Atlas Turntable and DCC question

[Anonymous]

I have searched the archives (ad-nausea) and could not find a direct answer to the following question:

Since the Atlas Turntable has automatic polarity reversing in it, do I still have to to create a reversing switch on my layout for the turntable?

I understand everything else as far as blocking goes but I could not find the answer to this question.

I am building a Walthers TT on top of an Atals one so that I can get the indexing ability that comes with the Atlas one and get the look of the pit type of TT.

Thanks

[rrinker]

I would feed the power to the rails on the actual turntable with an auto-reverser rather than rely on the Atlas's split rail (although I don't recall that the Atlas table DOES auto reverse, every Atlas book I have shows hooking it up to an Atlas Controller to use the extra reverse switch to change the table polarity). Anyway, split-rail reversing like that will generally work, providing the gap is big enough, otherwise it will short out as the table passes the mid point, and DCC systems react quicker to shorts. And if the gap IS big enough,a nd you have a sound-equipped loco on the table, the sound will be interrupted as the power goes away for a brief moment.
Bottom line, you CAN get away without using the reverser (if the table incorporates polarity reversal - which I was not aware that the Atlas did, unless the new ones are different from the old ones), but best practice would be to use a reverser.

--Randy

[cacole]

As long as you are going to operate only DCC, you may not need to worry about the polarity. It's all going to depend on how the turntable is mounted, and how many tracks you have leading away from it. At a certain point of rotation, the turntable's contact wipers automatically reverse its polarity. Try to visualize running a train onto the turntable with the right hand rail positive. You then rotate the turntable beyond the point of polarity reversal, so the left rail is now positive. The decoder in the locomotive doesn't care about this polarity reversal, but when you start to run the locomotive off of the turntable onto a track with its polarity set with the right rail positive, you create a short and the command station will shut down. The need for an auto reverser or toggle switch is going to depend on where in its rotation the turntable polarity reverses, and how you have the tracks leading off of it wired. If you know at what point the polarity is reversed, you can just reverse the wiring of the tracks leading away from the turntable and will not need an auto reverser or toggle switch. With DC block control, you would have to reverse the direction switch on the controller, or the locomotive would run backwards off of the turntable, but with DCC the locomotive will still run forward regardless of the track polarity, as long as the turntable and track leading off are of the same polarity.

I hope this makes things clear, because I get confused trying to explain it. [*^_^*]

[Anonymous]

rrinker:

I have the The Complete Atlas Wiring Book #12 and it does maker eference to the split ring and the fact that it does not need an additional method of changing the polarity on the turntable track.

This is what prompted my question, because of most of everything else I had read, said the exact opposite! Talk about confusion.

Cacole:

Your explanations were clear. And have given me something to look at when wiring the stall tracks as well as the approach tracks. And this makes perfect sense, either in DC or DCC.

I plan on posting pics of my progress.

Thanks guys.

[Anonymous]

shackscs
What were you going to do: power the Atlas table then run wires from those tracks to the other table? I like the idea as I wanted to incorporate it in my TT, but I hink the Atlas TT indexing is set at 15 degrees per track whereas my TT is 10 degrees per stall. My TT has 4 gaps rather than two to overcome shorts by the TT trucks bridging the gap in the pit rail. I have DCC and am going to use an auto-reverser just to be safe as the DCC booster is very sensitive to a short.

[Anonymous]

I should have stated that I am working in N scale. I was under the impresstion that the settings for the Walthers and Atlas were the same.

And yes, I am going to run power to the Walthers from the Atlas. I saw this on a website and am going to make a few mods to make this work for me.

[Anonymous]

I have an Atlas turntable purchased about a year ago, and am using it with DCC.
I wired it using the instructions furnished by Atlas and do not have any reversing methods installed. It works perfectly.
Marv

[Anonymous]

QUOTE: Originally posted by marvinstern

I have an Atlas turntable purchased about a year ago, and am using it with DCC.
I wired it using the instructions furnished by Atlas and do not have any reversing methods installed. It works perfectly.
Marv

Glad to hear that. My lovely bride just bought me one as one of my presents for our 21st anniversary, and from reading the documentation with it it did look like it could be wired so that you don't need an auto-reverser for DCC. My plan was to put the inbound/outbound tracks on the 'a' side, and the roundhouse/storage tracks on the 'b' side, and use some left-over Atlas selectors to feed the storage tracks so I could turn the power off to them. Sounds like that'll work just fine.

[Anonymous]

how do I wire a walthers turn table?

[Anonymous]

QUOTE: Originally posted by bilbetmo

how do I wire a walthers turn table?

You'll probably need to set that up as a reversing section, either manually with a DPDT switch, or with an auto-reversing module.