Ok you DCC junkies...

mtntrainman Mar 13, 2012

  1. mtntrainman

    mtntrainman TrainBoard Supporter

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    Questions for ya:

    I'm using n scale Unitrack now (Dont faint...LOL) :tb-nerd:

    For the sake of simplicity....envision a layout 32 inches wide by 44 feet long. Single main with numerous passing sidings. It will have turn arounds at both ends. The last 20 feet of the 44 feet will have a yard with double ladders...one on each side of the main...plus some industries. Now if my simple math is correct...that makes roughly 100+ total running feet of track...plus the yard.

    Questions:

    1) Will I need boosters?

    2) If boosters are needed do they need to be mounted near where needed...or...can they be mounted at one end of the layout and wires run to where the booster needs to be wired in ? ( hope that made sense )

    I realize in reality its probably more complicated...but simple minds need simple answers...for right now anyways...LOL.

    At some point I will probably put in a crossover somewhere which will probably double the single line trackage to near 200 feet. I know...I know...that introduces a whole different set of problems as far as boosters go...LOL :tb-wink:
     
  2. Avel

    Avel TrainBoard Member

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    no, but you will need feeders. Although a booster would be nice to have if you divide your layout into power blocks so that if there is a derailment and a short, the whole layout won't shutdown, just that one section.

    Also depends on the amount of engines you will be running at once. Just try out all of them in a line maxxed out against your hand or something and measure the amperage draw.

    Do you even have a DCC system?

    i actually have a loop of kato unitrack and at approximately 5 feet from the feeder(where power goes to the rail) there is a slight voltage drop and the engine runs noticeably slower. Really messed up my speed matching efforts until the realization hit, anyway..............

    Maybe you could try permanently soldering six foot sections of unitrack together and have feeders going to every section.
     
  3. mtntrainman

    mtntrainman TrainBoard Supporter

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    I will most likely do the power blocks...for shorts etc isolation. Yes...I have an older DCC system but will be 'upgrading' very soon. Most likely 4 locomotives at one time...max.
    :tb-cool:
     
  4. markwr

    markwr TrainBoard Member

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    The need for boosters is dependent on the number of locomotives you will be running. Add up the maximum current from however many engines you want to run at once and if this number is less then the output of your command station you don't need an extra booster.

    If you use extra boosters you can place them together or close to the section of track being powered. There are advantages to both ways. Placing the booster near the section being powered shortens the bus wires to the track feeders, so you can use smaller gauge wire without having voltage losses. Having the boosters close together makes easier to troubleshoot certain type of problems, as you can stay at one spot and check the outputs of all your boosters.

    If you did run with an extra booster positioning the boosters at the ends wouldn't provide the optimum setup. Using the dimensions provided, positioning the first booster at eleven feet and using it to power the track from zero to twenty-two feet, and positioning the second at thirty-three feet and using it to power from twenty-two to forty-four would keep all your track within eleven feet of a booster.

    In the end there is no one correct way. It's a matter of what's right for you.
     
  5. RBrodzinsky

    RBrodzinsky November 18, 2022 Staff Member TrainBoard Supporter In Memoriam

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    George,

    The JACALAR has approximately the same amount of track, all being run by a single Digitrax Zephyr, so no, you do not need boosters. I do have the layout divided into five power districts, for short protection. Two of them are also auto-reversing. The other three are the yard, the city area and the mountain area.

    As noted above, and as Bob will tell you, feeders, though, are a must.
     
  6. CSX Robert

    CSX Robert TrainBoard Member

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    The need for additional boosters is much more dependent on the power draw of the locomotives and any other accessories you have running off track power than the size of the layout. The exception to this is on really large layouts you do not want to have extremely long power runs so they may need more boosters than the power draw would suggest.

    With only four locomotives, you should not need any additional boosters(I say additional because the command station itself contains a booster). I would place the command station in the middle of the layout to minimize the length of the longest runs.

    You also do not need additional boosters if you want to setup power districts, you only have to add circuit breakers.
     
  7. Railroad Bill

    Railroad Bill TrainBoard Member

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    Agree with prior posts. Amps needed determined by engines running, not track length. Power districts for shorts control. Boosters (if needed) placed for convenience to wiring, mostly. Do suggest that you do a little trial and error which should be easy with Unitrak. Just set up the system you want with minimum wiring and some track mice then "see how they run." Start with simple version, then add trackage in phases. If you ever prove a need for more than minimum feeders, power districts, amps, etc. then do the next minimum addition to the power situation/wiring.

    Suggest that track joining is a key element of good running.
     
  8. mtntrainman

    mtntrainman TrainBoard Supporter

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    Okay...I think I'm getting it

    More and More running locos determines boosters

    Power districts...yes

    Feeders...feeders...feeders...feeders...cant have to many feeders !

    Next question:

    The buss wire...can it just be run down the center of the layout (underneath) and all track tie into it...or...or does it need to follow the oval of trackage ? In otherwords...44 feet versus 88 ?
     
  9. RBrodzinsky

    RBrodzinsky November 18, 2022 Staff Member TrainBoard Supporter In Memoriam

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    Forty four is just fine. Actually, the best way would be to locate the command station about halfway, so you really have two 22 foot sections
     
    Last edited by a moderator: Mar 13, 2012
  10. mtntrainman

    mtntrainman TrainBoard Supporter

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    AHhhhhhhhhhhhhhh....I gotcha...thnxs :thumbs_up:
     
  11. ken G Price

    ken G Price TrainBoard Member

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    If you're dividing it up with power districts with breakers for short circuits then you will run the first set of wires from the command station to what ever breaker unit you use.
    Then from there buss wires to each district.
    Then feeder wires off of the district buss to the track in that district.
    All of my buss wires from each breaker end up at the farthest piece of track in each district.
    The feeder wires are run from it.
     
  12. DCESharkman

    DCESharkman TrainBoard Member

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    George

    Split the layout in half by the length. Use one booster centered in one half and the command station in the center of the other.

    Now you add DCC Specialties PSX units to give you isolated power districts. The number of PSX's would be determined by your track plan. But judging by the description, a PSX-4 on each side should be sufficient.
    You will have trouble free operation as long as your feeders and buses are clean. You also have the protection against derailment shorts.

    Now all you need to do is figure out the power draw from all sources to size the booster and command station.
     
  13. nscalerone

    nscalerone TrainBoard Member

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    I have a room sized "Unitrack" layout with large yard. I use a single length run of "buss" wire (10 ga.) with 20 ga. solid wire for feeders. As to feeders, the best "rule of thumb" I've heard ( & used ), is feeders every three to four feet, and feed every leg of every turnout.
    Go Unitrack!!!!.........................
     
  14. rsn48

    rsn48 TrainBoard Member

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    Also don't forget to check out what size wiring you use for your power buses, if you put your booster in the middle, that is 22 foot runs, number 14 wiring should be good to go. 14 is the size of wiring used in house wiring. I had some left over so I stripped out the wiring from the general cover that surrounds both wires, this could save you money if you or a friend has some kicking around.
     
  15. Railroad Bill

    Railroad Bill TrainBoard Member

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    Am always surprised at the concern for wire gauge for bus, branches, and drops, as well as the total length of runs. My experience is not with very large layouts, but I have done 4x10 through 4x14 and now 2x8 w/o ever seeing issues arising from conductivity/resistivity. In fact, have allowed the electirc to be carried by the rails for some very long sections; I do not follow any rule like 1 drop per x feet. My rule is 1 drop per isolated section.

    So here's something to think about: How long a run (power pak to rail) before there would be issues? Do you think it, or have you seen it (multimeter or performance, DC or DCC?)

    Another think about thing: If you use common wire, common rail wiring, even for DCC, what about the difference in run lengths between the two wires? Signal timing for DCC & total circuit resistance in DC. Again, how big the layout before any of this matters.

    Being not so proficient or smart when I started, I chose two wire or parallel wiring method because I can see what wires go where and am not confused by the wire harnesses, etc. Simplicity and clarity were important then. Still are. Of course, occasionally flip the A/B rails when installing or repairing. Ouch. Again, I have soldered the black one to the wrong rail. Ouch, ouch.
     
  16. rsn48

    rsn48 TrainBoard Member

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    Bill, I don't pretend to be an expert on electrical issues, when I started in the hobby I knew how to turn a light on and off in a room, anything beyound that was pushing it. I do know many talk about wire size and length of run so I'm assuming their electrical know how far exceeds mine. Since electricity is energy it makes sense that a larger "pipe" (wire ) is need to push through the needed amount of amps. Can you imagine a northern oil pipe line that is the size of an outdoor garden hose.

    I also know when using demanding power tools outside, some distance from the house, or electric grass cutter, that one shouldn't rely on the crappy orange extension cord we all own, and preferably get one with 14 size wire in it instead.

    Here is from Gardner's blog on DCC wiring:

    "SUGGESTION #4-8: Put Your Boosters Electrically Central to Their Operating District

    Actually, calling this a recommendation is almost an understatement. It is now almost mandatory that your mount your boosters central to their power district.

    Be sure to read about terminating your bus wires in the section on track wiring. Modelers have found that when their wiring from their booster is more than 30' feet long, they have encountered problems. The worst of which is blowing locomotive decoders.

    Therefore, the conventional wisdom is now to locate your boosters in the middle of the track bus that they serve. Doing this will allow you to make a track bus that is 60' long. Just attach your booster to the middle of your track bus."
     
  17. Railroad Bill

    Railroad Bill TrainBoard Member

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    Well, you answered my question about when length becomes significant, i.e., over 30 feet to 60 feet. Good to know and as I've said, using my largest layout I've never approached those limits.

    My pique arises from reading routine posts about how many power drops, how great the wire gauge, all that soldering of joins, etc. Usually this is for garage layouts, 1 small room layouts, or, at most, the "round the wall" type. In my megalomanic dreams I don't see an exhibition sized layout in my future, so I'll take the convenient position of locating the power pak where its convenient for me, the layout and using whatever wire gauge is at hand (until I see/measure degradation.)

    My current garage layout is 2x8 and I use 22ga. drop wire for all wiring around the trackage and then a small 16ga. bus cut from larger bus of 4x14. The "bus" run is at most 24" from the DigiZephyr. All works quite well.

    Hope others understand that I'm not questioning using appropriate wire for appropriate bus circuits, but appealing for common sense in the recommendations. Never hurts to know what works.
     
  18. DCESharkman

    DCESharkman TrainBoard Member

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    No so fast........

    This 30 foot rule is actually easily defeated with proper wiring practice to include the wire materials themselves. Using high quality 16 gauge wire, I have driven over 50 feet from the power booster and not had any issues with either the DCC signal or the ability to detect shorts. Terminations on the bus are not founded in proper science, just trial and error in a case or two with no real information of the wire or the wiring technique used. I a very large layout with no bus terminators at all and have no issues with short detection or anything else.

    While I am an Electrical Engineer and wiring comes easy for me, I see and hear an awful lot of wrong interpretations of electrical behavior that are used to make even poorer electrical decisions, AKA NTrak and the ridiculousness of the 12 gauge wire requirement.

    Why is there a 30 foot rule? Because there was not enough attention paid to the overall signal composition of the DCC signal. All calculations were made using the base pulse repetition frequency and forgot about the frequency content of the signal inside the pulses. Using a combination of the Fourier Transform and the Convolution Integral for all of the signal components will yield the harmonic distribution and associated frequencies. There are two higher order harmonics that create an extinction signal that is 180 degrees out of phase. Due to the reactance of the wire, this extinction signal is either large or small based solely on the material quality of the wire. And in reality, bigger wire is not better with compound variable square wave signals, this is a false thought from looking at the American Wire Gauge. The problem there is that the values there are only good for DC and 50-60Hz sine wave systems. Neither of these are applicable to the frequency or the wave shape of the DCC signal.

    So the 30 foot from booster supply is due more to the wire you use than anything else. The extinction signal is what causes the the wave shape to degrade, this is usually called dispersion of the signal. The distance is then related to the amount of dispersion created to the point where the signal is no longer reliably recognized. Cheap 12 gauge wire has so much reactance, that the power stored in the harmonics can limit the length of the bus. The funny thing is that the same quality 16 gauge wire has 40% less reactance than the 12 gauge wire. So it wall actually have a cleaner signal longer.

    Very high quality wire works the way folks generally think. Yes with very high quality 12 gauge will be better for distance than 16 gauge wire of the same quality, and this is due to the large conductive cross section of the wire. The problem is, this very high quality wire is also very expensive. But there are a great deal of mid-quality wire at reasonable costs.

    Not all flexible wire is the same. It is comprised of many small solid wires. The key here is to get the highest count of wires. I have seen 18 gauge wire with only 6 conductors, very poor quality. And I have seen 18 gauge wire with a bundle of 24 wires, very good quality. The other thing that matters is the twist rate on the wire, higher twist rates are preferable to lower twist rates. This information is included with high quality wire, but not with any wire you will buy at home improvement stores.

    There is so much mis-information about something as simple as wire.........

    The true way to select wire is not by distance, but by calculating the power consumed over a distance. In many cases you may be shocked to find out that your power consumption is less than a 100 Watt light bulb. When is the last time you saw a 100W light bulb wired with 12 gauge wire?

    Do the math. 8 amps at 12 volts is 96 watts.

    Correct calculation of power is best way to get started, then choose the wire sizes. Things will be a lot more reliable then.

    22 gauge wire is a good starting point for track feeders, that is what I use. As for bus wire, that depends on what is is expected of the module, the power district or the layout.
     
    Last edited by a moderator: Mar 18, 2012
  19. RBrodzinsky

    RBrodzinsky November 18, 2022 Staff Member TrainBoard Supporter In Memoriam

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    David,

    Thanks for the explanation. That (to a technical person) is very clear and specific, and helps validate some of my own observations (but without ever hooking up a scope to observe the DCC signal).
     
  20. rsn48

    rsn48 TrainBoard Member

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    Dave, for the rest of us electrically challenged types, could you interpret this into English... thanks.
     

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