Multiple DCC areas?

Discussion in 'DCC & Electronics' started by Travellar, May 7, 2007.

  1. Travellar

    Travellar Member

    DCC works great for my layout as is, and this question doesn't even apply, unless...

    I've given previous consideration to the idea of expanding my layout into one or two new sections. More accurately, one or two entirely new layouts, with just enough interconnecting track to really make things interesting! The challenge is that there is no way I could run three layouts from my current operator's spot. I'd love to do three independant layouts, with three independent DCC systems. I'm just wondering about one of the technical issues involved.

    I thought of two, strictly DC, layed in series with eachother to provide isolation for two sets of DCC equipment? The question though, is whether a locomotive that runs from a DCC area of track into a DC area of track would understand that it needs to keep running?

    *edit* if this works, it could really change the way club layouts and modules are set up, as one operator could run a set of yards with switching, while more operators could run the mainlines.
  2. rogerw

    rogerw Active Member

    Im not sure but my guess would be no. Why not run all dcc?
  3. Travellar

    Travellar Member

    Well, I just did some expierimenting to test my own theory, and the answer appears to be YES! Although it's possible that not all decoders will play nice.

    I want to run all DCC, but I may wish to run two or more independant DCC systems. The idea of a DC section is just to isolate the signals between the different DCC regions. The first thing I learned was that an inductor is neccisary in the DC section, to avoid grounding out the DCC sections during the momentary short that will occur when the locos cross over. The second thing I learned is that the only inductor I have in the house has WAY too much resistance, and trains will only crawl along that section of track.

    Hmm.. I'd better go repeat this expieriment with my other locos, all of which use different decoders.
  4. Travellar

    Travellar Member

    Experimentation is complete.
    My first loco handled it fine, but needed more current to keep it moving at decent speed.

    My second loco took the sudden lack of an input signal as an order to stop, and began slowing.

    My third loco handeled everything just fine, although I'm concerned it may have simply switched to DC mode. (Dual mode decoder)
  5. steamhead

    steamhead Active Member

    You can set up a DCC system into what is known as "power districts", which is the equivalent of "blocks" in DC systems. Each power district has its own booster (power supply), and they're all integrated through the central command station. You can set up various outlets around the layout where you can plug in your throttles so you can follow your train around on its travels, or have fixed throttles at areas where the operations are localized (such as yards, or busy industrial areas). There is no need to do any "experimenting". It's already done for you. Most "major" brand systems have this ability to integrate a whole layout into one operating system.
  6. 60103

    60103 Pooh Bah

    Travellar: at one DCC symposium we were told to avoid all possibility of feeding current between a DC and DCC system as it could be very hard on one system (I think it was the DC). This was after a suggestion that DCC could be one block in a cab control system.
    I don't understand why you want to separate the DCC layouts, unless you have incompatible master controls. As steamhead said, you should be able to define them as separate power districts (if you need more power) but they can still be wired so that trains pass between them. If you don't need over 5 amps, you can wire them as one district.
  7. baldwinjl

    baldwinjl Member

    I think this generally falls into the Not a Good Idea category. I don't think I'd want to be shoving DC into the DCC system (which will happen when you go from on to the other), and I'm not confident the decoders will be happy in the long run. I am still struggling with the why part ot the question, though.

  8. BigJim

    BigJim Member

    I would think a RF walk around throttle would be less expensive than separate DCC systems. Unless multiple trains are running in the other sections there should be no power problems.
  9. MasonJar

    MasonJar It's not rocket surgery

    What he said...! :D And not just because of the electrical mysteries, but also simple practicality. Even in DC, you do not generally transfer one loco from one throttle to another. Rather you flip switches so the same throttle "follows" the loco around the layout.

    And I don't really understand the reasoning behind wanting to run different sections of the layout with completely independent DCC systems either...? :confused:

    The advantage of DCC is that is gives you control over any engine, anywhere on the layout, independently of any other engine. So separating the layout into completely different systems is going to make things more difficult, in my opinion.

    If the real concern is that you can't operate all parts of the layout from the "operator bay", have you considered walk-around? Just about every DCC system comes with this capability - all you have to do is install additional jacks for the throttle (or go wireless). That should cost you a lot less (and be easier to do) than setting up and isolating independent DCC sections/systems.

    Following up on what steamhead and 60103 said... you only need additional power districts if the total load of engines in any given district exceeds the capacity of the power supply. You may want additional districts for signalling, etc.

    Hope that helps.

  10. MasonJar

    MasonJar It's not rocket surgery

    Just a follow-up, re-reading what you have said...

    One can already do this with existing DCC systems. So I don't think that it would change anything. For use of a DCC system (Digitrax) for this scenario, look at Welcome to the HOTRAK website, my local modular club.

  11. Travellar

    Travellar Member

    I wouldn't want to feed DC into a DCC system, because the filtering on the DC side would act as a short to the DCC, thus endangering the DCC side. However, that problem is easily overcome with an inductor.

    I wouldn't want to link one DCC system directly across from another, because I know any locomotive with more than one pick-up axle is going to cause a momentary short from one track to the other. (think of a ballon loop, if you don't have a maens of reversing polarity on the loop before it gets back to the switch) It's not DCC to DCC damage that I'm worried about, it's the decoders not knowing whether that particular set of pulses was for it's address, or someone elses throttle. Or worse, Locomotive #3 gets addressed by one decoder, then picks up throttle bits from both decoders, and now thinks it's supposed to be going the other way!

    As for the "why" question that seems to be causeing so many confused emoticons, try not to think of this as a way of integrating multiple layouts. Instead, think of it as a way for multiple layouts to exchange trains.

    The real impracticality here isn't so much the suggested setup, as the building and operating of multiple full sized layouts in close proximity. After all, I'm not throwing my layout into the back of a pickup and driving over to anyone's house this weekend.
  12. baldwinjl

    baldwinjl Member

    IF I wanted to do this, I'd have a DPDT on the interchange track, and power it from one or the other system, maybe even have the switch deaden a protective section at the end of the non-controlling system. Drive the train onto the interchange, throw the switch, and drive it off with the other system. You could probably even throw the switch on the fly, so long as you know it's break before make.

    I don't like th inductor idea too much. The DCC signal isn't really fast, and it isn't really AC, and I think the inductor is going to mess up the signal on the track if you really got it to the point where it really protected things. I'll stand by my though that that method is not a good plan. A switch would make it easy.

    Most decoders can switch back and forth from DCC to DC, so that will probably be ok, even if you go from one system to the other. Some have a CV to enable/disable this feature.
  13. Travellar

    Travellar Member

    okay, just so I don't leave everyone with the impression I'm either being stubborn or trying to pick a fight, here's what I had in mind for the isolation section...
    *note* if you're using a very high quality DC supply, you'll want inductors on both DC feeds. (big ones!)

    The isolation section only needs to be a little longer than the longest set of coupled engines you will run. In fact, make it as short as possible!

    The inductor isolates the DCC systems during crossover from the DC regulation. The only thing not isolated is some DC bias.

    And I know it goes against the paradigm of one operator following one train around. This is more like one yard controller getting the trains out of City A stockyards, and City B's yard controller dealing with it once it arrives. (perhaps a dispatcher organizing traffic on the mainline between cities A, B, and D as trains arrive)
  14. Travellar

    Travellar Member

    actually, I think you just inspired a much better idea of how to do this. A double pull, double throw relay to select the decoder, and a set of sensors fed into an automatic reverse loop mechanism to drive the relay.

    with that, the only thing you have to worry about is whether each loco's programmed modes are compatable with each controller.

    (sorrey, I was typing out the previous post when you posted that.)
  15. MasonJar

    MasonJar It's not rocket surgery

    It's not that... it's just that you seem to be trying to do something for which there is 1) little demand, and 2) an easier way to do it in any event.

    I guess perhaps this is like Everest - "Why did you climb it?" "Because it's there." ;) :) :D

    If the systems are built to NMRA specs, and the decoders are NMRA compatible, then this should not be a problem. One other thing to think about though is how the receiving DCC system will "select" the incoming loco. Your scenario with the "change of crews" will almost cetainly be required, since the receiving system will have to "select" the loco with a throttle for operation. The locos will not be able to continue smoothly from one independent system to another.

    Don't get me wrong - interesting dicussion, but I am not sure where it is going... :)

  16. Travellar

    Travellar Member

    I suppose anyone with a walkaround controller could follow thier train from one setup to the next, provided there are connection points available one both sides of the track. Of course, then you get three people trying to drive trains in a set-up that really does seem kind of silly, so unless you're building a 60' layout in HO, N, or Z scale this really has looped around into sillyness.

    I've seen demonstration set ups, (usually modular) where the total layout actually is 60 feet or longer, travelling in a loop perhaps 15 feet wide. At one end was a switching rig, so the operators could pull thier trains into the staging track inside thier loop. What I was thinking was that a stand alone system could be used to allow one or two operators to act as "yard crew", staging trains and doing the switching operations that some people love so much, (and others seem to hate), before handing the trains off to thier "road crews". Of course, walkaround controllers render this idea redundant, as the chief benefit is that it adds multiple interfaces.

    So once again, this is looking like a specialized application. All things considered, it's not likely I'll be trying it anytime soon myslef, as I'd need to:
    a) finish the current layout,
    b) build a new layout,
    and c) spend about a thousand dollars on a cutting laser in order to even be able to cut the holes neccisary to lay the linking track. (but then I'd have a laser beam!)
  17. rogerw

    rogerw Active Member

    Whats the name of that contest that you have to build something simple with as many steps as possible. Its a real contest but cant think of name.
  18. BigJim

    BigJim Member

    I think it was "Rube Goldberg" after the cartoons that showed complex methods of doing simple things.
  19. rogerw

    rogerw Active Member

    Yep thats it ,travellar are you one of these contest?:-D:-D:-D:-D:-D
  20. Travellar

    Travellar Member

    Not at all! :D I'm a firm believer in keeping things as simple as practical, although I do on occasion over-engineer certain projects. Sometimes though, the simplest solution isn't the best. In other cases, while the simplest solution may work, something else involving a bit more effort may work better.

    Simplest: one DCC controller for every linked railway.
    Next simplest: DC isolation tracks, with large inductors to protect thier adjoining DCC track.
    Best: (for the original problem of linking multiple stand alone railways) DPDT relay controlling and switching the isolation track, controled by sensors and a switchover logic.

    the logic for that is actually quite simple, so I'll post a diagram of it shortly for no other reason than I think it'll be fun to work it out.

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