Category Archives: Electrical

Posts related to wiring, signals, DCC, etc.

Signals are Done!

While I haven’t posted much lately, work has been continuing slowly in and around work and personal commitments. I’m pleased to say that I finished configuration and checkout of the final control point tonight at South Chitina. CTC now works over the entire length of the mainline. (The actual trackside signals will be installed once base scenery is done – for now it’s just the fascia signal repeaters.) Most of the rest of the electrical is also complete. The only thing really remaining is to create and wire control panels for the various yards. Then it’s on to starting scenery.

The signal department at work, configuring the South Chitina controller

MRServo Lives Again

Some 11+ years ago, I started messing with servos and PIC microcontrollers as switch machines. Originally it was just for Ron Renner’s Wind River in Denver, where we didn’t want to spend the money to upgrade all the twin coil machines to Circuitron Tortoises. In an afternoon, I had a primitive workable design, and Ron’s layout eventually got dozens of them installed. Each was hand-built and installed in place using double-sided foam tape for both the servo and the PCB.

Those early prototypes then went on to become the basis for Iowa Scaled Engineering’s MRServo line a couple years later. The MRServo matured over the years, moving to surface mount components and then proper 3D-printed mounting brackets to make installation more reliable. But fundamentally, the design remained little changed from the earliest units.

We (Iowa Scaled Engineering) discontinued MRServo about three years ago because sales had tapered off, more large players had entered the market (Walthers) and we never got any sizable market share away from the dominant vendor, Tam Valley. There was nothing about our offering that was fundamentally compelling and differentiating from the others. Plus they were a pain to build and support for relatively little profit margin.

The MRServo Version 4

That’s not to say MRServo died, though. It just went from being a product back to a project. My layout still uses them exclusively as switch machines, with probably close to 100 installed. They’re great for me because they’re relatively inexpensive (especially if I’m building them myself), they’re low profile (so they fit up inside the benchwork without issue), and they take a logic level input to control them (so they’re easily run by the signal system). A few months back I got the itching to again improve the design. I wanted to improve the input protection structure, which often got static-zapped, and also move to an AVR so that I could make changes in C rather than PIC assembly. When I designed the original servo controllers, I was still using PICs regularly and programming in their assembly variant. However, having gone to AVRs and GCC around the same time, I haven’t used a PIC in a new design since.

One other minor change is that I’ve started putting 2-piece terminal blocks on the boards. That makes it significantly easier to connect wires under the layout, as I can pull out the connector, screw in all the wires, and then just plug it back in.

The newest version 4 of MRServo, including an upgraded microcontroller, better input protection, a surface mount regulator, and detachable terminal blocks for easier wiring.

Like all of its predecessors, the MRServo v4 is open hardware. The source code and design files are all available on Github.

Layout Update – Jan 22, 2021

Since I haven’t posted pictures of the whole layout in quite some time and it was all nicely cleaned up for the CR&NW’s first work night last week, I thought I’d show you the state it’s currently in. The track is complete, except for a few spurs and industry tracks that have yet to be positively defined. The backdrop and fascia is 99% complete. The lighting is done, the signaling is 95% done, and track power wiring is 95% done. I’m still installing switch machines at Chitina and Cordova, but that should be done in a week or two. I’ve also posted pictures on the backdrop to inform others and remind myself what some of the scenes are supposed to look like. It’s a combination of my photos from visits over the last decade combined with historic imagery.

Once I get those last few benchwork and electrical to-dos resolved, it’s on to scenery and painting!

CTC Comes to the CR&NW

The prototype CR&NW, running only a through train or two every day even at the peak of operations, never really had a use for signals. Operations were handed with train orders telegraphed to stations, and honestly from all evidence that survives, it worked just fine. There’s no record of any major cornfield meets anywhere on the CR&NW during its ~30 years of operation. (An astute observer may try to point out that there are no cornfields on the CR&NW, but my point holds.) The only signal we know of on the original line was a wigwag crossing signal in Cordova.

The N scale CR&NW, however, was always intended to be signaled. I love signals. I’ve been fascinated with them since I was a kid. I have two full size signals in my back yard and part of one in my kitchen. Since my Copper River is set nearly 80 years after the original went out of business, I can take a few liberties with how the line evolved. Plus, with keeping 3-4 operators busy during operating sessions, that’s going to be a fair amount of traffic in only ~10 scale miles of track.

I’m going to write a series of articles on the operation of and the technology behind the system over the coming weeks, but in the meantime I’m going to put up a screenshot of the Computer-Aided Dispatch (CAD) system that will be used by the dispatcher to route traffic. Visually it’s very nearly complete, and about 75% of the functionality is there under the covers. The display is a little boring since I’m developing it from Iowa and while it’s communicating with the layout back in Colorado, the layout is mostly not on and thus not sending any data back. The fast clock is the only thing up and running.

Let There Be Light!

As long-time readers (or others who know me) know, I have a bit of a fascination with layout lighting and making it part of the overall operating day experience. Plus, it’s easier to work on a layout – either from a construction, detailing, or operations standpoint – when there’s excellent lighting. So in today’s post, we’re going to look at what I settled on for lighting the Copper River.

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Powering the Layout

In addition to track power, which is something most of us have provided by our DC throttles or DCC systems, most of us have a ton of accessories. That can be as basic as things like switch machines or a hodge-podge of building lights, animated features, signals, sound modules, etc. Nearly every single one of those is going to have its own requirements in terms of voltages, currents, etc. Most layouts I’ve ever been on solve this by a maze of power strips, wall warts, battery packs, and old DC power packs repurposed once the owner converted to DCC. It’s a mess.

As an electrical engineer, some things about how people build layouts bug me far more than they should. Messy, disorganized power systems are definitely at the top of the list. I thought I’d give you a look at how power is distributed around my layout to run everything that’s not the track.

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The real CR&NW was completely timetable & train order operations, with no block signals of any kind.  There’s a lone, uncredited reference in Wikipedia about the CR&NW having at least one “wigwag” crossing signal, but I’ve never seen any evidence to support this.  Given the limited number of trains operated and the generally poor condition of local roads at the time, I sincerely doubt that the CR&NW ever had a single circuit for anything.  At least as of 1920, this is confirmed by the ICC’s “Annual Report on the Statistics of Railways in the United States”, where the CR&NW has nothing under the cost line items for “Signals & Interlockers” and “Signals & Interlockers – Depreciation”, and “Crossing Protection”.  There’s the possibility of them coming later, but I still doubt it.  (I would love to be proven wrong, however.  Anyone?)

Update (Oct 16, 2017):  Turns out, I’ve been indeed proven wrong!  See Robert Hilton’s comment below.  There’s a photo in an old Magnetic Signal Company catalog of an overhead, lower quadrant wig-wag in Cordova on page 9.  Now I have a plausible reason to build a working wig-wag for the layout.

The model CR&NW however, having evolved into a modern heavy ore hauler, would almost certainly have block signals.  In my “alternate history” leading to the present day, the railroad underwent extensive modernization and reinvestment in the late 1940s / early 1950s.  Radio dispatch (which didn’t become widespread until the 1960s-1970s anyway) would have been nearly impossible, given the remote country and deep canyons traversed by the line.

For inspiration, let’s look to a pair of near-contemporary prototype ore haulers in the far north – the Quebec, North Shore & Labrador and the Cartier Railway (Quebec Cartier Mining or QCM).  The QNS&L was built between 1951-1954 and was equipped with CTC from the start.  The Cartier was built several years later, in 1959-1961, but it too was equipped with CTC from the start.  Clearly equipping a remote ore line of a few hundred miles in length with CTC isn’t beyond the realm of feasibility.  Plus, I have a serious fascination with signalling, so…

A Showcase Miniatures N scale searchlight signalGiven a modernization date in the 1940s/1950s, searchlight signals would have been the standard of the day. (Again, looking at the QNSL and QCM, it’s searchlights all around.)  The US&S H, H2, H5 and GRS SA were both extremely popular and were the most common type of signal installed all over the US and Canada during the 1940s through about the 1980s.  Recently they’ve been falling in record numbers, as their inherently mechanical color changing mechanism (a relay with three small color lenses) requires regular inspection, testing, and maintenance, as opposed to modern three-light heads.  The preference for searchlight type signals works out just fine with me, since they’re probably my favorite signal type and they minimize the number of wires or fibers that need to go to each head. Showcase Miniatures / Century Foundary makes an absolutely beautiful N scale searchlight kit. They’re lit with fiber optics, which allows them to be very accurate in terms of scale. (Oversized N scale signals really, really bug me…) I’d purchased a couple of their kits some time ago, so I pulled one out tonight and built it. It really is a work of art and not nearly as hard to assemble as I’d feared.  (I still have some fear of doing a double or triple head…)  I didn’t feel like breaking out the airbrush, though, so it’s unpainted for now.

The problem is then feeding light into them. Railroad signals have a unique color to them that’s often not captured by LEDs. The AREMA standards (Communications & Signals Manual, section 7.1.10 – “Chromaticity”) require green to be between 498-513nm, yellow to be between 589-597nm, and red to be 627-660nm. Very few 3-color LEDs hit this or even get close, particularly for green. One of the few that gets very close is the Bivar SMP4-SRGY. It’s a small PLCC4, with wavelengths of 525nm, 591nm, and 631nm. To my eye, it looks nearly dead on for the prototype colors. The PLCC4, while fairly small, would still look huge on the head of an N scale signal, and would need four wires running down the mast.

A board with two SMP4-SRGY leds on it for driving two searchlight headsSo, given that my signal models of choice are based around fiber optics, I created a board with two LEDs on board and holes for clip-in light pipe holders that fit perfectly over the LEDs. (The light pipes are Dialight part 515119200550F if anybody cares.) A Showcase Miniatures searchlight connected to the LED board by fiber opticsI can then drill a small hole in the light pipe and glue the fiber into it. The signal LEDs and their wiring (attached through an RJ45 jack for easy connecting) stay attached to the layout, and the signals can be installed and uninstalled with the ease of just connecting or disconnecting the fiber and light pipe.

bcol3902-and-signal.jpgonlayout.jpgGiven their fragility, the actual signals will be one of the last things installed on the layout.  I’ll build some temporaries for initial operations and testing.  The LED boards, however, will be installed as part of the signal system.  I did a temporary install (using the power of electrical tape to hold up the signal) at one of the block boundaries tonight just to see what it would look like.  In the final install, the light pipes will be painted black to eliminate leakage, but as I said earlier – wasn’t in a painting mood tonight.

Learning to Love the DIN Again

As many of you know from my previous post, I recently converted from Lenz to NCE, largely for the wireless throttles.  Despite that, I’m going to put in fascia cab bus jacks just in case.  While I don’t have any intentions of running the layout with wired throttles under normal conditions, I can foresee a day when it might be necessary.  The last thing I want is to have to cancel an op session because one of my neighbours cranked up their 900MHz cordless phone and took down the wireless throttles.

The one thing I don’t particularly care for with NCE is the use of 6p6c (often incorrectly called RJ11, RJ12, or RJ25) connectors for the cab cables.  You know, those little modular connectors commonly associated with phones.  And it’s not just NCE – everybody seems to have gone to these now.

Why don’t I like the 6p6c modular connectors?  I find the little plastic tabs hard to release from the jacks, that they often break after any significant use, and that wiring fatigue and failure often happens near the jack as a result of inadequate strain relief.  Just a month ago I was at an operating session and we had two different operators lose control of their trains because the cable failed right at the 6p6c connector.

It’s not (just) a personal dislike based on anecdotal evidence.  Often times manufacturers of 6p6c jacks don’t rate the number of insertion cycles, and those that do generally have minimum lifetimes in the 300-500 insertion range.  Modular jacks just weren’t designed to be plugged and unplugged repeatedly.  They were designed in 1975 by Bell to provide a cheap, uniform connector for telephone cords.  Telephones don’t get plugged and unplugged all that often, unlike a guy following his train around the room.

The good news is that there’s a superior connector out there.  The 5-pin DIN connector, standardized as DIN 41524, was designed originally for connections between audio equipment.  The connector itself has robust pins and can easily be moulded to a cable with an integral strain relief.  There’s no little plastic tab to break off.  Plus, even the cheapest jacks are rated for 1000+ insertion cycles, double or more what the RJs can handle.  I first encountered it years ago when I was using CTC-16e as my command control system, and I was pleased that Lenz had used it when I first moved to DCC.

NCE offered a dual DIN fascia panel at one time (the NCE UTP-DIN), but apparently they’re out of production and no longer available.  (Update:  I’m told via the NCE Yahoo group that they’re just out of stock, not necessarily discontinued as many of the retailers state.  Apparently Tony’s Train Exchange has placed an order for 500 of them and should have them soon.)  Lenz still offers the LA152, but they’re rather pricey ($25-35 typically) when they’re not out of stock. Apparently everybody else has decided they can live with the god-awful little RJ connectors.  I can’t.

As Usual, Build My Own

That left me with – as usual – only one option that I was happy with:  design and build my own.  Fortunately, the cab panels are extremely simple – just a couple jacks for the cab bus, a couple DIN connectors, some mechanical board-to-faceplate bits, and a “cab bus power” LED.

Building my own allowed me to make a couple improvements.  The biggest change from the NCE version is that these use 8p8c (RJ45) connectors for the cab bus that follow the NCE Cat5 pinout.  I also added a self-resetting polyfuse and a terminal block for injecting power into the cab bus, should it be needed, along with a jumper to select whether to inject power or just pass it along.  This replaces the 1/8″ audio plug on the back of an NCE panel where power can be injected, and adds a bit of protection (the polyfuse) against shorts.

Here’s a few pictures of the first assembled prototype, plugged into the CRNW’s cab bus a few hours ago:

As a ardent supporter of Open Source Hardware, this project will be released under a Creative Commons BY-SA 2.0 license, just like everything else I build personally.  (Yes, the board says Iowa Scaled Engineering, but given that I am half of ISE, I can do that…)  That license basically means that as long as you give me credit for it and you share any modifications you make likewise, you’re welcome to do whatever you want with the design.

For the prototypes, I’ve sourced the panels through a PCB prototyping service called OSH Park.  I use them for all sorts of things, and they do high quality work.  If you just want some v1.1 boards just as they are, you can order them directly via this link.  You’re also welcome to use the design files below to create your own gerbers and have them made through whomever you’d like.  The schematic and PCB are designed using the popular open source gEDA suite of design tools

Design Files and Bill of Materials

Schematic (PDF – v1.1 / SVN r1114)
PCB Images (PDF – v1.1 / SVN r1114)
Design Files (gschem/pcb – v1.1 / SVN r1114)
Faceplate CAD Drawing (DXF or PNG)
Faceplate CAM File (Cambam)

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Note 1: F1 and J4 may be omitted if you do not intend to inject power at this cab panel.  Also, see note 2.
Note 2: J5 and the shunting jumper that goes in it (part 3M9580-ND) may be omitted if you don’t want to ever change if a panel can inject power or not.  Just solder in a small piece of wire to permanently connect the proper two holes in the board.
Note 3: There’s nothing magical about most of these parts.  The Digikey part numbers are provided as a reference, but pretty much everything except the DIN plugs are commodity parts that can be found from many sources and from many suppliers.

 What About DIN Cables?

The other half of using DIN plugs in the cab fascia is that you have to actually have to have cables to connect them to the throttles.  The standard offering from NCE has a 90-degree plug at the end.  Again, while it should work with my panels, it’s not my favorite.  I’m also not a huge coiled cord guy – I find they often get all tangled up.

My solution was to purchase a 25′ male-male DIN cord from Amazon and cut it in half.  I then stripped the ends and crimped on a 6p4c connector to the appropriate wires.  It took a little doing to get the cable forced in far enough that the casing would engage with the strain relief, but it is possible.

At least for the cable I used, the pinout worked out as follows (your mileage may vary):

1 – no pin
2 – White
3 – Blue
4 – Green
5 – Red
6 – no pin

IMG_1139 My DIN throttle cable


The Electrical Cabinet Lives!

Work has been keeping me insanely busy lately, but I have gotten the start of the electrical cabinet installed.  So far, it’s mostly the three power supplies for the DCC boosters and the fourth power supply for the auxiliary power bus, the DCC system, and one set of DCC breakers, but it’s a start.  And it’s enough to power up the helix and Nizina, along with bringing up the programming track.

The wiring is still a bit messy, but that’ll get cleaned up before it’s final.  I just figure there’s no sense lacing things together before all the wires are in place.


Movin’ On Up… to 24VDC

I know, I haven’t posted many updates lately, but there will be about four coming in the next few days.  There’s been lots of work, but little time to properly write things up.

I’ve decided to rev the LED lighting PWM boards again to accept a 24VDC input. 24V offers the advantage of more efficient large power supplies (the Mean Well RSP-2000-24 being the one I plan to use) and half as much current.  That means smaller wires, less heat loss, and less inductive kick.  While I could always put two 12V strips of the warm or cool white in series to make a 24V load, the RGB strip was always the problem, because there was no way to wire those in series.  About a month ago I found a 24V RGB strip supplier, so I rev’d the control board to handle 24V.

I assembled the prototype on Monday and tested it last night.  The results are spectacular.  It works flawlessly.  With confirmation it’s going to work, I’ll probably start putting up the final light bars before the end of the year.  I’ll also post the control board design this weekend.