My Digitrax Super Chief arrived a few days ago, so I spend most of a rainy weekend starting to convert my layout to DCC. I still would like to be able to run DC (I have about 130 Engines, so converting them all in one go is not practical or affordable), so my plan was to change one DC cab over to DCC, maintaining two other DC cabs. Initially everything went according to plan: I have updated the 220 Volt supply, integrated the DCC system into my main control board, converted 6 engines and tested programming them. So far, so good. One (major?) issue emerged when I tried to run a train around the staging loops. I have wired the loops using a bridge rectifier, so all DC trains will move in the same direction, no matter how you throw the direction switch. So whilst the train is in the loop you simply throw the direction, the train will stop, start again in the same direction and emerging from staging with your direction switch corrsponding to the direction of travel. So far, so good. But running a DCC engine into the loop gets a short. I have replaced one bridge rectifier with a manual direction switch and this works OK. Next stop is testing a automatic DCC reverser in place of the manual switch. I think it will work OK with the DCC trains, but I have no idea how DC will behave. I do not like the "singing" sound a DC engine makes on DCC: It really hurts my ears. So I guess that the Digitrax manual is true: I will convert to full DCC much faster than anticipated... Overall I am excited, and I am sure that I will master the "black art" of DCC (eventually). Cheers Dirk
Inasmuch as the DCC track signal is square wave AC, running it through a bridge rectifier will give you pretty much fixed DC on the track. Neither DC or DCC locos will work as intended in that case. Your DPDT switch will do the job as you found out. A DCC auto-reverse module can replace the DPDT, and will work well for DCC, but won't help you with DC, as an auto-reverser flips polarity right under the loco to correct the polarity mismatch across the rail gaps. DCC locos don't care about the track polarity, but a DC loco will, so you still don't have a universal solution. As long as you have a substantially mixed fleet, I would stay with the DPDT. Also, be sure that you protect against shorts between DC powered track and DCC powered track (as when a loco runs a gap between the two). Bad things can happen when the two are connected together.
It is a very bad idea to run DC and DCC on the same layout .. you run the risk of damaging your booster ..
There have been many articles written on effectively running "dual-mode" layouts, and I've seen it done in different environments a variety of ways. I did this on my former club's layout without incident even before I was aware of some of the gotchas, especially with rotary switches. The big thing is--don't run a block. You will effectively double (or more) the voltage going to your bridging locomotive which can be, as was stated, "real bad".
What you say is true .. and to err is human .. no matter how hard you try to avoid it .. it will happen .. if you are converting a little at a time .. then operate all your dcc one time, the next just DC ... its much safer ..
My layout is still in the planning stages, but I also want to be able to run DCC and non-DCC engines. I plan on wiring the layout in blocks, but instead of using a regular DC cab, I'll use a decoder mounted uder the layout. I'll have toggle switches that switch the blocks between the decoder output and the DCC ouput of the booster. This way, if there is ever a problem with a short, it will blow the decoder, but the DCC booster should be O.K. (Blowing a $20 decoder would not be good, but much better than blowing a $160 booster.) Another advantage to this is I will be able to use my walkaround throttles with my DC engines. I have not actually tried this yet, but I do not see any reason why it would not work. If anyone has any opinons on this idea or any concerns I am missing, comments would be appreciated.
Sage advice. This will prevent any possibility of the two supplies tying together and destroying something. I am designing a small layout for DCC but want to have it switchable between DC and DCC for the same reason - not every loco will be DCC initially. I will be using blocks for fault finding reasons with DCC, and for normal blocking with DC, and plan to have a master switch to switch all blocks between the two control systems at once. That way the whole layout will be one or the other, not both. Much safer in my book.
Dirk: Welcome to the world of DCC. You'll never look back. BTW, when you figure out a decoder installation for the RR 4-6-6-4 Challenger let me know. I have four waiting in the wings. Can't figure out how to isolate the motor from the frame. One is waiting to be converted into a Z-6. Stay cool and run steam....
Thanks for all the guidance and encouragement! Doug, using a bridge rectifier for DC is perfectly OK, provided that you want your engines to run only in one direction. I have currently 4 reverse loops wired using rectifiers, so for DC it is fine. But DCC is clearly another matter. I guess that I will stay with DPDT switches to continue DC ops, whilst an auto-reverser will take care of DCC. Right now I am not evne powering up the DC part of the system for fera to "burn" something. So it is either DC or DCC right now, not both. Bob, thanks. I will let you know when I figured the RR 4664. Cheers Dirk
When I build my layout, it will be both DCC and DC. I am going to have a double pole double throw switch wired to the DC side and DCC side. This way you can only operate one way or the other and not both at the same time. By doing this I will aviod any damge to any equipment. It will be wired with blocks for the DC side and thus can be used with the DCC side as well. I will be doing this as I have some units that I will not convert.
There are safe ways of doing it. Perhaps one of the easiest is to use a Lenz LT100 between the DC throttle and the track. The LT100 is designed just for this purpose and will quickly and automatically disconnect the DC when it sees a DCC signal coming from the track. If you are using a power pack that does not supply pure DC you might have to add a couple big capacitors so the LT100 does not get confused, but it works as advertised.
I've used that approach for testing decoders on a test loop, but I would recommend against it for operation. Whereas your $160 booster includes short-circuit protection, your decoder likely does not (at least on the motor leads). Every time you run a turnout (or cross into a DC block) could cost you $20. Better to run analog locos on address 00 (but don't let 'em sit too long). Doug
The Lenz LT100 is something I need to look at. I just built a store layout using selectable switches to go between a Control Master 20 and a Digitrax Super Chief. As to the reversing question... If you set up a DCC autoreverser on a reversing section, as a DC engine (running on address 00) enters the reversing section, it should continue on through the reversing section, but when it tries to exit, it will suddenly reverse direction - but if you slow down and are quick on the reversing button, it should keep moving. This statement is based in theory, not in experience - but I do plan to test this before the week is out. I'm adding a Digitrax AR1 to the wye on my Ntrak module this week.
Dirk, can you give me a few pointers? What are you using for a power supply for your Digitrax system? Being new to both Europe (US transplant) and DCC, I'm wondering what choices I have. I thought all Digitrax systems were for 115V 60 Hz. Everything here is 230V 50 Hz. -Mike
