DCS Passive Mode

No, it's main benefit I believe is that you can have more amps available at the track then the 10 max per channel that goes thru the TIU.

Engineer-Joe posted:

No, it's main benefit I believe is that you can have more amps available at the track then the 10 max per channel that goes thru the TIU.

That's the only advantage I can think of.  Big disadvantage is the red button to kill all power on the DCS remote won't work in passive mode.

Makes running conventional easy.

Steve,

How so?

I run passive using one of these to substitute the red button.

The other advantage of passive mode is the power doesn't go through the TIU, so the over-current issues folks like the NJ-HR has been experiencing and cooking TIU variable channels won't be a factor.

When in passive mode the DCS signal is not boosted!  Actually it is reduced. I have been taking DCS signal strength readings and saw as much as a 50% reduction in signal strength when in passive mode vs being in active mode.  Passive mode may have some  benefits but signal boosting is not one of them.  

Bob D

NJ HI RAILERS

I use passive mode out of necessity. In active mode, my DCS locos always miss the watchdog signal and start up right away. Then I have to go turn them off. Major PITA.  In passive mode, they stay dark until I decide to start them up. Not sure why the difference, but it works for me. 

Lack of stop button, no problem. My track power is provided by a Legacy Powermaster. So I can always hit the “halt” button on a Legacy remote sitting next to me. The Powermaster provides much smoother and more reliable control compared with the raggedy variable voltage generated by the TIU.

rad400 posted:

When in passive mode the DCS signal in not boosted!  Actually it is reduced. I have been taking DCS signal strength readings and saw as much as a 50% reduction in signal strength when in passive mode vs being in active mode.  Passive mode may have some  benefits but signal boosting is not one of them.  

 

Did you try the 22uh choke in series with the transformer connection to see if that improves the passive mode operation?  It'll never be "boosted", the object of the exercise is to get it back to the levels of the active connection.

gunrunnerjohn posted:

rad400 posted:

When in passive mode the DCS signal in not boosted!  Actually it is reduced. I have been taking DCS signal strength readings and saw as much as a 50% reduction in signal strength when in passive mode vs being in active mode.  Passive mode may have some  benefits but signal boosting is not one of them.  

 

Did you try the 22uh choke in series with the transformer connection to see if that improves the passive mode operation?  It'll never be "boosted", the object of the exercise is to get it back to the levels of the active connection.

Originally a choke was not used.  Retested the passive mode again with a 22uh choke and the choke fixed the signal loss.  Passive & active mode had  virtually the same signal strength.  This test used a Z4000 transformer.   

John - thanks for suggesting trying the choke.  

Nice to know there's a simple fix to increasing the signal in passive mode.  

Very interesting read guys as I am currently in the planning phase of my layout and would really appreciate being able to do it right the first time.

On an additional note, can you elaborate a bit more on the "22uh choke" ?

I use the Murata 1422311C, it's an 11A rated part.  The choke goes in the center track lead from the transformer to the track.  This isolates the transformer itself from the DCS signal on the track.  Note that the choke has to have a current rating that is greater than the current that might be drawn from the transformer.

  I use a DCS Remote Commander in passive mode:

so:

a 22uh toroid-wound choke in series (in the center-rail lead) and a TVS Diode across the transformer outputs.

I have my TIU in passive mode because I run more than 10 amps to the track using a Legacy 360 PowerMaster and two PH180s.  Based on a recommendation by gunrunnerjohn I use a 22uH 34A choke because of the higher voltage.

Any opinion about using one of these for the choke: 2305-H JW MILLER Ind High Current Toroid 22uH 15% 1KHz 16.4A RDL

From the data sheets:

JWM 2305                                             Murata 1422311C
22uH +/-15% @ 1KHz                          22uH +/- 15% @ 1KHz
16.4amps                                             11amps
7 mOhms max DCR                            14mOhms max DCR

And do I care horizontal vs. vertical mounting?

Thanks

Thanks for resurrecting this thread. I'm embarking on a new layout (long story) and have decided to add DCS after years of being TMCC only.  I have a multitude of postwar transformers that I run through Lionel Powermasters to enable CAB-1 control of conventional engines and, perhaps more importantly, to provide fast-acting fuses that come in the wiring harnesses. I might retain the powermasters for the new layout and run the TIU in passive mode, still debating. 

Rob, either of those choices are fine, and the mounting makes no difference, you can orient either in any position and the electrons won't fall out.

raising4daughters posted:

 ... I might retain the powermasters for the new layout and run the TIU in passive mode, still debating. 

My layout control is Lionel's LCS with PMs to control conventional trains.  It is pretty much the same as TMCC layout control.  The TIU is there only to control DCS locomotives.  Here is what I'm planning.  Think TMCC instead of Legacy for the components (plus only one transformer).  The CSM2 is there to control my DZ-2500 switches.

I think you could wire your new layout the same way you had your old layout wired and just add the TIU and 22uH choke of your choice and you should be good to go.

gunrunnerjohn posted:

Rob, either of those choices are fine, and the mounting makes no difference, you can orient either in any position and the electrons won't fall out.

Not sure about the electrons falling out, but having mispent years on British Iron, I worry about some pretty odd things what with Mr. Lukas and all...

Barry's book says only the fixed channels are used in Passive mode. If the variables are set to fixed will that work?  We want to try passive mode and see if it will keep us from  damaging TIUs.  We currently use all four channels to power a power district. Th districts are set up as right and left on two routes  . Do we only need to run one channel to all four sections as they are electrically isolated from each other except for common ground

You may be mis-reading the book, or Barry made the rare DCS mistake.  The variable channels work fine in passive mode, at least for me.

Thanks John, going to try it next week.  We have had too many TIU's fail on a large layout.

GRJ, a thought.  If, in passive mode, the choke boosts DCS signal, would it not also be a benefit in "active" (normal) mode?

KGSouth, was the cause of the failures high current flow through the TIU or the effects of a power spike caused by derailments and sparking?

RJR, there is a choke in the TIU power path before the DCS signal generator for active mode, so adding it for the transformer is not necessary.  Since in passive mode, you're connecting the TIU output directly to the transformer feed, there is no choke to isolate the transformer from the DCS signal.

RJR,  we think the cause is a spike or short through the non derail circuit.   

John or RJ. I ran passive mode on one power district of the layout and had 10's all over.But my concern is we have been frying the signal circuits in our TIU's  even with a TVS across the leads. In passive mode there is still track voltage back to the output side of the TIU.  Will TVS protect the circuit from a spike caused by a derailment or other short?

I actually fed power backwards through the TIU by accident. While it caused all kinds of issues while it was hooked up that way (actually worked with a couple of engines but not most), it did not fry the TIU. Either MTH designed it to prevent idiots like me from feeding power backward, or the design simply protects it anyway. I doubt you will fry your TIU in passive mode.

George

Passive mode shouldn't kill the TIU, but the signal generator is not any better protected than it is in active mode.  Cooking the signal generator IC is likely due to something happening on the layout, remember Adrian's experience at his train club.

kgsouth posted:

John or RJ. I ran passive mode on one power district of the layout and had 10's all over.But my concern is we have been frying the signal circuits in our TIU's  even with a TVS across the leads. In passive mode there is still track voltage back to the output side of the TIU.  Will TVS protect the circuit from a spike caused by a derailment or other short?

What power source are you using and what kind of breakers/fuses does it have?

kgsouth, your question about whether a TVS will protect from a spike can't be answered.  It does afford protection, but it is not an absolute guaranty of protection, and when it fails, there is usually no way to determine that it has.  Some of Gunrunnerjohn's recent posts indicate a large TVS may adversely affect DCS signal strength. 

I wonder why train clubs are having the problem???

We are using PH 180's    I am hoping in passive mode the will trip before the TIU sees a spike.   By the way does anyone know if the new shipment of TIU's  will still be Rev L?

Breakers have no effect on spikes, except when they open while a derailed train is running down the tracs, shooting sparks and also causing an amperage overload.  SPiking can also continue for a very brief period after the breaker opens, through induction at coils.

Not a chance, voltage transients are nanosecond or microsecond events, the circuit breaker on the PH180 is a few milliseconds.  It's an excellent breaker, but not a miracle worker.