DCC bus wires - full loop?

[Lu4472ke]

hello everyone

 

I am having trouble with DCC bus wires, more specifically the fact that they are not a full loop, and have some form of return in them. can they be a full loop? can I just solder the ends of the wires together?

[RAF96]

Not recommended to have it looped like a household ring main.

It is recommended you fit bus terminators on the open ends.

[Crosland]

hello everyone

 

I am having trouble with DCC bus wires, more specifically the fact that they are not a full loop, and have some form of return in them. can they be a full loop? can I just solder the ends of the wires together?

 

What do you mean by "some form of return"? How are you measuring the signal?

 

What size wire are you using? How big is the layout?

 

Linear, T, star, closed ring topology will make little difference if the wiring is up to scratch in the first place.

 

No harm in trying a loop. If it makes a difference then that is a strong hint of some other, underlying problem.

[traction]

Not recommended to have it looped like a household ring main.

It is recommended you fit bus terminators on the open ends.

 

If you have an oval of track, the track is already a loop so having the bus wires as a loop wont make any difference.

Same with bus terminators I've never fitted those and never had a problem.

 

Its one of those things that someone has mentioned and it seems to have stuck, I've read comments about not having a loop and fitting terminators but also read you can have a loop and you don't need to fit terminators.

 

My first point still stands though, if you have an oval of track then the track is already a complete loop so can't see why having the bus wires open ended will make any difference.

 

One day someone will actually do a proper test and show the actual results so we can all know once and for all what the ideal is, I've had loop bus wires on all of my layouts and all has been OK.

All of my layouts are very small though as I think this may have been mentioned of maybe causing a problem.

 

Cheers

 

Ian

Edited February 6, 2018 by traction

[Dagworth]

There is no need for terminators, where would you stop? One on the end of every siding? Every track section? 

 

If you have to fit terminators to make things work then you need to look far deeper at your wiring because you've got a bigger problem that needs to be solved at source. 

 

The only people recommending terminators will be people making money by selling them.

 

Andi

[WIMorrison]

Have a look at this thread, the answer is towards the end of it

 

http://www.rmweb.co.uk/community/index.php?/topic/104962-cobalt-ip-digital/page-2&do=findComment&comment=3034682

Edited February 6, 2018 by WIMorrison

[Brian]

There is no need for terminators, where would you stop? One on the end of every siding? Every track section? 

 

If you have to fit terminators to make things work then you need to look far deeper at your wiring because you've got a bigger problem that needs to be solved at source. 

 

The only people recommending terminators will be people making money by selling them.

 

Andi

Biggest load of uninformed tosh I have read in ages!

 

Firstly they are NOT Terminators They are Filters!  So get your facts right from the onset.

Secondly, I don't make or sell them, but I do know through many users and on my own layout too, they actually work!! 

Uninformed opinions are really extremely unhelpful to the many! 

 

While wiring/bus corrections can help, they do not overcome short circuit spikes induced onto the bus pair or poor quality DCC signals sent from the command station! Both can lead to decoder issues and with shorts possibly resetting of the decoder.

The filters simply help remove the spikes generated!!!

 

I recommend their use as they do not interfere with any DCC system, but can certainly help!

 

I don't make or sell them, so there is absolutely no gain financially or any other way for me as inferred!   I just know they work well and I recommend them if DCC problems as outlined are present.  

Edited February 7, 2018 by Brian

[RAF96]

I have three closed loops fed by loop to loop and radial feeds corner to corner.

 

i was having uncommanded sounds from locos sitting on track.

 

I cut the loops at a rail join to Break the closed loops and I still get the odd horn toot or odd spot sound playing.

 

Nex step is to fit RCs across the rails. By the way you would be hard pushed to make money from these as they cost pence to make.

 

I dont think it is practical to sit with a scope on track waiting hours for the odd spurious signal to occur and hope I catch it. Suggestions for how to capture such data welcomed.

 

 

Rob

Edited February 7, 2018 by RAFHAAA96

[Dagworth]

Biggest load of uninformed tosh I have read in ages!

 

Firstly they are NOT Terminators They are Filters!  So get your facts right from the onset.

Secondly, I don't make or sell them, but I do know through many users and on my own layout too, they actually work!! 

Uninformed opinions are really extremely unhelpful to the many! 

 

While wiring/bus corrections can help, they do not overcome short circuit spikes induced onto the bus pair or poor quality DCC signals sent from the command station! Both can lead to decoder issues and with shorts possibly resetting of the decoder.

The filters simply help remove the spikes generated!!!

 

I recommend their use as they do not interfere with any DCC system, but can certainly help!

 

I don't make or sell them, so there is absolutely no gain financially or any other way for me as inferred!   I just know they work well and I recommend them if DCC problems as outlined are present.  

So, my reference to terminators being useless was correct then...

 

If they are filters they are there for a totally different purpose. Terminators are intended to stop data reflection on the end of the line in RS485 applications and are irrelevant in DCC power buses, filters do a totally different job and I can see that there *MAY* be a use for them. My point on terminators was in reference to reply no 2

 

 

It is recommended you fit bus terminators on the open ends.

 

Please withdraw your nasty "tosh" comment

 

Andi

[Brian]

The only people recommending terminators will be people making money by selling them.

 

Andi

NO, I will not remove my comment unless you remove yours. Which is totally outrageous! Edited February 7, 2018 by Brian

[Dagworth]

NO, I will not remove my comment unless you remove yours. Which is totally outrageous!

Terminators = not needed, no one should be recommending them

 

Filters = maybe

 

my comment is correct

[Enterprisingwestern]

All this animosity over 2 wires!

 

MIke.

[SHMD]

On a different tack, what are the components/circuit for the "Terminators" and the "Filters" parts?

 

Are we talking of the proverbial 100R + 100nF pair in series for both?

 

 

Kev.

[Mod3]

All this animosity over 2 wires!

 

MIke.

 

Which will be snipped if things don't lighten up.

[Brian]

Filters for a DCC bus are a resistor of nominally 150 Ohm at 2 Watt and a series 0.1uF ceramic capacitor. The resistor value can be lowered to between 100 Ohm to 150 Ohm depending on DCC rail volts, but nominally 150R will be fine for most uses.

[russ p]

Where do these resistors go its the first I've ever heard of them

[Brian]

In series with the capacitor and the lot across the bus wires. 

Typically at the ends of the bus wires but could be along the bus wires run if necessary.

For more details see... http://www.brian-lambert.co.uk/DCC.html#On

[russ p]

I'm now wondering if I've done the right thing going DCC I haven't started wiring yet but it looks SO complicated I thought it was to make wiring simpler?

Got a nasty feeling my large layout could end up a diorama!

[Enterprisingwestern]

I'm now wondering if I've done the right thing going DCC I haven't started wiring yet but it looks SO complicated I thought it was to make wiring simpler?

Got a nasty feeling my large layout could end up a diorama!

 

It's as complicated as you want to make it.

It really is simple, take it from a luddite/technophobe/clueless wirer/bodge artist etc etc.

 

Mike.

[Enterprisingwestern]

It's as complicated as you want to make it.

It really is simple, take it from a luddite/technophobe/clueless wirer/bodge artist etc etc.

 

Mike.

 

Which bit are agreeing with Andi, the first or second line?!!!!!!!

 

Mike.

[russ p]

What happens if you don't have all the Gubbins? I was intending to have three power districts fed from a Hornby elite with a booster and have two reverse loop modules on one leg of a double track triangle

Will this work? Pictures on my layout thread

[Dagworth]

Which bit are agreeing with Andi, the first or second line?!!!!!!!

 

Mike.

Both, you can make it simple, or you can go complex. Both options are valid. It depends on what you want from your layout. With something like Ravensclyffe it gets pretty complicated, 100 or so track circuits, 5 power districts, three reversing sections, computer control of points...  Whereas Bow Locks has none of that, just two wires.

 

Andi

[Enterprisingwestern]

I understand that Andi and I'm with you there, I was just having a light hearted jest at you agreeing with the second part of the second line, you know me too well!

 

Mike.

[SHMD]

I'm now wondering if I've done the right thing going DCC I haven't started wiring yet but it looks SO complicated I thought it was to make wiring simpler?

Got a nasty feeling my large layout could end up a diorama!

 

It's different.

 

DC is one kind of electrickery and requires specific wiring (depending on layout), switches and controllers to run it/control it.

 

DCC is another kind of electrickery which requires a slightly different wiring regime (usually continuous but rated at much high current ratings), plus extra electronic gadgets and display/controllers.

 

The rest is a rich mix of much posturing of falsely remembered headlines made by sales/marketing applying general/simplistic rules to all situations and modellers who vehemently propose that their wiring solution is the answer to all ills.

 

Good luck, but do ask here as we (may) come to a consensus for you particular situation.

 

 

Kev.

[Phil S]

Back in Zero-1 days, I did experience the equivalent problem for which the added-filters are proposed.

I had IN EXCESS of the anticipated 25 accessory modules on a layout about 5m square around a loft, on 1.5 levels.

I found that the waveform shape deteriorated as the last (excess) modules were added - and this could be resolved on either / both of 2 ways:

1/ Reduce the length of the Bus Wires ( ex-30A ring main running separated beneath the layout with numerous droppers to the connected track paths above)

or 2/ Remove the filtering capacitor Hornby had placed across each Modules input on the extra modules ... either allowing the waveform shape to recover, as observed on an oscilloscope which I used to monitor the system (along with a 5A Moving Iron Ammeter)

 

With the wider addressing range of DCC decoders (after early-day restrictions) I would suggest that the system is designed to cope with more locos and decoder modules in-circuit than Zero-1 was  (16 locos and 25 modules - although they did say that modules could be overlapped, sharing addresses, which is what I was doing to operate 130 points and signals from 99 codes.

I don't know if any manufacturer HAS actually tested their system with the 'maximum' numbe rof modukes/locos .. I think it unlikely

I expect that some designs of Amplifier/Output stage are better than others at driving into the unknown and variable load of the modern model railway layout - complicated by the additional introduction of segmentation by PSX's and the like. - therefore it may be that SOME MAKES or MODELS of controller have a greater benefit (or need) of added filters - but I would not expect this to occur in 'smaller' layouts:

I have not needed to add any on my 00 or H0 or G scale DCC layouts - provided the 'coin test' shows that conduction is good in all parts.

 

HOWEVER - if TRACK GAUGE is ALSO taken into consideration - a large change in the balance of power distribution (track v bus wiring) takes place due to the differing rail cross-sections and materials used   Eg Nickel Silver or Brass and  N > 00 > 0  > G - in the latter, in the garden, with longer lengths than likely in 00/N,  heavy copper bus bars are a good idea (I use High Power Loudspeaker Cabling - Low Voltage but high current, and cannot br confused with Mains cabling!!! ), but the cross section of the track is also large ..... but over the years the fishplates will increase resistance unless treeated with Graphite/Coppr Grease - swinging th ebalance back to the bus wires as main conductor.

 

I have no experience of tunning N in dcc   (but I do have 009/H0e in DCC with long runs, indoors) - My brother's tell me the problem I ad with my Lone Star Trewble-O-Lectric '000' gauge was broken rubber drive bands  (belt drive locosl like record decks.   Too often the advice given here MAYbe more specific to scale or gauge or manufacturer(s) than realised - without this being stated in question or answer, or accurate measurements taken.