DCS Signal and Layout Common Ground Question

Cheryl,

Is this a possible stumbling block for the DCS signal?

Typically, an out-of-phase condition would manifest itself when a connection is made between two power sources that are out-of-phase.

Since all of your Commons are tied together, that means that any time a momentary connection is made between two out-of-phase Hot wires, there should be noticeable sparking and the possibility of a fuse blowing or a breaker tripping.

Typically, this would occur in out-of-phase electrical wiring when a train transitions from one track block powered by one transformer to a track block powered by another transformer that's out of phase with the first transformer, or when a switch track that is powered by a transformer that is out-of-phase with respect to a track power transformer, operates the switch track's automatic non-derailing mechanism.

If you aren't seeing anything resembling this, I would expect that your transformers are in-phase with respect to one another.

OK, that makes sense re: phase.  Now, how about not having accessory transformers tied into the track common.  Could that be part of the problem I've been having with DCS signals?

Cheryl,

Now, how about not having accessory transformers tied into the track common.  Could that be part of the problem I've been having with DCS signals?

I don't see how that could cause a DCS signal issue.

OK, just thinking...

The only other factor I can see causing signal problems is that FasTrack is sectional.  I've double checked all the wiring and it's in order.  The only other thing I could do is make smaller blocks of track sections.  Not really read to do that

The layout is running pretty good, but it has it's moments .

Thanks again for your help.

Are both outside rail connected to each other?

Usually a track block or loop can be as large as 90 to 100 ft and still operate O.K.  The two variable channels on the TIU can be set to fixed, which allows for four DCS fixed signal systems.

With our larger modular layout, (Fort Pitt Hi-Railers), we split two loops.  Use (2) Track outputs off the DCS for one loop, (1/2 the loop clockwise, Fixed #1, 1/2 the loop counter clockwise, Variable #1 set to Fixed). The loops are simply unplugged at the half-way distance.   This reduction in total track length per DCS channel is a relatively easy fix, may be a first step in solving your problem.  Input to the TIU Fixed#1 and Variable #1 is the same Output from one side of a Z4000 transformer.    

The phrase "Layout is running pretty good, but it has its' moments" leaped out at me with some thoughts.

Do you have several cars with constant voltage lights?   Do you have several TMCC engines?   Pull all of those off the track and check your DCS.   If everything suddenly runs perfect then I suspect that you have some CV (constant voltage) boards interfering.  

Mike,

Usually a track block or loop can be as large as 90 to 100 ft and still operate O.K. 

What is your basis for this statement?

The current guideline, as developed by Jim Barrett some time ago, sets the maximum length of a track block as having no more than 11-12 track joins. With all 3 foot sections of track, this would be a block that's 36 feet long, at best.

Cheryl, the only accessories that interfere with the DCS signal are the postwar operating accessories with the ac motors with brushes and they have to be running to cause interference. 

To keep my signals strong I occasionally have to retighten all my connections.  There's a gremlin in my Run Room that loosens connections.

The loose connections I find are at the TIU terminals and the wire screw clamps on terminal strips for track feeds.  All connections, including track joints, must be very snug.

I would make sure your switch transformers are in phase with your track power. If you have a derailment on a switch, it's possible you may not be protected by your fuses and get some high voltages. I learned this lesson the hard way! I know this is not related to signal strength, but this question of phasing was raised.

Try powering the FasTrack switches on track power. Put the jumper back, disconnect the separate source power wires and put them back in place.

I had some issues and while searching for a solution and finding other problems, it seems that unless you are running conventionally and need live switches in "dead" track situations, powering them from track power is the simplest and most reliable configuration.

They are designed to primarily run that way, use very little power, so won't really impact conventional operation.

I can't explain or speculate on an electrical reason, only that my research and experience with the recommendations of many reveals that they operate the best and cause the least amount of problems powered by track power.

Try powering the FasTrack switches on track power.

That's a very bad idea when operating in a DCS environment.

Barry, has anyone ever tried adding RF chokes to the Fastrack switches to eliminate this issue?  Just wondering if you've ever heard of a fix.  With the command switches, it's very handy to just plop them into the layout and not have to wire anything, that's the reason I ask.

John,

Running the DCS signal through a magnet coil or the coil of a motor is a different source of interference than that caused by a CV board. I don't know if an RF choke would nullify that particular form of interference.

I guess it just has to be tested.   However, Fastrack switches have a very small DC motor to activate the switch tracks, so there are no "magnet coils".  If you can run a locomotive around with a motor, it would seem these would be similar.

I like the idea of track power, but I suspect adding a choke may be necessary to solve the DCS compatibility issues.  Note that many Legacy and even some TMCC locomotives require an RF choke to avoid interference with DCS locomotives.  I suspect Barry's comment is based on experience with folks having issues with them on track power, so something would probably have to be done.

AFAIK, having a common that encompasses the switches should not affect the DCS signal.

John,

AFAIK, having a common that encompasses the switches should not affect the DCS signal.

You are correct. On my layout, I have tied all of the Commons from all power supplies: track power, accessory power, switch track power, and even the DC power supplies (-) for lighting, with no ill affects.

Interesting stuff, definately food for thought.  I'm thinking, as much as I love my PW ZW transformers, that maybe I should switch them to accessorie power and use my MTH bricks for track power.  Currently the bricks power switches and accessories. 

What do you guys think?

P.S.  FWIW this video is my layout.

Cheryl,

What do you guys think?

While anything's possible, I wouldn't think that would make any difference at all. A PW ZW is about the purest un-chopped sine-wave power you can use.

With input to the TIU Fixed#1 and Variable #1 is the same Output from one side of a Z4000 transformer.Variable #1 has been changed to Fixed#1.   What negative effects will this have?

None that I'm aware of. I've done this here.

Just so I'm sure, I'm powering my track via a Z4000 through a DCS TIU, and want to use a Z1000 14V output to power the DZ1000 switch motors on the Ross switches and use the non-derail feature with isolated track sections.  The transformers are in phase.  Do I tie the commons at the transformer outlets, or should I tie the Z1000 common to the TIU output ground?  I notice that if they are not tied, the track ground doesn't work to activate the non derailing feature.  Sorry if this has been covered, but I want to be sure.

Tom

Tom,

Do I tie the commons at the transformer outlets, or should I tie the Z1000 common to the TIU output ground?

Connect the Commons at the transformer outputs.

Barry,

I did this and got some strange behavior.  The only ground that will switch the DZ1000 properly, either from the controller or from the isolated track section is the Z1000 ground - independent.  If I common the TIU fixed 1 output to the Z1000 ground, the breaker on the Z1000 pops.  If I ground the TIU fixed 1 input (Z4000 output gnd) to the Z1000 gnd, the Z4000 will read 1.4V when the handle is at minimum, and won't advance past about 16V at max handle (seems to load it down).  Also, at some point, the 20A input fuse for the TIU channel 1 blew (not sure when, because I was focusing on the switches, and not running a train.

The only way I can get things to run properly is to operate the switches from the 3A 14V tap on the Z4000.  Is 3A enough to run the about 14 switches on the layout, realizing they don't all operate at once and only have momentary current flow?

I don't understand why I can't common the grounds for the Z4000 and Z1000.  They are both common vintage, both plugged into the same extension strip, both using polarized plugs, and I previously did the phase test, and they were in phase when wired per the color coding. 

Any thoughts?

Tom

One other thing - I was also using the 18v output of the Z1000 to provide aux power to the TIU - did I create some sort of a loop or conflict?

Tom,

If I common the TIU fixed 1 output to the Z1000 ground, the breaker on the Z1000 pops

If I ground the TIU fixed 1 input (Z4000 output gnd) to the Z1000 gnd, the Z4000 will read 1.4V when the handle is at minimum, and won't advance past about 16V at max handle (seems to load it down).

Also, at some point, the 20A input fuse for the TIU channel 1 blew (not sure when, because I was focusing on the switches, and not running a train.

You most likely have either an out-of-phase condition between your layout transformer sir some other wiring anomaly.

I was also using the 18v output of the Z1000 to provide aux power to the TIU - did I create some sort of a loop or conflict?

If you reversed the polarity for the Aux. power port vis-a-vis your track power from the Z4000, you generated a short circuit between the two outputs of the Z4000. I'd suggest using a different, separate, power supply for the Aux. Power port and see how many of your issues go away.

Is 3A enough to run the about 14 switches on the layout, realizing they don't all operate at once and only have momentary current flow?

That depends upon the switch tracks and whether they use bulbs or LEDs in the motors and the controllers.

The switch motors are the DZ1000 with DZ1002 controllers, all with LED indicators, probably about 20ma each.

I should mention that I never, under any combinations of ground commoning, to get the track ground to generate enough potential to throw the switch powered by aux 14v.  Do you think that the blown fuse in the TIU caused the ground to float or something on the track, decreasing the voltage between the track ground and the aux pwr?  I know that the center rail power should have nothing to do with it.

I'm a bit stumped at this point - - it should work but it doesn't.

Do you know how much current the DZ1000 motors draw when cycling?

Tom

Charly,

    I know Barry likes to power his switches with their own transformer, however

I have been running my FT CC switches with track power on my Christmas layouts and they have been working perfectly and I have no DCS signal drop, granted I only have a a few FT CC switches right now, we will see what happens as I add more switches to the FT layout.  With the voltage draw so small I do not think things will really change any.  Try using the track power to operate your FT Switches, and see what happens,

if you get the same results I did, you are going to want some Command Control FT switches, they really are seriously cool, and running in this manner eliminates all the switch wiring, which to me is a dream come true.

PCRR/Dave

Barry,

Mystery solved!  After replacing the 20A fuse in the TIU, I rechecked the phase of the Z4000 and the aux 14V output of the Z1000, and they were both in phase.  I then tied their grounds, hooked up the Z4000 to the track and the Z1000 to the switches and let the Z4000 fixed 1 input power the TIU, and all was well and the nonderailing worked!  I then tried it with the Z1000 18v plug to power the TIU, and the 20A fuse blew again.  Evidently the 18v and 14v outputs in the Z1000 are out of phase!  I replaced the fuse again, and tried it powering the TIU with a separate Z500 as you suggested, and all was well again.

Question:  Would you power the TIU separately, or let the Fixed 1 input power it?  I'm only using Fixed 1 at this point.

Looks like you can't count on even separate leads from the same transformer being in phase!!

Tom

Tom,

Would you power the TIU separately, or let the Fixed 1 input power it?  I'm only using Fixed 1 at this point.

I would use a separate power source, including aproperly connected 14 volt Z4000 output, for powering the TIU.

Looks like you can't count on even separate leads from the same transformer being in phase!!

Yes, you can. I've never heard of a Z4000 whose outputs were "out of phase with each other."

Evidently the 18v and 14v outputs in the Z1000 are out of phase!

First of all, there is no "18 volt" output from a Z4000. There are a pair of 5-22 volt variable outputs, a 14 volt fixed output and a 10 volt fixed output, all of which are in phase with each other.

What you did was create an out of phase condition by connecting the Z4000's Hot (red) 14 volt terminal to the TIU's Aux. Power port's Common connection and the Z4000's Common (black) 14 volt terminal to the TIU's Aux. Power port's Hot connection. If you reverse what you connected form the 14 volt output to the Aux. Power port, all will be fine.

This and a whole lot more is all in MTH’s “The DCS O Gauge Companion 2nd Edition", available for purchase as an eBook or a printed book at MTH's web store!

Barry,

I did not do what you suggest above. I've been referring to a Z1000 transformer, and you've several times referred to it as a Z4000.  I know very well what the outputs of my transformers are - the trick is to find what's in and out of phase.

The Z4000 outputs are all fine and in phase.  The only thing the Z4000 was connected to was the fixed1 input to the TIU. 

I used a SEPARATE Z1000 BRICK for the 14v accessory and AUX power supplies.  The 14V from the Z1000 went to track accessories, and the 18V (with concentric plug) went to the AUX pwr of the TIU.  That is when I discovered that commoning the grounds revealed that the fixed 18V from the Z1000 brick was out of phase with it's own fixed 14V accessory output.  The MTH Z1000 brick has a fixed 18V 100W output on a cable with barrel connector, and screw terminals for a fixed 14V 80W accessory output.

What I discovered is that commoning the ground of the 14V output on the Z1000 with the variable output on the Z4000 (track power) was OK, since they were both in phase.  Also plugging in the fixed 18V output of the Z1000 into the Aux Pwr on the TIU caused the 20A fuse in the TIU to blow. 

Using still a third transformer, a MTH Z500 with fixed 18V output only as the Aux Pwr input for the TIU was also fine.

This all tells me that the fixed 18V output of the Z1000 was out of phase with its own 14V accessory output.  I can verify that when I have time, but for now, problem solved.

Tom,

My mistake. Just substitute "Z1000" for "Z4000" and the mistake that you made is the same. Just reverse the Z1000's 14 volt output into your TIU's Aux. Power port.

Sorry, but no mistake was made.  The real issue was the two outputs (18V fixed and 14v fixed) from the Z1000 brick were not in phase - only the 14v was in phase with the Z4000.  When I tried to use the 14V for accessories and the 18V for TIU aux pwr, the problem occurred. 

Internal wiring of the Z1000 brick was the issue.  Others need to beware - that is the primary reason for continuing to belabor the point.

Tom