Runaway MTH engines

Galon & Barry:  Seems as if you have a semantic problem.  Sparks are created by a power issue.  Sparks would not be a problem with conventional reversing equipment (e.g., E-unit) but do affect a command receiver.  So is this a power problem or a command problem? 

This question can be resolved right after we determine how many angels can dance on the head of a pin.  We know the problem; we know the cause; what does it matter what we want to call it????

Since it happens only on one line, have you swapped the TIU that controls that line?  If so, did the problem follow the TIU, or did the "bad" TIU work in the new location.

Let's assume the answer is yes to those questions.

If that's the case, I'm wondering if there is something about that line that is shunting the DCS signal so that randomly locomotives aren't seeing the DCS signals.  Currently running locomotives would continue to run, just lacking any control, but stuff just powering up could come up in conventional mode.

This seems to be something associated with that section of the layout.

Take a look at the following thread.  GRJ even identifies a specific TVS.

https://ogrforum.com/t...cal-surge-protection

Of course this assumes the "trigger" is in fact a over-voltage transient...albeit that's the consensus du jour.

The beauty of the TVS is it can't hurt anything, and it's cheap to try.  I do have my doubts as this only happens on one of the lines, that seems to point to some wiring flaw of some kind to me.

GRJ, if a TIU has a TVS on each circuit, wouldn't this tend to preclude the effect of a spark from affecting other TIU circuits?  I'm fairly sure (not absolutely certain), that when I have such a derailment spark, locos on that TIU channel tend to start up more often than do locos on other TIU channels, and that rarely or never do locos on the other TIU start up.

I do leave locos shut down on powered tracks to keep the batteries charged, as risk of unwanted starts.  I figure that the chronometer running is a problem for my executors and grandchildren.

It's not clear what is causing the issue, only that it seems to affect one area of the layout.  If the TIU's have been swapped, that would seem to lay the issue at the doorstep of some wiring/power issues.

John,

that would seem to lay the issue at the doorstep of some wiring/power issues.

Really?  No kidding?

Barry, if I'm not mistaken, I'm agreeing with you.

John,

 if I'm not mistaken, I'm agreeing with you.

What took you so long?

Is there a low-cost transient event voltage detector for O-gauge? 

It seems if such a widget existed you could monitor different blocks to see if some are more prone to transients than others.  Yes, the well-heeled could pony up for an oscilloscope but I'm thinking $10 or so.  Perhaps it has a different LEDs indicating the size or character of the transient and maybe a way to quantify how often the transients are occurring.

I'd take the low-cost solution and simply move all the transformers and TIU's from the offending loop and see if the issue moves with them.

     Stan 2004; Yes I read that thread it's what prompted the question.

     Gunrunnerjohn; Is a TVS 1.5KE36CA at Digikey the right component to install in my engine to try and eliminate this behaver? Would placing one of these at every TIU channel boundary on the track or even every block boundary be beneficial? I guess there would need to be one at every power distribution panel too. I'm thinking the spike surge or what ever is using the outside rails to get from one engine to the other.

    One other question in Bob1949 post how did you eliminate the engines simply being locked in one direction as a possible cause?

     Barry: Why does this condition only affect parked locomotives and not the active ones?

Thank you for your help

Galon Tonell

Galon,

Why does this condition only affect parked locomotives and not the active ones?

I would expect that's because the active engines are already in DCS operating mode and their batteries keep them from falling into conventional mode.

Conversely, the parked locos are not yet started up and, when power is interrupted, start looking for a watchdog signal and don't see one. That's because power is interrupted downstream from the TIU channel outputs and a watchdog signal is only generated when power goes from 0 to something higher at the TIU channel outputs.

I think that trying to lock engines directionally will cause more problems than it solves, if one errs when doing it.

You might try sprinkling those TVS diodes around the problem loop as you suggest and see if it makes a difference. 

When I tried to get the same behavior to happen with a dark engine on a siding, it took a power interruption of 9-10 seconds to get it to enter conventional mode, similar in time to what happens when they're running and get a power interruption.

Those LED's just blink, right?  There doesn't seem to be any latching capability.  I love all the sparking and arcing.

Yep, they just blink. 

Keep in mind this is the $1 version...the one you get at DollarTree!

Hmm...  I looked at Dollar Tree, and I didn't see those.  Must have been out of stock!

John,  here's your cue... do your magic and make us one that latches!

Stan,  I just love the way the music stops when you short the track - that's brilliant; an audio alert to indicate that you've had a de-railment somewhere on your layout!!!

Best,

Dave

Looks like a lot of arc marks on the track now.

That's pretty perceptive that you caught that!  I think that's the mic circuit in the video that automatically adjusts the recorded audio level.  So the relatively loud spark sound causes the background sounds (music) to drop.  It does trigger another idea for a diagnostic tool.  Presumably a breaker will trip on a derailment and that ought to be a pretty good indicator.  But what about transient "shorts" on the track caused by mis-aligned trucks rolling over a switch that don't trip the breaker?  Perhaps another item to pick up at Dollar Tree is a simple over-current detector that flashes or has an audible indication when transient currents exceed 5 Amps (or whatever).  I guess it would be like current detectors used for block-occupancy detection but needs to cost... wait for it ... $1.  Then you put this on various loops or power districts to see if some are noisier than others. 

I just looked carefully at the track and you're absolutely right!  I'm hoping no one reports me to the SPCS (Society for the Prevention of Cruelty to Screwdrivers).

But you brainstormed yet another diagnostic method I hadn't thought of! Since these runaway events seem to occur more often on particular sections of a layout, I'll bet if one had the time, eyesight of a teenager, and dogged persistence, a careful study with a magnifier might reveal more arc marks around switches, joiners, whatever on the suspect sections.

It remains my opinion, and you brought it up too, that while surges may be the root cause of the runaways, the root cause so-to-speak of the surges may be wiring - specifically excessive inductance in certain areas of the layout.  So if the spikes/surges are caused by the rapid change of current (from a brief short) the size of the transient will be proportional to the inductance in the track and track wiring.  This will be very location dependent.  So even if each TIU has a TVS, it might be tens of feet away which may not suppress the spike before it has triggered a runaway in an engine parked closer to the transient.  This is why I thought of a traveling surge detector on a rolling truck.

Speaking of which, I'm still waiting for your TMCC traveling signal-strength indicator!

Stan,

If you're going to Dollar Tree, don't overlook some tratenfromps, a frannyframin and a couple or oscillating decraminator valves (electrical version) - eventually they'll come in handy for your upcoming project...  

Best,

Dave 

Don't be holding your breath for that one.

I posted recently on the 3 Rail forum, and will repost here, since my problem is related.

i recently had a similar event - 1 to 3 MTH locos taking off at full speed from a dark condition.  This had not happened until I added a turntable with storage spurs to my layout.  The start ups happen randomly to random engines, and with one exception, I can't get the same thing to happen each time.

Here's my situation - appreciate any help/thoughts you all might have:

On my layout, I have a single TIU powered through the aux pwr with a Z500, and use a Z4000 for track power.  I use a Z1000 14V output for accessories/switches with the gnd commoned to the Z4000, and everything but the Z500 has been tested to be in phase.  I operate a single DCS loop for all the track from Fixed 1 on the TIU, in standard mode.  I recently added a turntable with 8 stalls/spurs.  I powered the spurs by running a track power feed to a terminal strip, then star wired the grounds and power leads from each spur to the terminal strip.  All track power goes back to a common terminal strip.  When I turn on track power, all tracks are powered simultaneously, including the bridge on the TT.

Here's what happens now (didn't happen before TT/spur installation):

- I turn on the accessory and TIU power, then power up the track power on the Z4000.  One of the engines (MTH RK Evolution Hybrid) powers up immediately (without the DCS remote even being on) with full sound, but just sits there.

- I power up the remote, and select the Evo to power it down, and one or more of the other locos starts up without sound (I think) and starts moving.  I've had to pluck them from the track or power down, since they're heading for the TT (try that sometime with 3 going at once on different spurs!!!).

- I've reset the TIU, tried both fixed 1 and 2 (with different results), tried it without seperate TIU power, and reset the engines in question. 

- I will mention that a little while ago, while trying to power the TIU Aux Pwr using the 18V output of the Z1000 that was also suoplying 14V to the switches, that the Z1000 18V output was out of phase with the 14V output, and blew the TIU fixed 1 20A fuse a couple of times - wonder if it affected another part of the fixed 1 circuitry???

I can't reproduce the same occurrence twice.  I've tested the track for shorting or other issues, and as far as I can tell, all is OK.  There's no sparking going on since everything is just sitting when this is happening - no trains running.

Forgot to mention, I recently added the Legacy Cab2/Base2 to my layout - standard install, not linked to DCS

Any ideas?

Thanks,

Tom

Tom,

This sounds like the Z4000 is supplying power to too many engines at once. Look at the ammeter on the Z4000 and report how many amps it's putting out. If the amp draw is to high, an engine  (like your EVO) can miss a watchdog signal and come up in conventional.

The could possibly also cause the other antics your engines are experiencing.

The other possibility is that you crested some kind of a power issue when you added the new tracks and turntable.

stan2004 and gunrunnerjohn,

Did either of you analyze the hi-railers circuit for surges? I would be very interested in hearing your opinions. I saw this in another thread a while back, but I'm not smart enough to really tell what it does or how well it would do whatever it does? Might be a fun project to try if you guys thought it would be worthwhile.

I would be interested in a wiring diagram of your 'dollar store' version too, that might be interesting to try also.

And I'm with GRJ, like the sparks. I do that here also, for testing purposes only, of course. Did it quite a few times with the PSX-ACs I got only they don't usually spark as much.  

Barry,

When I first turn on the Z4000 with no engines running, the ammeter goes up to about 3.1 amps, then gradually settles back down to 1.9-2.0 amps.  I have two lighted cabooses and 3 lighted passenger cars on the tracks, and 7 mth and 1 lionel loco sitting dark as well.

UPDATE:

I've switched to fixed 2, and things are much better.  No random conventional starts, and the EVO doesn't start up on it's own anymore.  I do notice a couple of quirks. 

1.  I have an MTH set Imperial SD70ACE PS3 loco that doesn't seem to like one of the TT spurs - it gets to a point and stops responding to the remote.  All of the other locos function fine on this spur.

2.  The EVO still insists on starting up sounds when I just power up the track and go to move it, without hitting the start button.  Sounds and lights fire up as soon as I enter 1 SMPH.  Any thoughts on that?

I guess I'm slowly coming to the realization that, just like the computer I'm typing this on, that DCS or any other remote control system like it are going to have bugs and quirks that will either have to be endured or fixed, if possible.

Questions:

1.  Should I ground both rails of the TT spurs?  I only have one grounded now.

2.  Would you recommend setting up a switch or relay setup where I can power up only the spur needed, and keep the rest powered down and dark to avoid issues? 

3.  I read in your book that if track power comes up too slowly, that the train may miss the watchdog signal.  How slowly would that be?  I have to manually raise the power on the Z4000, since it will only turn on at 0 Volts.

Sorry for the long post.

Tom

New PS3 locos will start up and move if they are selected and thumbwheel scrolled, without pressing startup.

I would ground both outside rails.  With traction tires, some locos have problems getting ground.

Are you sure TT outside rails don't brush a spur center rail?

RJR,

I know they will move with the thumbwheel without starting up, but are the sounds supposed to start up as well?  Other PS3 locos that I have will move and respond to direction control, etc., but sounds don't start until I do the official "start up".

I've looked very closely at the TT rails where they line up with spurs, and I see no shorting.  I generally have at least an 1/8" gap between the two ends.

Tom

Tom,

The EVO still insists on starting up sounds when I just power up the track and go to move it, without hitting the start button.  Sounds and lights fire up as soon as I enter 1 SMPH.  Any thoughts on that?

That's an intentional feature of some, but not all, PS3 engines. It's equivalent to pressing Startup followed by scrolling up the speed. You can read all about it on this thread.

Would you recommend setting up a switch or relay setup where I can power up only the spur needed, and keep the rest powered down and dark to avoid issues?

Yes, I would. All of my engines sit on sidings that are toggle-switched for power.

I read in your book that if track power comes up too slowly, that the train may miss the watchdog signal.  How slowly would that be? 

Starting with DCS 4.00, the watchdog signal became 5 seconds in duration. It was previously 1/2 second.

Tom, the PS3s with this new feature do a complete startup, with all the bells&whistles.  I do recommend each spur be fed through a toggle switch.  That's the way I'm set up.  When I think I'm really alert, I will turn the switches on to let batteries charge, but usually they are off.

Also ground both outside rails on the TT.  If you look at the bottom of a diesel, you'll see that one side of each truck is insulated through traction tires.  If loco were to straddle a TT & a spur, each with one side grounded, you could have a dead spot.  Steamers without well electrically-connected leading or trailing trucks also may have a problem.  (But that's another story.)

Robert,

That's not quite accurate.

There are 4 traction tires on each diesel, two per truck. However, they aren't both on one side of the truck, rather, they are on opposite sides of the same axle. It's typically not necessary to have both outside rails tied together to accommodate MTH diesels.

Barry, I am quite accurate.  If the diesel is straddling  turntable and a spur, and each have only one outside rail wired to ground, there is a 50% chance loco will stop, depending on which end of turntable is involved.  Same can happen if both outside rails are insulated from next block, which can unwittingly happen at switches.

Robert, Barry,

Thanks for all the insight and help.  I didn't know that not all PS3's were created equal.

I'm going to give very serious thought to toggle switching all of the spurs/stalls for the TT, since I'm pretty sure I'll be unable to control all potential issues.  I was very lucky the 2 times the runaways occurred.

Barry, what did you think of the amps drawn that I mentioned?  Also, it appears things are much better on fixed 2 of the TIU - could some of this behavior I mentioned mean that fixed 1 has a problem and needs service?

Thanks,

Tom

Robert,

This could be affecting my SD70, but it's not stopping while straddling the TT - spur junction.  It gets fully off the TT into the spur, then just stops taking DCS commands reliably.  Sound stays on, it doesn't shut down, and still reacts slowly to speed commands.  It won't reverse direction, and won't accept the shutdown command.  Funny, but I can't get any other engine to do that on that spur, and the SD70 is fine on all the other spurs.

It happens that the TT (Millhouse River 28") only has one outside rail grounded, and I grounded the opposite rail from it on the spurs.  I'll ground both outside rails on the spurs just to be sure, although when I measure continuity between the outside spur rails with the loco sitting on it (no track power), the loco effectively shorts the two outside rails together.

Tom

On the problem locomotive, I'd suggest doing a track signal test while it transitions the problem area.  See what signal strength is reported back as it moves through that section.

John,

I'll try that, but as I said, the loco stops responding to DCS commands for the most part.  I don't know if it will continue to read and transmit signal strength.  Also, other locos are fine on the spur.  It's just a 30" piece of isolated spur.

Tom

BTW, can you just switch the center rail connection, or is it necessary to isolate both hot and common?

You only need to switch the center rail wiring.