Bus wires

Post all your DCC only problems, solutions and discoverys here.
crazypotter
Posts: 77
Joined: Tue Nov 28, 2017 10:15 pm

Bus wires

Postby crazypotter » Tue Feb 11, 2020 4:47 pm

Hi all. Being a novice with regards dcc wiring I have what you may consider a simple question. I am running two bus wires below the baseboard. I assume two ends run into the controller. However, I am unsure what to do with the other ends. Do I need to connect them to some sort of connection block or maybe just wrap insulation tape around them. I am pretty loathe to just leave them hanging loose and maybe a safety hazard. Cheers.

Dad-1
Posts: 6283
Joined: Sun Aug 24, 2008 8:05 pm
Location: Dorset - A mile from West Bay.

Re: Bus wires

Postby Dad-1 » Tue Feb 11, 2020 4:54 pm

Yes just insulate safely and attach well out of the way so they can't get caught or pulled accidently.

Geoff T.
Remember ... I know nothing about railways.
viewtopic.php?f=22&t=32187 and Another on viewtopic.php?f=22&t=28436&start=60&st=0&sk=t&sd=a

abenn
Posts: 237
Joined: Thu Jun 05, 2008 11:03 am

Re: Bus wires

Postby abenn » Wed Feb 12, 2020 7:59 am

Certainly tape them off or attach them to a terminal block so they can't get snagged accidentally, as Dad-1 has said.

If it suits the shape of the layout I would suggest making the buss wires a continuous loop with both ends connected to the power supply. Maybe overkill, especially if your wires are a heavy gauge, but at least it keeps the ends tidy.

User avatar
RAF96
Posts: 680
Joined: Tue Feb 19, 2008 1:39 pm
Location: Dereham, Norfolk, UK

Re: Bus wires

Postby RAF96 » Wed Feb 12, 2020 9:59 am

If you see interference problems with the DCC signal you can attach terminators to the said terminal block end. These comprise a low ohm hi watt resistor in series with a ceramic capacitor connected across those free ends. This device damps any spikes seen say during a derail that could affect your decoders.
RAF Halton Brat - 96th Entry
http://www.halton96th.org.uk/robs_rails.html
β-tester

gppsoftware
Posts: 255
Joined: Thu Mar 09, 2006 5:34 am

Re: Bus wires

Postby gppsoftware » Fri Feb 14, 2020 6:16 am

'Terminators' or 'snubbers' are one of those things that some people say you must have but the vast majority of layouts don't need them.

Unless you have a problem, I wouldn't fit them. Just terminate a bus in a terminal block.

One thing not indicated by the OP is whether the layout is a circle, in which case, you can make a ring-main and tap off of it in parallel to a command station ('controller'). This has multiple benefits, not least that power is evenly distributed.

No need to fix what don't need fixing!

User avatar
Bufferstop
Posts: 12350
Joined: Thu Mar 11, 2010 12:06 pm
Location: Bottom end of N. Warks line

Re: Bus wires

Postby Bufferstop » Fri Feb 14, 2020 4:17 pm

The purpose of putting a terminator on the end of a bus is to stop "reflections" these are unlikely to be a problem at the frequencies used by DCC. The DCC protocol works on the basis that a command will continue to be repeated at intervals as long as it is required, so reflections aren't a problem the most that will happen is the controlled device will stp doing what it was told to do a fraction of a second later than it should have.
I suspect many of the souls who preach the need for them are the self same little monsters of the 80s and 90s who discovered that removing the terminator or simply open circuiting the bus would bring a school network to its knees in very short time. In the first few weeks of the college year I was waiting for them with my scope sitting on the cable I could count the reflections from each connector up to the big one where the plug had been loosened then walking down the room count the connections and stop at the loose one. I would stand there until someone asked what I wanted, "oh I'm just waiting for you to put the plug back" I was obviously in possession of special powers and not to be messed with.
Growing old, can't avoid it. Growing up, forget it!
My Layout, My Workbench Blog and My Opinions

User avatar
RAF96
Posts: 680
Joined: Tue Feb 19, 2008 1:39 pm
Location: Dereham, Norfolk, UK

Re: Bus wires

Postby RAF96 » Sun Feb 16, 2020 6:50 pm

The magic of using a time domain reflectometer to find out where a cable break was...
RAF Halton Brat - 96th Entry
http://www.halton96th.org.uk/robs_rails.html
β-tester

User avatar
Flashbang
Posts: 3569
Joined: Thu Oct 18, 2007 1:07 pm
Location: SE United Kingdom
Contact:

Re: Bus wires

Postby Flashbang » Sun Feb 16, 2020 7:08 pm

Hi
First of all they are not "Terminators" as used on IT network cabling.
They are filters.
They are extremely useful if you suffer from a short circuit e.g. loco derails causing a "Spike" of power on the DCC bus which can cause some decoders to self reset to their default address. They can also help with poor quality DCC signals, but that is not their main goal.
They have nothing what-so-ever to do with Network IT Terminators nor anything associated with IT data transmission.
[Image << Click the Icon to go to my website
Broken? It was working correctly when I left it.

User avatar
Bufferstop
Posts: 12350
Joined: Thu Mar 11, 2010 12:06 pm
Location: Bottom end of N. Warks line

Re: Bus wires

Postby Bufferstop » Sun Feb 16, 2020 8:26 pm

If they go on the end. Of the bus they are acheiving the same effect, sinking the unwanted spikes, the coax terminator stops the reflection which would otherwise raise the voltage on the bus and spook all the transceivers to back off for a random period.
RAF96 Wish that it had been, we were using a superannuated server with a network card that had been heavily modified by some wizard at the manufacturers, and some software that created the same functions only just for the expected range, ( the max length of a coax segment was actually useful for once).
Growing old, can't avoid it. Growing up, forget it!
My Layout, My Workbench Blog and My Opinions

User avatar
pete12345
Posts: 1013
Joined: Fri Apr 14, 2006 7:53 pm
Location: Coventry

Re: Bus wires

Postby pete12345 » Mon Feb 17, 2020 8:17 pm

Just attach the last pair of track connections to the end of the bus wires. Job done :)
Once an engine attached to a train, was afraid of a few drops of rain...

gppsoftware
Posts: 255
Joined: Thu Mar 09, 2006 5:34 am

Re: Bus wires

Postby gppsoftware » Tue Feb 18, 2020 11:27 pm

Flashbang wrote:Hi
First of all they are not "Terminators" as used on IT network cabling.
They are filters.
They are extremely useful if you suffer from a short circuit e.g. loco derails causing a "Spike" of power on the DCC bus which can cause some decoders to self reset to their default address. They can also help with poor quality DCC signals, but that is not their main goal.
They have nothing what-so-ever to do with Network IT Terminators nor anything associated with IT data transmission.


I often wonder what people are doing to get all these shorts, 'spikes' and poor quality DCC signals. Sometimes I think problems are exagerated by those who are trying to sell a 'solution' to these 'problems'.

All of the mainstream command stations output signals which meet the NMRA standards which means that if people are having problems, the issue must be their wiring, workmanship and use if inadequate cabling and materials.
Since this topic has been written about for years and years, it amazes me that people still have these issues!

If I had decoders which reset themselves upon a short circuit occurring, I would be replacing them. Decoders these days are relatively cheap, so there is no need to persist with old decoders that don't behave properly!

User avatar
Peterm
Posts: 1597
Joined: Fri Nov 09, 2007 1:26 pm
Location: Bribie Island. Australia

Re: Bus wires

Postby Peterm » Wed Feb 19, 2020 12:13 am

gppsoftware wrote:
Flashbang wrote:Hi
First of all they are not "Terminators" as used on IT network cabling.
They are filters.
They are extremely useful if you suffer from a short circuit e.g. loco derails causing a "Spike" of power on the DCC bus which can cause some decoders to self reset to their default address. They can also help with poor quality DCC signals, but that is not their main goal.
They have nothing what-so-ever to do with Network IT Terminators nor anything associated with IT data transmission.


I often wonder what people are doing to get all these shorts, 'spikes' and poor quality DCC signals. Sometimes I think problems are exagerated by those who are trying to sell a 'solution' to these 'problems'.

All of the mainstream command stations output signals which meet the NMRA standards which means that if people are having problems, the issue must be their wiring, workmanship and use if inadequate cabling and materials.
Since this topic has been written about for years and years, it amazes me that people still have these issues!

If I had decoders which reset themselves upon a short circuit occurring, I would be replacing them. Decoders these days are relatively cheap, so there is no need to persist with old decoders that don't behave properly!

Except for those people that can't afford to replace X amount of decoders. I'm a known Zimo user but some just can't afford to upgrade.
Pete.

gppsoftware
Posts: 255
Joined: Thu Mar 09, 2006 5:34 am

Re: Bus wires

Postby gppsoftware » Wed Feb 19, 2020 12:31 am

Peterm wrote:Except for those people that can't afford to replace X amount of decoders. I'm a known Zimo user but some just can't afford to upgrade.

I'm an ESU and Zimo user, but one doesn't have to use these top-end decoders to get proper results - there are plenty of decoders around these days which are cheaper and don't suffer 'reset' issues. For example, I've never had such issues with TCS or NCE decoders. I haven't heard of reports of all the Lenz and ex-Lenz decoders being an issue either.

Perhaps what would be helpful to everyone is that those who have these 'reset' problems tell us all which decoder experiences the issue. Then we can all avoid that decoder rather than operate on the basis of 'urban rumours'.

There is also an answer to the 'too many to upgrade' argument: you don't have to do them all at the same time. Do it over a period of time and then only on those which have experienced a problem.

User avatar
Flashbang
Posts: 3569
Joined: Thu Oct 18, 2007 1:07 pm
Location: SE United Kingdom
Contact:

Re: Bus wires

Postby Flashbang » Wed Feb 19, 2020 2:09 pm

Well each to their own... I know I would rather spend around £0.30 on the two components needed to make a filter than spend x£s on new decoders!
[Image << Click the Icon to go to my website
Broken? It was working correctly when I left it.

gppsoftware
Posts: 255
Joined: Thu Mar 09, 2006 5:34 am

Re: Bus wires

Postby gppsoftware » Wed Feb 19, 2020 11:38 pm

Obviously, it is each to their own, but there is a reason for decoders resetting. The fact that something fails is telling you something and it is telling you that something needs fixing.
Adding a 'snubber' which costs 30p is all very well, but it only band-aids the problem. It doesn't fix it.
Band-aids are only temporary solutions. If you keep them on long term, infection tends to set in and then you have a much bigger problem to fix. In our hobby space, that tends to reveal itself as other electrical problems and then you end up with a string of problems where you can't work out where the cause is due to all the band-aids.
In our hobby, we should be sharing 'best possible advice', not approaches which don't fix problems and have the potential to cause others issues down the road.


Return to “DCC Forum”

Who is online

Users browsing this forum: No registered users and 10 guests