DCS and isolated outside rail

I've done it without noticing any DCS issues.  I used a relay between the isolated track and the accessory.  It has been a while.  Maybe someone else can post details, or maybe that is covered in the other thread.

The other thread started out as a phasing question and I didn't want to hijack it, so I posted here.

I've seen it mentioned that it's better to use both outside rails in common, so I'll be interested in the answers as well.

There are lots of threads on using relays in isolated rail applications.  

I didn't notice an issue with my DCS signal.

John,

  Interested in what others have to say their experience is with this also.

PCRR/Dave

I use one outside rail for detection without any negative effects on DCS operation.  In fact, GRJ, you've seen my layout operate using only one outside rail for common/DCS and the other for detection.  No signal degradation, but be careful to be consistent about which outside rail is common and which one is isolated.  This can get confusing in areas with lots of switches and interconnected tracks.

I have had major issues with isolated outside rail with some MTH steam engines on the shop layout.  The length of rail was about 10' on each side of a signal bridge used to trigger the signal.  I think the issue has more to do with the 2/3 rail trucks.  The engines were PRR 2-10-4 and K4s to be specific.  When the rail was re-connected, the engines worked fine.  The track work is pretty solid on 2x6 frameing covered with 5/8 plywood.

I think you might be OK with short sections of isolated rail.  I have opted for the IR activated relays because of this.

Dave

I sure have Pat, I've just seen comments here about using both rails, so I figured it would be interesting to see what other folks suggest.

Dave,

That sounds more like an issue with power to the engine, rather than DCS signal.  It would have been interesting to see if that engine had the same problem in conventional operation.

What I mean is that those engines might need the ground on the side of the isolated rail for some reason.

George

I am familiar with relay use, as I have three 2RC controllers from Three-Rail Innovations that I used on my old layout, plus standard relays I used to run 252 crossing gates. I can use short sections with the 2RCs, as they have timers and many, many other features. Each has two relays to work with. I also have one for lighting, but I'll probably input that one with toggles. I'm asking this question because I can't find any information searching previous posts.

My layout is wired with only one connection to an outside rail on each pair of power wires. I also connect both outside rails when necessary to insure a Common rail for engine power, typically around switch track non-derailing control rails and isolated rails for trackside accessories, such as crossing gates, signals. etc. My trackside accessories use a separate, phased AC power supply that's rectified to DC. The DC return (-) is phased with AC track Common.

I have no DCS signal issues whatsoever.

I believe that many times operators relate an engine losing power as being caused by poor DCS signal strength, which is rarely, if ever, the case.

Marty, so you recommend that in the area between every switch, one install a jumper across the outside rails, and the contact made by a train's wheels (subject to they're being dirty) is not enough?  I have frequent drops to outside rails, but have not installed jumpers.

Is this for DCS signal or for electrical distribution reasons, or both?

I also plan on a separate power supply for accessories and relays with a DC or AC supply sharing the common from relay coils. I will set one up before I do the whole thing. My layout is a 20 by 16, 7' wide U shape. The longest isolated section is about 5'. Thanks to all for the advice.

Guys, throw out your results.

What I should do is try both methods. What choices are there for sensors that aren't 40 bucks a pop?

I use DCS on my layout, and I also have an automatic block signal system on the entire layout. One of the outside rails has +12VDC and the other outside rail is ground. When the outside rails are shunted, a relay is energized to control a signal. I have never had a problem with either the DCS signal or the operation of the signal system.

The system works great with PS2 locomotives, as these locomotives have solid axles. However, PS2/3 locomotives have insulated axles, and this can cause lots of problems with both locomotive operation and signal operation. I have used work-a-rounds to solve these problems.

The original question was whether or not isolating one outside rail for signaling, etc. would degrade DCS signal and cause control problems.  Some of us are doing just that and without problems.  Some of the MTH engines that are capable of 2 or 3 rail operation are sometimes problematic when only one rail is used as a common.  In my experience this can be attributed to some poor electrical path within the engine, often somewhat difficult to find.  Dirty wheels or track and too much lube in diesel trucks are frequent culprits.

There are other sensor options, but all are much more expensive and complex than good old isolated rails.  

Barry's approach - tying the outside rails together just where you need to and isolating those sections from detection or sensor sections is what works for me and has been working for years.

My layout has only one outside rail connected. I was also going to use the other for signals, crossings and maybe some other things. It is the same outside rail everywhere, it does not cross or connect to the other outside rail anywhere on the layout. It has been that way for 1-1/2 years (since it was built) and I have yet to have any DCS problems. The DCS system has operated flawlessly so far which is better than it ever did on my previous temporary layouts. I never blocked any of my temp layouts thinking they were not big enough to matter. I'm now convinced that was incorrect thinking on my part, and blocks do make a big difference. At least they did here.

To qualify this a little further, I don't have any steam engines, diesel only and all of them are MTH PS3 (I have one PS2, but it's put away in it's set box and has never been on this layout). I also have a Legacy system, but only a couple of Lionel Legacy diesel engines. They also work just fine with the layout and with DCS and all at the same time.

My layout is 6'x16' with two loops of Atlas track (and Atlas switches) with 4 spurs and 2 sidings. The loops are isolated from each other. There are 4 blocks per loop and each spur and siding is isolated and has a separate power switch for each track. Two PH-180's power the layout, one on Fixed 1 and the other on Fixed 2. OGR wire powers all the track using MTH terminal blocks. Wiring follows Barry's book fairly closely, with only a couple of deviations.

The longest loop of track is less than 45' so it is not a large layout like some folks here have. I have no experience with anything larger, but an expansion is planned that I hope will at least double the current layout size. No idea if I will have problems or not when the expansion gets underway, but after reading all this, I will be watching for them.

John H posted:

What I should do is try both methods. What choices are there for sensors that aren't 40 bucks a pop?

Im unsure what the current policy is for posting links to the auction site, but I'll give it a try:  

Each price was the first link I clicked.  All of these parts are further discounted if you buy in lots of 10 or 20.  You could also use a single, larger power supply for all the modules on your layout, and/or use relay boards with many relays on them that substantially lower the cost.  

99 cents or less depending on quantity:   IR detector module.  

72 cents or less: Relay module.  

77 cents or less: DC-DC buck converter module. 

No links, but about 25 cents for a bridge rectifier and capacitor.  

So you're looking at well less than 3 bucks each.  Probably under 2 bucks if you are in need of a dozen or two such units.  

JGL

Doesn't seem to affect the signal strength using a single running rail for the return. What affects the signal more is having multiple feed drops within a single block.

I realize Lionel and MTH use inherently different command control schemes, but would the solution for weak signal propagation that Mike Reagan describes in this Lionel video at about 7:20 work for DCS?  Lionel video  Mike describes one potential problem with S gauge TMCC/Legacy signal propagation--the fact that both rails would not normally propagate the signal (similar to isolating one of the outside rails in O gauge) and correcting it by using a capacitor to transmit signal to the second (in our case, second outside) rail while preventing current flow.  I have not tried this, but I would like to use the third rail for signal activation in my future permanent DCS/Legacy layout as well.

I love the conversation about using Relays for the operation for the Signals  

Thanks, Johh

I use one outside rail for DCS control and the other outside rail isolated for signal operation. I have had no problems with DCS signal strength that are due to only using one outside rail for the DCS signal.

When I have signal strength problems, the cause is typically due to poor pin connection, dirty rails, or dirty engine wheels. I test my signal strength at 10smph using a PS2 engine, and typically get 9&10's with the odd 6-8 around switches, which only last for one "click", which does not affect real operation.

Joe K

JGL,

I would gladly try detecting trains with your components, but I would need help in the "how to". I already have the power supply (5v output from a PC power supply). A diagram might be enough for me to try one or two. A while ago there was a discussion on an 8 relay Arduino relay board triggered by -5vdc. Would that apply here? I couldn't get my head wrapped around how to do the -signal, but I'm sure I can find help here.

John H, 

The setup is fairly straight forward in this case.  Vcc +5 volts DC from the power supply to the VCC connection on the IR module and Relay module.  GND 0 Volts from the power supply to the GND connection on the IR module and Relay module.   Lastly a wire between the IR sensor's output pin and the relay module's trigger input pin.   Whatever you want to trigger is connected to the relay's contact terminals, which operate like a SPDT switch.  

From what I can tell reading a few reviews of both modules they are both "Active Low" devices.  This means that for the sensor, when something is in front of it, the output pin is low (0 volts), and when nothing is blocking the sensor it is high (5 volts).  The relay works the way, applying a Low to the input pin will turn the relay on and a High will turn it off.  I mention this only because it is possible that you could get a sensor or relay that is 'Active High', and that would require something between the modules to flip the signal over.  

You could also add some features by using a timer relay board for a few pennies more, so that your signal or accessory could be set to function for some set time after the train passes.  If you wanted to get even more complex, you could add a $2 micro-controller in the mix that would allow you to do pretty much anything you could think of  with the sensor.  

One last thing I would mention is that it would be prudent to give this a try by buying 1 or 2 sensors from a US seller first for maybe $3-4, just to test that they work well enough to detect when a train is in front of them.  I've not used these particular IR modules, so I can't verify that they are sensitive enough, though I can't think of a reason they would not work.   

If you have any questions or need some help, feel free to shoot me an Email.  

JGL

George S posted:

Dave,

That sounds more like an issue with power to the engine, rather than DCS signal.  It would have been interesting to see if that engine had the same problem in conventional operation.

What I mean is that those engines might need the ground on the side of the isolated rail for some reason.

George

George,

I agree, but not center rail.  It is an outside rail issue with the 3/2 trucks.  That is the reason I shy away from outside rail isolation.  It just eliminates potential problems.  I also recommend that operators connect the outside rails as suggested above.

Dave

Dave, thanks for your input.  You are a guy who has built a layout or two.