DCC question

Discussion in 'FAQs' started by billk, Jul 5, 2001.

  1. billk

    billk Active Member

    Don't know much about DCC, and don't plan on using it for now. BUT, is there anything that should be done to get ready for maybe adding it later? I understand the size of the wiring providing the juice to the tracks typically needs to be larger when DCC is used. Is that right? Any other gotchas?
  2. Woodie

    Woodie Active Member


    I've done a lot of research on DCC and how it works. For proper DCC "ALL" you track should be live. You can't rely on frog switching to provide power to certain parts of the track. This is because DCC operations can include sound, lights etc, and you would want your engines sitting there idling in the yards, with lights on etc maybe when not in use. The reason for heaftier wiring is that all power to the layout is provided through one transformer/circuit and all loco's requirements are provided through that single circuit. ie. you may run 2 -3 controllers now with each controller powering "blocks" or one for the yards, and one for the mainline and the other for the second mainline etc.

    With DCC there is a constant 12 V DC across the track. The voltage does not vary. It's the digital signals the DCC systems places on a "sub frequency" (if I can call it that) that the decoders utilise to power everything. Sorta like having a mini-controller in each loco.

    Analogue controllers are really designed a provide enough power to run a single loco. Try running 3 - 4 - or five loco's through the one controller, and see how hot it gets. Too much draw on the power. You will need to wire the track to cater for 12 V DC at about 5 amps. The wire you are using to wire the track should be sufficient for that. Just make sure you have power to ALL parts of the track. You can use a "block" system in the meantime, then install DCC, and then just switch all you blocks on all the time. Most DCC systems provide 12V DC at about 5 AMPS. If this is insufficient for the entire layout (running more than 5 - 6 locos, including stationary ones, with lights on, sound etc) then you will need a "booster", If you have "blocked" your layout, adding a booster would be simple. Just divide your sections in two, and connect the "booster" to half of the blocks. IF you have wired you layout as a single circuit, then adding a booster could be a little more difficult.

    With the booster, you will have (say) 5 amps to one half the layout, and 5 amps to the other half. The digital signal from the DCC box will be superimposed over both sections.

    Most DCC decoders are capable of drawing up to 1 AMP from the tracks. (sound, lights on/off, motor etc) also stationary decoders can be used to switch points, signals, requiring one 1 circuit of AC to all the point motors etc, instead of individual circuits.

    A properly wired analogue system should take DCC easily, however if you start with DCC in the first place, then wiring a layout is much simpler, but there is no going back. ( no need for blocks, just run a single 12v DC circuit under the layout board that follows the track, and pop it up onto the track where necessary. Maybe two section (blocks) if you intend to have lots of loco's. (and require a booster). DCC also provides for auto reverse/loops as well, without having a double pole switch.

    This help a little?


    DCC is an excellent method, however is pricy!!!

    [This message has been edited by Woodie (edited 07-05-2001).]
  3. Gary Pfeil

    Gary Pfeil Active Member

    Billk, Woodie has given a most thorough answer and everything he says is correct. I use DCC and have built several railroads in the past with cab control. Cab control wiring isn't all that complicated, there's just a lot of it. FYI, I use Digitrax, and the booster is 5 amp. I have run six locomotives with lighted passenger cars with no problem. The current requirement for a given loco is determined by the loco itself, the decoder only has to be able to handle it. I have only installed decoders in relatively efficient locos, ones that draw .3 to .5 amps. The decoders are rated at 1 amp, so no problem. You are supposed to check current draw of each loco by measuring current while preventing the motor from turning (stalled). I have not done this. That .5 amp could go over 1 amp stalled. In all my years in the hobby, I have never seen a loco stall. Spin its wheels, oh yeah. My advise DCC or not, never weight a loco to the point where it won't spin its wheels.

    I run 14 gauge wire, black and white(north and south rails, respectively)under by roadbed, and use 22 gauge drops from the rail to the bus. If you are using turnouts which are non power routing, you can just put drops as required for maintaining reliability, there is another thread on this forum dealing with this. However, if your turnouts are power routing, you need to gap and feed much like conventional cab control. There are auto reversing units available too, you can operate thru reverse loops without flipping any toggles.

    My advise would be to check into DCC and if you are going to use it, don't bother wiring for cab control. You still may want to have a couple blocks for troubleshooting reasons, or, as Woodie said, to add boosters later. This can, of course, be added later, by cutting gaps in the rails, and cutting the bus wire also. My reference to troubleshooting means this: If there is a short, the whole railroad goes down. Where is the short? Sometimes it can be hard to find. If you have several blocks, you can turn them off one by one to isolate the problem. My shorts are usually a microswitch controlling frog polarity didn't throw, needs adjustment, or I left a tool across a rail somewhere.

    You may want to check www.digitrax.com They have a lot of info on their site, as well as links to other informative sites.

    Good luck!
  4. billk

    billk Active Member

    Guys - One good reason for "adding DCC later" is if you're doing N-scale. The decoders are still a little too big for many applications, but like everything else electronic, they will pprobably shrink over time. Does anyone know the smallest decoder currently out there, or have a feel on how they have shrunk so far?
    Gary - re your comment about stalled locos. If you have gotten a short from leaving a tool on the track, what if you leave something on the track that doesn't cause a short but does stop a loco? I used to work at Underwriters Labs (UL) and we used a stalled motor condition as the "worst case" load for whatever equipment we were testing, even though in some cases the chances of that condition occurring was pretty slim.
  5. Gary Pfeil

    Gary Pfeil Active Member

    Billk, Yes, you are right about N scale. I wasn't thinking about that. I have a friend who operates on my railroad and loves the freedoms that DCC brings, but his layout is n scale and he also isn't crazy about losing weight to fit a decoder. Sorry, didn't realize. Concerning stalled locos, yes I know you should plan for the worst. If one of my locos runs into an obstacle, it will spin its wheels. At least I think it will, hasn't happened yet, as I follow my trains around the layout. The only places the train would run unseen is the hidden staging areas, where I never lay anything down. (Yeah right!) I'm a bit of a gambler, I guess. Probably rethink this strategy after I burn up a decoder. Perhaps I should now tell you to do what they say, not what I do.
    I think I'm pretty well covered since the proto 2000 units, and Stewart, draw .2 or .3 amps, and the digitrax decoders I use handle 1.5 as I recall. I have some old Athearn units which as I remember draw about.8, I haven't yet installed decoders in them (the newer units are so much better, I just haven't felt the need to) but when I do, I will install decoders which handle higher current. I hope that the day comes soon when you N scalers will be able to easily use DCC-its awesome.

  6. billk

    billk Active Member

    Gary et. al. - Another question - apparently you can run with some, but not all, locos converted to DCC with decoders and all, right? No need for a lot of detail, I'd probably just get confused.
    Bill K

    [This message has been edited by billk (edited 07-06-2001).]
  7. Furtak

    Furtak New Member

    Yes, in most DCC systems you can run analog on the 0 circuit. I can control one analog engine from my DCC control unit (DigiTrax). A lot of anolog trains run poorly on the digital track. Kato and Atlas seem to run the best.

    I didn't see it mentioned in earlier responses, but, Atlas is making most of their trains either digital installed or digital capable (plug and play). All of my digital installed Atlas units run both analog and digital. Digiframes also makes lead conversion frames for older analog units.

    Hope this helps,

    Jason Furtak, Boynton Beach Florida
  8. Gary Pfeil

    Gary Pfeil Active Member

    Billk, All the DCC systems I know about allow you to run one analog loco (or one mu'd set). The thing to remember is that all analog locos on your layout will respond, so you need to be able to store the analog locos you do not wish to respond on a track you can turn off. Power routed turnouts leading to stub ended tracks are good for this, turntable leads with on/off switches would be ideal.

  9. Squirrel Run

    Squirrel Run New Member

    billk Remember to have a siding or track block you can control completely (power to it only and the rest of your layout not powered. This is for the programming of decoders. Almost a necessity.

    Railroading is fun.

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