To DCC or not to DCC

[Anonymous]

I have recently decided to change over to DCC. Fortunately I am starting a new N Scale layout from scratch, in a room approximately 10 by 15 feet. All my current locomotives are DC but less than three years old. I plan on buying a Lenz DCC system and the decoders for N scale. My problem is converting my locomotives over, I have never had one appart. Any help for a beginner would be appreciated. I have Kato Mikado, Kato SD 40, Model Power 4-6-2, Roundhouse 2-8-0, Atlas Trainmaster X2 and Atlas RS-2.

This problem worries me enought that i may reconsider DCC if it all looks to hard.

Secondly, I have read that DC locomotives can be reun on a DCC layout but what I do not understand is how you controll the speed and direction?

I have some experience with electronics and software but am somewhat rusty. I have also spent most of my life building one kind of model or another. However, this is my first venture into Locomotive rebuilding.

[ericboone]

I am not into N scale, but I can answer your question about running a DC locomotive on a DCC layout. DCC layouts are powered by a AC square wave. The decoders turn it into a DC current for the locomotive motors. To run a DC locomotive, a DC voltage is simply put over the AC square wave.

A WORD OF CAUTION!
Be careful if you do this. Many decoders can be set to allow both DC and DCC operation. If you are running a DC locomotive on a DCC layout, make sure the DCC decoder equiped locomotives are set to run only on DCC. One time at a club I was in, a DC locomotive was being run and a couple of DCC equiped locos set to run dual mode took off and took the big plung before we could stop them.

[rrinker]

QUOTE: Originally posted by ericboone

I am not into N scale, but I can answer your question about running a DC locomotive on a DCC layout. DCC layouts are powered by a AC square wave. The decoders turn it into a DC current for the locomotive motors. To run a DC locomotive, a DC voltage is simply put over the AC square wave.

Not exactly. To run a Dc locmotive on DCC, the 0 bit is stretched out. Stretch out the 'top' of the square wave, and one rail is positive compared to the other, and the locomotive will move in one direction. Stretch the 'bottom' of the square wave and the opposite rail will be positive and the loco will move the other way.

QUOTE:
A WORD OF CAUTION!
Be careful if you do this. Many decoders can be set to allow both DC and DCC operation. If you are running a DC locomotive on a DCC layout, make sure the DCC decoder equiped locomotives are set to run only on DCC. One time at a club I was in, a DC locomotive was being run and a couple of DCC equiped locos set to run dual mode took off and took the big plung before we could stop them.

If you are talking about the Atlas 'dual mode' decoders which don't detect Dc or DCC automatically, but require you to switch a jumper. yes. But this should NOT happen with any DCC decoder that does automatic analog conversion - if with zero stretching, a DCC decoder will still see and be able to respond to the DCC signal, and should NEVER just take off.

--Randy

[rrinker]

QUOTE: Originally posted by bbnd

I have recently decided to change over to DCC. Fortunately I am starting a new N Scale layout from scratch, in a room approximately 10 by 15 feet. All my current locomotives are DC but less than three years old. I plan on buying a Lenz DCC system and the decoders for N scale. My problem is converting my locomotives over, I have never had one appart. Any help for a beginner would be appreciated. I have Kato Mikado, Kato SD 40, Model Power 4-6-2, Roundhouse 2-8-0, Atlas Trainmaster X2 and Atlas RS-2.

This problem worries me enought that i may reconsider DCC if it all looks to hard.

Secondly, I have read that DC locomotives can be reun on a DCC layout but what I do not understand is how you controll the speed and direction?

I have some experience with electronics and software but am somewhat rusty. I have also spent most of my life building one kind of model or another. However, this is my first venture into Locomotive rebuilding.

Most newer N scale locos have a decoder made by someone that will repalce the existing light board. Remember, just because you are buying a Lenz DCC system doesn't mean you are stuck using only Lenz decoders. Older N scale locos are usually a bit of a challenge as they oftern have no board to repalce AND no room for a decoder. There are several services that will mill the frame for you to make room for a decoder. As for the Model Power engines, I'm goign to guess that will be a DIY job as well. At least on a steam engine you can usually install the decoder in the tender where there's (relatively) a lot of room. The critical factor to rememebr is that the motor MUST be isolated from the frame. Otherwise, instant POOF and time for a new decoder. N scale locos usually are not set up this way, rather, the two halves of the frame are the 'wires' for the motor. This is not hard to solve though, you need to take the frame apart, solder some wires to the motor, and put something insulating like a strip of electrical tape over the points of the motor that touch the frame. Now the motor is isolated and you can connect the decoder.

--Randy

[NZRMac]

I'm running one dcc loco with soundtraxx decoder and one dc loco. they both run ok but the dc loco buzzes when stopped because the track is live with ac.

Ken

[challenger3802]

QUOTE: Originally posted by rrinker

Not exactly. To run a Dc locmotive on DCC, the 0 bit is stretched out. Stretch out the 'top' of the square wave, and one rail is positive compared to the other, and the locomotive will move in one direction. Stretch the 'bottom' of the square wave and the opposite rail will be positive and the loco will move the other way.

Further word of caution!

Bit stretching is the easiest way to cook a DC motor. Also only one DC loco can be run on the layout at any one time. An alternative and far safer way is to wire up a conventional DC power supply to the layout and unplug the DCC system.

Alright it does defeat DCC ethics a little but its far safer on the non-DCC locos!

[rrinker]

Only if it's a high quality (and expensive!) coreless motor. They have no way to dissipate the heat. You can fry those even with a DCC decoder, if it's not a 'supersonic' or 'silent running' type.
Just don't leave it sitting still for long periods of time. In HO I've had no problems even with the Canon and Buhler motors in Stewart (since decodered, but test run before the decoders arrived), and Athearn, well, I think it's nearly impossible to destroy one of those. After a bunch of laps around my test track, none were even warm. Leave one sit still for a hour or so while you run a different loco and the reults will likely be different.
N scale is a little more sensitive, if only because the motors are smaller. But keep them moving and there shouldn't be a problem.

That said, running a DC loco on DCC without a decoder will likely be disappointing, speed will be greatly reduced and depending onthe motor, will 'sing' quite loudly. Plus running a DC loco through zero stretching increases the response time of DCC locos on the same track. Not a problem on a small layout, but if there are a lot of DCC locos in operation while running a DC locomotive, responses of the DCC locomotives will slow down due to fewer packets being transmitted. But it's fine for testing until you get the proper decoder installed.

--Randy

[Anonymous]

Many thanks to all those that responded to my question(s). To avoid the pitfalls of runing both types, I think I will add my current DC power pack to the layout and run it while I sort out the installation of DCC decoders. It seems rather risky to try running both at my stage of experience. As a newbe to DCC it seems best to proceed with caution.

Which of the locomotives would be the least problematic as a first DCC conversion?

[rrinker]

At a guess, I'd say the Atlas Trainmaster. Since Atlas sold them both with and without a decoder, there is a direct replacement that should be VERY easy to fit. If your RS-2 is fromt he same run where they offered both versions, it also should be very easy to do. And the Kato SD40 should be another easy one. Check out the Digitrax and NCE web sites for their decoder selections for various locos. Digitrax probably has the most N scale varieties of all. They get VERY specific sometimes, as a lot of these N scale decoders are more or less custom made to fit a particualr model.

--Randy

[Anonymous]

I definitely would not want to go back and install DCC Decoders in any of my N-Scale engines! While some guys can do it and have fun, I'm not one of them.
You might find a Hobby Shop that will do this for you, but it would have been much easier if you could have bought them with the Decoders already installed.
You also should as yourself the question "Just how many trains/engines can I safely run at the same time?" For me, the answer is "1" maybe a second one, but I doubt it.
Now if you layout was large enough where you would have several operators at the same time, this is different. But most home model RR's are not any where large enough to need DCC.
If I thought I had a large enough layout for 2 operators I would simply use a DPDT toggle switch to go from cab 1 to cab 2 with the center position being "Off."
I like walk-around throttles as I like to be right where the train is to throw switches, un-couple cars, etc. I don't need or want DCC.
Good luck,
gtirr

[rrinker]

Nothing ventured, nothing gained! Really though, the newer N scale locos that have drop in boards for DCC are TRULY easy to convert, generally no soldering or any of that tricky stuff.
It's the older ones that need frame milling and motor isolation that get tricky..

--Randy