I am fairly new to the hobbie and as i was reading some of your posts on DCC controller ?'s i saw that you were saying something about twisting? or turning the bus wires. please explain what you mean.
Dear tford,
Until Jim responds, Google "twisted pair" or "twisted pair wiring".
Wiki has a pretty good write-up.
Hope this helps.
Sincerely,
Joe Satnik
You basically twist your bus wires together, one around the other, 3 or 4 times per foot of bus. Keeping the bus wires close together helps the DCC signal reach the far end without degrading. It is not really necessary on a small layout (one or two sheets of plywood) but when you start getting larger, it may help. I am not convinced that it is absolutely necessary, but it is easy to do when installing bus wiring and devilishly difficult afterwards.
Jim
Thanks Jim & Joe, I am so glad I found this form Ive learned so much just reading what everyone has to say on so many different subjects.
Thanks again and I will be asking a lot more stupid guestions.
The main effect of twisting the wires together (twisted pair) is to reduce the electromagnetic noise that the DCC system picks up. The signal level does not change, but there is less back ground noise on the line for the decoder to try to "hear" over - just like a noisy telephone line.
As Jim says, length does make a difference, and the shorter the lines are, the less susceptible they are to noise.
would 30' of 14 gauge copper stranded be safe from noise?
Quote from: pdlethbridge on October 03, 2009, 12:12:33 AM
would 30' of 14 gauge copper stranded be safe from noise?
It entirely depends on the environment. There is always noise picked up, it is a matter of the amount. Making the bus a twisted pair (as explained by Jim above) is free insurance - hopefully it is not needed, and if you do it at the start, it is easy - if you have noise problems later; it is a do over.
stranded vs solid makes no difference.
Hey Jim Banner, will Broadway Limited Imports locomotives work with EZ Command or will they require different equipment? Thanks for any help in advance.
Good question, Alex. I don't own any Broadway Limited locomotives to test, but as far as I know, their decoders are close enough to NMRA conformance that they should work. If you want a definitive answer, start a new thread and someone who owns both an E-Z Command and a BL locomotive will be able to answer your question.
Jim
Quote from: Alex Butner on October 06, 2009, 05:57:32 PM
Hey Jim Banner, will Broadway Limited Imports locomotives work with EZ Command or will they require different equipment? Thanks for any help in advance.
You could run this past the folks over at the BLI forum, they have a factory rep who follows their forum daily.
http://www.broadway-limited2.com/forum/index.php
My gut reaction is yes they will work, but I have no idea how the custom sound functions and the like might be restricted by the EZ command. Also are you asking about Blueline, Paragon, or Paragon II locos? There are a number of BLI product lines and they use different DCC setups. Blueline locos have no built in DCC but are DCC ready. I run a selection of BLI loco's but not on EX command.
Jim,
I am working on a railroad with two other guys and one of them is the
"wiring" guy. He is tapeing the buss wires together every few feet, primarily to allow the busses to be pulled thru the bench work easily. Does this tapeing of the wires accomplish the same thing as twisting the wires? Also, I have a fairly large railroad and knew nothing about the twisting and everything seems to run fine. What would I see differently if I had twisted the wires?
I have the same question Bob has. I have one buss line that is about 55 feet long and is not twisted. It would be the devil to try to twist it, but fairly easy to tape it every few feet.
Gene
usually depends on buss length. people like to argue aboutthis.
http://www.google.com/search?hl=en&q=dcc+buss+twist&btnG=Search&aq=f&oq=&aqi=
Taping the wires together will reduce noise radiation and pickup although not as much as twisting them. As far as ringing is concerned, it should work equally as well. Ringing occurs on the leading edges of fast pulses when a transmission line is inductive while rounding occurs when the line is capacitive. To make a line more inductive, make it enclose more area i.e. move the wires apart. To make it more capacitive, put the wires closer together to decrease the area between them and to also raise the capacitance between them. If the line were perfectly tuned, the inductance and capacitance would cancel one another and the corners of the rectangular waves would have neither spikes nor rounding. If you have the choice, a bit of rounding is better than spikes. Most decoders measure the time the pulses are above or below some level, so a bit of rounding does not matter. But most decoders have an absolute maximum voltage limit around 30 volts so spiking to 2 or 3 times the height of the pulse can kill a decoder. Ringing gets worse and worse the farther you get away from the command station. Two ways of dealing with it is to put a limit on bus length or to add snubbers to the end of long busses.
On small to medium layouts, there is rarely a problem. On large layouts, there can be. Every time I hear of someone taking his/her locomotive to their club and bringing it home dead, I have to wonder if that was the problem, particularly when they have been running their locomotives on their own layouts for a long time with no problems.
Needless to say, some types of decoders are more sensitive than other types of decoders. And within a type, there will be random variations in sensitivity as well.
Bottom line, if your layout is working well, don't pull out the wiring just to twist your bus. But taping the bus wires together every foot or two sounds like an excellent alternative to try if you are having problems.
Jim