I'm about to install an MRC 470 (I think that is the right number) Auto Reverser into a reversing section currently without track power. Does it matter whether I use the same poliraty as the main section where the DCC controller is when I hook up the track power or do I need to wire it in a reverse polarity? I think I want to wire it so the polarity changes when it enters the reversing section, because if it is wired to reverse polarity when it leaves the reversing section, wouldn't that affect all of the trains running in the main section?
If I'm over thinking this, then I'm not clear on how these auto-reversers work.
Mike
Mike,
I would think that it would need to have the same polarity as the section before. Once the train is safely "inside" the [isolated] reversing-section and begins to enter the section with the opposite polarity, the auto-reverser immediately detects the "short" and changes the polarity to correct it.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
It doesn't matter because a properly functioning auto-reverser will immediately sense reverse polarity and flip to correct the polarity.
The key is to correctly gap the rails to isolate the reversing section.
The only feeder wires that should be connected to the input side of the auto-reverser are feeder wires from the bus wires outside of the reversing section.
The only feeder wires that should be connected to the output side of the auto-reverser are feeder wires to the rails inside the reversing section.
No feeder wires inside the reversing section should connected to the bus wires.
Rich
Alton Junction
Thanks Tom and Rich for the replies thus far.
Tom. If I do what you suggest, doesn't that create the problem I mentioned in the original post? Assuming it is wired so that the transition is from main section to isolated reversing section and back into main section, wouldn't the auto-reverser flip polarity for the entire main section as the train left the isolated reversing section with obvious consequences to other trains running in the main section?
Rich. Your answer has confused me. This auto-reverser has two red wires designated to be attached to the main section and two yellow wires designated for attachment to rails in the isolated reversing section. There is no designation for an input or output side of the reverser.
Does the reverser provide electrical flow from the main section, through the reverser to the isolated reversing section, thereby negating the need for any electrical feed off the buss directly to the isolated section?
Surely this is a standard issue that applies to auto-reversers generically.
In a nutshell, yes. The red wires are the input, the yellow wires are the output. There should be NO conenctions whatsoever fromt he main bus to the isolated section OTHER than from the yellow wires of your sutoreverser, otherwise this totally defeats the auroreverser. The isoalted section MUST be completely isolated from the main section of the layout.
As far as polarity of the connections - it won't matter, because by definition a reverse loop will not match the main section polarity at one end or the other. Depending on which way you connect the wires of the autoreverser, whichever end matches will change. Until the first loco crosses the gaps and the autoreverser swaps to make the main and isolated sections match - as it should. The autoreverser will then flip polarity again as the loco exits the isolated section.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
It sounds to me that you are still thinking in DC while trying to wire for DCC! Reversing the track polartiy in DCC does not affect the direction of a train. The polarity reversal is necessary to make the polarity of two adjoining lengths of track match in order to avoid shorts. It will not matter whether a train is entering or leaving a reversing section with the MRC reverser. Only the reversing section will change polarity and it will change to match whichever section of track the train is leaving or entering. The train will not change direction and should not hesitate if all is working properly. Yes, the wiring of the MRC reverser is indeed as simple as it sounds. The two red wires are connected to your main DCC bus (polarity does not matter) and the two yellow wires connect to the rails of the totally isolated reversing section (again, polarity does not matter). Do not connect the main DCC bus to any part of the reversing section. That's all there is to it! The MRC reverser will take care of the polarity matching automatically. Just make sure to use isolating rail joiners or cut rail gaps in both rails at both ends of your reversing section.
Hornblower
Yes, I'm thinking in DC terms, but that, to some extent, is because I'm trying for figure out what I need to disconnect and what I need to keep from my layout that was mostly built and wired before I added DCC. For example, the isolated reversing section that prompted the initial question is currently managed using a DPDT switch wired to the buss through an Atlas Selector. Clearly, thanks to everyone's help, I now understand that I need to totally disconnect that.
There is a second section (a hinged 'duck-under') where a reversing situation occurs, and now that I understand that track power is provided through the auto-reverser, I won't have to do some tricky wireing to that section.
Thanks to all.
mreagant Rich. Your answer has confused me. This auto-reverser has two red wires designated to be attached to the main section and two yellow wires designated for attachment to rails in the isolated reversing section. There is no designation for an input or output side of the reverser.
Sorry for any confusion. Randy answered your question in his subsequent reply.
Keep us posted on this.