Running both DCC & DC locos on the same layout.

[CRL]

Here’s my dilemma: I have a significant collection of older DC locos from pre-DCC era. Not all of these are easily converted to DCC using the “split” boards from TCS... specifically the small switch engines.

I’ve also acquired enough (whatever that is) DCC compatible locos that I have not yet converted to DCC. I’m designing my home layout, and I may have a large enough branch line section that could be set up for the DC locos only, leaving the bulk of the layout under DCC.

Are any of you running such a combination? Was it worth the additional effort to keep your DC legacy locos?

[davefoxx]

Not me.  Once I went DCC, I went all-in.  Of course, I've been known to purge the fleet now and then, e.g., moved from HO to N in early 2000s and went back to HO in 2017.  Those purges do make it easier.  Perhaps you would consider selling some/all of the DC engines to help fund the decoders needed for the DCC ready locomotives or upgrading the remaining DC locomotives.

Since I went DCC, I would never consider going back to DC.  And, since I went to DCC and sound, I would never consider going back to silent locomotives.  This, of course, required major surgery on a few locomotives in the fleet, but this has become a fun break from working on the layout.  In fact, I'm becoming comfortable enough with this that I just bought a 1990s-era HO scale Life-Like Proto 2000 E8, which I will be gutting to upgrade from DC to DCC and sound.

Hope this helps,
DFF

[nickelplate759]

It doesn't have to be a lot of effort if you can make the DC-only area one large electrical block.  In fact, if you do that, you can add a DPDT switch to change from DC to DCC (or back) at a moment's notice.  If I were to do that, I'd still treat it as a  separate block when running DCC, and provide it's own short protection (I like the DCC Specialties PSX series).

At the very least this will be handy for troubleshooting loco problems as you are converting them over to DCC - remember the advice from @mmagliaro (paraphrased) - first get the loco to run well on straight DC, then add DCC.

[CRL]

Thanks. Good advice. My dilemma is complicated by being in n-scale and being a bit of a locomotive junkie including a couple (ok - maybe more than a couple) of Japanese prototype diesels I envision as using for industrial switching. This doesn’t count all the locomotives not in my regular rotation but squirreled away in boxes and forgotten about.

Maybe I need to attend some Locomotives Anonymous meetings first.

[C855B]

Don't forget that layout design also works into this - the plug'n'play auto-reverser boards depend on DCC as does a lot of available block detection. If you plan to have reverse loops or wyes, DC starts getting slightly complicated.

[Dave V]

Can't speak for other systems, but one of the things that brought me over to Digitrax back in my N scale days is that at least back in 2005, it was the only system I knew of that allowed for simultaneous operation of DC and DCC locomotives.  No special power blocks and no toggle switches are necessary.  That's still the case.

DC locomotives operate on Digitrax with address "00."  Now if you have multiple DC locomotives on the layout at once, they'll all respond to that "00" address.  But that'd be the same in DC without blocks or sections you can toggle on/off.  While your engine operates on 00, you can operate all your DCC locomotives independently as well on their assigned addresses.

I'm gonna also recommend something that may be considered DCC "heresy" but I believe in it.  My club is modular, and back when it was DC only they had "kill switches (simple toggle switches)" to kill power expediently if one train were in danger of rear-ending another (it's single track so all trains follow the same direction).  When the club went DCC, we found the kill switches were great for parking DCC engines so that they didn't stay hot when not in use.

I've done that to the RGS...  Virtually all yard trackage has kill switches so that my DCC engines aren't "cooking" while not in use.  I figure--perhaps ignorantly--that decoders all have a finite number of hours before the big poof and the stinky smoke.  No sense in letting the meter run when the engine is, say, in the roundhouse or sitting in staging.

In fact I'm probably going to go back in and do the same for several passing sidings on the line.  Any place I might like to park a train for a meet, it'd be good to be able to power off the track.  It's almost always just me operating so trains may stay in place for some time before I'm able to move them along to the next station against other traffic.  I know...it's the RGS and I should be running one train twice a week, LOL.  But more trains = more fun!

[dougnelson]

Are any of you running such a combination? Was it worth the additional effort to keep your DC legacy locos?

Yes, and successfully so.  My layout is basically a double track system with 2 blocks per track.  It was originally built with 2 DC cabs and each block could toggle between cab A or B with three-position toggles (Cab A, Cab B and off).  When I acquired my DCC system I simply switched out one of the DC controllers for the DCC system.  I can now run one track with DCC and the other with DC, both tracks DCC, or both tracks DC.  I was amazed how simple this was and I really have no need to convert my DC locos.  I was surprised how simple it was with no changes to the layout.  Here is a photo of the control panel and the layout plan.

[peteski]

Just make sure that you never ever, ever,ever, ever allow a locomotive cross between live DC and DCC power blocks.  Did I mention "never"?  SInce we know that mistakes can and will happen, it would make sense to keep the DC and DCC parts of the layout completely separate (no possibility of crossing).

The early DCC system's DC loco operation  using "pulse stretching" technique was deemed to be too much trouble (along with possible motor damage) and was deprecated on most (if not all) DCC systems.  Does Digitrax even still have that capability in their newer command stations?

[nickelplate759]

Just make sure that you never ever, ever,ever, ever allow a locomotive cross between live DC and DCC power blocks.  Did I mention "never"?  SInce we know that mistakes can and will happen, it would make sense to keep the DC and DCC parts of the layout completely separate (no possibility of crossing).

The early DCC system's DC loco operation  using "pulse stretching" technique was deemed to be too much trouble (along with possible motor damage) and was deprecated on most (if not all) DCC systems.  Does Digitrax even still have that capability in their newer command stations?

I've never tried this.  What would happen?  I presume the escape of magic smoke would be part of the experience.

[peteski]

I've never tried this.  What would happen?  I presume the escape of magic smoke would be part of the experience.

I don't dare to find out, but I'm sure it will not be pretty.  Better to avoid it.  If the DC throttle is old-style rheostat-based, that will likely survive, but even with short circuit protection, since we could be back-feeding voltage into the booster, the DCC booster's output transistors might give out the ghost.

[Steveruger45]

If it were me I think I would wire the layout for both DCC and DC operation but only use either dcc locos or dc locos at any one operating session.  You can still enjoy either style locos that way just not simultaneously.  In fact that’s how my layout progressed.  As it was a dc only layout first that I converted to dcc and did exactly as mentioned until I dcc’d all my locos.  My layout still has this ability but never used now as a dc layout.

[CRL]

Frankly the combo approach seems dicey to me. I would envision having a separate branch line or industrial spur with isolated interchange tracks where the DC and DCC locomotives remain exclusively on their own trackage with any dual system interchange tracks accessible only using a LOTO (lock out tag out) switch.

[peteski]

If you only planning on a single booster and single throttle, safest approach would be to feed power to the track through DPDT switch to select either DC or DCC.  That way there is no possibility of having both power types ever being connected together.  Of course that requires the layout to be single block.

[Maletrain]

If you only planning on a single booster and single throttle, safest approach would be to feed power to the track through DPDT switch to select either DC or DCC.  That way there is no possibility of having both power types ever being connected together.  Of course that requires the layout to be single block.

I am thinking about doing something similar, but in my case it is to be able to run DC locos around an outer loop for testing and break-in before converting them to DCC.  The tracks inside an inner loop have reversers, PSX breakers, etc. that I think don't work on DC, so I do not want to switch the whole layout from DCC to DC, I want to switchjust the outer loop.  That loop is isolated from the inner loop, yard, etc. by track rail insulators at the crossovers.

My idea would be to have a switch that feeds DCC to the whole system, or DC to only the outer loop.  So, effectively, there are (at least) 2 power blocks.  All get fed through the PSX breakers by the DCC command station, or only one gets fed by the DC power, and that feed bypasses the PSX breakers and reversers, so that the other block(s) remain unpowered while I have DC on my outer loop block.

I am wondering if I can do that with a quad-pole-double-throw switch.  One pair of poles would connect or disconnect the DCC command station before it feeds the PSX breakers and reversers to all of the blocks, while the other pair of poles disconnects and connects the outer loop block directly to the DC power pack/throttle or to the output of the PSX breaker for that block. 

My concern with that arrangement is that an inadvertent use of the crossover between my inner and outer loops while the outer loop is in DC mode and the inner loop is unpowered would potentially connect the output of one PSX breaker to the DC power, and, maybe through that breaker, connect the inputs of the other PSX breakers and reversers to DC power, as well. 

If it is an issue to be certain to not back-feed the DCC breakers with DC power, another way to deal with my specific layout design would be to move the pair of QPDT switch poles for the DCC connection to be located between the PSX breaker outputs from the inner loop only.  That way, the DCC would still be connected (but maybe turned off anyway) to the other DCC blocks inside the inner loop, but those would be isolated from the live DC block by a completely dead inner loop block.  So getting a locomotive to bridge the gap between a DC powered track and a piece of track with DCC breakers/reversers still connected would not be possible. Unless maybe I am dumb or unlucky enough to run a DCC engine from the yard onto the dead inner loop at the same time as I run a DC powered loco from the outer loop onto the dead inner loop.

The only other way I can see to do it with more than two power blocks would be to have a "2xN"-pole-double-throw switch for "N" power blocks, or have "N" relays operate off a single switch, both of which seem really complicated.

So, does anybody know what happens if you back-feed a DCC breaker with DC power, assuming it is not connected to a DCC system when that happens?

[Ed Kapuscinski]

Can't speak for other systems, but one of the things that brought me over to Digitrax back in my N scale days is that at least back in 2005, it was the only system I knew of that allowed for simultaneous operation of DC and DCC locomotives.  No special power blocks and no toggle switches are necessary.  That's still the case.

This.

Digitrax lets you run both. DC operation isn't perfect, and you may not want to do it for long periods of time, but it works.