Anyone Have a Part DC and Part DCC Layout?

[PeyRil]

Another vouch for dual controled Ntrak. I too am a member of a club with a mix of DC/DCC members. Our layout has the option for DC or DCC on each of the four lines; red, yellow, blue, green and an independant staging yard. Each is set by a DPDT switch. We've been running like this for about five years now. Thee have been shorts from one system to the other but no major issues yet. I'll also second DCC from preventing issues too. We have had a few trucks melted too, but they were all on DC operation. Thd DCC has always picked up the slightest short and shut down before any damage was done.

To C855B, that is a pretty interesting idea for the"adapter decoder". I never thought about going that route. That seems a pretty easy way to give the DC guys the benefits of wireless operation.

[chicken45]

I know BANTRAK has a DC/DCC switch per line.
Don't a lot of folks have yards that are just DC?
I remember someone at Atlas "scolded" me for running a DC engine on DCC track on 00.

[Nato]

         The Wasatch N Scale laout http://www.wasatchnscale.org is divided into blocks with add on selectors, boundries are set by the size of the layout at various shows. A Rotary switch dial on each selector is numbered 1-6. Operators with DC trains would select numbers 1-5 six was is reserved for DCC which can be turned on while usuing DC. The problem we encountered were DC trains forgetting to observe a 6 on the dial and wait for the DCC train or tarins to clear the block. After a couple of shorts that damaged DCC locomotives we have instutited a new policy. A sign up sheet at shows the first person to sign up for a two hour or so time block lists wheather his or her train is DC or DCC. then all trains in that time block will have to confirm to being the listed mode. We try and be fair to the few DC only members we have left in the group and not hog all the time with DCC. Besides many locomotives do have dule mode decoders so I can run a decoder equiped locomotive on wireless DC if DC trains are running, or run it as wireless DCC if that is the mode during that time block. My home layout which has been wireless DC forever has no blocks, so soon I will allow for DCC ops by flipping a switch, then run DCC locomotives , or flip it back to run DC.                                             Nate Goodman (Nato).

[djconway]

My old layout was started in 1990 as a pure DC layout. DPDT toggles and 4 position double stack rotary switches up 4 cabs were in use at any time.
In Feb 1996 I decided to go to DCC, with 88 locos in the roster and decoders running $35 a pop I thought it was going to be a long drawn out process to convert.
I purchased 2 Aztec frames, 2 DN93 decoders and an Atlas GP-38-2 with factory DCC.  Removed one cab and installed a Digitrax Big Boy system in its place, threw all the switches to that cab, and was running the GP-38-s in about 5 minutes, added a analog loco (address 00) and was running 2 locos in the same block. 45 minutes later one of the Aztec frames was under a SD-45 - now I could control 3 locos at once.  I was in hog heaven .  I don't think I switch back to DC for 3 months, then it was to run my steamers.

Not all of the 88 locos were converted, some just couldn't be justified $30 loco, $35 decoder = shelf queen, others $300 I1sa $300 M1a and other steamers are still on the to do list.
Come on in the water's fine. 

[tehachapifan]

Thanks for all the great replies! You have convinced me to convert my local (switching) line to DCC. Now I need to decide which system to get.

[djconway]

... Now I need to decide which system to get.

and that is a whole new can o' worms.

[ChristianJDavis1]

BTW, I think it's much easier to melt down a loco on DC than DCC.   DCC is more often better at sensing shorts and shutting down.

I can attest to this. A friend of mine just recently melted both the truck and walkway of his new MicroTrains SW1500 when it derailed on a switch (on DC power). When on DCC, however, the short normally triggers either a sound indicator or the power will cut out, making it easier to save derailed locomotives/rolling stock.

[mmagliaro]

Heh... I really must poke my nose in here and stir the pot.

Just to be clear, there is nothing more inherently "wheel melting" about an all DC system than a DCC system.
The reason folks have had these horror stories is because they are using, in all liklihood, power packs
and other throttles that rely on a simple thermal breaker to protect against overloads.

Those thing take seconds to blow, and if it's not a dead short, but just an overload, they might take 30 seconds,
or not blow at all.   The nice electronic protection circuits that are built into a DCC system are something
that people should have in their DC throttles as well.   

I build this stuff for myself, so at the moment, I can't think
off-hand of anybody that makes a little module you could wire in front of your throttle to provide this
kind of protection, but I'm going to go looking so I can suggest some.

I am saying this because, if you intend to run a mixed DC/DCC system, why not
provide the same kind of fast-acting protecting for your DC throttle?

And also for the record, I have heard plenty of horror stories in the other direction.  A DCC booster
rated at 5 amps can happily deliver 5 amps at the full track voltage without tripping its overload,
and if an errant wheelset  lodges itself in a switch, for example, and conducts a good deal of that current without
tripping the 5 amp limit, it will melt like eggs on a summer sidewalk.   Just speaking from experience.

[mrhedley]

"And also for the record, I have heard plenty of horror stories in the other direction.  A DCC booster
rated at 5 amps can happily deliver 5 amps at the full track voltage without tripping its overload,
and if an errant wheelset  lodges itself in a switch, for example, and conducts a good deal of that current without
tripping the 5 amp limit, it will melt like eggs on a summer sidewalk."

That's exactly the scenario I could envision and am looking to prevent.  I haven't had a meltdown problem anywhere on the DC side because my Innovator system has excellent circuit protection.  If it were to happen anywhere it would likely be on the local cabs, one or two of which are just old trainset powerpacks.  And on the DCC side it's not a concern with the 1 amp Easy Cab starter, but a 5 amp booster will be necessary if I want to power the whole layout.  And given how long it's taken to get the layout to this stage, I will be in the ground before I install decoders on the rest of my loco fleet.  A DC/DCC hybrid for the rest of the layout seems like the answer.

[craigolio1]

A hybrid layout will likely be in my future as well.

I have a question about wiring though. You always hear of people running a bus of 12awg or similar wire for a DCC bus and then short feeders.

With a system based on blocking, do you then have to basically home run a pile of 12awg wires for each block back to the switch locations? Or can smaller wires be used because you don't have one pair of conductors feeding the entire layout?

Thanks.

Craig

[mrhedley]

Craig, I suspect the easiest solution would be a primary buss with each block acting as a separate power district.  The buss would be rated for the full 5A so that will be 12ga, and each power district approximately 1A, so either 14 or 16 gauge would be adequate depending on how much voltage loss the track and accessories would require.  The secondary feeders (power district) will feed a number of terminal blocks located so that track feeders are limited to 3' or less of 22 gauge solid wire.  At least that is how I plan to do it.

[jnevis]

I have considered building a layout that uses DCC for most lines but using DC for a light rail commuter line around town, maybe even expanding it slightly to include something like CalTrain/Amtrak CA trains between towns, setting up optical sensors to stop and hold a train for a few seconds before sending it on its way.  Of course it's the proverbial "dream layout" at this point.  I've seen my trains a few times in the last year or so.

[jagged ben]

A hybrid layout will likely be in my future as well.

I have a question about wiring though. You always hear of people running a bus of 12awg or similar wire for a DCC bus and then short feeders.

With a system based on blocking, do you then have to basically home run a pile of 12awg wires for each block back to the switch locations? Or can smaller wires be used because you don't have one pair of conductors feeding the entire layout?

Thanks.

Craig

The reason we oversize bus wires is to reduce voltage drop.   Since voltage drop depends on distance, how important it is depends on the distance of your runs.   If you have a small layout, the practical difference between #12 and #14 wire will probably not be noticeable. 

[mmagliaro]

Correct.  The distance of the runs is what really drives the gauge of that bus.
I don't know why you would think that the 12 ga bus would only be needed for DCC.   
A DCC bus has to support every engine running on the system, so yes, you need a heavy
bus.  Or... you could physically divide your layout into electrically isolated sections, and run
one heavy bus wire out from the booster to each one, so that each bus only has to carry
the load in that section.  This is a good idea anyway, to diagnose any future problems.

A plain old
DC common-rail system still needs block feeders running from the control panel block selector
switches all the way out to where the block is.  If that distance is long, you need heavy wire.

It's all a matter of distance, how many engines, and how much voltage drop you can tolerate.

Let's say you plan on being able to pull a full 5 amps, whether it be DCC or DC.

I would also suggest that any more than a 1/4 volt drop and you are going to notice it.

Heck, even at medium cruising speeds around 6 volts, I used to notice it on my old layout when a 2-engine
pair reached 12 or 16 feet away from the nearest block feeder and the voltage would drop by 0.25v.
(I installed more feeders!)

So...
E = IR   
0.25 = 5 x R
R = about .05 ohm

If you have more than .05 ohm in the wire, you will see too much drop.

Now you can go look at the AWG wire tables to see if 12 gauge is okay.

Here's a handy on-line calculator:
http://www.cirris.com/learning-center/calculators/133-wire-resistance-calculator-table

10 feet of 12 gauge is .016 ohm, so 12 gauge is plenty big enough for a 10 foot run.  (And remember,
that means OUT and BACK, so only 5 feet away from the DC throttle or the DCC booster).

10 feet of 16 ga is .04 ohm, still low enough for our example case.

How long are your wire runs?  That's the key.