Can I run a layout on DC & DCC without frying things?

[Alantrains]

Hi all,

I am about to jump into the DCC world, but I have some old small brass locos that I still want to run on DC because they are too small for decoders and I am too old to try to squeeze decoders into them.

I have a bedroom sized layout that is wired for two cab control. I plan to use cab A as a DC controller and Cab B as the DCC controller. Has anyone tried this and will it work? What problems could I experience?

I know some DCC decoders work on DC but I have read that only one DCC decoder at a time can be used this way.

TIA 

[MisterBeasley]

What you should think about is running your entire layout on DC, or running your entire layout on DCC, not trying to run it half-and-half.  I'm not sure if that's your idea or not.  When switching over, remove all power and then do the switch, don't try to do anything "hot."  More important, though, is that you should never cross a track boundary where one side is DC and the other is DCC.  That's likely to fry your decoder and/or your whole DCC system.  If you run only one or the other, this won't happen.

Most decoders will run on DC.  Some sense this automatically, and some need to have a CV set to allow/disallow DC operation.  Some older decoders won't run on DCC.  Hopefully, someone who knows can give us a better breakdown that "most" and "some."  Since a DCC engine running on DC is like a DC engine, you can put as many as you want on the layout and run them, but they will obey the rules of DC.

You can also run DC engines on DCC, but not with all DCC systems.  My Lenz system allows this, and some other do too, but some definitely do not.  Again, you'll have to wait and see who comes in with a list on this one.

Contrary to popular belief, you can actually run multiple DC engines on an appropriate DCC layout, with a couple of gotchas.  First, they will all behave the same.  They will revert to being DC-like engines, so you control not the direction of the engine but rather the direction of travel, just like with DC.  This isn't bad if you want to run two DC engines in a consist, for example, because they'll always move together, but you will not have independent control of two separate engines.  The second gotcha is auto-reversers, one of the neat gadgets available with DCC.  These just don't work with DC engines, because reversing the track polarity, which does not affect the direction of motion of a DCC locomotive, does alter the direction of travel of a DC locomotive.  Finally, most DC engines just don't run very well on DCC until you install a decoder in them.  You won't like it.  They make horrible buzzing sounds, too, and there are stories of DC engines burning up, although only a few of them.

[jfallon]

From experience with a modular group, you can run both as long as they are completely electrically isolated. If at some point the DC throttle and DCC booster get connected (such as a locomotive crossing the boundry) there is a good chance that you will fry one or the other, or maybe both. The best way to isolate is to run only one system at a time.

[cacole]

One or the other, but never both at the same time.  It would be too easy to run an engine across the DC/DCC boundry by mistake, and destroy the decoder, the DCC command station, or both.

Although some decoders claim that they can run either way and automatically detect whether they are on a DC or DCC track, many of them malfunction on DCC if CV 29 is set to allow DC operation.

[floridaflyer]

If you have blocks in the dc system using the two cab controls, you would have to insure that any block that an engine enters is set to the proper system. If your idea is to run both systems at the same time and control it with the blocks, that could get interesting very quickly. If your idea is to run only one of the systems at a time, and all blocks would be using the same system at the same time, that is much easier to do and would give you the chance to run your brass. Total layout on one system is ok, If you have two independent loops that are insulated from one another both systems could be used at the same time as long as the systems stay independent . Using the cabs would work. I can run one , or a consist of more than one, dc engine on my DCC Digitrax Zephyr. But the performance leaves a lot to be desired. Trying to mix the systems using the blocks  is not a good idea. 

[Alantrains]

Thanks everyone,

looks like it's all or nothing. I might build a small shelf layout to try out the DCC conversions before I convert the whole layout.

I appreciate your practical help everyone.

cheers 

[CSX Robert]

Actually , Lenz makes a module specifically for having DC and DCC blocks on the same layout:http://www.lenz.com/products/modules/lt100.htm

[jeffrey-wimberly]

My layout is set up in blocks, as it was originally constructed for two cab DC operation. I set the DCC up on cab one and the DC power pack is on cab two. Power is routed to each block through it's own DPDT switch. Using these I can run DCC on part of the layout and DC on another part.

[Alantrains]

Thanks Jeffrey,

Do you use a common rail or do you switch both rails with your cab switches? Others have said you shouldn't bridge between an analogue and a DCC section or things will go up in smoke. How do you prevent this from happening? Do you run them at different times or both at once?

The LT100 Analogue protection module from Lenz looks like a solution for operating my logging branch on DC all the time. 

This is one of the locos that is full already and can't fit a decoder.

 

cheers 

[jamnest]

I do not believe that you should try to do both DC and DCC on the same layout.  Too great of a risk of an accident wich could fry everything. A Digitrax DCC system will allow you to run one DC locomotive on your DCC powered layout.

Also Digitrax makes a very inexpensive Z scale Decoder that is rated at 1 AMP and is very small.  I have used severeal of these DZ123/DZ125 decoders to convert some of my Athearn BB switcher locomotives to DCC.  Hardwiring these locomotives was easy once a place could be found under the shell to place the decoder.

[Vail and Southwestern RR]

Thanks Jeffrey,

Do you use a common rail or do you switch both rails with your cab switches? Others have said you shouldn't bridge between an analogue and a DCC section or things will go up in smoke. How do you prevent this from happening? Do you run them at different times or both at once?

The LT100 Analogue protection module from Lenz looks like a solution for operating my logging branch on DC all the time. 

I'll start by saying I don't really like the idea, though I know Jeffrey has done it, and as far as I know, so far, avoided trouble.

I don't think there is any way to do this common rail.  That would have the outputs of the two systems half tied together, and can't be a good idea.  If I was really going to do this, I would make it impossible to have a DCC block contiguous with a DC block, I would force a dead block in between.  It would take some thinking to figure out how to do that, but that would be my plan.

As has been said, a little Z scale decoder will fit in almost anything, I think Lenz has one smaller than the Digitrax one.

 

[jeffrey-wimberly]

Thanks Jeffrey,

Do you use a common rail or do you switch both rails with your cab switches? Others have said you shouldn't bridge between an analogue and a DCC section or things will go up in smoke. How do you prevent this from happening? Do you run them at different times or both at once?

I switch both rails. I got away from common rail a long time ago. I usually run DCC and DC at the same time. The DCC trains run on the main while the DC locos work the yard and inside loop. There's a track section between the yard and the main that trips an alarm if a DC loco goes onto it while the main is switched to DCC.

[Alantrains]

Thanks again Jeffrey,

I'll probably do the same and only run DC on the logging branch, it already has the neutral section between it and the rest of the layout.

Thanks everyone else for your help.

regards 

[Cannoli]

My old 4x8 HO layout was setup as Jeffrey described, originally for two block DC but then when I moved to DCC I hooked the system up to CAB A and left CAB B connected to a DC pack. I would always ensure that the block switches were all set for CAB A and that the power switch on the DC pack was in the off position before turning on the DCC controller. This worked well for a year before I tore down the layout to make room for a bigger which was DCC from the beginning.

[CSX Robert]

When I first read this thread, I remembered reading about using DC and DCC on the same layout using a light bulb for protection, but I could not remember where I read it, so I did not mention it. I came across it again tonight, and it is from the Digitrax SuperChief manual:

4.10 Using DC and DCC together on the same layout

When running between DCC track sections and adjacent conventional
DC powered tracks, both rails must have insulating gaps.

The DC supply used must have some form of current control. A 5 to 10
Watt 12 Volt lamp placed in series with one of the DC power pack
track leads will work for this purpose. This allows the DCC booster
to drive the locomotive onto the DC track with minimum interruption
and stress to the booster, decoders and locomotive wheels.
When the lamp lights as the locomotive bridges the gaps it acts as a
“shock absorber” between the DCC and DC track sections. It is best

to cross these gaps quickly and not bridge the DCC and DC sections
for any longer than necessary.