Stop always exactly at the same place?

[Per Olsen]

Hello !

I still have an "old" problem, with trains not always stopping at exact same spot every time. 

Some of my routes I need to tweak so that one exact length of train always will stop at exactly the same spot every time.  This because it must fit exactly in one track on the station, so that it will not interfere with other crossing trains.  The "easy" solution would be to use a shorter train, and stop well in front of the turnout, but in many cases this is not an option here.

I have programmed the routes very carefully, and MOST times, the train stop at exactly the correct place.  But sometimes it does not, it sometimes stops after some more cm than normal.  And than I have a problem.

What have I tried:
I have programmed the speed and braking so that the train has a VERY low speed just before the braking.
I have changed to a much faster PC.
I have checked/rechecked the S88-feedback for false/missing feedback.
I am still using Intellibox (with some restart-problems), but have ordered a new TAMS controller.
In the PC I have un-installed all virus-protection programs, and I have disconnected the network.
Nothing of this has helped....

The problem seems to increase when increasing number of trains running (normally max 3 at any time).
With just 1 train is running, the problem seems less (may be in my imagination..).

Doe you have any idea as to what more I can try?  I really need this fixed.

Best regards,
Per.

[Gerard Moggré]

Hello Per,

What is your baudrate-use?

Kind regards,
Gerard

[Per Olsen]

Hi.

Intellibox-max, that is 19200.

Per

[Gerard Moggré]

Oké Per,

Some more questions, are your trains driving with "profiles"?
What kind of computer do you have?

It looks like, when the rate of your communication between the computer via the IB to the modelrailroad rises, results in a lower rate of communication. You will see, when you are using the Tams with a baudrate of max.57600, the communication will be much faster, and the commando's to your trains will be quicker then they used to be. For instand, a stopcommando to one train will arrive faster to that train, so this train will stop a bit earlier.

[Markus Herzog]

Hello Per,

I would suggest to wait until you own the Tams MC.

Many users reported, that they achieved a better stopping accuracy after changing to the Tams MC.

I have made the same experience with my Tams MC, all trains stop now with ~ +/-0.5cm (normally up to 12 trains running simultaneously).

The different baud rate is not the problem (IB:19200, Tams:57600). The difference between the Tams MC and the IB can be found in the response time.
Each command send by PC has to be acknowledged by the IB/MC, because sometimes the device tell to resend the command, because they are busy etc..
The PC may not send any new command before receiving the acknowledge for the command before (time between command and acknowledgement = response time). This time is for the IB  ~30ms and for MC ~5ms.
Let´s calculate: 1s/30ms = 33 commands per second to the IB and 200 commands to MC.
If we take a look at the IB/MC protocol then we know, that these devices have to be asked to report for S88-changes/locomotive events etc. (in contrast to the Märklin Interface 6051 they report only changes, but they don´t send these changes automatically to the PC as Lenz/Selectrix/ECoS/CS). This means a intervall of 100ms will lead to a minimum 10 report questions to the IB/MC per second (10 minimum because every report will lead to additional questions by the PC)  and then we have just 23/190 commands left for locomotives/solenoid devices.

So, wait for the Tams MC...

BEst wishes
Markus

[Per Olsen]

Hello !

Thank you Gerard and Markus! 

I am not using profiles (yet).  I know how to use them, but I have decided to fine-tune all routes etc as much as possible first, and next use the profiles to perfect them.  But then I have to rely on the trains to stop where I want them to stop, and not 5cm later at times.

The PC is 3GHz with 4GB Ram, Windows XP sp 2.  All brand new, and the XP new-installed.

I agree with Markus, I do not think baudrate is the (biggest) problem.  It may play a part, but probably only a small part. 

Yes, I look forward to the TAMS, but it is still some weeks away, it is being sent to my daughter in Denmark, and my wife will bring it home from there in about 3 weeks.  So untill then, I will have to cope with the IB.  The main reason for leaving the IB, is the irregular restarts, and loss of communication.  Just 1 hour ago I had a big crash, as the IB did not respond to stop-command from WDP. 

Stop within +/-0,5cm sounds OK.  This is the kind of precision I want.  Right now I have to consider +/- (3-5)cm (at least, in some cases). 
And still worse, the restarts.

Thank you for your responses !

Best regards,
Per
Bergen, Norway.

[Per Olsen]

Markus, I wonder:

If I have a lot of locos in the "Layout" status, even though they are not active just now, will this slow down the communication?  Is it better to set all non-active locos in status "Vitrine" ?  It should make sense...?

Does an in-active loco (in Layout status, not in Vitrine) slow down the communication just as much as an actually running loco?

Per.

[Markus Herzog]

Hi Per,

this should not make any problems, because every time an IB or MC reveices a command for a specific loco by the PC they will send directly the command to the loco (indepedent of the current amount of locos in the refresh cycle). From my opinion you shouldn´t have any problems with many standing locomotives on your layout.

Best wishes
Markus

[Per Olsen]

Hello again.

OK, thank you.  It did seem to make a difference, but maybe it is my imagination..  I thought perhaps there was a stream of datas for each loc all the time, and only the contents of the stream was changed when a command was sent.  But I understand now that there is no traffic from PC to IB when there is no change in command to the loco.  Only the change is sent, if I understand you correctly.  If that is so, it should not make any difference how many locos there are, as long as they are not running (receiving commands).

I really DO look forward to receive the new controller.  2 weeks from today.    I am counting the days...

Best regards,
Per.

[Peter Ploch]

Hello Per,

The only problem is, when you start WDP, it needs a little bit longer to read the information’s from all engines. So I set all locos which I don’t need to “Vitrine”. But this is only ones when you are starting. Much fun with Tams MC, I think it is the best controller in connection with a PC.

Don’t count only the day, don’t forget the hours!!!

[Per Olsen]

Hello !

OK, thank you!  That extra time at startup doesn't matter.  But it is still a bit "cleaner" when not all the un-used locos appear at startup.  So I will still keep all the others in "Vitrine", I think.

Yes, I look forward to the new controller.  Hope to get rid of all the problems. 

Best regards,
Per.

[Oliver L.]

Per,

quite frankly, I think you're aspiring to an accuracy that is beyond this hobby (or even reality). I use N gauge and still I allow for a minimum of 5 to 10 cm for a stop. Demanding more will soon get you to issues like warming up engines etc, which tend to cause variations no matter what. Why do you get in trouble with a 5 cm overshoot?

Oliver

[Frank Mondorf]

Hello Per,

Stop within +/-0,5cm sounds OK.

We solved that for our tram (+/- 0,5 cm  on 40cm braking in flat terrain or  +/- 2cm on +/-5 Percent Pitch/Slope) with Lenz Silver loco-decoders with "constant Braking" and a local Circuit to the track called "ABC". The creator of the tram-layout with selfmade tracks has not considered any breaking-tolerance  .

It works because the loco-decoder is asked to break directely by an analog signal by the ABC-Module when the module detecs the occupancy of the stop track. When getting the analog stop-signal (without any digital data-transmission oder computing), the Decoder himself stops after a constant number of motor-roundings.

By this way you can stop nearly all so equipped trains exactly at the same place. The braking has to be the same in the whole layout and also individually adjusted to each loco.

In a Windigipet-Solution there surely will be special things and expenses to do for integration, an using the BM3-module is a little bit expensive.

best regards
Frank

http://www.lenz.com/products/modules/bm1.htm
http://www.lenz.com/products/modules/bm2.htm
http://www.digital-plus.de/pdf/SILVER_Manual_e.pdf
http://www.digital-plus.de/pdf/b_22620_e.pdf

[Per Olsen]

Hello again.

When I started building my layout, I had to make some desicions about how long stop-tracks to use.  Most stop-sections are no problems, and allow for at least 10cm "overshoot" from time to time.  Other places I need to stop very accurately, so not to collide with other trains passing the turnout in front of the loco.  (The next time I build a new layout, I will allow for longer stop-tracks...).

I try to minimize the problem by having the loco brake to a very low speed before entering the stop-section.  This helps, as the train move a shorter distance in the same time, if the start-speed is slower.

Anyway, I have still problems.  Loco that normally stops at one place, sometimes moves maybe 10-15cm further before it stops.  Not very often, but it happens.  And then I have a crash...

I need to be able to rely better on the running of the trains.  WinDigipet seems to be very stable, I have no crashes caused by WDP itself.

After several recommandations, I have orderen a new Tams controller.  I will receive it on sunday.  I have been told that the problem will be much less then (see the other replies to my original message).

Best regards,
Per.

[Frank Mondorf]

Hallo Per,

If youre not use a 2-track system , don't read the following:

My theorie of Braking is a little bit complicated. So i'll try:

The length of braking for the loco using a normal 2-track DCC equipment should at least be 15cm, because the loco should stop complete (with all axes) within the Stop-Area.

If loco is going to the braking point with i.e. 40 km/h (in a long area before entering the stop-section), which in my opinion is a good value to get a dynamic traffic,  the braking looks nice when happens within 30cm . The resulting length od the stop-area in this case should be at least 45 cm , better 60cm. Afterwards you can make some fine-tuning by programming the loco-decoder to get a stop within +/- 6 cm at the end of that area.

You can also have short stop-areas (30cm), but you have to break to a very slow speed before. To get the loco complete into the stop area, You may have to use windigipit-profiles, not to break to early.

The problem with a loco standing in the stop area not with all axes, is that you can't be sure that the feedback-decoder recocnizes the loco, because the current may run through wheels on another area.

Not only when braking differs unexepected, it may become better, using the Feature "Immediate-Stop" (hope this is check-box label of the english version) in the loco-database.

But before cutting the rails, You should wait for th TC, to see how the differences will be.

Best regards
Frank