Help Needed with Strand House Light Dimmer

crippit

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Feb 11, 2021
Location
Montreal
I'm looking for some help with moving over the control of our house lights to a DMX controller. We currently are using this rather antiquated Strand console, whose only function in life now, is to override the wall switches for the house lights for shows, and dim the house lights from a central location. We have done a bit of exploring and we have discovered that:
  • There appears to be an 18v control voltage
  • The dimmers for the FOH have been cut and put into a DMX Multiplexer in the past
  • We know what each pin does from the console, and what the voltage changes are on each pin.
So the question that we want to answer is can we control these house dimmers using the current DMX Multiplexer or do we need additional hardware? If we need hardware what would you suggest?
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RonHebbard

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Location
Waterdown, ON, CA
I'm looking for some help with moving over the control of our house lights to a DMX controller. We currently are using this rather antiquated Strand console, whose only function in life now, is to override the wall switches for the house lights for shows, and dim the house lights from a central location. We have done a bit of exploring and we have discovered that:
  • There appears to be an 18v control voltage
  • The dimmers for the FOH have been cut and put into a DMX Multiplexer in the past
  • We know what each pin does from the console, and what the voltage changes are on each pin.
So the question that we want to answer is can we control these house dimmers using the current DMX Multiplexer or do we need additional hardware? If we need hardware what would you suggest?View attachment 21499View attachment 21500View attachment 21501View attachment 21502
Calling @Ron Foley
Toodleoo!
Ron Hebbard
 

microstar

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Location
Lawton, OK
The labeling at upper right on the PC board photo says it is a DEmultiplexer, so presumably it is taking a DMX input and outputting an analog control voltage to each dimmer. But a bit puzzling as your houselight console looks too old to be able to output DMX. Is the input to your dimmer rack DMX or analog?
If you already have a DMX console for your stage lighting, you can either daisy-chain the DMX from your dimmer rack to the DMX input of the demultiplexer or you could buy a small DMX splitter and feed the console DMX out to the splitter input, then out to the dimmer rack via one split and out to the demultiplexer from another split. Looks like this will need some clarification.
 

RonHebbard

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Location
Waterdown, ON, CA
So our house lights don't output DMX that's the whole issue, we want to connect them to the demultiplexer (sorry I made a mistake in my original post). We're using the dot2 software via a DMX > Ethernet module for our FOH. Our concern is the voltage of the lines for the house lighting which appears to be 18v. The dimmer rack appears to be a 1969-1971 Strand JTM.
In the dusty crevasses of my mind, I'm recalling JTM racks in two physical sizes, 20 or 40 bolt in modules; narrower with one "Tom Terrific" hat / fan atop or double width sporting two "Tom Teriffic" hat / fans atop.
Typically dimmers were 2KW although larger dimmers 3KW and 6KW were offered. 2KW and 3KW's were physically identically sized while 6KW's were physically larger with fewer mounting in a given rack width.
In either case, I could be wrong, I'm recalling 0 <10 DC volts; I can't recall if they were negative or positive common.
Toodleoo!
Ron Hebbard
 
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crippit

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Location
Montreal
In the dusty crevasses of my mind, I'm recalling JTM racks in two physical sizes, 20 or 40 bolt in modules; narrower with one "Tom Terrific" hat / fan atop or double width sporting two "Tom Teriffic" hat / fans atop.
Typically dimmers were 2KW although larger dimmers 3KW and 6KW were offered. 2KW and 3KW's were physically identically size while 6KW's were physically large with fewer mounting in a given rack width.
In either case, I could be wrong, I'm recalling 0 <10 DC volts; I can't recall if they were negative or positive common.
Toodleoo!
Ron Hebbard
Yes! Ours ia a triple width with the house lights being at the far end!
 

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RonHebbard

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Waterdown, ON, CA
Yes! Ours ia a triple width with the house lights being at the far end!
How many dimmers in total; could be a double wide with a single wide mounted next to it or three single wides? I don't believe I've ever seen a triple wide manufactured in one contiguous piece with 3 "Tom Terrific" hat / fans atop.
Where's @Ron Foley when we need him?
Toodleoo!
Ron Hebbard
 

crippit

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How many dimmers in total; could be a double wide with a single wide mounted next to it or three single wides? I don't believe I've ever seen a triple wide manufactured in one contiguous piece with 3 "Tom Terrific" hat / fans atop.
Where's @Ron Foley when we need him?
Toodleoo!
Ron Hebbard
Here are some better photos
 

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RonHebbard

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Here are some better photos
@Ron Foley (In Guelph, Ontario) would have been working in / for Strand Toronto at that point and (Quietly under my breath) Sean Johnson, Johnson Controls, builds Strand replacements better than Strand's originals [Yes, even for 1970's analogue JTM's and their controllers].
Toodleoo!
Ron Hebbard
 

microstar

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Jan 19, 2014
Location
Lawton, OK
18V will require a custom DMX to analog converter, or a standard 0-10V one with a home brew amplifier board. Johnson Systems can probably help you. https://www.johnsonsystems.com

Doug Fleenor Designs makes converters, but I don't know if they would brew up a 0-18V version. It can't hurt to ask.
Dove Systems' MTX converters are natively adjustable 0-28vdc output and Northlight DMX converters can be ordered for 0-15vdc (18vdc may be possible as well). If the OP only needs 3 channels, then Northlight's 8-channel converter would be the most economical.

But the OP may not need another converter if there are unused channels on the one he already has.
 

microstar

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Location
Lawton, OK
OK. Looking closer at your photo of the demultiplexer board reveals it is a standard Gray Interfaces (now Pathway) model LCDM-48. It appears that channels 41 thru 48 are unused since there are no wires connected to those outputs. Therefore you could drive 8 of your 16 houselight dimmers from this interface. According to the Gray spec sheet, each output can supply 5 ma. Depending on how much control current one dimmer requires, it MIGHT be possible to drive two dimmers from one output but you would have to measure what one dimmer draws before attempting this.
Also odd that you are measuring 18vdc control voltage, as the Gray unit only goes up to 15vdc (unless it has been modified in some way). James at Northlight DMX can modify his DEC08M for 18vdc output but it will then require a 24vdc power supply instead of the normal one.
I have a Lightronics 24-channel demultiplexer that can be modified for up to 0-24vdc output.
PM me if you are interested.
Gray LCDM-48.png
 

crippit

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Feb 11, 2021
Location
Montreal
We're going to look and see if we can actually get our school board to replace the entire system and then control the house lights from a new demultiplexer.

Thanks for the heads-up with the boards! Really appreciate your help.
 

crippit

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Feb 11, 2021
Location
Montreal
OK. Looking closer at your photo of the demultiplexer board reveals it is a standard Gray Interfaces (now Pathway) model LCDM-48. It appears that channels 41 thru 48 are unused since there are no wires connected to those outputs. Therefore you could drive 8 of your 16 houselight dimmers from this interface. According to the Gray spec sheet, each output can supply 5 ma. Depending on how much control current one dimmer requires, it MIGHT be possible to drive two dimmers from one output but you would have to measure what one dimmer draws before attempting this.
Also odd that you are measuring 18vdc control voltage, as the Gray unit only goes up to 15vdc (unless it has been modified in some way). James at Northlight DMX can modify his DEC08M for 18vdc output but it will then require a 24vdc power supply instead of the normal one.
I have a Lightronics 24-channel demultiplexer that can be modified for up to 0-24vdc output.
PM me if you are interested.View attachment 21520
So essentially connecting the 18v to that board will just end up with less dimming? Or everything partly dimmed all the time? We're essentially losing the top end of the dimming capability?
 

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