# DCS Wiring Part 2



## Tom Bray (Jan 20, 2009)

Since the original post sort of got derailed into a topic about rail corrosion, I figured I better start a new thread.

This evening I went and installed 5 lights around the outside loop of the layout. That made a major improvement in the behavior in the one loop. Since there weren't any additional lamps put on the inner loop, it still doesn't work correctly.


Each loop is broken into 4 segments that are fed from a single point, a star type configuration. I have isolators on both rails at all 4 points. The two straight sections are fed in the middle of the sections, the curves (ends of the ovals) are both fed at the ends closest to the main bench to conserve wire. I do a drawing but I don't have a good way to do that right now.


The signal strength with both loops connected and before I added more lamps was pretty much impossible to measure. The outside loop, isolated from the inner one, gave me readings as high as 2 and a whole bunch of "out of range" messages.


When I added the first lamp, which is the straight section on the bench, the readings for that segment climbed to between 8 and 10 for its whole length. These reading got progressively worse as the train went around the track. I then added light for the curves and 2 light at each end of the other straight section. This got good readings all the way around except for an occasional low reading at random points around the track (probably dirty track).


The lamps got installed as follows: on the straight section on the bench, the lamp is at the track feed point. On the curved sections, the lamps are at the opposite ends of segment relative to where power is applied. The other straight segment has a set of lamps on each end of the segment (this is the longest section of track and has the longest run of wire to it. 


I tried measuring the DCS signal with a scope but my TIU/Remote sends signals that don't correspond to the examples posted in Part 1 of the DCS Wiring thread. There was a continuous sine wave in addition to large periods of high frequency activity. There was no reliable way to trigger on the actual signals to get anything that might be measurable.

Now I have to figure out what to do with 5 lamps hanging from the track that don't look particularly appropriate. I also have to figure out a good way to waterproof them. I have to order some more bases and lamps, I think I have bought out all that there are in the two closest cities (at least at the Radio Shack's I know of).



As soon as I get more parts I will attack the other loop and see if that fixes all the problems.


If I get a chance, I will do a sketch of how the wiring is connected. 


Tom


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## John Allman (Jan 2, 2008)

Tom - could you please review exactly how your TIU is set up also? There has been so much off topic stuff that I don't really know anymore. 
Thanks.


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## stumpycc (Jan 2, 2008)

Tom, 
Could you also take and post pictures of your track setup so we can see what it looks like? As for the lights on the track, how about making little buildings to cover them so they look like little sheds? I don't think anyone has ever used an O-scope to toruble shoot the signal problem before, but it is diffrent. I am glad you started a new thread, because the other one went out to left field then jumped the fence. I have had problems with my DCS setup before too, it is usually something simple that was just over looked. 
Cliff


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## Greg Elmassian (Jan 3, 2008)

When you review the setup, please specify your power source. Also you have a sine wave on your track, do you have an AC power supply? What is the frequency of the sine wave? And the amplititude? 

Why does not the capacitor and resistor combination work for you, instead of using the light bulbs? All you are doing is a noise filter... isn't it a .1 mfd cap and a 221 ohm resistor in series? 

Pardon the dumb questions, but I thought the problem was solved long ago... it should not be this difficult. 

Regards, Greg


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## stumpycc (Jan 2, 2008)

Posted By Greg Elmassian on 06/30/2009 7:07 AM
When you review the setup, please specify your power source. Also you have a sine wave on your track, do you have an AC power supply?


Regards, Greg


Greg,

He is using an MRC Power G power supply, input is 120Volts AC, output on the throttle is 0-22 volts DC. The fixed or Accessory output is 22 VDC. It's in the original thread.

Cliff


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## Greg Elmassian (Jan 3, 2008)

Thanks Cliff! Well, if he has a sine wave on his track, there is a problem, right? Maybe he needs to check the output right at the power supply, and then work his way out. With a scope, it should be simple to track down where the noise is entering... (although a 60 or 120 hz sine wave should not interfere with a 3-10 mhz signal) 

Regards, Greg


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## Road Foreman (Jan 2, 2008)

Greg, 

I thought the reason for the lamps is they act like inductors & kill the haromics of the DCS signal.. 

BulletBob


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## John Allman (Jan 2, 2008)

Greg - please try to slow down. None of that is going to matter if he doesn't have the original set up correct. Lets not confuse him just yet. I bet the answer is quite simple, but we (ok, well I) dont quite understand the initial conditions because there has been too much off topic debate. 

Now I understand that what you ask may well be able to find the problem and therefore the solution. But it may well be we dont need that much info either. My understanding of the bulbs is they do work like an inductor, so I have one and only one on my track (300+ feet) that is on the output of the TIU. I do not use passive mode on the TIU because after a long discussion with MTH I decided the benefit of never letting the smoke out of the TIU was more than offset by the issue that the signal is weaker. Why that is, I don't even care. But it is that way and therefore makes a difference in how someone's toy (they are toys, right?) works. The fact that Tom uses 5 light bulbs and two ports on the TIU and has much weaker signals coming from his brand new system than my almost 9 year old system that has been outside the entire time indicated to me that something basic is amiss.

Anyway I am sure there is enough experience here to get the system running. Lets hear what Tom says next. 

Regards, 
John


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## Greg Elmassian (Jan 3, 2008)

Right, I assume something basic is amiss... that's why I asked about the power supply, about back to as basic as you can get, the source of the power first... 


Regards, Greg


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## Tom Bray (Jan 20, 2009)

The sine wave is essentially 1/2V P-P. It is enough to screw up triggering on the DCS signal though. I think it may be coming from the TIU since it didn't appear to be either 60Hz or even 120Hz. I will try more experiments tonight if I get a chance. If there is no power on the track, there was very little noise being picked up which was a bit surprising.

When I was watching the signals, hitting the "read track" button caused a lot of activity for several seconds. There seemed to be additional activity at random intervals on the track also. I certainly didn't see the nice short blips of messages that were shown in the part 1 thread.

Here is a general drawing of the the layout. The inside loop doesn't have the lamps on it yet since I have run out of parts. The arrow on the right side that doesn't have any caption is actually where all the power gets distributed from, the star point. It is not a huge layout. The little red rectangles are track isolators, the black dots are where power comes in, and the orange things are supposed to be light bulbs. The layout is approximately 44' x 17' for the outer loop.











From what I am seeing, the lamps are functioning like resistors or terminators. Remember the old ethernet cables (thin or thick) that needed the 50 ohm resistors at each end ... I have a feeling that this is functioning similarly.

Tom Bray


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## Greg Elmassian (Jan 3, 2008)

Tom, if you have a scope, you can read the frequency. 

Let me get this straight, it's ALWAYS there? 

If so, start back at the power supply and work forwards with the scope, to see where it comes from... you know, disconnect everything from the power supply, check for waveform... if not there, then connect TIU and check... then check TIU output with nothing else connected... 

I know it may seem like working backwards, but if you can see something that should not be there, and you have a scope, you can track it down... 

My personal opinion is that if the facts given are correct, the lamps are just bandaids on a more fundamental problem. 

Regards, Greg


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## John Allman (Jan 2, 2008)

Ok, let me see if I have this right. The reverse loop is completely isolated from the other tracks. 

From a systems point of view you only have one track and one loop - since any part of it can be reached from any other and it is not bi directional. In practicality, this means both engines on both tracks will have to face the same direction. If you isolated one loop from the other, you could reverse the wires, (and the switch in the engine) and run the locomotives in opposite directions. 

So here are a few suggestions: 

Power the track from inside and outside the switches. That means your wiring should go from the FIXED 1 output to each track outlined in blue AND also to each of the two tracks on the top of your diagram. I would put the wires right where you have marked DCS Controlled track. Try the whole thing on just FIXED 1 before you go and add the second output. The light bulbs - to me- work best across the output of the TIU. Make sure you have one there - even if it means taking one off the track... Add jumpers across the switches. This was one of the best things I did to my track. I used 12g wire (cause I had it free, not because you have to use it) and ran a wire from the clamp on each end of the switch to the clamp on the other end. Plus I also ran wires from the divergent track to the straight track. (just to save wire) This ensured that nothing in the switch could affect the signal transfer from one side of the switches to the other as there was a path around the switches. 

Now here is where I show my ignorance: 
When you used fixed two output, you did so by inputting power to fixed 2 input - right? The reason I say that is the track would be powered either way. Look carefully. The power can go from the far left outside rail up to the switches through the frog and back to the far left inside loop left rail. Ditto the inside rail. If this is accurate, dump the isolators, as they dont do anything. Not only that, but they could then be messing with the signal by reflecting it back on itself. 

Anyway, I am probably wrong, but this is what I see. 

best of luck Tom, and I hope you do not need it.


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## Tom Bray (Jan 20, 2009)

Oops ... need to fix the drawing. This may be a little harder to read though (I am trying to maintain the 640 x 480 limitation)

The switches going into the two wyes are all isolated before the reach the wye switches. The wye switches are powered by the same power that is on the spur.

There are 3 isolated loops. It is possible to move a train onto the wye fed spurs, switch the power, and move it to the other loop. The 3rd loop on the inside currently can not transfer a train to or from the other loops.

Right now, powering the loops is a single MRC G Scale DC supply feeding two channels on the TIU. This configuration gave the worse performance before I started adding the lights compared to running the TIU in passive mode (hook the output of the TIU to the power supply and then feed the two loops).

As it is currently wired, the spur is hardwired to one of the loops, it will get adjusted at some point to have a DPDT switch so that it can be transfered from one loop power source or the other. 









I placed an order at RS for the rest of the parts that I need, cheaper than driving around trying to find the parts.

Tom Bray
I will take a look at the signals on the track again tonight.


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## stumpycc (Jan 2, 2008)

Tom,

I think I see what your problem is; You are trying to feed 2 lines from ONE transformer. In ex., you are using one power output from your transformer and splitting it before it goes into the TIU. So, when you try to run both loops at the same time, you basically trying to run the system at HALF power. 

Try plugging the throttle side of the Power G into the FIXED 1 port of the TIU and then running a power cable from the 22 Volt Accessory terminals to the FIXED 2 port of the TIU. I think this will solve your problem. That way you are getting 22 VDC at both inputs and outputs of the TIU to each loop of the track. This should fix your problem. Please let me know if this helps.

Cliff


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## GG (Jan 1, 2009)

Posted By stumpycc on 06/30/2009 4:49 PM
Tom,

I think I see what your problem is; You are trying to feed 2 lines from ONE transformer. In ex., you are using one power output from your transformer and splitting it before it goes into the TIU. So, when you try to run both loops at the same time, you basically trying to run the system at HALF power. 

Try plugging the throttle side of the Power G into the FIXED 1 port of the TIU and then running a power cable from the 22 Volt Accessory terminals to the FIXED 2 port of the TIU. I think this will solve your problem. That way you are getting 22 VDC at both inputs and outputs of the TIU to each loop of the track. This should fix your problem. Please let me know if this helps.

Cliff




Cliff, if this works YOU are good ! 

Wow. I'm taking notes like mad here. 

gg


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## Rayman4449 (Jan 2, 2008)

Ok this diagram helps. 

I didn't read through all the replies because of time, but the first thing I see is if you are trying to run with isolators like you are, you need to move the power feeders for the outside curves to the center of the oval as close to center between the two isolator ends as you can. (doesn't have to be exact, I would run them to the next nearest rail joint). On those side oval sections sections you are essentially dropping your power feed on one end of the length of track and using light bulbs on the other. By the book, if you move the power feeds to the middle instead of on one end, that should make a big difference. 

Also remember not all bulbs are created equal and if you are using a lower amp bulb like the 1819 that Radio Shack sells you won't get as good an improvement in track signal levels.

http://www.rayman4449.dynip.com/DCS_Tips.htm#Use_of_light_bulbs_at_the_TIU_outputs._(or_at_the_block_distribution_block):

Overall through I agree with John, need to make sure you've addressed the other fundamentals that have been mentioned in the prior post. 


I've added red circles where the power drops should be and 'X'ed out where they are now and should be removed.












Raymond


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## Rayman4449 (Jan 2, 2008)

With regards to the non-light solution (filters) instead of light bulbs, there have been mixed results and in my own personal tests in deactivating bulbs and trying to replace with filters (tested in many different new locations in addition to a by the book deployment of them) I saw minimal improvements. There are others in the O gauge community with similar results. 


Raymond


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## Tom Bray (Jan 20, 2009)

Here is the story after spending most of the evening playing around with the system. There is a lot of stuff packed into this. I probably should have taken the computer out with me and took slightly better notes.


Here is a quick summary: 


Model Rectifier Corp power supplies don't have any filtering in them. They output a 120Hz pulsating DC. I have two different MRC models and they are identical, a full wave bridge after the transformer, no capacitor.
The TIU will modify the pulsating DC so that it is more of a rectangular wave. It definitely clips off the tops of the waveform. I think this is why a good (not necessarily great) digital meter like I have will read a higher voltage after the TIU compared to before it. 
In the interest of being able to actually look at the waveforms, I decided that I needed something that was putting out DC so I could trigger the scope on the messages. I grabbed one of my amateur radio switching power supplies (a MFJ model with meters that can put out 25A) that has a variable output, goes all the way up to a whopping 15V. I was concerned about how the TIU would work with it since there have been lots of reports that DCS doesn't get along with switchers ... It worked fine.
The switcher worked far better than the MRC did as far as getting DCS signal to from the TIU. Using the switcher I consistently got 10's back for the track signal strength. Nothing else came close.
Even though the switcher was only able to put out 15V, the train seemed to run about the same. There probably was some top end difference but it was hard to measure.
Adding a capacitor to the MRC makes the voltage higher but it doesn't work any better with the DCS system.
 Here are the details:


I hooked up the switching supply, first to the track directly to see if the Hudson would respond to it ... it did and it ran about the same as it does with the MRC G Scale supply. So a nice flat 15V is almost (but not quite) equivalent in performance to the pulsing 22V out the transformer. The math doesn't quite hold up but ...


Then I hooked up the TIU in series with the switching supply. It seemed to work fine. I ran the train around on the outside loop with the lamps and the first couple of times it got perfect 10's all the way around measuring track signal strength. After it got dark and there was some dampness, I would get a couple of 9's randomly around the track, but the rest were 10's. In other words, it worked great. One thing I did not try is running the TIU in passive mode using the switching supply.


I hooked up the second loop that doesn't have any lamps on it yet and the system went right back to its old behavior ... the train didn't want to initialize, the remote almost never saw a response from the engine, etc. I disconnected the second loop for the remainder of the testing this evening.


Then I hooked the MRC transformer back up to the TIU. The system started up fine and it ran around the track fine. I then ran it around looking at the signal response. With the MRC, I got everything down to about 2 (once or twice), plus a lot of every other possible number. Near the feed points and lamps, the values were usually pretty high, near or at 10.


I got the worst readings along the back straight away which is fed in the middle and has lamps at both ends, I got considerably better results on the two curves which are fed at one end and have the lamps at the other. As a comparison, last night when I was hooking up the lamps, with a lamp only on one end of the straight away section I got consistently 5 or less, with the two lamps, I got a few 5's but the rest were in the 7 to 10 range. I don't remember if I tried a lamp at the feed point last night or not. 

The curves are just a bit shorter than the straight away, coming in a little over 25' long, the straight away sections are both around 32', the one on the bench is shorter due to the switches at the ends. It may be that the various recommendations as to where to put feeds and lamps may jump around based on track length. The straight section on the bench, which has the lamp in the middle along with the power feed, if it has a low reading, it is near the ends of the segment, never in the middle. The straight section along the back, if it has low readings, they seem to be between the power feed and the lamps, at the edges and in the middle it gets consistent 10's for signal strength results.




To complicate all the testing, I went into my junque drawer and found a large capacitor, something like 51,000 uF at 40V (not high enough voltage as permanently attached capacitor but good enough for a bit of testing. I hooked the cap up to the MRC and tried running it directly to the rails. The Hudson was a lot faster with the capacitor compared to any other testing, I had to back it off as it approached a curve which I have never had to do. The lights in the passenger car got pretty bright too. The voltage went up to 24.4V according to the scope. 


The interesting thing was that when I hooked it up to the TIU and ran the train around, I got almost identical signal strength results compared to the MRC power pack without the capacitor. There was still some ripple but not very much, in the 0.1V range.


The last thing I did was put the switching supply back on the track and make sure that I still got the same results. I ran the train around several times and got consistent 10 signal strength reports with a couple of 9's in random places. So it was still behaving just fine.


As far as DCS signals on the track go, for the most part there were 4 different sets of signals that I saw:

At startup there was something like 20 seconds or so of pulses being output by the TIU (I may be way off on how long the pulses lasted). I assume that this tells the engines that there is a DCS system out there.
When starting up the remote or doing a read all command there are long periods of signal on the track
When key press commands are sent there is a short pulse and an obvious short one at a low voltage level that appears to be coming back from the engine.
At random intervals there are long stretches of signal on the track, not sure what would tirgger them although it may have been commands that were not acknowledged. I was blowing the whistle around the track to see if it was delayed or got stuck. Same thing with the bell.
 So that is the story. I have ordered more lamps and stuff so that I can do the other loop. I figure after I get it to work, I may play with some of the different lamps and such but for now I am going to stay with what I have been testing with. But, if the system with two loops works as well as the single one is now, I will probably go on to something more interesting. Fine tuning the DCS system is not a priority at this point, as long as it runs reliably ... finishing more of the layout and starting the garden and the various settings is.

One last note, since it has been asked somewhere, the meter on the switching supply indicated that I may have used at most 2A at any one time, usually 1.5A max. Now that is at 15V so the current should be low. But it is the best I have at this point.


Tom


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## Rayman4449 (Jan 2, 2008)

Very interesting, sounds like your biggest issue was actually the MRC power supply. If you were getting superior signal strength with a switching power supply (and it was that drastically different) then the MRC should be (and are going to on my website) on the avoid/do not use list. This makes sense as I've never seen this kind of problem with getting good DCS signal on a layout of this size before. (I know other DCS users here have been equally puzzled) Even with the turnouts/switches you should be getting very usable signal levels pretty much everywhere.

The switching power supply I used (24v/40amp retailed for $800) yielded good results (at lower amperage levels) on shorter lengths of track 120ft or so but as soon as I pushed it out to 200ft+ (i.e. tried to provide signal to ever longer runs) I had increasing levels of signal issues. Also, when you started increasing the amp levels with long passenger trains, the signal strength would deteriorate further. It wasn't until I hooked up my Bridgewerks Magnum SR15 that I saw a tremendous improvement in the total feet of tack I could provide good signal to and even at the higher amp levels. It was explained to me that the switching power supplies produce increasing levels of "hash" etc as the amp levels increase. After my experience, it's another reason why I do not recommend switching supplies for use as the permanent power solution for a DCS layout even at lower amp levels. It's also why I recommend Bridgewerks because I know they work very well. And after going through the learning process as you are I know it's not worth the aggravation to try and save a few $ on your power supply. 

This kind of now leads into the AC power question since it sounds like the MRC may not be good to use as your long term solution. My Bridgewerks Magnum SR15 has AC outputs that I plan to use soon on some testing to compare the signal strength results between DC and AC. And with me being able to use the same power supply to provide both AC and DC I will be able to get as close of an apples to apples comparison as I can get. Will share the results when I get them but will probably post in your other thread. If using AC power yields superior results then I will be in the market for a good AC power supply.(although my Bridgewerks regulated powersupply works great) Will want something at least 24v/30amp. If you by chance know of good sources of higher amp 24v power supplies, please let me know. I've done some searching but haven't had much luck in finding them pre-made. As a note for others, I know the bridgewerks Magnum SR line has AC outputs but they only go up to 15amp models. I'm not sure if their 20amp version that is close to the SR has them. The TDR25 does not. 

Yes, at 15v DCS will work ok and just like you said it will limit the engines top speed.

Thanks for taking the time to provide so much detail info on your results. Had some very interesting information and will definitely help others in the future.


Raymond


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## Greg Elmassian (Jan 3, 2008)

The funny thing is that the DCS system is supposed to work on an AC power supply no problem. Well, the unfiltered output of the MRC is just AC with half of the waveform inverted. The shape of the curves is exactly the same. Other than switching noise from the full wave bridge in it, it seems there should be no difference to the DCS (the polarity should not be an issue). 

I'd be very interested to go into the MRC and take the raw ac and put it on the rails. Maybe DCS is much better on DC than AC, but I cannot believe it's vice versa after all this research, at least not on Tom's layout. 

Very educational thread. 

Regards, Greg


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## Tom Bray (Jan 20, 2009)

I was considering doing exactly that ... take out the rectifiers out of the power pack and see what happens. That is going to have to wait for the weekend though. I also want to compare passive vs active modes of the TIU. 

The part that I was very confused about was when I added the capacitor to the output of the MRC, there wasn't a measurable change in the DCS performance. I figured it would either get better or worse, not stay the same. 

For testing and getting the layout stable, I plan on continuing to use the MRC G Scale power pack in its stock form. I figure if it works reliably with that, then it should work with anything that I use that may improve the performance. 

Tom


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## Greg Elmassian (Jan 3, 2008)

I may be "going against the flow", but if the system is designed to work on AC, (and DC) then rectified DC should be the same to it as AC... and that would tie in with your "filtering" attempt. 

The DCS signal uses the constant power as a "carrier" so it should not matter. 

Of course all of this is theory... it could be that there's 2 gerbils inside of every TIU with some batteries and wire! Ha ha, just kidding folks! 

Regards, Greg


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## stumpycc (Jan 2, 2008)

_ Of course all of this is theory... it could be that there's 2 gerbils inside of every TIU with some batteries and wire! Ha ha, just kidding folks! _ 

Good one Greg!!!!! 

Cliff


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## Rayman4449 (Jan 2, 2008)

I just tested my Bridgewerks Magnum SR15 on my layout (one 235 ft loop with 90ft of ramp line) using both the DC and AC outputs. Using the DC outputs I got all 10's except for two readings of 9 in one corner. Using the AC output terminals my readings dropped to in the 4's or so. So, it would seem that it can't be assumed that AC will provide better track signal. (which is honestly what I was expecting.) Now the question is since this was accessory outputs can the power not be as 'clean' as the ones from the DC throttle outputs? Will a more proper AC throttle type power supply like MTH and Lionel uses be better? Can't say for sure without more testing. But the important thing here is to note that your resulting tack signal strength can vary under AC power as well. Based on my experiences so far I'm going to stick with my recommendations of using Bridgewerks DC throttle type power supplies with DCS.

I now need to get my hands on an MTH or Lionel AC throttle type power supply.


Raymond


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## John Allman (Jan 2, 2008)

Tom - now that you know much more - does it run? 

I run an LGB track cleaning loco on my RR when I first decide to run. It does a superior job to everything except perhaps a dry wall sander. I have all brass track and split jaw clamps. Do you? I don't remember but I think I read that you do. And I have only one light bulb which is - still - right across the fixed 1 output despite my track being longer than yours.The light bulbs you have installed are not, and your system isn't working all that well. So try something different and put a lightbulb across the TIU and not the track. 

I will admit if I don't clean the track I have some problems getting the locomotive to respond. So rather than worry about that, I do the easy thing and clean the track. Every time. Do you? All I remember is that track is now, which does not mean it is clean. So I would suggest you do that too - since you are having trouble. 

Why don't you get one loop to work, then get the other to work, then worry about joining them together? I think I said this before, but I am going to repeat myself. Put jumper wires around the switches. Maybe the capacitors in the microswitches in some turnouts degrade the signal. Maybe not. Maybe yoiu dont even have turnouts with microswitches and capicators. Either way you have no reason to care, since you can put a jumper around the switch. You will also find that helps in a few years when your switch fails, and you don't even know it did because you jumped them. 

The isolators don't do anything that matters, so why have them? Again, if you need them, its because your track plan has a reverse loop. Otherwise you don't need them. You will need to provide a power input between the switches. It is not the isolating of the track that is improving your signal strenght. 

For now, drop the passive TIU idea. You can go back to it when you get everything up and running. Run the power right through the TIU, light bulb and fuse to the track. 

Why use AC? It didn't seem to help, and only adds complexity to the finding of a solution. So I would not persue that either. I am not trying to be difficult here. Stop using the scope. The laws of physics are not different where you are, and people without fancy engineering degrees somehow manage to get the system to work. (not only that, but people with fancy degrees probably did make the system after thousands of hours of effort - so can you expect that altering the system is easier than altering the track?) 

Anyway, one last suggestion. Ray runs his system a lot, as does Chuck. If it were me, I would focus very carefully on what they suggest, since they have more experience with DCS than just about everyone else combined. 

Regards, 

John


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## Tom Bray (Jan 20, 2009)

I find it interesting that running the system on AC has a similar behavior as what I am seeing with the pulsating DC. I don't think there is much difference between an AC transformer and one that has the variable taps to set the voltage. Add a full wave bridge and you have the MRC G type power supply. 

I am going to try putting a choke in series with the transformer type supply and see if that changes anything. The one power supply I was testing with, while it is a switcher, is know for its fairly low noise output since it is designed to be used with radios. That may be why it worked as good as it did in my testing. I have another supply from a different manufacturer that I can set to about 16V and I plan on trying that one too. 

I haven't had a chance to run the system with all the lights installed yet ... was going to this afternoon when bad weather decided to set in. 

I have been running the system in active mode for now since that seems to be the more critical way to run the system. 

I recalculated the track in the two loops. The outside loop is 115 feet long and the inside loop is 110. 

Breaking the loops into segments was based partially on the MTH documentation recommending extra feeders and the fact that the DCS portion of the system got worse every time I added another feeder. Breaking the loops into segments means that there are no electrical "loops" in the system, ground or otherwise except for a brief instant that the shoes short out the isolators. It simplifies behavior of the system dramatically and make it possible to ignore the length of the loops, the length of the wire, size of the wire, etc. The extra feeders made a noticeable improvement in the general DC characteristics of the system, both engines run around the track at close to a constant speed if run directly on DC instead of DCS. I figure it won't hurt to break up the track and it allows me to break into the segments if I ever need to, so I will probably leave them in place. 

As far as how clean the track it, I haven't noticed any real issues with it. My first line of a test is whether the lights flicker on the passenger cars ... if they don't the track is pretty clean. 
Right now the loops are fully isolated (assuming that I drew it correctly ... I have checked the real system with an ohm meter also). I will be able to run one loop, get it to work, then switch to the other loop. Finally I will be able to run both loops at the same time. The track is stainless steel and I have run a rag with a little alcohol or lightly used a little Scotch Brite but that so far has made no difference in the track. Early on cleaning the wheels on the cars and the pickup shoes made a big difference. 

Weather permitting and no other commitments, I may have more information tomorrow night. 

Tom


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## Rayman4449 (Jan 2, 2008)

Adding a choke to the output will very likely lead to better results for sure as that is what I've found. Generally speaking I've found that you can improve the signal strength on a switching power supply with one but can't bring it to the level of a Bridgewerks. You will still have larger zones of reduced signal strength. In your case maybe you can get the level of improvement you're looking for. (In my case I found it wasn't worth the headache in the end.)

I was originally using a switching supply (original MSRP of around $800 when new so it should have been putting out relatively clean output as well) but after I switched to the BW, it was still like night and day. With your ovals being under 120ft, you should have no problems with signal strength. Even when I was using slider joiners on my original 120ft loop and had only one power connection to the track I didn't have problems.(was only then using lights on the TIU output too.) 

I'm still surprised that MRC was so bad for this application. 

Has the original loop been in place for very long? (wondering how dirty the slider joint connections may be) I don't think it was till after maybe a couple of years before I had the buzzing / hot to the touch joiner.


Raymond


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## Greg Elmassian (Jan 3, 2008)

Well, stuff is making more sense to me as you guys reveal your experiences. With a "carrier type" signal, it SHOULD be easier to extract it from a constant DC, than on a varying waveform, but 60 HZ (or 120HZ if you are full wave rectified AC) is SO low in frequency compared to the signal it's very strange that this should make a difference with modern electronics. I guess thinking about how long ago the system was designed, this could explain it, but I would think MTH would have advanced the technology in decoding the signal. 

That leaves me to assume that the lower signal (2 v pp) and the method of decoding it is just more problematic on a large layout with multiple "connections" whether they be separate feeders, or whatever. 

If we take the premise that DCS is sensitive to 60 or 120 Hz "noise", then definitely any artifacts from a switching regulator, which normally work in the ultrasonic range (20kHz and above) would likewise be problematic. 

One theory I have is that the slight differences in resistance at rail connections are the classic points of "impedence change" as in any system using RF (the DCS signal is in the RF range))... these are well known opportunities to create "reflections" of the signal, which can help cancel the existing signal (like the RF nulls that handheld R/C systems can have).... that could explain it... 

It would be very interesting to find this out, but I think it's beyond the capability of most people, and other than keeping everything as clean and tight as possible, what could you do? 

Sounds like it's BFC time.... 

Regards, Greg


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## Chucks_Trains (Jan 2, 2008)

MTH has always recommended using a pure sine wave power supply when using ac power. I know of many large o gauge layouts powered by DCS using ac power that obtain very good DCS signal strenghts everywhere on the layout. Seems to me that using a powersupply that produces a chopped ac sine wave will tear up the DCS signal. 

Then add that there's something like 4 different TIU vesions floating around too complicate things as some TIU's produce a very poor DCS signal while swapping out with a good TIU will raise the DCS signal strength. 

My layout is wired completely backwards of the approved recommended star/home run wiring MTH approved practice but I get 10' & 9's everwhere. My layout has buss wiring with swing up bidge sections along with a mix of stainless steel & brass track but it is very stable..infact it uses very few light bulbs and track feeders. 

It's well documented that 2 types of problems can exist..signal reflection (which can results in packet collision) and signal distortion esp. with large wiring runs that can be reduced by using twisted feeder wire pairs. 

Aristo-Craft switches tend to tear up a DCS signal unless re-wired as Raymond has proven. On that I highly recomend re-wiring any switch by removing any microswitches and removing all frog power but leaving the lead rails powered if needed. Personally all my DCS engines have plenty of power pickup points to where un-powered switch frogs is a moot point and it eliminates any short circuits via slider shoes and/or reverse polarity.


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## Greg Elmassian (Jan 3, 2008)

The sine wave from your outlet in your house should be pretty clean, but there is a possiblity (remote in my opinion) that the rectifiers in a pack COULD be noisy... rare, but possible. Diodes are so cheap nowadays, but you never know! 

Even though I am DCC, all of my Aristo switches are "bypassed" with large gauge jumpers from the stock rails to the inner 2 "frog point rails".... the frog on the #6 is powered independently. This solved a number of poor conductivity issues. 

The Aristo #6 frog is pretty long, and shorter locos need a powered frog, unfortunately. (My Lionel Atlantic would slide to a stop on the frog unless going 100 smph!). 

Regards, Greg


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## SteveC (Jan 2, 2008)

Greg

Maybe the following will be of help in figuring out how the internal workings of the control functions work. If you've never been to the U.S. patent & Trademark office to view the drawings you'll need to install the browser plug-in TIFF viewer which can be found at the following link. *AlternaTiff* 


PAT. NO.

Title
1
7,210,656

Control, sound, and operating system for model trains 
2
6,662,917

2 rail to 3 rail conversion apparatus for use in model trains 
3
6,655,640

Control, sound, and operating system for model trains 
4
6,619,594

Control, sound, and operating system for model trains 
5
6,604,641

Low-power electrically operated coupler 
6
6,491,263

Power supply unit and rail switching mechanism for model track layouts 
7
6,457,681

Control, sound, and operating system for model trains 
8
6,281,606

Plural output electric train control station 
9
6,019,289

Modular track segment for model railroad track and electrical accessory therefor


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## Greg Elmassian (Jan 3, 2008)

Thanks Steve, I read several.... I think I have a clue about the difference between AC and DC in the TIU, apparently in "pass through" mode, it is really NOT pass through, at least for variable outputs... maybe all outputs, there is some circuitry involved. It's possible that the varying AC waveform get more "noise". 

I will say one thing, MTH is doing a great job at claiming lots of things to patent, even couplers and smoke. 

Regards, Greg


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## Tom Bray (Jan 20, 2009)

I was playing around again this weekend and have now tried 3 different power supplies. The MRC G Power, a Samlex 1235M switching supply, and the MFJ 4225MV switching supply. Ranking them from worst to best in performance are: Samlex 1235M turned in the worst performance, the MRC G Power was solidly in the middle, and the MFJ 4225MV was the best by a long shot. 

So the best and the worst were both switching power supplies. Since I haven't figured out what the differences are between the two supplies I can't tell if the behavior is a fluke of the manufacturing processes or is repeatable with across more than one power supply. Both switching supplies were limited to 15V - 16V. 

With all the landscaping that we have done, the MRC isn't performaing quite as well as the last time I rant the tests. There is a little bit of performance reduction using the MFJ but it occurs at identifiable sections of the track, which I figure I can improve upon. The lower voltage only becomes apparent with the Hudson engine when it is commanded to go faster than about 55 SMPH, it sounds like it is trying to accelerate (the sound system is obviously dectecting a difference in the commanded speed and the actual speed) but the engine doesn't seem to go any faster. 

Tom


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## Greg Elmassian (Jan 3, 2008)

I always recommend a regulated power supply wherever one can be used, more consistent operation. The 10 amp MRC is not a regulated supply, so not surprised it might not be as good as a 25 amp, highly filtered highly regulated supply. The Samlex is pretty cheap for a 30 amp supply and may not be as well regulated or filtered. 

This all makes sense. 

Regards, Greg


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## Rayman4449 (Jan 2, 2008)

When you have the Protochuff feature enabled (which is for playing a labored chuff during relatively fast accelleration and a drift duff under releatively fast deceleration) it will cause the engine to play the Labored Chuff when you command a speed higher than it can attain because the track voltage level is too low. If you turn this feature off it won't go into labor chuff.

With regards to power supplies and resulting DCS signal performance, I've found through testing that regulated supplies yield slightly lower performance compared to the throttle types. (comparing the Bridgewerks 25amp regulated power supply and the Bridgewerks Magnum SR15) This is why I recommend the throttle type over their regulated version. The only time I found a difference was when trying to run 700ft of track with a single TIU port (i.e. a ton of track) and even then the difference wasn't that bad. I still use the Bridgewerks regulated supply and have solid 10's everywhere now providing signal using two TIU ports instead of one. (well maybe an occassional 9 in a corner.)

When I ran with my Magnum SR15, I don't recall the voltage changes between max and no load to have been of any significance to cause a real issue or concern. I stay with the Regulated supply because it works fine and has an extra 4-5 amps (25amps @ 24v) or so output compared to the TDR25.


Raymond


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## Greg Elmassian (Jan 3, 2008)

Raymond, you did not mention what voltages you were seeing for these different supplies. I'm curious as to what voltages give you scale speeds. I went through this with DCC... 

Regards, Greg


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## Rayman4449 (Jan 2, 2008)

Greg, 

The voltages can be varied with either the regulated or the SR15. Both power can put out less than 18v and more than 24v. I always run with them set at 24v. 

The only thing voltages lower than 24v does is impact the max speed. Any speed up to that max point (for the given track voltage on the track) runs at the precise scale speed. If you have say 12v applied to the track and you are running two engines running at a dialed 20 SMPH, they will both run at the proper speed for 20 SMPH. If you jump the voltage to 24v (either quickly or slowly) the engines do not change speed, they maintain a proper speed for 20 SMPH. 


Raymond


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## Greg Elmassian (Jan 3, 2008)

I got the lower voltage part, since you have absolute speed accuracy. What I am wondering why you found the difference, i.e. what voltage you actually measured. Your statements seem to imply the unregulated supplies put out a higher voltage than the regulated ones, so I am wondering what that voltage is. 

Thanks, Greg


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## Enginear (Jul 29, 2008)

Nothing to do with the current thinking maybe but I was shopping for DCS and went with the Lionel 180watt power brick. For the money it has great results. Its AC power for about 75 bucks its the best power per buck I could find. MTH power bricks would equal these results. I ran for years with one brick and now I've added a second. I'll be building my new O scale layout soon and may add more as needed. The MTH TIU has four channels that I could put a brick on each. I could also switch to passive wiring if I needed more than the four 180watt bricks????? Joe


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