue lights to? I guess Im just wondering why you cant use mic cables. If they run out of them, you clearly have a problem anyhow, right? Saves you from having to buy too much new stuff as well.

I suppose in the end I will go with XLR3. The DIN connectors, though they will work, seem to be less durable and they don't lock. I am concerned with longevity of the system, because after I leave it will likely be a long time before someone comes along who cares to maintain it.
We have had problems in the past with mic cable shortages, until it was discovered that there were a great many of them running under the stage dating back to who-knows-when. Even now, we have problems with intercom cable (XLR4) shortages. Every proposal I submit for new cable seems to be ignored...

 

[hsaunier]

Might be a little overkill, but nuetric makes a "PowerCon" connector that I have seen used to connect stringers for stage power. The connecter is the same principle as the standard NL4 speakon but has a different stud pattern so they will not interconnect.

 

[Chris15]

Using Powercon would be a really dumb idea.
It nigh guarantees that at some point, the box is going to get mains put across it.
That will not end well
Don't do it. EVER.

Powercon is for mains power and mains power only.

btw, neither Powercon nor Speakon would meet the request for a connector that can be extended in line...

 

[Traitor800]

btw, neither Powercon nor Speakon would meet the request for a connector that can be extended in line...

Neutrik makes both male and female genders of both panel mount and inline speakon connectors, so it could be a viable option for this project. One thing to keep in mind is the speakon genders are not as obvious as some other connectors. In a typical audio system the panel mount is considered male connector and the inline is considered the female.

 

[hsaunier]

Well there you have it.

 

[Chris15]

Erm, There is no NL4MX.
Yes, there is the NLT4MX. It's from the 40A rated metal bodied family and that series is somewhat more pricey than the NL series.
Of course there are Chinese males abundant, generally of typical Chinese quality though.

I'd have thought we still had a risk at this point of getting a far greater voltage across the cue light system than it's designed for. A decent amplifer can easily dump north of 100 volts across it's load... (Without me doing any impedance or voltage sums - it's late.)