DC wye wiring

Model Railroader Electronics and DCC
21

Most of my dislike comes from those Atlas wiring books, which rarely if ever show more than oone single feeder to the common rail fooor the entire layout. That might work on a simple layout, and with very tight rail joiners, but even out 4x8 temporary layout we put up every year had extra feeders - actually, the layout was not common rail at all, all gaps were made with insulated joiners in both rails. This was the way my Dad did it, and he learned electrical wiring in the US Navy, so I figured it was good enough. I just kept doing things the same way when I built layouts myself. Common rail is pretty much right out for DCC, so I haven’t had to do anything really different since going with DCC.

Sure it’s less wire, but hooking up wires never scared me, even as a kid - I was 5 or 6 when I figured out where my Dad left off on the wiring and completed it and had trains running when he got home from work. Almost everything we had was train set type equipment, even the diesels had split pickup, I don’t think ANYTHING we had at the time had all wheel pickup outside of a small 0-4-0 pr a little 4 wheel switcher. It all worked and was easy to understnad = you need 2 wires for a complete circuit and every block had 2 wires, simple and to the point. We used some Atlas components but most of the block toggles were standard toggle switches mounted in a metal strip my Dad made. Another panel with an aluminum plate for toggles and a back plate of plexiglas (so like a triangle with 2 sides) with bolts used as terminals was used to control structure lights and other accessories. Some sections were independent and not connected to the main loops in any way, they just had dedicated power packs. Wish I still had some of the old photos but they have all gotten lost over the years. My Dad built most of it, but I was the only one capable of operating it all without deriling trains.

22

reading about old technology is like looking at a classic car from 30 years ago, a steam engine or many GA aircraft still flying after 50 years. All are fascinating. but technology improves, usually more reliable, less complicated but denser in capability and less expensive.

i’m not that familiar with Tortoise switch machines and had to read about them. Unless your controlling them locally with a DPDT switch, it seems difficult to control them remotely without using a relay of some sort.

I think a latching SPDT relay and a dual power supply may be the least expensive solution to controlling Tortoise machine remotely. And one benefit someone explained to me is that the turnouts remain unchanged from the last time the layout was used. (you can detect the turnout position from the tortoise switches).

it seems that single 12V AC supply and diodes to provide +12 and -12V half wave is a less expensive that having either two +12/-12 or +24/+12 supplies.

while even 4PDT relays may not be real expensive, and while relay logic may not be much more complex to figure out and wire than using TTL for applications on model railroad, it just seems simpler and cheaper to implement such logic in software (leodarno). one leonardo can replace a bunch of relays or TTL gates

it’s ironic that i agree that the clicking sounds may be an attraction. And doing things in ways that you are confident in and comfortable with is also very important.

i keep thinking of <

23

Thanks for the additional information, Randy.

Until quite recently, my layout, about 200’ of main line (not counting double track, staging tracks, and industrial sidings) was powered through one wire to the common rail and one wire to the other rail. However, all rail joiners (except those at the bridges, which are removable) are soldered, then gaps were cut where necessary to afford on/off control to some sections of track, usually, but not limited to, passing tracks.
When I added the partial upper level, roughly 65’ of mainline, and again not counting double track, industrial sidings, and staging tracks, the layout still ran without issue, and that included operations with multiple locomotive on heavy trains and often steep grades. There was never any difference in locomotive performance or a perceptable drop in speed, even when additional locomotives were added.
However, after reading of the necessity for additional feeders, even for DC operation, I did relent and added a couple more pairs of wires. As expected, there was no change in locomotive performance, but the wire had been on-hand, so the only expense, a very minor one, was the labour to put it in place.

I will admit that if I had wanted to have multiple operators running their own trains, I’d have likely opted for DCC. However, the layout itself is totally unsuited to such operations, and I’d guess that my layout “design” deliberately reflects my preference for solo operations.

Wayne

24

Greg,

Your questions, perspective and replies are always interesting.

I don’t know how old you are, but from my life perspective at age 61, thirty year old cars don’t really represent the previous technolgy, this does:

That is me, at age 20, in 1977, I had just finished restoring and hot rodding that 1963 Chevy Nova SS. 283 cid, 350 hp, 4 speed, etc. Did nearly all of it myself, just a little help from dad and a friend of his.

And I will admit, I have no desire to go back to those days for a daily driver…

As I have explained, I have programed PLC’s, but for me, building solid state circuits, or programing micro processors, is not much fun.

Buying off the shelf solid state solutions are expensive and often not well suited to specific goals.

Reliablity? Well relays served the signal systems on America’s railroad until just recently…and we are not building the Space Shuttle…

Simpler is a matter of perspective, I will grant that. And as you point out, doing what you know is a big part of that perspective.

Tortoise machine? What kind of switch machines do you use? It has been the dominate product for several decades or more?

Back to cost for a minute. Years ago I looked at all sorts of products to control signals and turnouts, I considered DCC, I considered building my own solid state system, I considered computer/software based systems. In the end, you still need all the same inputs and outputs, and that takes wire - and some sort of “driver”.

But in the end, DC with the Aristo wireless radio throttles, and the lighted pushbutton relay based controls for cab assignment, turnouts, signaling and CTC was the lowest cost approach as a total package.

I use one slightly expensive off the shelf solid state item, because I am too lazy to build them - Dallee inductive current detectors. But g

25

Greg,

I may have forgotten to mention, and therefor you may be over looking one very important point.

I developed my fully intergrated Advanced Cab Control system for the Aristo wireless throttles more than a decade ago. I have built several versions of its features, on several layouts for myself and others.

When I was developing it, DCC was more expensive than today, and many of the current processor solutions for signaling and control, and other model railroad specific products did not exist.

But here is one of the big things for me, with most anything in my life, I don’t replace things that are not broken and still do what I need them to do.

Despite any skills in technology, I don’t just upgrade stuff because something new comes along.

In 1996 I bought a high quality lawn tractor, I still have it, it will likely last the rest of my life.

My house has home automation, for some things, and manual mercury thermostats for the five zones of heat…

I still listen to my 1700 vinyl records - because they are better than digitally stored music. And I listen to them on REAL speakers with 10" woofers, not some “cubes” and distorted base from some electrically processed sub woofer.

I love the MR archives, as a search engine, then I go pull the hard copy from my MR collection, nearly complete from about 1947 to now.

I still have flip phone, because it has better acoustics for talking - I have a Samsung tablet for all that other stuff…

But I really hate touch screens, never to be found in my train room as a control interface. It is after all September 1954 on my layout…

But I have a smart TV, fully intergated with my HiFi/Suround sound, BlueRay, Netflix, Amazon…on my fiber optic cable service…

Newer is not always better, sometimes it is just different…

I have the relays, the Dallee detectors, the Aristo throttles, they work fine, why would I spend more money?<

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Indeed, newer is not always better. Relay contacts are essentially immune to any power being applied fromt he wrong end. Try that with a lot of power MOSFETs like you’d need to handle equivalent current, and without designing in protection circuitry, you may end up with a slab of inert silicon. Stationary applications, perhaps you have room for ample protection circuitry, but miniatureized applications like DCC decoders - forget it. Notice how quickly a decoder is fried if power gets applied to the motor drive?

I’ve always been an advocate to switch machine contacts and/or relay to flip polarity for reversing loops, instead of complex electronics. Why detect and then correct a short when you can avoid one in the first place? That DCC makes it stupidly simple since the phase of the signal on the rails has nothing to do with direction of travel makes it even easier.

Jay Leno’s steam cars? I’d LOVE to own one like that. About the only thing they don’t have compared to a gosline engine car is quick startup. Otherwise - he’s gotten a speeding ticket in one that is over 100 years old. They can easily keep up with modern traffic. They are incredibly simple machines, as well, far less complicated than internal combustion vehicle, even a diesel. That fact they they all run, and he is able to drive them, after over 100 years, says something.

I have plenty of tech on my layout, including lots of microcontrollers. But sometimes, the simple ways are better. My servo switch motor controllers - sure, I could switch frog polarity with solid state switches, but relays are dead simple and are easily driven by the micro using a transistor, resistor, and a diode for BEMF protection. I’ve had great success using the Digitrax PM42 circuit breaker which uses relays. No problems with sound decoder inrush even in purposely contrived tests. They are about the ONLY DCC circuit breaker than actually breaks BOTH sides of the circuit instead of just one leg l

27

It appears that my request for Sheldon to post his relay circuit for polarity reverse started a very interesting exchange from Sheldon, Randy, Wayne, and Greg. I have enjoyed reading it and am trying to learn. Heck, I wouldn’t know what relay to even buy. I will say that I can at least relate to Sheldon’s Nova - I traded my ‘50 Chevy for a brand new ‘62 Chevy II. I hold two mechanical engineering degrees. I even had an elective circuits class in college around 1960 - we studied tubes. Never made it to relays much less the “new” solid state stuff. My locomotives are all DC steamers that were kits or RTR in the ‘60s and ‘70s. i have done motor upgrades and lots on CalScale. I’ve soldered simple circuits that are published in our magazines because they say which diode, transistor, resister, capacitor, or bridge to use. So, if the relays in Sheldon’s diagram we’re to have part numbers or whatever, I can build it. I’m dreaming of a passenger operations layout in modules based on the Filmore Avenue Roundhouse (it has a great website) but using a reverse loop for return instead of the rolling units. Again, thanks Sheldon for posting the diagram and all you others for helping to lead this old structural engineer thru the relay maze.

Steve

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regarding the original question … couldn’t the toroise switch contacts be used to reverse the polarity of the wyes reverse section automatically depending on the position of the turnout.

as I said earlier, i believe a dual coil (set and clr) latching relay can be used to control each tortoise. three momentary buttons (or pair in parallel) can be connected to the set or clear of the 2 relays for each route. no need for any “explicit” logic

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Yes it can. My circuit has other benifits, it will insure the whole route is clear before allowing the train to proceed.

Yes, latching relays will work - they cost more money.

Typically, my system uses one relay or less for each CTC controlled turnout. Single turnouts require two, because normally closed LED lighted push buttons are simply not to be found in the size and type I want for my control panels.

But other groups of turnouts generally require only one per turnout, some require only one for two turnouts - it averages out.

The other thing is this, by using the same core circuits, and same parts, there is economy of inventory and method.

The track diagram and its added benifits beyond simply reversing the polarity are coming.

Again, while it may be more than the OP, or Steve, requested, my circuit is part of and Adv

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I would not use Tortoise contacts to change the polarity under a powered track. They can CARRY plenty of power to power a frog or whatever, but they aren’t rated to SWITCH much power. Plus if you use both sets of contacts to make a DPDT switch, you have no contacts to power the frog or activate signals. What you can do is use one set of Tortoise contacts to power a relay with DPDT contacts. Or glue or some other way attach lever switches so they get activated by the Tortoise arm and use those contacts to switch the track power.

–Randy

31

As promised, the track power wiring for the automatic wye:

OK, it works like this:

The wye is a junction between two mainline blocks, lets call them east (on the right), and west (on the left).

Your train is in the east block, headed west toward the wye. If the route is set straight thru on the main, route B-C, and the west block is set to your throttle/train, you proceed thru.

Your train is in the east block, headed west, and now the wye route is set for the wye leg from your direction, route A-C. Your train has power into the wye leg.

After your train is in the wye leg, you change the route to A-B, and you want to reverse your train and back out onto the main.

BUT, your train will still be moving WEST. So you do NOT reverse your throttle direction switch, you simply align the route to A-B, this will effectively reverse the polarity to the train. Your train will now back out on to the mainline still proceeding west, but now in reverse.

After you clear the wye, and set the route back to the main, you could now reverse your direction switch to proceed east, back the way you came.

Other features:

When the route is set to B-C, the rest of the wye is dead, a train or loco can be parked there.

When the route is set to A-B or A-C, the trackage between B-C is dead, preventing a train from the other direction from running the fouled turnout.

There you have it, complete control of a DC wye with only three push buttons.

Remember, with DC, direction is absolute, you are setting the track - EAST or WEST - it has nothing to do with the front or back of the locomotive.

If you use 4PDT relays like I do, there will be enough relay contacts for both the control and track circuits, but you will need repeater relays to drive the switch machines, unless you use the switch machine contacts for the track power.

Again,

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Not a big model railroader, just a switching layout at the moment, but my dad started me with a 4x8 plywood central in 1958. I have been following the DC DCC debate here for a year and have gotten some recommendations from Sheldon on sources to read about re the advanced DC control systems that have been developed over 70 years or so. Linn Wescott, a very bright and resourceful model railroader and part of MR for years desigined his version of DC “route control” and that story ran in 1957, in MR, starting with the May Issue I believe. It is amazing looking back at the history of this stuff, just how good a thinker the men from long ago were, to develop stuff like this. The articles are fascinating and easy to follow, if you understand how basic electricity works.

Many men developed these systems that were constantly improved over many decades. Ed Ravenscroft was a genius and inspired Sheldon. I have read his pieces also and some tremendous thinking went into that too.

Another model railroad electrical genius was Paul Mallery, reading also recommended by Sheldon. Paul was a Bell Telephone engineer that developed many useful things for the telephone company and holds numerous US patents on those. He has written several handbooks on basic electricity for model railroaders. I have the first edition of his 1955 hardcover book, the latest versions of his handbook for model railroaders along with older versions of those books. He was deeply involved in developing transistors so has seen all sides of the model railroad world one could say.

Re the topic at hand he developed a wiring diagram for a wye, with the north leg being a “stub” used just for turning an engine or train, using only one button to operate the wye turnout at the appropriate time. He made it an “X” section as Sheldon has mentioned. I have a d

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sheldon

i understand that this is how you wired your wye, that you understand and are comfortable with relay circuits and know where to get them cheaply. I see, because of the 3 relays and the extra gaps, that this circuit can unpower each branch of the wye. But i think this is overkill for a conventional wye as the OP asked about.

for a conventional wye, where the track above A is a stub long enough for a locomotive so that it can be turned, i see no need for the B & C relays. The connections to the uncommon contacts on relay A can be directly to the mainline tracks which you identified as blue and red. And there is no need for the isolation gaps between B & C.

The coloring of the connections between the A stub and common contacts of relay A depends on the position of the relay and would be opposite for the A-C route. Not sure if this is clear to the OP

i’m not sure, but i believe there is no need to power route the frog (if it needs to be), it’s always connected to the bottom, red rail of the mainline track.

there is no need for relay A if the tortoise switch contacts are used. If a tortoise is not used, then relay A could be controlled along with turnouts A, B and C using the same switches (discussed previously) to select the route. If a pushuttons are used to control the turnouts, relay A needs to be latching, either a latching relay or a 4pdt relay

34

Greg,

A few points.

First, we have no idea what the OP’s real requirements are, he never responded to my offer to post this info, and has not responed at all since my posts begain. It was a different poster, stevetx, who requested I post this.

I’m not assuming the intended use is only to turn locos. In my case, the stub end of the wye is an 8 track hidden staging yard.

Yes, the number of relays, and the features, can be scaled back as needed.

Yes, the A frog can be hard wired to the south rail. As you can see, I omitted all frog wiring, only mentioning it was possible.

Note - I use Atlas Custom Line turnouts, which are feed thru. Users of PECO or other power routing turnouts will need gaps and wiring appropriate for those turnouts.

Again, based on my vast experiance with relays, I would avoid latching relays in favor of hold circuits.

I don’t use toggles because of the need and desire to have control stations at multiple locations, local tower panel and CTC panel. And the lighted pushbuttons make a better user interface in a control panel.

The gaps between B and C assume two mainline blocks, which allows one train to exit/enter the wye, while another approches the wye. Again, no assumptions about the desired operations. And again yes, if this is just an engine terminal wye, it can be made much simpler - facts not in evidence from the OP or stevetx.

Since the B and C relays are there, the buffer circuit guards the turnouts in the two block senerio.

Maybe you are comfortable with the 1 amp Tortoise contacts, but I run four unit powered lashups pulling 50 cars, I’m not trusting them for anything beyond frogs or control signals. I know modelers who have burned them up…

And lastly, as a complete layout wiring practice, consistant methods and protocals make for neater, easier construction and easier trouble shooting if necessary.

Of couse as it turns out, the relay cab control system I i

35

sheldon

as an engineer, i’ve struggled to understand others when they dive into a topic or answer a question without providing background or explaining the unque aspects of their problems.

i’ve made the assumption that the OP is not very experienced with model railroading or at least wiring.

i’ve found your circuits confusing until you explained how they fit into your layout. i think the needs of your layout and your preferences make it easier to understand your circuits.

i’ve felt misled when starting out in various hobbies, when i’ve tried to follow more advanced hobbyists who do things in ways that were correct for them but unnecessary for a novice to be concerned with, much less appreciate.

again, i’ve learned a lot from this discussion. another tool to consider for solving problems.

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I am back with some explanation. I have been watching this thread, and (in my opinion) it is getting complicated. I work in dcc so that is why I dont know much about this. I also have a workable level of wiring knowledge (I can install a decoder), so that is not the problem. I appreciate the wiring diagrams, but frankly, they are over my head. Hopefully I didn’t come across as non appreciative…

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If, as greg said, the A track is a stub foor turning locos - the same simple setup would work for DCC as well. There’s never be a short, no need for an electronic autoreverser.

Yes, the Tortoise contacts are rated to carry 1 amp. But there’s no way those little wiper fingers on a PCB trace are going to switch 1 amp. At least on a regular basis. They are fine for frogs because 1) noremally there is ZERO current flowing when the frog polarity is switched (unless you precisely stop a loco right on the frog befor lining the points - but you shouldn’t get that close normally). And even if the loco IS parked with a wheel on the frog, other wheels will be on other parts of the turnout, so the current switched throough the frog should be minimal. At MOST, absolute worst case, a 4 wheel loco that picks up from only 1 wheel per side, parked on the frog, yoou’d have a max of one loco drawing current when the frog is switched - not many locos draw 1 amp these days, in HO and smaller anyway. However, oon a full reverse loop, or a wye that is turning an MU consist - now ALL of the track is powered by those Tortoise contacts, not just the frog. 3-4 units MUed, especially with sound decoders with keep alive (thus inrush) - you’re going to be switching a lot more than 1 amp. Much better to use the Tortoise contact to trigger a relay with 5 amp or so contacts.

–Randy

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I assure you, no offense taken in any way. And I hope all my comments have been received in a friendly spirit as well.

I surely understand that many people do not have prior experiance with this kind of wiring. I 'm sure you could learn it, but I understand as well why it may not be important to you.

For me, and many others who have been in more advanced aspects of this hobby long before DCC, these concepts and methods are part of our experiance in the hobby.

I have used DCC, I understand DCC fully and have helped build many DCC layouts. It is actually this experiance with DCC that keeps me using DC.

Respectfully, the skills and knowledge base required for DCC, are dramaticly different then the skills and knowledge base for the circuits I published above. So again, I understand your position.

Sheldon

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Greg,

I understand what you are saying, but I must say I don’t agree, and I don’t “operate” that way. I do not try to “guess” what peoples needs, experiance level, goals, and prior knowledge base are. I would rather they told me, but in the absence of that, I will still try to offer information. I try to avoid assumptions about others, but sometimes people take suff as condesending either way…

I have been accused on here before of “talking down” to people because I sometimes over explain…

But I don’t, and won’t try to decide for others what their needs are. I just try to p