See title
Helps reduce the slack/droop/dangle of the wires. Makes for a nice, neat bundle instead of a rats nest. Helps with determining which wires are which if you need to troubleshoot.
I’m not an electrician, but I do all my own layout and decoder wiring. I don’t believe it’s necessarily about DCC, but the wires are conductors and they move energy from one point to another.
Maybe the better title would be, “Is There Any Reason To Twist DCC Bus Wires Together?”
Rich
If the wires are twisted, it reduces (or eliminates) induced false signals from one wire to another.
There are digital communication protocols like J1587 or J1939 that require the signal wires to be twisted, but I really do not think it is necessary in a model train DCC system.
But… it sure won’t hurt anything.
-Kevin
Twisting the bus wires loosely (or even keeping them together using cable ties) reduces the impedance of the bus. That is the only benefit to it.
That is the only benefit from twisting the bus wires together. The downside is a tight twist will create a capacitor, whose leakage currents can confuse any detection coils in use.
There is no possible way twisting wires will change the impedance in the conductor. Impedance is fixed (for the most part) based on the physical properties of the conductor.
The reason for twisting wires in any digital communication bus (I am most familiar with J1587 and J1939 (CanBus)) is to prevent a false signal from being induced into the bus.
This is caused by the magnetic field created as current flows. We could go through the right hand and left hand rules about field formation and collapse, but that is not necessary.
Anyway, twisting the wires lowers the possibility of INDUCTANCE, it does not change IMPEDANCE.
You might have just typed it wrong, but the distinction is important.
-Kevin
Impedance is a function of inductance. Reducing the inductance reduces the impedance because 3+4=5.
Bundling cables together will reduce the inductance, thanks to the mutual inductance.
the bigger effect is the loops created by twisting allow interfernce to be cancelled out down the length of the wire
Fifteen years ago when I started this layout I landed two leftover spools of 12G wire each with 300’ on them. There was a bit of a different clientele on this forum back then and I was criticized on this forum for using such heavy wire even though I paid very little for it compared to what I could have paid for a lighter gauge. I pulled the two lengths of wire down my driveway a 150’, stuck it in the drill, and had it twisted in seconds.
Now I am a bit of a [D)] when it comes to the electronics side of this hobby. While I can and have wired houses it was a little different than wiring a DCC layout. Being a very proactive type of person I started reading a lot and decided that twisting the wire was probably a good idea.
I have been having some minor issues with programming newer Loksound chips and spent the day reading about how signals get from point A to point B. I learned about the skin effect, something I have never heard of before. What caught my eye was how a signal was carried in stranded wire versus solid wire. There have been great debates on this forum when it comes to solid vs stranded wire and I have made up my mind about which is better for DCC.
Twisted buss wires, solid or stranded, number of feeders, and how far apart, all these seemingly little things on their own might never cause an issue but all together may result in less than perfect performance.
Proactive or reactive? Personally, I do everything to prevent problems that may occur down the road.
I know that in the Army, we used “twisted pair” wire on our field phones. I was told by our Battalion Signal officer that it eliminated cross talk between circuits. Not being a Signal Corps type, that’s about all I knew about it.
Being a big truck and heavy equipment mechanic for far too many years and being in the trench when electronic controlled engines and drive trains came out. I can open up a four inch diameter bundle of wires and tell you every pair of wires going to an induction probe. Every speed sensor had twisted pair wiring right up to the ECUs. There were four just in the transmission of a front loader. Two or sometimes three on the engine. Electronic controlled ABS could have ten or more. Repair of twisted wire had to be done right or codes would pop up. Especially with a cam sensor. Now trucks have more position sensors than you can imagine, all with twisted wires.
I build my DCC modules with a twisted buss for insurance. Peace of mind. Weather it makes a difference, I don’t know or care.
Pete.
“Interference” is a red herring in DCC wiring.
To really impact any crosstalk or interference takes a lot more math and effort than the average modeller would be willing to undertake. The nature of the DCC signal is aready a robust transmission method, so interference is almost a non-starter. If that were true, every AC wire in your house would be twisted to prevent radiation or reception of interference.
The main reason to twist, or even keep the wires close together is to reduce the reactive component in the bus impedance. Full Stop.
In comparison to a network cable, whose twists, wraps and how they are orgranized is carefully engineered to result in the desiried electrical characteristics for that cable’s application. Plus the addition of a shield to provide a path to ground for any induced currents.
so what is the effect of the “reactive component” for us model railroaders? why should we care?
what is the effect on performance? packet corruption, voltage drop, signal loss?
what is the quantitative difference between twisting and not twisting? how much better is twisting?
Me too! Were you around when the Cummins PACE and ECI systems were first put out? I would love to go back to 1988 and warn all the old techs that said they were too complicated to hold onto their butts, because you have no idea where we are going with this!
My first nightmare with a cam position sensor was on a CELECT+ M11. The cam thrust had worn to a point where when the cam was all the way forward the gap between the cam sensor and the tone wheel would excede 0.025" and the engine would lose good signal. It never induced a fault, and the only symptom was a miss under hard accelleration.
That was why I was refering to J1587 and J1939 in my previous answers. I found more than one owner-induced problem due to improper wiring harness repairs.
Same here. On the DCC layouts I have been involved in building,we always used twisted 12 TFFN AWG wire for the main bus wires.
If there evere were problems to troubleshoot, we would know it was not for lack of care during assembly. Being able to rule out possible causes prior to beginning troubleshooting is a real time saver, and good for peace of mind.
-Kevin
What is the reason to twist dcc bus wires together?
Answer: There is no reason to twist DCC bus wires together.
I have been running multiple trains on a large DCC-powered layout for nearly 19 years with 14 gauge solid copper untwisted bus wires with absolutely no problems. None. Nada.
I also started out with no snubbers, later added snubbers when they were in vogue, and now don’t use any snubbers. I had absolutely no problems with or without snubbers.
Home-based layouts just don’t seem to need any of that stuff that may apply to huge club layouts or other sophisticated electronic or electrical setups.
Rich
[quote user=“SeeYou190”]
wrench567
Being a big truck and heavy equipment mechanic for far too many years and being in the trench when electronic controlled engines and drive trains came out.
Me too! Were you around when the Cummins PACE and ECI systems were first put out? I would love to go back to 1988 and warn all the old techs that said they were too complicated to hold onto their butts, because you have no idea where we are going with this!
wrench567
Especially with a cam sensor. Now trucks have more position sensors than you can imagine, all with twisted wires.
My first nightmare with a cam position sensor was on a CELECT+ M11. The cam thrust had worn to a point where when the cam was all the way forward the gap between the cam sensor and the tone wheel would excede 0.025" and the engine would lose good signal. It never induced a fault, and the only symptom was a miss under hard accelleration.
wrench567
Every speed sensor had twisted pair wiring right up to the ECUs.
That was why I was refering to J1587 and J1939 in my previous answers. I found more than one owner-induced problem due to improper wiring harness repairs.
wrench567
I build my DCC modules with a twisted buss for
it’s unreasonable to suggest that because you’ve never had a problem that no one would ever have a problem.
Back in a 2014 thread on the same topic, you seemed to agree with me and others that twisting bus wires was not necessary.
https://cs.trains.com/mrr/f/744/p/228673/3411813.aspx#3411813
I did go on to say in this thread that home-based layouts just don’t seem to need any of that stuff that may apply to huge club layouts or other sophisticated electronic or electrical setups.
So, I think that it is reasonable to suggest that based upon my personal experience, it is unlikely that most home-based layouts would experience a problem with untwisted bus wires.
What I look for in threads about the topic of twisted bus wires is a summary of problems, if any, that do occur with untwisted bus wires. I emphasize “do occur”. In other words, do any model railroaders actually experience problems on their home layouts that are caused by untwisted bus wires?
Rich
On my layout (2 level HO 15x11) the bus wires were kept separate for ease of connecting all the feeders. DCC operation was fine for the 12 year life of the layout.
This “twist or don’t” topic came up then, and likely a handful of other times without (IMO) firm resolution.
That said, I have a simple question - which I don’t believe has been asked before…
Has anyone every experienced any “crossfeed” problem from twisting or not twisting their wires?
crossfeed from what? the other DCC line?