Connector and wiring blues! What to do? Motors, decoders, and lights, Oh My!

[jviss]

I know there's an NMRA standard for decoder connectors and color codes, but I feel large scale gets short shrift from the NMRA.  For example, that only standard I can find covering large scale in-loco wiring with DCC is for motor and track connections only, unlike the HO scale 8-contact standard.

I'm venturing into adding decoders and rewiring some things, and I'd like to do it in an easy, reversible, modular, sensible way.  For example, my generation 3 BBH Pennsylvania 4-6-0 headlight and smoke unit wiring was connector-ized to the chassis via a pair of .025" square pins and mating connector shell and receptacles.  Great, that's a start! 

I would like to able to switch from DCC to analog, swap decoders, etc., via a good connector system.

I would sincerely appreciate your views and experience on this.

Thanks,

jv

[JerryB]

Sorry I can't help you with your specific problems, but as a life long model railroader, and life member of the NMRA since the mid 1970s, I would like to respond to your statement, ". . . I feel large scale gets short shrift from the NMRA."

First, there was, and continues to be a strong feeling among many LS model railroaders that there is no need for standards. Some folks who tried to overcome this attitude in the early days when LS was becoming popular were literally shouted down by very vocal folks, mostly saying like, "We don't need no stinkin' standards!".

Second, you need to understand that the NMRA is virtually a 100% volunteer organization. With the exception of a few paid office staff that run the administration, library and other support functions, the NMRA is dependent on members, manufacturers and vendors to propose, set and adopt standards. With the attitude exhibited in my first point above, it has been virtually impossible to get standards set and maintained for LS trains.

Third, it is my opinion that this lack of standards really hurts our hobby. Things as diverse as scale and gauge specifications, common trackage and electrical standards, and advanced developments like DCC only exist due to the efforts of volunteers in user organizations like the NMRA. Most of those LS initiatives do not exist in the NMRA.

Meanwhile, the NMRA, with something around 20,000 members in 18 divisions, continues to be a strong component in the model RRing hobby. We just don't have much participation in the LS segment.

BTW, you can help overcome this lack: Join the NMRA and become a volunteer, joining in or perhaps leadomg some development effort in an area that interests you!

Happy RRing,

Jerry

[jviss]

Hi Jerry,

I'm sorry if I offended you and any other NMRA volunteers and supporters, no offense was intended.  I am familiar with standards work, having done my share professionally with the IEEE, and I know it can be a tiring and thankless undertaking. 

Perhaps short shrift was too negative a term.  It's only that I'd like to have an 8-pin standard for large scale just as HO has, and I don't think it would have taken more than a day, or even an hour to jot something down, or even to just declare a an abstract 8 pin layout and assignment, without even choosing a connector.  Choosing a connector is among the most contentious things a standards body can do, so I say just choose something and move on.  The primary issue is current carry capacity, and this is made more difficult still in small, multiple-contact connector housings, as opposed to loose wires, for thermal reasons.  But even so - I'd like a standard. 

And ideas on a good connector for an LS version of the NMRA HO connector standard?

jv

[Hunt]

You must verify factory wiring before connecting to it.   You cannot depend on the wire insulation color to identify its purpose. Only DCC decoder wiring harness follows a wiring color code.

[Kevin Strong]

The standards are there; it's up to the manufacturer to adhere to them. It's not the fault of the scale or the standards organizations that the manufacturers do their own things.

To your particular quest, check out all-electronics.com. They've got an array of multi-pin connectors that you can probably use to install your boards and make things interchangeable. When you do that, write your own standard and stick to that, and don't worry about what this or that organization say, or this or that manufacturer does or doesn't do with regard to existing standards.

Alas, I have found in my experience that each of my installations is unique. I toyed with the idea of a standard connector, but then one loco has working class lamps and a headlight that I can turn on and off, where others don't. Most have chuff triggers on the drivers, but some don't. So despite how nice it would be for simplicity to say "all connections between loco and tender will be this," it just hasn't happened.

Later,

K

[jviss]

Thanks all.

BTW, Kevin, it's http://www.allelectronics.com, without the hyphen.

jv

[StanAmes]

Actually the NMRA did indeed create a draft standard for an interface for Large Scale.  Bachmnann currently uses the draft of this standard in its Spectrum locomotives and several manufacturers build DCC and RC products that plug into this interface.

Currently the Europeans are looking at a the possibility of a different connector to base a future standard upon.

Stan Ames

[Hunt]

The Bachmann large scale K-27 is equipped with the plug & play electronics board Stan Ames is referring to.

Click Here for more info.

[jviss]

Thanks Stan and Hunt.  I read the doc and all the child docs that Hunt's link points to.  Very interesting.  I confess I have only learned of this now, but I can't detect that there's a single decoder available that actually plugs and plays.  Am I missing something?  All of the ones documented require at least one of trace cutting, soldering, component additions, and so forth. 

Stan, when you say "the NMRA did indeed create a draft standard for an interface for Large Scale" I take it to mean it never made it to publication as a standard; is that so?  Is the draft available?

If the draft isn't available, can you say what the motor current maximum is for this interface?  Other electrical characteristics?

One curious thing, Bachmann says "first Large Scale locomotive with totally isolated electronics, which allows for easy installation of the control system of your choice" and then has pins on the interface for locomotive ground and locomotive positive.  What could these be?

Has anyone else implemented this?

I would prefer a connector-based standard that didn't require such a wide header; 12 pins presumably on 0.1" centers makes for a cable-mounted header about 1.5" wide - tough to snake through spaces.  And, the entirety of the keying feature is implemented with a blank position, requiring the PCB to implement the keying feature.

Thanks,

jv

[StanAmes]

Thanks Stan and Hunt.  I read the doc and all the child docs that Hunt's link points to.  Very interesting.  I confess I have only learned of this now, but I can't detect that there's a single decoder available that actually plugs and plays.  Am I missing something?  All of the ones documented require at least one of trace cutting, soldering, component additions, and so forth. 

Stan, when you say "the NMRA did indeed create a draft standard for an interface for Large Scale" I take it to mean it never made it to publication as a standard; is that so?  Is the draft available?

If the draft isn't available, can you say what the motor current maximum is for this interface?  Other electrical characteristics?

One curious thing, Bachmann says "first Large Scale locomotive with totally isolated electronics, which allows for easy installation of the control system of your choice" and then has pins on the interface for locomotive ground and locomotive positive.  What could these be?

Has anyone else implemented this?

I would prefer a connector-based standard that didn't require such a wide header; 12 pins presumably on 0.1" centers makes for a cable-mounted header about 1.5" wide - tough to snake through spaces.  And, the entirety of the keying feature is implemented with a blank position, requiring the PCB to implement the keying feature.

Thanks,

jv

JV

Both Zimo and QSI build currently offer plug and play DCC decoders for this interface.  Soundtraxx announced one but to date it has not been released.  There are also several RC units that plug and play.

In the locomotive's released after the K27 Bachmann provides a board with wires that can be used to easily use decoders with screw terminals.

The draft was approved as a draft by the NMRA DCC WG but it was never promoted to a standard.  At the time the NMRA was waiting for more than a single manufacturer to fully support the draft.  Accrucraft may be placing the socket in their 1:29 models but we will have to wait and see what they have done.

The + and - on the interface are used to power the internal locomotive electronics such as the fans and the chuff circuits.  They are also used for the high power smoke current, the actual on off for the smoke is through a different pin.

The +-, track, and motor pins must be large enough to handle the current.  The other pins need not be as large as they do not carry any real current. 

I can forward you a draft of the standard should you shout me an email.

Stan

[jviss]

Thanks, Stan.  I'm looking forward to reading the draft.  I have concerns; those .025" square pins are marginal for LS, for current rating.  I've seem them conservative rated at 3 Amps max, 'though some vendors rate them higher, as high as 6.3A, with constraints on number of current-carrying pins per housing or header. 

This brings up another issue.  I see in the existing NMRA standard a distinction among DCC interfaces according to scale.  For example, the 8-pin interface in S-9.1.1_Connectors_2013.07 is limited to 1.5A, and aimed at "medium," i.e., HO scale, yet one can purchase a 4A HO decoder; and the "large" at 4 Amps seems marginal, not for me, but for what I've heard folks talk about.  The definition of "peak" is missing, too. Oh, well.  It's easier to be critical than correct, as they say.

Thanks again,

jv