Scroller cable

[RoyF18]

What cable/connectors do you use for scrollers when you make up scroller cable? As with most cables it's obviously going to be a lot cheaper making my own. By the way, I know it's 4-pin XLR, I guess really I should've said who supplies scroller cable (by the metre) and sells 4-pin XLRs?

Thanks in advance

Roy

[Ian Ferguson]

Please contact us off list, we have cable and connectors in stock

[gareth]

who supplies scroller cable (by the metre) and sells 4-pin XLRs?

 

Any reputable lighting equipment supplier will be able to sort you out with the bits to make up scroller cables. You're probably more likely to get best prices from the 'big boys', though.

 

Having said that, unless you've only got a fairly small quantity to do, it mightbe worth considering buying them ready-made. Of all the types of cable termination that a lampy might be called upon to do, scroller cable is (to my mind, at least) by far the least pleasant.

[Tomo]

XLR-4 free socket, Farnell part number 414-9993

 

All I could find in ten sec on the Farnell site, but I'm pretty sure they have free plugs as well.

 

As to cable, shielded dual twisted-pair is better. If you can get 120 ohm impedance, that's best!

[gareth]

XLR-4 free socket, Farnell part number 414-9993

 

All I could find in ten sec on the Farnell site, but I'm pretty sure they have free plugs as well.

 

And get decent quality (e.g. Neutrik) connectors. You'll be glad you did!

 

As to cable, shielded dual twisted-pair is better.  If you can get 120 ohm impedance, that's best!

Not quite correct. Scroller cable has two data cores and two power cores. The power cores carry the 24vdc power supply for the scrollers. If you make up scroller cables using data-type cable to carry the power you'll end up with problems - your cable won't be chunky enough to carry the required current (a fully-loaded output on a scroller PSU can be delivering current in the order of several amps if all the scrollers are moving at once), and on anything but short runs you'll get ludicrous amounts of voltage drop. If you're making scroller cables, use the right stuff!!

[Nicktaylor]

I have made my own cables and bought them ready made. By the time you have bought quality connectors and the cable, plus spent the time fiddling soldering what appears to be 10A cores into the XLR 4 you will be cursing. Yes it works, but is not worth the effort. From memory buying them ready made appeared to be not much more than the sum of the parts.

 

Nick

[Tomo]

The power cores carry the 24vdc power supply for the scrollers.

<{POST_SNAPBACK}>

Do all scrollers use 24vDC? Been considering building some DMX-controlled practicals that use a scroller PSU to power them - means that the cable to the unit can be much tinier.

I've been thinking about ways to make sure the unit doesn't care which core does what and I think there's a few, but if any use voltages higher than 24vDC it will make that design more difficult. (Heat dissipation is already an interesting problem for LED-based units)

[gareth]

Do all scrollers use 24vDC?

 

I believe most of them do, yes. All the ones that I've ever used certainly do.

[Stu]

The old Strand scrollers use 240v mains. I also believe some of the Wybron scrollers are wired differently if that makes a difference?

 

Stu

[Tom Baldwin]

Of all the types of cable termination that a lampy might be called upon to do, scroller cable is (to my mind, at least) by far the least pleasant.

<{POST_SNAPBACK}>

My money's on 125A 3-phase Ceeforms. Scroller cable's certainly no fun, but 125A 3ph feels like you're wrestling an elephant's trunk. With a disgruntled elephant still attached.

 

The old Strand scrollers use 240v mains. I also believe some of the Wybron scrollers are wired differently if that makes a difference?

<{POST_SNAPBACK}>

 

But surely the Strands don't put 240V AC down a 4 pin XLR?

I'm not aware of any scrollers which use anything other than 24V, and the pin-out for the 4-pin XLRs is almost standard; they agree on which pins are data, and which are power, but as Stu rightly says, the polarity (of power only, not data) is reversed on the Wybrons wrt everyone else. Nothing a bridge rectifier couldn't sort out.

I do know of a Strand scroller pinout which used 5 pin XLR, so as to be able to include a dedicated screen as well as data +/- and power.

 

I've been thinking about ways to make sure the unit doesn't care which core does what and I think there's a few, but if any use voltages higher than 24vDC it will make that design more difficult. (Heat dissipation is already an interesting problem for LED-based units)

<{POST_SNAPBACK}>

 

Do you mean polarity insensitive, or just downright indifferent to pinning? Given there's 4! combinations of potential pinout for a 4 pin connector, that sounds awfully clever... care to share?

[martinw]

I'm not aware of any scrollers which use anything other than 24V, and the pin-out for the 4-pin XLRs is almost standard; they agree on which pins are data, and which are power, but as Stu rightly says, the polarity (of power only, not data) is reversed on the Wybrons wrt everyone else. Nothing a bridge rectifier couldn't sort out.

The only exception to this is High End's Color Command and Color Merge fixtures which send 40V down 4 pin cable, using the Wybron pinout.

 

Martin

[Tomo]

Do you mean polarity insensitive, or just downright indifferent to pinning? Given there's 4! combinations of potential pinout for a 4 pin connector, that sounds awfully clever... care to share?

<{POST_SNAPBACK}>

Totally indifferent to everything.

 

A full-wave rectifier will give suitable power, DMX is a differential protocol and so once you've identified the two pins which supply it, the 'break' can be used to determine phase.

 

As to determining what does what, the +v input will be the one that has the highest voltage on it, and the DMX pins will fluctuate.

 

The hard part is finding ground. That's what I've been struggling with, as I can't be certain that the sheath is grounded or even connected at all.

 

I'm guessing I can use the fact that the DMX signal usually fluctuates between ground and 5v, and use the DMX lines as a temporary ground during detection.

Got to be careful to keep the current extremely low while doing that though.

 

On the other hand, if everyone agrees on which two to use for data and which for power, that's unnecessary.

[gareth]

The old Strand scrollers use 240v mains. I also believe some of the Wybron scrollers are wired differently if that makes a difference?

Strand ones? Hmm, that must have been before the Strand ColorCalls, coz they were just rebadged Rainbows (but Strand being Strand, and having to be bloody-minded and awkward, decided to swap the 4-pin connectors for 5-pin ones ....).

 

I do vaguely recall once using some scrollers which needed a 240v power input separate to the data input - I think they might have been some rather old Lightpaint ones, but I'm not sure.

 

I think you're right about Wybrons - the pin configuration is different on them (so scroller cable for Rainbows/ChromaQs is not interchangeable with calbe for Wybrons) - IIRC, with Wybrons the addressing is done at the PSU, and not at the scrollers themselves. My memory is a bit vague - the last time I used Wybrons was on an opera festival about 4 years ago. I do remember them being very tempremental, however.

[gareth]

Of all the types of cable termination that a lampy might be called upon to do, scroller cable is (to my mind, at least) by far the least pleasant.

My money's on 125A 3-phase Ceeforms. Scroller cable's certainly no fun, but 125A 3ph feels like you're wrestling an elephant's trunk. With a disgruntled elephant still attached.

Hmmm, 125A 3-phase isn't especially pleasant, I'll grant you that - but as long as you've got plenty of space in which to wrestle with it there's something kinda satisfying about working with cable as big and lumpy as that! And it doesn't have the same "fiddly factor" that scroller cable does - I guess I'm just cack-handed enough to be of the opinion that the bigger the cable is, the easier it is to work with! <_<

[Tomo]

IIRC, with Wybrons the addressing is done at the PSU, and not at the scrollers themselves. My memory is a bit vague - the last time I used Wybrons was on an opera festival about 4 years ago. I do remember them being very tempremental, however.

<{POST_SNAPBACK}>

You seem to be right.

Looking up the stuff for them, they've got some kind of proprietary bi-directional protocol between the scroller heads and the PSU, rather than repeating the DMX signal like everyone else does.

 

Seems that I needn't bother with the very clever bit - just assume Chroma Q pinout, bridge the power pins and detect DMX phase.