# Clean power for LED's from a Original Strand CD80 Rack



## YMCA-TD (Sep 27, 2015)

I'm in a small venue just looking for a couple of 20 A constant power circuits on one of my electrics. I know that there are some new retrofit and DMX relay modules out there, but because i have a couple of spare dimmers in stock I'm wondering if there is any way to convert a Dual 2.4k pack into 2 constant power circuits just controlled by the breaker? 
Is there a way to bypass the SSR and choke to give me clean power from the buss to the circuit that i could use to safely power Led's and other non-dim loads.

Additionally could anyone familiar with the original Strand CD80 Packs tell me if a Dual 2.4K NN module would work in my situation as well?

Thanks!!!


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## Les (Sep 27, 2015)

YMCA-TD said:


> I'm in a small venue just looking for a couple of 20 A constant power circuits on one of my electrics. I know that there are some new retrofit and DMX relay modules out there, but because i have a couple of spare dimmers in stock I'm wondering if there is any way to convert a Dual 2.4k pack into 2 constant power circuits just controlled by the breaker?
> Is there a way to bypass the SSR and choke to give me clean power from the buss to the circuit that i could use to safely power Led's and other non-dim loads.
> 
> Additionally could anyone familiar with the original Strand CD 80 Packs tell me if a Dual 2.4K NN module would work in my situation as well?
> ...



Unfortunately, I don't think there is a modification the user can do (at least not one that is UL/insurance approved; too much risk). There are a lot of companies who service these packs and could possibly do a similar but professional-grade mod. I don't know much about the CD-80's so I'll let others chime in on the particulars. Here are a couple of links for you to start out with:

http://www.dimmer.com/

http://www.litetrol.com/


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## JD (Sep 27, 2015)

Although one would think you could bypass the SSR and choke, that's not a good idea! Besides voiding out any UL or other approval for the unit, something else happens:
The "dead short" current skyrockets when you remove the choke and SSR, which both act as resistors in a dead-short scenario. Because of this, the breaker must be able to function at a higher flash current without self destructing. Constant power modules are designed with this in mind.


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## BillConnerFASTC (Sep 27, 2015)

I thought their non-dim modules were dry contacts. If do, they should be fine.


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## TCJ (Sep 29, 2015)

Just a termination clarification, but... wouldn't the dimmer pack use TRIACs or SCRs?

As I've always understood the terminology, SSRs only switch on and off at the zero crossings of the AC power. (Even though SSRs as I understand are typically built from FETs or IGBTs, I've always heard the integral triggering circuit monitors the AC power and only activates the FET/IGBT gate when the zero crossing is reached.) Someone please correct me if I'm wrong here.

TRIACs and SCRs can switch on at any arbitrary point, and remain on until the instantaneous "holding current" through the load drops below some very small threshold. That's what makes them work in dimmers and variable power controllers. (I know this one for sure, as I've repaired and even designed dimmers and motor speed controls that use TRIACs and SCRs.) They are my first-choice "go to" components for "phase-chopped" power control; I've always regarded SSRs as something for when you need simple on/off -- without "dimming" or "variable power" -- and when mechanical contact relays are inappropriate. (Though I've never designed anything with SSRs yet.)


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## DavidNorth (Sep 29, 2015)

While a SSR can be made with a MOSFET or IGBT, most SSRs in dimming are merely a package of two back to back SCRs and they are available in zero crossing and non-zero crossing [for dimming]. SCR SSRs are a very prevalent package and are indeed what we mean when we say SSR on CB.

I think you'll find that designing with SSRs is a bit easier than SCRs as there is much less wiring to do and they are easier to mount.

Back to the OP. Are you using CD80 packs or dimmer racks. CD80 packs, that have typically 12 dimmers in them, do not have an option to make them act as a non-dim or provide constant power. CD80 racks do have some module options from Strand and Johnson Systems.

David


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## mikeydoesstuff (Sep 29, 2015)

There ARE cd80 non dim cards. They're pretty simple and easy, but it would always be safest to acquire a professionally made one, rather than try to make your own. Personally I've had great luck with using them to power non dimmable items.


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## BillConnerFASTC (Sep 29, 2015)

I'm confused. Is what David North (and I and I <think> many others) would call a "module" what the op YMCA-TD called a "pack" and what mikeydoestuff just called a" card"?


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## Amiers (Sep 29, 2015)

Is the Test Outlet on every pack or just the big ones?




The last time I used one of these packs that was not controlled and always on.


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## mikeydoesstuff (Sep 29, 2015)

I use "card" to refer to the removable/replacable "modules" in the racks. I assume a "pack" refers to the (photo above) 12 dimmer unit.


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## Scenemaster60 (Sep 29, 2015)

There are really only 2 safe and legal ways to do this:
1. Buy a Johnson control systems relay (c. $500) or constant power (c. $300) module that is UL listed. There MAY be other companies that make these as well, but I do not know who they are.
2. Hire an electrician to move the wiring from the circuits you want to use as constant power to a nearby branch panel with regular circuit breakers.


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## microstar (Sep 29, 2015)

Scenemaster60 said:


> There are really only 2 safe and legal ways to do this:
> 1. Buy a Johnson control systems relay (c. $500) or constant power (c. $300) module that is UL listed. There MAY be other companies that make these as well, but I do not know who they are.
> 2. Hire an electrician to move the wiring from the circuits you want to use as constant power to a nearby branch panel with regular circuit breakers.



Not so sure Johnson Systems modules are "universal" for any CD-80 rack. Quote from their website: "No warranty or product return is available if these products are used, even temporarily, with any OEM controls as they are incompatible.
The inferior drive signals in certain controls may damage this equipment." Sounds like they are only useable with the Johnson Systems retrofit control electronics, which would be unfortunate.


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## Scenemaster60 (Sep 29, 2015)

I hadn't thought of that. However, that would only affect the relay modules. The constant power modules would have no interaction with the electronics in the rack.


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## BillConnerFASTC (Sep 29, 2015)

Scenemaster60 said:


> There are really only 2 safe and legal ways to do this:
> 1. Buy a Johnson control systems relay (c. $500) or constant power (c. $300) module that is UL listed. There MAY be other companies that make these as well, but I do not know who they are.
> 2. Hire an electrician to move the wiring from the circuits you want to use as constant power to a nearby branch panel with regular circuit breakers.


If its a CD80 rack - yet to be determined - why not the non-dim module made for it - with dry contact relays? Seems perfectly legal.


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## Scenemaster60 (Sep 29, 2015)

BillConnerASTC said:


> If its a CD80 rack - yet to be determined - why not the non-dim module made for it - with dry contact relays? Seems perfectly legal.



I was under the (perhaps mistaken?) impression that those Strand-made modules are very difficult to find at this point in time. That's why I didn't mention them. I am certainly familiar with them since work with a number of legacy CD-80 systems that have them installed to control magnetic ballasted lighting.


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## BillConnerFASTC (Sep 29, 2015)

Scenemaster60 said:


> I was under the (perhaps mistaken?) impression that those Strand-made modules are very difficult to find at this point in time. That's why I didn't mention them. I am certainly familiar with them since work with a number of legacy CD-80 systems that have them installed to control magnetic ballasted lighting.


When I googled the other day, I found them for sale from multiple dealers, to my surprise, including nn, nd, and dn. And I think literol could supply them.


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## Scenemaster60 (Sep 29, 2015)

BillConnerASTC said:


> When I googled the other day, I found them for sale from multiple dealers, to my surprise, including nn, nd, and dn. And I think literol could supply them.


Well, in that case, it would be my first choice. 
I suppose that just enough of these systems are being taken offline right now that modules are coming onto the market!


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## YMCA-TD (Sep 29, 2015)

Yes !! it is in fact A CD 80 rack populated with dual 2.4k DD modules
It has also been upgraded with JS CD 2000 with both DMX preset and analog stations. ( sorry, I was remiss for not mentioning that in my initial post.)
Of course Safety is always the overriding factor, so I am now looking for the most cost effective, option to replace 1 or 2 modules .. 
Based on what i've read above it looks like a strand NN would provide safe power for my needs. Im seeing a few sources for them online, but want to be sure that would be a appropriate solution to power LED or 120v accessories. The module(s) will be single tasked to constant power usage, so I won't need a switchable dim / non dim module. Although a dmx triggered relay system sounds handy, IMO Its not really a priority for our use, as the rack room is Just off stage and and and easy to access. 

Thanks again to all of you, for your response and support!


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## STEVETERRY (Sep 29, 2015)

Guys, an observation:

Sometimes, the forward march of technology dictates that old equipment should be retired and replaced with new equipment that is suited to (and Listed for) the application. 

Even though we have may have "clever" solutions to this problem, they might not be safe or compliant with applicable standards, as others on this thread have pointed out.

I know we generally feel poor in the theatre, but this might be one of those cases where buying new gear is the right approach. After all, LED's are not going away.

Just sayin'.

ST


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## BillConnerFASTC (Sep 30, 2015)

STEVETERRY said:


> Guys, an observation:
> 
> Sometimes, the forward march of technology dictates that old equipment should be retired and replaced with new equipment that is suited to (and Listed for) the application.
> 
> ...


Is a true CD80 non-dim module not listed for use with LEDs? 30 years ago I put non-dimmed circuits in a lot of projects, one or two at each lighting position. I'd hate to think they were not useful for any constant load. Granted I did not envision LEDs but did assume discharge lamps, fluorescents, and effects.


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## mikeydoesstuff (Sep 30, 2015)

BillConnerASTC said:


> Is a true CD80 non-dim module not listed for use with LEDs? 30 years ago I put non-dimmed circuits in a lot of projects, one or two at each lighting position. I'd hate to think they were not useful for any constant load. Granted I did not envision LEDs but did assume discharge lamps, fluorescents, and effects.



I was taught (for what thats worth) that they put out a really nice non-dim, safer than what CC or RF Sensor modules do, since its not chopped up first. -That the CD80 ND is essentially a power passthrough - always on.


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## Scenemaster60 (Sep 30, 2015)

The CD-80 non-dim modules that I have worked with were a true "non-dim" that came on at about 50%. Since the ones I used were still being fired by analog AMX driven cards the 50% was not an absolute value. Some came on at 48%, some not until 55%.


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## BillConnerFASTC (Sep 30, 2015)

Scenemaster60 said:


> The CD-80 non-dim modules that I have worked with were a true "non-dim" that came on at about 50%. Since the ones I used were still being fired by analog AMX driven cards the 50% was not an absolute value. Some came on at 48%, some not until 55%.


In terms of at what point in a curve they switched, I think that was configurable, but the main point is that they were dry contact relays IIRC.


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## microstar (Sep 30, 2015)

mikeydoesstuff said:


> I was taught (for what thats worth) that they put out a really nice non-dim, safer than what CC or RF Sensor modules do, since its not chopped up first. -That the CD80 ND is essentially a power passthrough - always on.



Neither Sensor CC-20 constant modules or R-20 relay modules chop up the waveform because they don't have SSR's in them. I don't know what a "RF " Sensor module is.


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## mikeydoesstuff (Sep 30, 2015)

microstar said:


> Neither Sensor CC-20 constant modules or R-20 relay modules chop up the waveform because they don't have SSR's in them. I don't know what a "RF " Sensor module is.



Sorry, the F was a typo.


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## Ford (Sep 30, 2015)

At Cornell U., we had large CD80 Racks in our main stage, Flexible, and Black Box theatres (the Dance theatre, and light lab used portable CD80 packs). I had about a dozen relay modules, that I swapped in when we were locating a projector, or hazer, or LED fixture, or even a computer in various spots throughout the theatre.
They looked very similar to the standard dimming modules, except that they were grey (instead of black), and weighed a fraction of a standard 2x2.4k dimmer module because they had no chokes or SCRs... just relays.

The modules were manufactured by Strand. They were just dry contact relays (like Bill said). As a default, they turned on at 50%, though I sometimes modified the channel in the console to "on at 1%", too.

Because they were relays, and not SCRs, they did not modify the sine wave, at all... they worked great for powering electronics throughout the nooks and crannies of the theatres.

If you have big CD80 racks, this is what you're looking for. If you have the smaller CD80 dimmer packs (like the photo above), you'll need to get replacement cards, and install them. these are not as easy to work on as the big racks.

HTH,
-Ford


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## STEVETERRY (Sep 30, 2015)

BillConnerASTC said:


> In terms of at what point in a curve they switched, I think that was configurable, but the main point is that they were dry contact relays IIRC.



The bigger issue here is fault current coordination. If the original rack contained no non-dim modules, then the fault current coordination was done using the SCCR of dimmer modules with current-limiting chokes. Back in CD-80 prime time in the 1980's, fault current coordination might not have been a big issue. Now it is.

If you change a rack from all dimmers to some dimmers and some non-dims or CC (breaker only) modules, you need to make sure that the fault current coordination is still valid.

BTW, this is a life-safety issue.

ST


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## BillConnerFASTC (Sep 30, 2015)

STEVETERRY said:


> The bigger issue here is fault current coordination. If the original rack contained no non-dim modules, then the fault current coordination was done using the SCCR of dimmer modules with current-limiting chokes. Back in CD-80 prime time in the 1980's, fault current coordination might not have been a big issue. Now it is.
> 
> If you change a rack from all dimmers to some dimmers and some non-dims or CC (breaker only) modules, you need to make sure that the fault current coordination is still valid.
> 
> ...


I forgot that not every rack had silver sand fuses which I think solved this. Maybe not.


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## STEVETERRY (Oct 1, 2015)

BillConnerASTC said:


> I forgot that not every rack had silver sand fuses which I think solved this. Maybe not.



If the non-dim or CC module has a current-limiting fuse, that can solve the fault current coordination issue by maintaining the original SCCR of the rack.

ST


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## MikeJ (Oct 2, 2015)

STEVETERRY said:


> Guys, an observation:
> 
> Sometimes, the forward march of technology dictates that old equipment should be retired and replaced with new equipment that is suited to (and Listed for) the application.
> 
> ...



Guys, an observation: I read the thread, and a safe and legal solution made by the OEM has already been found, and suggested to the original poster. There is no reason to replace the current system. I'm sure that this solution is drastically inferior to a brand new ETC contraption, but replacing the whole rack does seem like a solution in search of a problem. 

Also, "clever" sales tactic.


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## STEVETERRY (Oct 3, 2015)

MikeJ said:


> Guys, an observation: I read the thread, and a safe and legal solution made by the OEM has already been found, and suggested to the original poster. There is no reason to replace the current system. I'm sure that this solution is drastically inferior to a brand new ETC contraption, but replacing the whole rack does seem like a solution in search of a problem.
> 
> Also, "clever" sales tactic.



Mike-

I'm sorry if you read my post as "clever sales", but that was surely not my intention. Nor did I mention any potential replacement product by name or features--on purpose. For those that know me, "clever sales" is not in my repertoire or MO. Rather, I view this as a pure safety issue, where "caveat emptor" comes into play for the informed consumer, especially where the relatively new issue of fault current coordination is involved.

ST


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## BillConnerFASTC (Oct 5, 2015)

I know a number of folks at ETC that wish Steve would engage in "clever sales" and not be so helpful and so product neutral here. Where else in our industry would people designing, installing, and operating theatre lighting systems learn about Available Fault Current Selective Coordination?


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## TCJ (Oct 6, 2015)

Question of curiosity here...

Why would retrofit modules, supposedly designed specifically for the CD80, but using mechanical relay contacts, have an SCCR issue?
If they are being sold as a drop-in replacement, shouldn't they already be designed to have the necessary chokes / PTC-thermistors / fast-blow fuses or circuit breakers, so as not to compromise the dimmer pack's safety ratings?
(And if they don't, how are they being sold as approved modules?)


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## TCJ (Oct 6, 2015)

Oh and another question...

Why is the "switch-on level" (be it 50%, 53%, whatever) even an issue? I'd think if you're using a light channel as a simple on/off, you want to stay as far away from the threshold levels as much as possible, to ensure the system doesn't go into oscillation. (Are the hysteresis characteristics even specified for these units??) Anyhow, that would mean your lighting controller puts out 0% when you want the channel off, and 100% when you want it on. So wouldn't the finer details of the threshold, be it 50%, 53%, 10%, 90%, etc. be irrelevant?


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## BillConnerFASTC (Oct 6, 2015)

TCJ said:


> Question of curiosity here...
> 
> Why would retrofit modules, supposedly designed specifically for the CD80, but using mechanical relay contacts, have an SCCR issue?
> If they are being sold as a drop-in replacement, shouldn't they already be designed to have the necessary chokes / PTC-thermistors / fast-blow fuses or circuit breakers, so as not to compromise the dimmer pack's safety ratings?
> (And if they don't, how are they being sold as approved modules?)



CD80s were designed and manufactured before the issue was fully recognized as a potential hazard. It was added to the NEC in early 2000s iirc. 

Can you keep using it? Yes, just like ungrounded systems and receptacles in wet areas without gfci protection may be continued in use in some circumstances. Should you? Is it a smart choice? Is it safe? Maybe but probably not. And what industries other than entertainment technology would? To many people in our industry are too willing to accept too little. 

In this case maybe the current safety standards and codes can be met but I think modifying a system with different components requires it meet the codes and standards in effect today, and perhaps it can. It would require research and I don't know if some of the after market products are even listed. Lots of gear is not, and I won't specify or accept it myself, as many inspectors would not accept it.


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## STEVETERRY (Oct 6, 2015)

TCJ said:


> Question of curiosity here...
> 
> Why would retrofit modules, supposedly designed specifically for the CD80, but using mechanical relay contacts, have an SCCR issue?
> If they are being sold as a drop-in replacement, shouldn't they already be designed to have the necessary chokes / PTC-thermistors / fast-blow fuses or circuit breakers, so as not to compromise the dimmer pack's safety ratings?
> (And if they don't, how are they being sold as approved modules?)



Dimmer modules or non-dim modules that plug into a dimmer rack are UL Recognized components. UL is happy to recognize a non-dim module without current-limiting fuses or a choke. In that case, the SCCR of the entire rack falls to the native AIC rating of the circuit breaker in the non-dim module. Let's say the original rack was full of dimmers with chokes and the rack had a 100,000 amp SCCR. Once that non-dim module goes in, the SCCR likely falls to 10,000A, which is a typical AIC rating for the type of breakers used in these modules. 

But what if the engineer laying out the original system specified a transformer, wiring length, and switchgear layout that makes 40,000A of fault current available at the rack? No problem for the original, which had an SCCR of 100,000A. Big problem for the non-dim module, which now reduces the rack SCCR to 10,000A. That breaker in the non-dim may not be able to safely clear a fault with 40,000A of fault current available.

Thus, with a retrofit module, the fault current coordination issue falls to the specifier, engineer, or end-user--not to the NRTL that recognized the new non-dim module.


ST


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## TCJ (Oct 6, 2015)

Well, heck, suppose this thing was installed right in a power plant, on the first step-down transformer next to the turbine hall! The fault current could be astronomical. So it seems a little silly to me for equipment... _any equipment_... to have its ratings based on an "assumed type of connection" to the AC power mains.

Am I wrong to figure when selecting and overcurrent protection device, the resistance of just the device's own conduction path (power cord, thermistor (if present), rectifier (if present), the protection device itself, etc.) should be used to calculate the short-circuit current? And then ensure the disconnect occurs fast enough before heat build-up melts something in (or near) that conduction path? (I don't specialize in power systems, but I'm genuinely curious.)

This brings up another curiousity:
Given that switch contacts almost always have higher AC ratings than their DC ratings (relying on the zero-crossing of AC power to assist with extinguishing the arc between the contacts)... and I wonder if this applies to fuses too... does AC line frequency become significant when dealing with overcurrent protective devices and their response time? Does a legacy 25 Hz system have far more demands than an aircraft 400 Hz system, for example?


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## STEVETERRY (Oct 6, 2015)

TCJ said:


> Well, heck, suppose this thing was installed right in a power plant, on the first step-down transformer next to the turbine hall! The fault current could be astronomical. So it seems a little silly to me for equipment... _any equipment_... to have its ratings based on an "assumed type of connection" to the AC power mains.
> 
> Am I wrong to figure when selecting and overcurrent protection device, the resistance of just the device's own conduction path (power cord, thermistor (if present), rectifier (if present), the protection device itself, etc.) should be used to calculate the short-circuit current? And then ensure the disconnect occurs fast enough before heat build-up melts something in (or near) that conduction path? (I don't specialize in power systems, but I'm genuinely curious.)
> 
> ...



For more information, see the excellent article "Fault Current Demystified" by Ken Vannice on page 40 of the Summer 2013 issue of Protocol here:

http://edition.pagesuite-professional.co.uk//launch.aspx?eid=d8524bce-4e49-4823-806d-1a3c0166a79d

ST


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## RickR (Oct 6, 2015)

TCJ said:


> Why is the "switch-on level" (be it 50%, 53%, whatever) even an issue? I'd think if you're using a light channel as a simple on/off, you want to stay as far away from the threshold levels as much as possible, to ensure the system doesn't go into oscillation. (Are the hysteresis characteristics even specified for these units??) Anyhow, that would mean your lighting controller puts out 0% when you want the channel off, and 100% when you want it on. So wouldn't the finer details of the threshold, be it 50%, 53%, 10%, 90%, etc. be irrelevant?



This is an issue of our industry default control being an analog slider so you need a switch point in the console. Back in the day, 0-10V control was also typical so you need a switch point in the rack. There is always the possibility of getting a transitory level so you can't depend on only 0 or 100%. 50% is as far away from the "normal" settings of on/off as possible. I last used 'on @1%' when I wanted something to be 'first on, last off' as it was a semi-safety issue. Sure I could have done other console tricks, but that was best in that situation.

I'll let others address the electrical engineering questions. Thank you @STEVETERRY for being far clearer than most EEs I've known!


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## Ford (Oct 6, 2015)

STEVETERRY said:


> For more information, see the excellent article "Fault Current Demystified" by Ken Vannice on page 40 of the Summer 2013 issue of Protocol here:
> 
> http://edition.pagesuite-professional.co.uk//launch.aspx?eid=d8524bce-4e49-4823-806d-1a3c0166a79d



Thank you Steve, this is a great article!
I had not really pondered that many of the systems that are being "upgraded" for LED fixture distribution were not designed for this, and lack the proper circuit protection. It's a little counter intuitive to think that the lower power draw of electronic fixtures could actually be more of a hazard than running through dimmers and then out to a higher wattage fixture...

Thanks for broadening my perspective.


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## TCJ (Oct 6, 2015)

RickR said:


> This is an issue of our industry default control being an analog slider so you need a switch point in the console. Back in the day, 0-10V control was also typical so you need a switch point in the rack. There is always the possibility of getting a transitory level so you can't depend on only 0 or 100%. 50% is as far away from the "normal" settings of on/off as possible. I last used 'on @1%' when I wanted something to be 'first on, last off' as it was a semi-safety issue. Sure I could have done other console tricks, but that was best in that situation.
> 
> I'll let others address the electrical engineering questions. Thank you @STEVETERRY for being far clearer than most EEs I've known!



I was actually thinking in terms of 0 - 10 V analog console. What I meant by 0% and 100% is where the operator should position the board's sliders for "off" and "on", not the threshold level as determined by the relay box's design. (Anything safely away from the extremes of the signal range should work as suitable thresholds at the rack.)
Though I think I see your point now (correct me if wrong) about having a small bit of "controlled sequencing" (first on, last off) across multiple devices when sliding the master X or Y? Or if multiple relays (for multiple devices) are slaved off the same control channel?


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## tomthetechie (Oct 19, 2015)

BillConnerASTC said:


> Is a true CD80 non-dim module not listed for use with LEDs? 30 years ago I put non-dimmed circuits in a lot of projects, one or two at each lighting position. I'd hate to think they were not useful for any constant load. Granted I did not envision LEDs but did assume discharge lamps, fluorescents, and effects.



The ND modules should be perfectly fine for the jobs you have spec'd. Strand does make passthrough modules that would be better for LED's and movers BUT you have to flip the breaker to kill it. Strand ND's haven't caused us any grief with modern fixtures thus far.

Edit: After reading the rest of the thread, I see that this was already answered. My bad.


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