DCS Signal and Layout Common Ground Question

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