spiral video cables

[Jesse Meehl]

Hello everybody,

 I am looking for a spiral(like a phone cord) video cable to run down my post. I was wondering what type of cables(S-video, bnc, ect)everybody is using and where they got them. Did you have them custom made? Do they also provide power to your camera? Anything else you can tell me would be appreciated.



jesse

[Phil Rhodes]

This is one of the few things about commercial rigs that I simply don't understand. It is a fact that, unless they're using gold-cored cable or something, there is not enough physical space for big enough cables to carry the current required by, say, the notorious Arri 435 on startup. A sled designed to cater to hi-def video monitoring may have three or four video lines, as well, and there is a certain minimum diameter required by properly balanced video cables. They are clearly relying on diversity (The fact that the power loads are not constantly very high) and the fact that video will stand short transit down basic shielded lines.



There are various camera and particularly ENG-style DAT to camera hookup cables with multiple screened cores. Look around and find something that's suitable. Otherwise, if you can only find it in a straight cable, you can try the technique whereby you wrap it around a pole and soften the sleeving with a hot-air gun.



One electronics design I ran up needed three high current power lines, two low current or switching lines, and three video lines.



Phil

[wfrancom]

It's hard to find, but it does exist. There is a shop about 2 miles from me (Salt Lake City, Ut) that sells spiral wound multi-cable that comes in 3, 5, 8, and 10 wire capacities.It's a thicker wire, but I don't know of it's ability to handle the power loads as well as transmitting signal. You can probably get two or three lengths of this cable inside a 1 1/2 inch post comfortably, with no jamming. If you're just looking for something to get up to 15volts of power to the camera and a signal to your screen, this is the cable you probably need. Email wfrancom@yahoo.com if you want me to ship you some.

[Charles King]

What price are we looking at?

Charles King

       

[Jon Collins]

Hi Guys,

You can have any type of sprial cable made with any combination of cores, but your quanities would be too low, and the cost would be too high!!!!

Do you want to see how Steadicam do it on the ultra http://www.steadicam.com/manuals/ultra/Page16Postsandclamps.pdf

Two pieces of elastic cord running down the inside of the post, then select your cables, nice fat ones for power, maybe some extra flexiable test lead wire, and some thin flexiable video coax's, spiral them around and secure with tie wraps?

Comments

Jon

[readw]

That looks like a great way to get around the problem.

Warren

[Wade Francom]

Sorry about th delay in my response to your  querry, Charles. I check this site at least two or three times a week, but don't venture into the forums too often. As far as the coiled cable is concerned, it's basically 5-wire CB radio cable. The wires are 20 gauge insulated, copper braided wire. One is braid shielded. The coiil diamter is small enough that you can fit another cable run down a 1.5" to 2" post without jamming. I know the video and audio signals will be fine, but I'm not sure if the thin gauge wire is enough to handle the power load. I may run a separate single power wire in the Steadicam fashion illustrated in this post, with bands and zip-ties, and the coil runnin through the center of it.

Any ideo how much load a 20 gauge wire will handle?

Wade Francom

[Wade Francom]

I forgot to state the price I got them at. I get them at a shop locally here for about $6 a cable, unterminated, with a max reach of 6 feet.

[Kevin Clark]

Wade,

I don't know what camera you are powering but for the sake of argument I'll assume it requires a 12v supply and draws something like 1.5 amps. -  which is ok for #20 braided copper wire which is 0.03196118 in diameter. On a run of 6 feet you would have about a 0.2 volt drop giving you 11.8 volts on the load end which is well within most operating paramiters. Using #18 wire on the same 6 foot run would only drop 0.1 volt - twice as efficient.

Kevin

[Jon Collins]

Hi,

Yes, you would get a volt drop if the power cables are too thin, but more worrying, that volt drop has to go somewhere, and that somewhere is heat. If you pull too much power down too thiner cables, they will heat up, melt, or catch fire!!!! (only in worst case). I don't know what camera's you intend flying, but a pro camcorder like a DSR570 would take about 2.5A fully loaded. This is why I said use some heavy test lead wire as its nice and flexible, and can take some decent juice! Also, remember to put some fuses in the system. If your chosen feed to the top of the sled is capable of carrying 5A say, put a 5A fuse in the base, just in case you get a short, or a camera fault. Lead acid batteries and similar can deliver very high currents!!!

Jon

[Wade Francom]

Thanks for your input, guys! I love this forum!

I have settled on a hybrid wiring plan. I think I'm going to run a 5-wire spiral cable w/ 20 gaugewire for low voltage needs, and a bundle of 18 gauge wires for power in the same manner as the Master Series post (rubber bands, top to bottom, with wires spiral wrapped around them).

This is where I need everyones help. I'm no electrical engineer, and I don't want to do anything I'll regret. I'd appreciate as much input from anyone, no matter how stupid I sound.

Here's what I was thinking:  12v, 7Ah battery at the base w/ room for another 12v 7Ah battery linked for 24v needs. Split the power into 3 runs, one 24v/12v switcheable, another straight 12v (monitor), andthe last adapted to 9v for my XL-1. The 24v/12v wire and the 9v wire ran from a donkey box at the bottom to a box at the top of the post. The 24v/12v wire and the 9v wire have inline switches, as well as an inline switchfor the monitor supply, and a main switch for the whole thing.  The spiral cable is for 2 wireless mics, or can be adaptedfor stereo or other needs. I'm still debating on combining the video signal into the spiral cable, or to run a thinline coax with the power bundle to the donkeybox.

Anybody have any input? Like I said, I don't really know what I'm doing, so treat me like I don't know anything. I won't be hurt. I'd rather get help and do it right than do it alone and screw it up.

Wade

[readw]

I don't see any advantages in running a 9v supply for the camera.  It seems to add additional complexity and you already have the batteries available on camera why not just use them and keep the 12/24v circuits separate for the accessories?   Maybe I am missing something here?

[Jon Collins]

Hi Guys,

A couple of things then....

The reason for powering the camera from the rig is so that you don't have the weight burden of the batteries at the top of the rig. I suspect the batteries on the XL1 are relatively light, but with a pro camcorder a decent capacity battery could weigh 2kgs or more. If you plan on having that switchable 12/24v supply, you may want to have a good think first, just in case the switch was to get knocked and you blew a 12V accessory up with a good belt of 24V!!!!  Maybe not have a switch, but have a different connector for 24v or have a 4 pin connector with 12v on 2 pins, and 24v on the others, and use a special lead?

With reference to the 12v 7ah batteries, have a good think about the weight distribution and the balancing? A 12v 7Ah battery weighs about 3kgs? if you have  an XL1 at the top,  a post of say 750mm, and 1 or 2 batteries and the monitor at the bottom, you want the rig to balance with the gimbal up towards the top? if the bottom is too heavy compared to the top, you wont be able to get the drop time you want?

Jon

[Wade Francom]

It's been a couple of months since the last post here, but I'll voice anyway.

Jon had it correct. I'm building a rig that is capable of handling my camera, an XL1 (9v), all the way up to the big guns with multiple voltages. Even though I will be running my rinky-dink 9v XL-1 alot, I wanted to pre-wire a post with multiple voltage runs to the top & bottom boxes.

And thanks for the recommendations Jon. I am going to run each voltage on its own circuit, with some type of a switch to ensure only one circuit is in operation at a time.