I'm trying to hook up a set of DB4 Color Blocks. The short little cables that came with them has a pair of 22 ga wires and a pair of 14ga wires. If you can recall, how critical is that configuration? I found some shielded 16/4 here locally, but not that odd configuration. I did find a place online but they were really proud of it.
Thanks
@lilricky I have
ZERO personal familiarity with your units but while you're waiting for a more knowledgeable poster I'll offer a few thoughts. I strongly suspect you're going to find the following: The 16
gauge pair likely conduct
power and are most likely twisted as a separate pair. The 22
gauge pair most likely carry data. The two pairs will be individually twisted, possibly in different directions and / or different number of twists per
foot to minimize cross-talk. Are either of the pairs shielded? If so, the
shield would most likely enclose the smaller 22
gauge data pair, again to minimize coupling / cross-talk.
If there is a
shield it may be connected at one or both ends and most likely to whichever contact offers the lowest
impedance path to
ground and / or a metallic enclosure.
There you go Sir! My best pure guesstimates gratis and worth every penny I've charged.
Further thoughts: How long are the cables you have? How long are the cables you're hoping to fabricate? Twice as long or twenty times as long?? Do you have enough of your short cables to couple them together and test the longer length you're hoping to acquire? How expensive is the 16 / 4 cable with overall
shield you've located locally? Are you able to
purchase only the length you need or is it only available to you in 1,000' put-ups? Can you source the connectors you'd require to fabricate the longer cables you desire? How badly do you want your longer cables? How much do you value your time?
I suspect you see where I'm going. How much have you got to lose by making a cable, metering it carefully for correct connections, pin-outs and absence of any unintended shorts and giving it a go?
One last thought from my past for you.
Back in the early 1990's I was playing IA Head Electrician for a scenery and automation shop fabricating custom scenery for Canada, Broadway, London England's West End and even one opera set for Red China. Our shop provided the first automated AC Servo drives on Broadway when all the other shops were still doing DC drives.
Here's the pertinent part of this novella:
The manufacturer of the motors, resolvers and motor-drives we were using were more accustomed to controlling precision turret lathes and similar automated machinery often associated with CNC routers and automobile assembly lines. Based on their experiences in those environments they were recommending maximum cable lengths of 15 to 20 feet between their ACservo motors with their internal resolvers and their drive electronics. In their user
manual they suggested contact the factory prior to considering any interconnecting cables longer than 25 feet.
The factory laughed A LOT when we contacted them asking about 50
foot cable lengths. This was for our first application in Toronto.
We worked with our dealer, fabricated our own 50
foot cables and perceived ZERO problems.
(There is a considerable difference in repeatably precise positioning required for a precision turret
lathe machining automotive crankshafts and a
system positioning theatrical scenery across a 50 or 60
foot proscenium.)
Over the course of approximately 100 automated AC servo drives in a dozen or so productions we'd extended our custom cables to 100' for many of the 24-ish automated AC servos in the first production our shop built of The Who's rock opera "Tommy". When we landed the contract to
build "Tommy" again for Offenbach / Frankfurt, Germany in 1995 we visited the
venue then headed home to fabricate our first 150' cables. One year later we were building all of "Tommy" AGAIN this time for London's West End, I believe "The Shaftesbury" was the
theatre. My memory's getting a little hazy on the name of the
theatre but I definitely remember having to fabricate 200' cables for the
venue, back
stage was tiny but we had drives everywhere from barely below
grid level to down in the basement
trap room below SL but all of our drive racks were stacked and clustered on a small
mezzanine high above
stage level on SR. Don't ask me to remember if SR is PS or OP (Prompt Side or Opposite Prompt) as we had to pre-label everything prior to shipping to England.
Our AC servo drive dealer was impressed and the manufacturers were incredulous but we kept on buying their drives, rarely ever requiring factory service and generally being happy campers.
Getting back to one of my theories for successfully making ever longer cables.
We were purchasing our raw cables wholesale, usually in 1,000
foot lengths and often in 5,000
foot lengths.
Every time the owner of our company'd get a lead on a new production and ask if I thought we could do cables of an even
longer length, I'd neatly and correctly install connectors on the free end of a reel, spool off a length
twice as long as our owner anticipated needing, chop the cable and temporarily add connectors to this double length, connect a servo motor and resolver to its drive electronics and see if, how well, it worked.
- If it worked flawlessly GREAT!
- If there was the slightest hint of a problem, I'd chop the cable in half down to the length the owner was requesting and test again. By using this approach our cables successfully got ever longer and longer until we were shipping 200' cables to Great Britain with complete confidence and zero loss of sleep.
Back to my point @lilricky What have you got to lose by trying?
Epilogue: The cables connecting most of our motors to their drives were stranded 12
gauge spiral twisted 4 conductors with an overall foil
shield and stranded drain
wire to minimize radiation of the drive's bridge
power from escaping too far and annoying the sound lads with their wireless mics and keep our drives from bothering the pick-ups on the
electric guitars.
The cables linking our resolvers to their drive electronics were a smaller
gauge but again stranded and with an overall foil
shield to minimize the intrusion of the sound lads' RF and lighting
dimmer hash into the sensitive positioning input of each drive's drive electronics.
In addition to our bridge
power and resolver cables, each automated axis also had a cable for a DC operated mechanical brake which was energized to
release and de-energized to apply the brake. Normally the drives maintained their positions but the brake was de-energized and applied whenever the drives were being shut down and / or the
E-stop applied. Experience taught us that gravity isn't your friend if you
power down an AC servo while it's supporting several hundred pounds of scenery high overhead. The DC brake cable was another stranded twisted foil-shielded pair, this time to suppress radiation each time the brake was applied and the sudden collapse of the brake's magnetic field resulted in an intense
spike similar to your grandfather's Ford model T's ignition coil. Of course we had suppression diodes across all of the DC brake coils as well for good measure.
Each automated axis also had a fourth cable which was normally four conductors, a common and one
conductor for each of three mechanically operated rotary "hard" limit switches, one for each absolute end of travel and the last to provide an accurately repeatable homing reference location.
There you go
@lilricky More than you NEVER wanted to know about automated AC servo drives and their associated control cables. All the best with your longer cables.
Toodleoo!
Ron Hebbard