# Lighting Control Questions



## ship (Dec 26, 2005)

369) What is the difference between Analog dimmers and SCR Dimmers?
370) How many wires are used in the control cable to a 24 channel Analog light board?
371) What is the voltage range and type (Alternating Current, Direct Current, or Alternating Direct Current) of Analog Control?
372) How many dimmers can be controlled by a single DMX cable?
373) What is the difference between Lee and Rosco/Gam gel?
374) What color is Rosco/Lee 27?
375) Can you dim a Neon Lamp, if so which type of stage lighting dimmer is best for it?
376) Describe what a linear dimming curve is?
377) Describe what MIDI control is?
378) 1/2CTB Gel does what to lamp output?
379) What effect does a spot of oil on a frosted gel have?
380) On a two-scene pre-set light board, how do you control independent dimmers, and will moving the master effect them?
381) One point of change on a light board equals how much change at the dimmers?
382) If you have a three-count fade down on a manual board, do you count to three and fade, do you wait three seconds than fade, or do you do which of the above two counts while you are fading?
383) On a two scene preset board, how do you fade to a complete blackout while at the same time have one dimmer lag behind the others in rate of fade?
384) What is the purpose of a terminator on a XLR/DMX line?
385) What is the usual cause of a fixture ghosting in a system?
386) What was DMX designed to do, and what is it used for?
387) What size resistor is used in a terminator and why?
388) What is the purpose of an opto-splitter and how does it work?
389) When you hit the “Go-Back” button on a timed fade to cue, does it instantly go back to the last cue, or does it reverse the time to fade count?
390) In general practice, which component of a light board / dimmer system should be turned on first, and why?
391) How does a Auto follow work on a light board?
392) How does a scroller being controlled by light board choose what color to bring up?
393) What is the difference between a sub-master and a group master?
397) What is Last takes Precedence, and is this good or bad?
398) What is necessary to be done when using a Martin RS-485 standard controller on a Mac 500?
399) How many DMX channels does a Martin 600E in mode 4 require?


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## propmonkey (Dec 27, 2005)

384) What is the purpose of a terminator on a XLR/DMX line?

to stop the signal from reflecting back and effecting the dimmers or other dmx controlled objects. often a fix to ghosting.

and i believe its 120 ohms resistor.


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## ricc0luke (Dec 27, 2005)

QUESTION 369)

Sillicon Controlled Rectifier-
It’s a thyrister. It’s a type of dimmer that is only used with AC power. (A Triac is another thyrister). It’s a dimmer were there is a PNP and NPN resistor… when a small voltage is applied to the NPN it will provide current for the PNP and the whole electrical circuit works.

now… what it actually does is cut the AC sine wave at different intervals. this cutting up of the wave it what causes the noise

With the SRC’s you generate lots of noise and lots of heat, though the two have nothing to do with each other.

The triac’s are very similar and works in basicly the same way only the small about of current to turn the circuit on are applied in short pulses… triacs produce much less noise… i’m not sure about heat. This is the new generation of dimming, but most currently are all still SRC.

(oh… in all the above when i mention noise, i mean noise in the signal… the noise that will jump to nearby audio cables, from here on, when i say noise i mean like noise that you can here)

i assume by analog you mean a rheostat- they are risistance dimmers… aka the dimmers that make a bunch of noise. they reduce the about of current flowing to an object by adding resistance to the line creating lots of heat and noise… the kind of noise you can hear. it doesn’t change the sine wave, it just slows it down.


There… i think that’s about right… please correct me if i’m wrong… I try to find a website that better explains it because i’m sure someone else can do a better job at explaining that.


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## ricc0luke (Dec 27, 2005)

370) 25 or 27 i think but not entirely sure... and damn i was just at the theatre tonight i could have looked...

371) alternating direct current but once again i am not entirly sure

372) 0 to 10volts

373) i forget the proper terms for all this, but Lee applies color to a clear polymer, rosco sandwichs color between 2 clear polymers, and gam takes a clear polymer and dips it in something (i once knew what it was) that opened up the pores in the polymer and then the color is applied and then the polymer will close up again sealing the color in side... thats the jist of it

374) 

375) You can't dim a neon light with a stage dimmer as far as i know... but please tell me if i'm wrong i would love to know

376) linear dimming curve is really an oxymoron... a simple example of this is patching a dimmer into a board at 50%.... then 100% on the board is 50% at the dimmer... 90% at the board is 45% at the board... and so on.... that is an example of a linear dimming curve...

377) MIDI... Musical Intrument Digital Interface... it is a form of communication for elecronic music equipment light DMX is to lighting... it is a standardized form of communcating notes and rythems

378) 

379) The oil will retain the lights heat and burn the gel.

380) Moving the masters for scene A and B will not affect the independent masters. Moving the grandmasters will. You must assign a dimmer to be independant. This is normally a button about the slider. (I never thought i would use my knowledge of the MACRO ELECTRONICS TSP light board the local HS has.

381) every light board i have ever worked on it is a 1 unit to 10% ratio. One spot on the lightboard is 10% to the dimmer

382) i have always been taught that 3 second fade means that it should be out on three... now i am a band person... so i would say you count to 3 using the full 2 seconds to dim and then you should hit zero when it reaches 0%

383)

384) as already been stated it keeps the signal from reflecting

385) in my experience- human error... but thats probably not the answer you were looking for.

386) DMX is signal used to control lighting in the entertainment industry

387) 120ohm resister that basicly eats up all the extra current or signal

388) 

389) reverses the fade

390) the dimmers should be turned on fade


ok... thats all i can do for now... how bad did i do ship?


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## krhodus (Dec 27, 2005)

372) How many dimmers can be controlled by a single DMX cable? 

512 I believe.

389) When you hit the “Go-Back” button on a timed fade to cue, does it instantly go back to the last cue, or does it reverse the time to fade count? 

On an ETC it takes the time to go back (Turning on Quickstep makes cues instantenous)


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## jumpjet (Dec 27, 2005)

381) One point of change on a light board equals how much change at the dimmers? 

1/2.56?

392) How does a scroller being controlled by light board choose what color to bring up?

By DMX code. Each value 1-255 corresponds to a specific place on the color scroll, and it runs to that color when it receives the specific signal.

397) What is Last takes Precedence, and is this good or bad? 

I think this is when the most recently called cue takes prescedence over all previous cues. When the last cue gives information for lights or dimmers, it overrides that of previous cues. Like tracking, this can be good or bad, depending on how you have decided to program and run the show.


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## soundman (Dec 27, 2005)

378) 1/2CTB Gel does what to lamp output?

Corrects to blue, raises the color tempature of a light.


388) What is the purpose of an opto-splitter and how does it work?

An opto splitter is used to isolate the dmx run from the console by converting the signel from electrical to light then back to electrical. That way the board will not be affected by a short in the system. It can also be used to split a universe, if you wanted to take univers A and run it several differnt places with out daisy chaining all over creation an opto spliter would do the trick. 
390) In general practice, which component of a light board / dimmer system should be turned on first, and why?

Board on first last off, to avoid ghosting

391) How does a Auto follow work on a light board?

Lets say cue 11.1 auto follows cue 11. When I hit go cue 11 the board waits a preset amount of time before going to cue 11.1

398) What is necessary to be done when using a Martin RS-485 standard controller on a Mac 500?

Set the protocol to mart

399) How many DMX channels does a Martin 600E in mode 4 require

14


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## ship (Dec 27, 2005)

ricc0luke said:


> 370) 25 or 27 i think but not entirely sure... and damn i was just at the theatre tonight i could have looked...
> 373) i forget the proper terms for all this, but Lee applies color to a clear polymer, rosco sandwichs color between 2 clear polymers, and gam takes a clear polymer and dips it in something (i once knew what it was) that opened up the pores in the polymer and then the color is applied and then the polymer will close up again sealing the color in side... thats the jist of it
> 375) You can't dim a neon light with a stage dimmer as far as i know... but please tell me if i'm wrong i would love to know
> 376) linear dimming curve is really an oxymoron... a simple example of this is patching a dimmer into a board at 50%.... then 100% on the board is 50% at the dimmer... 90% at the board is 45% at the board... and so on.... that is an example of a linear dimming curve...
> ...




Well attempted and the intent of the questions. It's a hope that these questions are a challenge and that there is stuff to learn from here and further debate and questions rise in the education and shared knowledge of all. Post your own questions you think good and useful for others to learn and quiz themselves from if they were useful. Also remember that the national ME certification test is coming up - in theory this spring. Don't know what will be on the test but much of these questions might just be or in not knowing might be things to study.

370) What you can't figure it out without counting pins and wires?
373) Very nicely stated.
375) Not a trick question. Now how do the new LED Little Lights dim them than? What type of dimmer is on a LittleLight?
376) I should refine this question further. A old theater I used to work at had a reason to plug it's cyc lights into one over another set of dimmer banks. Of the two available were some Cypress Creek vintage 1926 dimmers that were getting hard to get parts for, the others were some Kliegl new ones. One was linear (no soft patch mentioned in the question) it was a direct 1:1 ratio from 0 to 100 of what the dimmer would be outputting. The other was more of a bell curve in having a lot of control in the middle but not much towards the extremes. What is the name for this type of dimming system? Which will have been better for the cyc lights? And describe of the two described how each works in controlling the dimming.
380) Good trick in cross fading between scenes and having a light linger when going to black out. There is some magic on a quality two scene preset that is more difficult to do on a computerized light board - especially if you want that lingering light to linger as the mood of the scene necessitates from night to night.
381) Don't think you fully understand the question, or it could be a local thing. When the designer calls over the headsets to bring up the level "one point", what do they mean as far as how much you are bringing up the dimmer level?
382) Perhaps a good debate and important when working with a designer.
385) Nope!
389) Is this correct in not saying it's the wrong answer but looking for conformation besides me in something I have not done in seven or more years now.
390) "The dimmers should be turned on fade?" Would you like to refine your answer or spelling? Would anyone else like to chime in on what should be turned on first so as to prevent the lights from going crazy in an older system that lacks something?


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## ship (Dec 27, 2005)

ricc0luke said:


> 379) The oil will retain the lights heat and burn the gel.



This is an old stage hand/designer trick similar for a hint to cutting the center out of a gel so it's more of a colored donut in design concept. As for the oil, yes it retains heat but don't worry about that because it is a valid technique. Spray denatured alcohol on exterior frosted lamp is a hint. What do you see?


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## ship (Dec 27, 2005)

ship said:


> 389) Is this correct in not saying it's the wrong answer but looking for conformation besides me in something I have not done in seven or more years now.



Make that at least eight years and the best show I ever saw or worked. Ertha Kitt doing Billy Holliday in "Lady Day at Emerson's Bar and Grill." Great show in spit or her night to night wandering around in what scene she would be in. She sings just as well if not better than her past friend. For that show in figuring out what scene she now was in, I'm glad I was not the stage manager because hitting the go back button was the lest of our problems. In spite of wandering about in scenes, she was a total pro in doing her performance and excelled every night no matter the order of presentation of the show. By far too bad this show did not hit Broadway.

This show had another question that is related to the cyc light refinement of which dimmer to control it from. As opposed to or similar to the cyc lighting, If you have a neon sign saying "Emerson's Bar and Grill" as about the only scenery, and at some points it dims, and at other points it is either on at full or out, which type of dimmer would you be using to control it? Either the Cypress Creek or the Kliegl? Given a linear curve or the other type by way of control of the neon lamp so as to control it's dimming best?


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## ship (Dec 27, 2005)

jumpjet said:


> 381) One point of change on a light board equals how much change at the dimmers?
> 
> 1/2.56?
> 
> ...



Repeting the questions is much easier for readers to read and not have to scroll up or down to the origional post is a good thing. In answering, this should be the format where possible. (Given the question is already posed above I won't re-ask.)

381) ???? I have no idea of what you mean. Is this "New Math?"

397) In part, though doesn't what is in a cue dictate what lights are still shining? What happens if you loose control board signal?


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## ship (Dec 27, 2005)

soundman said:


> 378) 1/2CTB Gel does what to lamp output?
> Corrects to blue, raises the color tempature of a light.
> 388) What is the purpose of an opto-splitter and how does it work?
> An opto splitter is used to isolate the dmx run from the console by converting the signel from electrical to light then back to electrical. That way the board will not be affected by a short in the system. It can also be used to split a universe, if you wanted to take univers A and run it several differnt places with out daisy chaining all over creation an opto spliter would do the trick.
> ...



Nerd or ringer... well done in me not checking answers. Choose your title and stat in helping others to post your question of the day questions also please. This as with all thinking that "Candy Questions" are a good thing no matter the question or level of experience. You got a question or say read your new screw gun's manual and think it of interest to ask what on a DeWalt provides a torque of 40 inch pounds is the proper setting for the clutch, post away. Have that what gear would be governed by the reverse 2&3 on Martin gear to watch out for question, post it. Get the idea?


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## soundman (Dec 27, 2005)

A bit of both, I know where to look and know a little bit off hand.


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## ricc0luke (Dec 29, 2005)

for Q #390 I ment the dimmers should be turned on first... not fade... it was just a typo... you turn them on first because you don't want the board on and calling for dimmer 20 at 100% right when you first throw power to the dimmers... you want the dimmers to turn themselves on and start sending those minute amounts of current through the system... (not to mention if that lamp on 20 was a GLC lamp the filiment stands a good chance of blowing if you do that.) BUT by the way to mentioned older systems, i would say that the board should be turned on first to ensure that when the dimmers are turned on they have a control signal... and thinking about it, we always had to make sure that the board at the HS overode all the other signals...

so, i would say that the answer you are looking for is board first and then the dimmers... but i think i'll stick with dimmers board where i'm at...

for #376... Don't LED's dim by varying the voltage? I don't know, I've never tried.


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## ricc0luke (Dec 29, 2005)

for Q #390 I ment the dimmers should be turned on first... not fade... it was just a typo... you turn them on first because you don't want the board on and calling for dimmer 20 at 100% right when you first throw power to the dimmers... you want the dimmers to turn themselves on and start sending those minute amounts of current through the system... (not to mention if that lamp on 20 was a GLC lamp the filiment stands a good chance of blowing if you do that.) BUT by the way to mentioned older systems, i would say that the board should be turned on first to ensure that when the dimmers are turned on they have a control signal... and thinking about it, we always had to make sure that the board at the HS overode all the other signals...

so, i would say that the answer you are looking for is board first and then the dimmers... but i think i'll stick with dimmers board where i'm at...

for #376... Don't LED's dim by varying the voltage? I don't know, I've never tried.


a second guess at #385... excess voltage bouncing around in the signal cables or interference?

#376... right... when i went back and read my answer it doesn't fit the question... anyway... you can set the dimming curve on newer dimmers for many reasons... 1 of which is to match older dimmers, and also to combine the dimming curve of tunston halogen bulbs and incodecents... the bell curve you discribed i believe would be refered to as a logrithmic curve. anyway... i would say i prefer the linear curves as opposed to those where you have very little control at the extreames... what is your opinion ship?


> Spray denatured alcohol on exterior frosted lamp is a hint. What do you see?


Will it take the frost off?


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