mechengr wrote: Have read that power buss and cab buss wiring runs should not be too close to each other.Will be using Digitrax Super Chief DCC system.How much separation should there be to avoid electrical interferences? Thanks for your suggestions/recommendations.
Have read that power buss and cab buss wiring runs should not be too close to each other.
Will be using Digitrax Super Chief DCC system.
How much separation should there be to avoid electrical interferences?
Thanks for your suggestions/recommendations.
As stated above, twisting the power bus wires at 3-4 twists foot is not a bad idea. The DCC bus signal is a differential DCC signal where each lead is 180 degrees out of phase with the other. The signal is not large enough, the frequency is low enough and the impedence of the Loconet bus is low enough that it is just about impossible to radiate a signal from the power bus to the Loconet bus. Even so the voltage level on the Loconet would ignore any induced voltage. The main advantage of twisting the power bus is to cancel out signal distortion noise on long runs. Another thing sometimes done is to terminate a long bus with an RC network to soften the rise time overshoot of a long inductive run. Twisting can help avoind the need for this. In any case, for smaller layouts, none of this ever really becomes an issue.
Engineer Jeff NS Nut Visit my layout at: http://www.thebinks.com/trains/
Looks like the original Q was answered but I thought I'd chime in too anyway. Been reading my NCE PowerCab manual and it says if you're including a cab buss to put it at the front with the power buss at the back to avoid cross-talk. It suggests giving the power buss wiring a 2-3 twists per foot of run. Dunno if that adds anything to the discussion but thought I'd add it since it's from an 'official' source - I imagine they've done quite a bit of testing on the subject.M
Richard
Another thing that some may not be aware of. You can service two tracks within a power district with 1 power bus.
For example I have two main lines that run together around the outside of the layout for some continous running while doing things in the yard or industrie area. Since both main lines comprise a power district I have 1 power bus running under the two tracks, no problems what so ever.
The key here is feeder distance,as long as your feeders are kept short (about 10" max) with #20AWG your ok.
For example: If you have a yard thats 20" wide you may be able to feed it with 1 power bus if you run the bus down the middle of the yard, 10" feeders left, 10" feeders to the right. If it's 36" wide you would want to run 3 busses to keep your feeders short, trust me it's important to do so. Do not connect the busses at the end of the line/yard etc. This can under some cercumstances cause DCC signal distortion/reflection. Remember, your DCC operating signals are imbeded in the power bus. Not to be confused with Loco Net or other signal data busses.
Jules
You guys are making too much of the original question. Yes, twisting the track bus is good practice, but that's not the OP's question.
Mechengr, it is a recommended practice that there is a separation between then track bus and the cab bus - Loconet in your situation, especially on larger layouts with longer runs. As stated in ONE reply it is recommended that when the two cross it should be at right angles. The distance between the two need only be a few inches, such as 6 - 9 inches. This is done to prevent crosstalk between the two bus lines. The idea is to avoid running both buses as part of the same wiring bundle. Instead, run your cab bus at the front of the layout right behind the fascia and run the track bus towards the rear or middle of the layout. If you don't, it doesn;t mean that you'll suffer terrible problems, but as the length of run increases, so does the likelihood that interference will happen between the two bus lines.
The use of shielded cable for the cab bus will help with the crosstalk problem.
Here's the scoop as I understand it: if your two power bus wires, which necessarily also carry your DCC signal superimposed on, or embedded in, that current and voltage, are running for extended distances around a very large layout, say 40 feet and up, you will be well advised to twist the two wires every couple of feet or so. I don't think this applies to you...right?
Your question relates to what might happen if the spiral cord carrying your throttle (cab) inputs that you dial in on your handheld throttle is running close to your main bus. Answer...nada.
I defer to the learned gentleman who seems to know quite a bit about the technical stuff as to what you might be cautioned over when your loconet or similar cables are running close to, and perhaps largely parallel to, the main bus. It seems he is sayng you may want to wrap your bus wires around each other for really cheap up-front insurance and keep your loconet cables at right angles to the bus whenever possible. I hope I got that right, but he is sure to set us straight. As far as I know, though, you don't have to fear anything over your cab's spiral cord.
Power busses/track buss usually black/red should be twisted.
Cab/signal is they same thing. Cab wiring should not be run right next to power wiring stuff. As i said, if you must cross a power bus with a Cab bus or any signal wiring it should be at right angles. This minimizes any interference between the conductors.
As I stated above, CAT cabling is better than any flat cable. I use CAT 5e for my Loconet because I have 2 1000' almost full reels of the stuff. It hase much better Data integrity than flat cable. I installed all manner of computer and tel/ signaling systems. Retarded now, but still got CAT cable!
JulesB
Sorry - didn't mean to confuse by my wording. I am speaking of physical separation of the cab buss (for Digitrax with Loconet, usually a "phone line" type wiring) from the power buss for the track. Am not speaking of twisting the two together in any manner.
My reading about this was quite time ago when I first began looking into using DCC, and I may have misread what was written about power buss and cab buss. Possibly it was referring to signal buss, not cab buss.
It's not UNIQUE to Digitrax or anyone elses system!
What it is is good wiring practice gleaned from years of experiance.
I've seen problems crop up that I had to correct because those pratices were not followed. Furthermore if you used flat cable rather than CAT 5 your experiance may have been different. Shielded CAT would also make a possible difference.
Why not advise the guy with proper concepts???
This may be a problem unique to Digitrax or some other systems, but on our 20 x 40 foot HO scale club layout the track power buss and cab Cat V cabling run parallel to each other with no crosstalk or interference problems.
Twist your power bus wires, you don't have to go crazy, 3-4 twist per foot is fine.
When crossing any power buses, even power to/from wallwarts etc. Allway's cross at right angles, do not run signal wiring next to or parralel to any wires carying a higher voltage than the signal wire. Some guy's run 110 to plug stuff into. Keep those on 1 side or the other of the layout.
Keep signal wiring away from flourecent light fixtures, be it computer network or train signal, loco net or other wise.
Computer Network wiring (If you use Railroad & Co) has a built in twist. Like CAT 5e-6 cable. The reason is it's required to some time run dozens of CAT cables together. The twists keep down Cross Talk, they don't interfere with one another. I had to run over 60 CAT cables tied off in a bundle through a AC duct one time. No problems!
I don't get the strong feeling that both persons have interpreted your question the same, or else I have misunderstood. You are not talking about winding the twin bus wires and also winding the twin cab wires due to possible induction problems...? If you are, then the one with the images shows what the common insurance against induction is. Wind the longer runs of any DCC power bus. If you meant that the cab wires should be well separated from any bus wires, I haven't heard that it should ever be a problem, poximity or not, so that would make Art's answer more germane.
ARTHILL wrote:I have read lots of answers, but where mine are even twisted together, I have no problems. Remember, the Digitrax cables for their loconet are connected in a single casing.
I agree that twisting the pairs works well, especially one some of the very long runs. On a small layout just keeping them separated a few inches should be fine.
This is on a large club layout where we have some runs of up to 60'
The suitcase connectors and the twisted pairs have worked flawlessly for many years now.
Modeling B&O- Chessie Bob K. www.ssmrc.org