G Scale Model Train Forum banner

1 - 20 of 31 Posts

·
Premium Member
Joined
·
243 Posts
Discussion Starter #1
I have gone through the list looking for some good information related to implementing reversing loops but I haven't found what I need. Most of what I have found seems to be focused on LGB system, controls, and their accessories. While I do have a LGB trolley, the bulk of the rail system will probably be powered by MTH locomotives and ultimately their DCS system. The track is Aristo-Craft SS and most likely the switches will be too.


In the process of designing my layout I am trying to decide whether or not to include a reversing loop in the system. I like the idea of being able to turn the a train around and have it go the other direction but I am concerned about the mess this is going to make out of the controls. Regardless, I may want to run trains in the opposite direction.


It appears that using DCS, the polarity of the track voltage and the polarity of the control signals must be matched to the direction the train is facing. I assume that all I need to put a double pole double throw (DPDT) switch into the system to deal with trains running in different directions, regardless of whether I do it will a loop or manually pick the locomotive up and turn it around. Correct?


Can the track controllers, particularly the MTH ones, assist in automating this activity? Is there a way, using sensors, to tell the track controllers to do this automatically? Is there a controller that would adapt to this environment from another manufacturer? (I know I can do this pretty easily with an independant controller, such as a Basic Stamp or other micro controller but ... at least for now, I would rather not go that route)
 

·
Premium Member
Joined
·
4,716 Posts
Sorry, I have to say it



Reverse loops don't bother battery powered locos.
 

·
Premium Member
Joined
·
420 Posts
Tom - if you send a DCS controlled loco through a reverse loop, the engine will continue on exactly the same speed and direction as before. But you are correct that the DCS signal would not be getting to a PS 2.0 equipped engine. So to regain command control, you need to reverse polarity. You can do that with a DPDT switch. You could also connect that switch to the AIU connected to the TIU, and control the polarity from the remote.
 

·
Super Modulator
Joined
·
21,004 Posts
No you don't have to say it Tom.

DCS does not need a battery car, or drilling holes in your loco for a charging plug, or recharging when it's most inconvenient, or chargers for that matter, and DCS users can run smoke and lights all day without worrying about running down the batteries faster. There's other advantages.

Now when I say "sorry I have to say it".... that makes it reasonable and helpful?

Back to the subject, I'm not a DCS expert, but cannot you run DCS on AC? If so, possibly a DCC autoreverser would work.

Maybe Chuck or Raymond know.

Regards,

Greg
 

·
Premium Member
Joined
·
243 Posts
Discussion Starter #5
I thought about running the system on AC but based on reading the MTH online manual, it appeared that I still need to have the DCS signal going to the correct set of wheels which negates the advantages of AC. So it came back to the need to swap the signals regardless of whether or not I ran AC or DC. Is that correct?


I also see the there is an opinion that AC has more noise, or whatever, and that the DCS systems have more trouble communicating. I have no idea if this is a totally valid view or not or if it is a carryover from the O Guage community.


The other problem with AC is that if I want to be able to run guest trains, I may need to be able to switch to DC power and run the whole thing on manual mode.

Batteries aren't really an option right now. I am trying to control how much technology and cost I throw at this thing to get my feet wet. My goal is to get a basic layout functional, then add DCS, and finally add any additional automation that I can dream up.
 

·
Premium Member
Joined
·
420 Posts
Yes, AC will not work in the way you want it to. It works for 3 rail as you desire. Stick with a method of reversing the polarity. You could even use an LBG accessory switch motor to automatically change the polarity. I think your idea of getting the RR up and running is a good idea. I have found that once the RR meets up with outside conditions, it's best to keep things simple. Therefore, if you don't need the reverse loop, don't use it. If you need it but are able to create a loop in addition to the reversing path, do that.
 

·
Registered
Joined
·
938 Posts
It is true that polarity need to be correct for the engine to operate right but once you have it running you will follow the same rules after that as any track power based engine... You have to flip the polarity on the return track to keep the engine from shorting out when it re-enters. So, if you put the TIU between your power source and the reversing loop controller it will work fine as the signal will always be on the + lead. The only question would be would the reversing loop electronics negatively impact the DCS signal. My guess is probably not but it is a possibility. If it does I think I know of a way to fix it, just report back. Actually report back anyway, I will be interested to hear of a successful implementation and would like to document it on my website for other users.

That is an interesting idea Greg as on a DCC reversing loop setup. Something to look into.

I like John's suggestion too, get up and running and see if you really end up wanting or needing it.

On the difference between AC and DC power and it's effects on signal strength, the opinions I've heard so far indicate there isn't a difference. (But that doesn't mean there isn't. I've heard some good reports from AC users on long linear feet loops.) The biggest impacts I have seen so far that impacts DCS signal is 1) Stainless steel track over Brass. I think the electrical resistance of the SS rail is detrimental to the signal over longer runs or higher amp levels. Good feeder lines really help with this. Folks using brass rail can run long loops with no feeders and never seem to have track signal issues. 2) is power supply type. If you are using what I hear are called a 'linear' supply (which are more expensive and are heavier[from the large copper wound transformer inside]), you will get better track signal than if you use the much cheaper and lighter 'switching' type supplies.

If you know you're going track power then I highly suggest you do it right from the get go and use all direct to rail stainless steel railclamps (I like splitjaws) and add your feeder wires. On my DCS tips page on my website I have information on the type of wire I used and how often I connected the feeder wires. I did a buss configuration so I only had one set of wires going from the house to the track then ran jumps every 24 feet or so from that point till I made a complete loop. If you do it right from the start, you will save yourself aggravation and time. With my setup, I haven't had to mess with anything and I'm going on 3 years now.

Good luck and let us know how you make out.


Raymond
 

·
Registered
Joined
·
297 Posts
I run my MTH on AC. It has many advantages and no noise problems. AC packs are cheaper! A good DC pack is required or you'll suffer. There are rules on the wiring and it would be easier to direct you to the correct site. I have been told that dcs will operate on a reverser but I've never tried it. Ray's site is excellent for startup info on dcs. http://www.rayman4449.dynip.com/ look at the dcs pages and save this site. For great help in any DCS problem got to http://ogaugerr.infopop.cc/eve/forums/a/frm/f/93360682
these guys will answer and help out future problems.
For wiring remember to break up loops, only connect one feed to each block of track so the dcs signal does not double back on itself, and connect a light bulb or resistor to clean interference as needed. Joe
 

·
Registered
Joined
·
938 Posts
Yeah I would read the info I have on my site so you can see what my experience has been too. I've found that us in G scale don't seem to have the same issues regarding maximum feet of rail that can be served per block. I've heard of G scale folks with 230+ ft loops with brass track and clamps and have power wires going to only one spot on the loop and they have perfect 10s all the way around. From all my testing and experimentation, I went with a buss feeder wire configuration which does go against the conventional wisdom on the O gauge forums but I've gotten mine to work great. That is just my experience.

Very interesting on being able to use cheaper style AC power supplies, I hadn't heard that and will need to try that out when I have time. If we can in-fact just use cheap regulated AC power supplies with no negative effects or even better results then this is really great news! Joe, how many amps is your power supply and about how much did it cost? Is it a constant voltage AC power supply?


Raymond
 

·
Super Modulator
Joined
·
21,004 Posts
Ahh!! you will not find a regulated AC supply, they are pretty expensive...

The upside of regulated supplies is that voltage (and thus the running speed) will stay constant under load... so 2 more locos are started, and the rest that are running are not affected.

Running an unregulated supply can make a noticeable difference in speed when you change the load a lot... notice the words "can" and "a lot"

I noticed a difference on my DCC layout but I run consists all the time 2-6 locos.

Talk about varying load!

I still think that I would try AC and various DCC autoreversers.

Question, when running on AC, does a DCS loco not care about track "polarity", i.e. it will go forward, no matter what way it is placed on the track?

Regards, Greg
 

·
Registered
Joined
·
297 Posts
Hey Ray, it took so long to type, you replied before me. Anyway all I use is a Lionel 180 power brick that's under $80.00!!!! It's only going to give about ten amps so I'll need to buy another one soon. I thought it was the best value for the buck. You could hook up one to each of the four channels of a TIU I'm told. Ray, I know you run passive so your not concerned with TIU amp capacity. An electrician at work said a good computer supply might have worked also. Joe
 

·
Registered
Joined
·
297 Posts
Gregg, with AC you still have to "worry" about polarity. I don't know if the engines will short or just run without dcs signal. I'm told that DCC reversers will function with dcs. Joe
 

·
Registered
Joined
·
938 Posts
Ok. Thanks Greg and Joe.

You do still have to get the polarity correct even on AC. Of course the polarity switch on the engine makes correcting the polarity quick and easy.

That Lionel 180 I bet is a 180 watt (~ 10amp at max 18 volt output?)

Hmmm.... I'll need to look more into the AC power supply thing. Thanks for the info.


Raymond
 

·
Super Modulator
Joined
·
21,004 Posts
If the polarity matters, then you may need something more sophisticated, entering a reversing loop means the loop might have to reverse... leaving the loop, the main line HAS to reverse. if you put an autoreverser on the main line, and then set the switch entering the reverse loop to SELECT the route that "matched", then when you exited the reversing loop, the autoreverser would change the main to match your polarity.

I could make this work...

Regards, Greg
 

·
Registered
Joined
·
938 Posts
Oh and the computer power supplies I think are going to be just like any other standard switching power supply I bet (as far as impacts to signal strength) and we are talking DC power now with that. Another issue with the computer power supplies is that they have constant 12v and 5v outputs.

Thanks for the confirmation too on the DCC reversers, good to know!

Would a DCC reverser need to be used with AC track power only or could it work under DC?


Raymond
 

·
Registered
Joined
·
938 Posts
Posted By Greg Elmassian on 01/21/2009 8:46 PM
If the polarity matters, then you may need something more sophisticated, entering a reversing loop means the loop might have to reverse... leaving the loop, the main line HAS to reverse. if you put an autoreverser on the main line, and then set the switch entering the reverse loop to SELECT the route that "matched", then when you exited the reversing loop, the autoreverser would change the main to match your polarity.

I could make this work...

Regards, Greg


I don't know much about how auto reversers work, but I agree with that. You would have to reverse the main line polarity. If you put the TIU between the power supply and the autoreversing unit then you hopefully shouldn't have any issues.

Isn't that how they normally work, the engine enters the loop and when the last car enters the loop the main line polarity flips?


Raymond
 

·
Premium Member
Joined
·
243 Posts
Discussion Starter #20
I have a feeling some poor beginner looking at this thread is going to run away screaming ...

Lets clear a couple of things up.

When running on AC, there isn't polarity. The train isn't going to be able to tell which track is on which side of the AC power. It does swap the relative phase of the AC signal but I don't know of any motor that will run on 2 AC wires that is sensitive to this difference (with 3 phase, that is a different story but we only have 2 rails). Most likely the motors are really DC motors and there is a full wave bridge rectifier built into the motor controls to convert the AC into to DC.


If you take a Lionel train set to go forward and you swap the wires going to the rail, it still goes forward. Additionally, the center rail is used on the Lionel as one half of the signal and both outside rails for the other half, turning the train around still has the positive DCC signal in the center and the negative on the two ouside rails, so there isn't a problem there either. One thing this approach does is that it makes doing a reverse loop a piece of cake because there is no way to short out the power through the trucks as locomotive goes across the turnout.


Now back to the more realistic stuff we run with only 2 rails. If doing a reverse loop, we still need to somehow swap the AC signals so that the engine trucks don't short out the power as it goes across the turnout. It is possible to switch the polarity within the loop as the turnout changes position but that requires dropping the power momentarily during the turnout transition. The transition must be what is called a break before make action which means that power goes to zero for an instant on the loop track. The engine electronics may not like that, then again maybe it will just deal with it because there are already going to be small interruptions in power as the locomotive moves around an imperfect set of rails.


So can someone illuminate this loop controller or whatever it is called, that has been mentioned and where can I find more information on it?


Thanks

Tom
 
1 - 20 of 31 Posts
Top