LCC I - Layout Command Control

Three years ago, in 2012, the NMRA published their first standard related to a layout control bus, at the time known as NMRAnet. This was standard S-9.7.1 NMRAnet: CAN Physical Layer, which defined the electrical characteristics of the bus (e.g., details of the wire, connectors, bit rate, and voltage levels). Several companies were producing useful circuit boards based on the standard, although their functioning depended on capabilities not adopted at that time.

This standard, and the not-yet-adopted parts used to make the first implementations, were based on something called OpenLCB, which stands for Open Local Control Bus (not "Layout Control Bus"). Open LCB was one of several competing proposals for NMRAnet. The OpenLCB team demonstrated how this would work at the 2010 NMRA convention, and has a page of videos and other information from then. Over the subsequent two years it came out on top as the solution of choice. However, some of the potential demonstrated there does not seem to be fully fleshed-out in even the current standards. We're not done with the development of LCC by any means.

But we have had significant progress this year. Back in February the NMRA adopted 21 additional documents, 10 more Standards and 11 clarifying Technical Notes. They also renumbered them slightly, and changed the name to Layout Command Control, or LCC. These were formally adopted with a six-month comment period that ended on September first. Updates based on those comments are still possible, so the standards aren't quite done yet, but they're probably very close to their final form.

Track, Turnouts and Servos

If you follow the RSS feed on the main page, you can see that my interest in signals continues. However today’s topic is about what signals describe: track, and in particular the turnouts, or track switches, or just switches, used to direct the motion of trains, although I do mention the relation to signals briefly. And yes, it’s finally a post about the layout, even if it is about the as-yet unbuilt future layout.

I’ve been spending some time thinking about how I’ll do turnouts on the new layout. As part of my overall design, I’m planning to use code 55 rail on a mixture of concrete and wooden tie track (I’m undecided between PECO and Micro Engineering). And I may custom-build some track to replicate slab-type track, which is used by both Shinkansen (sometimes) and in some newer construction for narrow-gauge track, particularly in stations and on viaduct. Although I dislike unnecessary work (and hand-laid track is, to me, generally more effort than it’s worth), I do plan to put substantial effort into getting the track to both operate reliably and look as prototypical as I can. And thus hand-laying some portion of it for appearance purposes may be worth the effort.

Note: some Japanese models have issues with code 55 track due to larger-than-spec wheel flanges, and I’ll need to do some testing. But most of my models are Kato, and they generally use low-profile flanges that should work.

I’m also planning for very wide radius curves, although I have not yet picked a specific standard or minimum radius. I want both Shinkansen and commuter stock to look good on curves, with minimal overhang. That means I need much wider curves than the minimum operating radius. I may skimp a bit for storage and yard tracks, including modeled layover terminals where trains are kept off-peak. But mostly I’m considering track radii in the 30” or larger (750 mm or larger) range. And that raises the related question: what type of switches do I want to use?

Occupancy Detection Yet Again

About fifteen months ago work on adding occupancy detection to Sumida Crossing stalled. That was in part because I’d planned to use the BDL168 detectors to also do transponding, and a few months earlier had abandoned that plan since I was unable to get that aspect to work reliably, even on a simple test track. The number of solder joints on the BDL was also a nuisance that caused me to put off further work.

Recently I’ve been rethinking my approach. The BDL168 is an amazingly cost-effective solution. Ignoring the transponding part, you get 16 detectors on a board that includes a LocoNet bus interface for US$120 (street price). That’s $7.50 per detector (if you can use all 16). That’s really hard to beat for a bus-connected detector. I’d originally planned to install one per table on the layout, and my cost would have worked out to around $10 to $15 per detector on average.

On the other hand, I’m thinking that I might want to move to either a OpenLCB/NMRAnet bus (if I want a feature-rich bus for the future) or a really dumb serial bus (like S88 or C/MRI). The latter is attractive since I can potentially interface to it with an Arduino, opening up some room for home-brew devices. Of course I could do that with NMRAnet, but today that requires a US$45 shield to add to the Arduino (or one with it built in), which kind of takes away from the appeal of using $10 Arduinos to do things like drive signal masts.

While thinking about this, I went off and started researching what was available commercially or as home-brew circuitry and software libraries for these busses and for doing occupancy detection with them, as the latter would be a good way to get my feet wet and solve my “don’t want to solder those #$@! BDL168s any more” problem.

But in the past week I’ve been sidetracked into looking at homebrew inductive-coil detection circuits.


NMRAnet - Why You Should Care

In August, the NMRA adopted standard S-9.7.1, NMRAnet Physical Layer, and a short article about it appears in the November issue of the member's magazine. What is this, and why should you care about it?

Well, if you care about Digital Command Control (DCC) for controlling a model railroad, it's an important addition to model railroading that will enhance that. And if you don't care about DCC, it's compatible with other control systems, and you may still want to use it. Read More...

LocoNet: A DCC Control Bus

DCC is really about getting power and control information to the track. But there’s another side to it: how do the commands from the throttle (the controls) get to the DCC system, and how do different parts of the DCC system communicate with each other? The first part isn’t covered by the NMRA’s DCC standards, so each manufacturer does the throttle-to-command-station link in their own proprietary manner. The second part is partially standardized, as the NMRA has Recommended Practice RP-9.1.2 Power Station Interface to describe how a command station sends commands to booster stations, but they don’t say anything about how devices like stationary decoders or occupancy detectors report their status, although there’s a draft of a standard for an “NMRAnet” control bus being developed which will probably fill this gap, someday.