ABC stopping distance for signals

[John-357061]

Looking at HM7000 documentation it does support ABC. Setting up a DCC system.

Ordered

ABC DCC Brake (asymmetric DCC Generator) 860065

from Aliexpress.

For the TT scale trains what is the stopping distance? Minimum and prototypical?

Trying to figure out the track sections needed while laying track.

Also does the brake in track need to be both sides or just one?

Basically trying to figure out all the things I need to plan for laying track. Where the breaks need to be and where there is track power.

Thanks for any help.

[ntpntpntp]

So are you using traditional track powered DCC or HM7000 bluetooth + constant DC in the track? I think ABC only works with track powered DCC as the decoder is looking for the DCC signal being slightly modified within the braking section. I'm not sure how it can work with plain DC in the track.

[P-Henny]

I recall this topic being discussed in a recent thread. The outcome of that discussion IIRC was that the HM7000 implementation of ABC is only relevant when you are using ABC in a DCC powered layout environment.

Given that you stated that you are setting up a DCC Controlled layout, then the HM7000 decoders should be compatible with an ABC configuration.

Sorry, but no idea about stopping distances except that they will be affected by the Acceleration & Deceleration configued values and will also be subject to motor specifications and hauled weight etc. In other words I suspect you will have to perform some testing of the locos & trains you intend to run to observe & measure the distance values you require.

[John-357061]

Thanks for your replies. Using traditional track powered DCC.

I guess I will have to set up a test track and experiment.

[P-Henny]

Just be aware, but not sure if this is relevant. If you add the Power Bank (stay alive) to your HM7000 decoders. Not sure if that will make the locos run on when ABC Braking is implemented. Something to consider and check for. May be a red herring.

[Britannia Builder]

I tried ABC yesterday on my 00 gauge layout. I made up a circuit board with 4 1N1007 diodes in series in one direction, and a single one facing the other way in parallel to these, then inserted this into the track feed on one rail of my programming siding - I used this siding because it already had insulated joiners and a separate track power feed.

I set the CVs on one of my locos (which has a power bank) to detect ADCC on both rails, and to stop in a constant distance and then reverse after a 5 second delay. It did work as advertised - it appeared to react a second or so after the pickup axles were in the isolated section, and then stopped in a short distance irrespective of the initial speed. I left the stopping distance CV at the default which I think from memory is 25, although it doesn't say what the units of this are. So it appears that you can program the stopping distance, but I would suggest doing some tests before ballasting everything down.

It was interesting to try this, but I probably won't use it further.

Regards, John

[Fishmanoz]

If you check out pp104-6 of the HM7000 manual, it describes the feature as:

“The decoder can detect a normal DCC signal and can detect when it changes to an ADCC wave form i.e. goes out of “balance.” The decoder can then be programmed to 

automatically carry out an action on detection of the ADCC signal”.

Paul, because it relies on detection of the out of balance signal, after which action is taken based on CV values including stopping, it is not affected by a power bank.

Going back to John’s OP questions:

• you can program stopping distance and I’m assuming the question is what would be the prototypical to program?
• how many rails need to be cut? The answer is one. However, it seems from the manual that the detection is rail sensitive based on CV27 value so you could have cut sections at different places on different rails and be able to program different actions

[Britannia Builder]

Going back to John’s OP questions:

• you can program stopping distance and I’m assuming the question is what would be the prototypical to program?
• how many rails need to be cut? The answer is one. However, it seems from the manual that the detection is rail sensitive based on CV27 value so you could have cut sections at different places on different rails and be able to program different actions

 

 

Although you can choose which rail to detect on, I don't think that there's any way to program different actions in a single loco depending on which rail has been detected.

I was thinking of setting my DMU up to shuttle between platform sidings in my two stations, but the rail cuts would have to be at different distances from the buffers since the power pickups are in one end car of the 3-car DMU. Another issue, at least for RailMaster users, is that the ABC reversal doesn't change the direction shown on the RM screen (obvious when you think about it) so the controls get out of sync. I suspect that the app would be the same.

Regards, John

 

 

 

 

[Fishmanoz]

John, see page 106 of the manual on the function of CV27 where you can choose to detect on one rail or the other or not at all for values 0-2.

[Britannia Builder]

I think page 106 is incorrect where it says that the range of CV27 is 0-2 - Appendix 8 says the range is 0-3, 3 being both rails (ie either rail will trigger the action), and that's what I've been using.

Regards, John

[John-357061]

Thanks for your replies. Very helpful.

you can program stopping distance and I’m assuming the question is what would be the prototypical to program? Yes

Currently have 4 A1-A4 locomotives. Given a flat surface and going as fast as possible. Would 2x locomotive length be reasonable, about 40cm. Given that I plan to get also more modern trains, will this work?

Sounds like you can set the stopping distance, so does this mean I can go with a length that "looks nice", prototypical when space allows. Is this correct?

For my stations, I would like the train to stop in exactly the same place, so the carriages are covered by the platform, when the signal says stop. Very typical thing to do.

The other use case is protecting blocks.

Testing is one of the challenges with TT, given the limited range of locomotives.

[Fishmanoz]

I think page 106 is incorrect where it says that the range of CV27 is 0-2 - Appendix 8 says the range is 0-3, 3 being both rails (ie either rail will trigger the action), and that's what I've been using.

 

 

Well spotted John but can I suggest that both means what it says, not either. With range 0-3, there are 3 options for triggering.

And note it incorrectly refers you back to Appendix 3, it should be 4.