# Question about having DCC and DC sections on a layout



## spacomp92653 (Jul 5, 2018)

My question is, if there is an outer loop wired and running DCC, and an inner loop running on DC only,

can I connect the 2 loops using 2 turnouts where the connectors from turnout to turnout are the isolating

type, and have it work ok? So if a loco on the outer DCC track puts front wheels onto DC turnout but the rear wheels

are on the DCC turnout, what happens? Do I burn everything up? Is there a correct way to do this? I though about a

section of track between the outer DCC and inner DC that is longer than the loco, is electrically isolated, and is on a

toggle switch. Bring the loco onto that section, stop, and flip switch to DC, then proceed. What is a good way to do this

or is this a foolhardy notion I should forget?


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## Mark VerMurlen (Aug 15, 2015)

If you've got locomotives that will do both DC and DCC, why not just use all DCC for both loops? DCC uses a form of alternating voltage on the rails. I don't have any experience trying to tie DCC together with DC, but I don't really see how its possible.


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## spacomp92653 (Jul 5, 2018)

I should probably sell off my DC only locos and Keep It Simple


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## flyboy2610 (Jan 20, 2010)

DCC is a square wave alternating current, so you would have DC going in one end and AC going in the other end. Sounds like a very effective way to let the magic smoke out of the decoder to me.


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## flyboy2610 (Jan 20, 2010)

Instead of selling off your DC locos, why not install a decoder in them? It's really not that hard. There may even be people on this forum that would do it for you.


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## spacomp92653 (Jul 5, 2018)

well, my favorite is an Atlas N scale GP-9 and I did not think a decoder would fit. And I did not know that DCC was AC voltage. So those tiny decoders take AC current and

make it into DC current to the motor? That is pretty amazing.


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## J.Albert1949 (Feb 3, 2018)

_"can I connect the 2 loops using 2 turnouts where the connectors from turnout to turnout are the isolating
type, and have it work ok? So if a loco on the outer DCC track puts front wheels onto DC turnout but the rear wheels"_

Crash! Boom! *Bang! POP!!!!*

You DO NOT want to do this.

There must be NO CONNECTION (electrical or track) between the DC and dcc portions of the railroad.

I'm not saying it's impossible or undo-able.
*But...* without REALLY knowing what you're doing, unintended consequences will result.
Along with burned-out equipment...


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## DonR (Oct 18, 2012)

As others have said...under no circumstance can you have DC and DCC currents on
CONNECTING TRACKS. The loco wheels spanning any insulated joiners would
get a jolt or both AC and DC and the loco likely go poof.

You can however, have EITHER DCC or DC by using a DOUBLE POLE, DOUBLE THROW (dpdt)
switch. Thrown one way the entire track is DC, thrown the other way it's DCC. A word of
caution tho: A DC locomotive cannot be permitted to sit idle on a DCC track. It will be damaged.

I don't know the N scale loco you refer to, but DCC decoders are available that are tiny
enuf to install in Z scale locos so you could use one of those in a crowded situation.

Don


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## spacomp92653 (Jul 5, 2018)

well that is kind of useful to know that a DC loco sitting idle on DCC track will be damaged. no one has ever mentioned that to me while shopping locos.


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## Lemonhawk (Sep 24, 2013)

I'm not to thrilled about even using a DPDT switch to set the entire layout between DC or DCC. Too much risk of inadvertent leaving a DC locomotive on the track when you make the switch to DCC and not noticing the hum and smoke while the Locomotive is destroying itself. Pick one DC or DCC and live with it!


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## vette-kid (May 2, 2020)

Lemonhawk said:


> I'm not to thrilled about even using a DPDT switch to set the entire layout between DC or DCC. Too much risk of inadvertent leaving a DC locomotive on the track when you make the switch to DCC and not noticing the hum and smoke while the Locomotive is destroying itself. Pick one DC or DCC and live with it!


I was actually considering doing just this. reason for doing so it's too simplify things for my 7yo if I'm not around. If the DCC system isn't working, he can switch back to DC just with a limited loco line up. HOWEVER, his trains are running loco genie decoders and CAN operate on either DCC or DC. We only have a few pure DC locos and I'm working on decoders for those. The locos with regular decoders are dual mode as well, so there is little risk of damaging one in our case. Unless he leaves one on the track and cranks the DC power up to use the loco genies and it goes flying around the track into something.

Sent from my Moto Z (2) using Tapatalk


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## traction fan (Oct 5, 2014)

spacomp92653 said:


> I should probably sell off my DC only locos and Keep It Simple


spacomp;

Keep it simple, yes. Sell of your DC locos? Not necessarily. Unless they are very old clunkers, it might be better to upgrade your DC locos to DCC, by installing DCC decoders in them. 
On your original question regarding having DC on one loop and DCC on the other, NO don't do that. 
A more common, and much safer for your equipment, solution is to install a DPDT( Double Pole Double Throw) electrical switch on your layout. Connect the layouts track feeders, or bus wires, to the center pair of terminals on the DPDT switch. Connect your DC power pack to the pair of terminals on the left, and your DCC controllers output wires to the pair of terminals on the right. Now, by throwing the switch, you can run either DC, or DCC, but not both at the same time. The DPDT switch will prevent the output of the DCC controller from connecting to the output of the DC power pack. If that ever happened, it would probably damage your DCC controller.

Traction Fan 🙂


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## flyboy2610 (Jan 20, 2010)

spacomp92653 said:


> well, my favorite is an Atlas N scale GP-9 and I did not think a decoder would fit. And I did not know that DCC was AC voltage. So those tiny decoders take AC current and
> 
> make it into DC current to the motor? That is pretty amazing.


Here is an NCE decoder for an Atlas "Classic" GP-9: NCE 524142 (N12A2) Plug and Play Decoder for N Scale Atlas "Classic" GP7, GP9, GP30, GP35
These are designed to replace the existing light board in the locomotive. If your loco has a light board that resembles this (without all the electronic components, of course) then this will simply replace the light board and you have DCC!


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## mesenteria (Oct 29, 2015)

You can run one layout on both DC and DCC, but never....and I do mean NEVER...concurrently. One OR the other. And that's why you are advised to force yourself to have to reach to a hidden toggle, maybe behind the fascia of your layout, and flip it. That toggle should have 'either/or' logic, or 'lockout' logic in its design, and therefor the switch of choice is a DPDT.

You CAN run all modern decoders on DC current. They have to have CV29 configured to do that. There are CV calculators on line for CV29.

You CAN run DC engines on DCC current, but the system must allow for it. Digitrax does, but I don't know if any other does...I don't have familiarity with any other manufacturer's specs. On Digitrax systems, you acquire Add "00" on your throttle and begin to advance the throttle. The locomotive will slowly begin to move and then to speed up as you dial in speed, just like your decodered engines.

If you do elect to try running a DC locomotive on DCC powered rails, expect generally poor performance and a lot of unpleasant noises. The reason is that the DCC current is actually a digital current, zeros and ones, and they alternate, but not in a predictable sine wave the way household current does. The 'zeros' get stretched in time, some of them quite 'long', to get slower speeds from lower throttle settings. This alternating current makes the motor's motion alternate in concert, and the result is a lot of buzzing, squealing, and groaning from the slop in the drivetrain. You'll hate it after 12.7 seconds.

Finally, yes indeed, never forget and leave a DC locomotive unattended/forgotten on DCC powered rails for more than a couple of minutes tops. The motor will quickly heat up due to that inherently binary current when the rotor can't turn because of the configuration of the signal.


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## MichaelE (Mar 7, 2018)

Dun't duit Laddie...


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## CTValleyRR (Jul 26, 2014)

spacomp92653 said:


> well that is kind of useful to know that a DC loco sitting idle on DCC track will be damaged. no one has ever mentioned that to me while shopping locos.


That's because they want to sell you a loco. Telling you it can't sit on an energized DCC track doesn't help get a sale.


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