DCC++ and auto-reverse question

Erik84750 · Dec 4, 2017

w8one said: ↑

View attachment 181804
Sensor 3 will show you which way the train is going. See if 1st sensor has been tripped within a set time then set sensor 2 to switch the polarity and the points (or signal whatever controls the turnout to change them). If the points are changed sensor 3 can tell your turnout controller to change the polarity to match the points.
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Hi w8one, in hindsight, and after so many months, I must concede I had missed the point of your post. Sorry for that: indeed, if the controller is to direct the polarity of the DCC signal inside the loop then this controller can just as well direct the points of the loop switch.
I will have to rewrite the software for that purpose; as it is written now the assumption is that a third party decides the setting of the loop switch, my software is conceived to just control the DCC polarity regardless of the position of the switch.

Erik84750 · Dec 4, 2017

JimDo said: ↑

Eric,

I thought I would chime in. I am just getting into model railroading now. I realize that I am late to the party. I have been thinking about AR for a while as I struggle with how to set up my loops without the use of short circuit detection. I think the flowing is the complete list of scenarios. Using 3 detection blocks in your example, DET-a, DET-b and DET1.

Additional assumptions:
Train must fit in its entirety in DET1. As a result, train wont be in all 3 zones at once. This is important for other reversing scenarios not depicted here.

Default state of relay should be low. If I understand the micro-programming logic, this is arbitrarily assumed to be equal polarity with DET-a.

An additional variable is need to keep track of train entry point into the loop, to know where it came from since keeping track of the state of the relay is not sufficient. In the loop, this will tell us the polarity of the next zone to be encountered.

Logic will set loop polarity to that of the default whenever possible. First two cases ensure loop is set properly upon entry.

Use Case DET-a DET-b DET1 FromZone Action

blk-a HIGH ---- ---- ---- Set NextZone=HIGH, Relay-LOW

blk-b ---- HIGH ---- ---- Set NextZone=LOW, Relay=HIGH

All blks empty LOW LOW LOW ---- Set Relay=LOW

Enter Det1 from blk-a HIGH LOW HIGH ---- Set Relay=LOW

Enter Det1 from blk-b LOW HIGH HIGH ---- Set Relay=HIGH

Det1 only LOW LOW HIGH ---- Set Relay=NextZone (once train fully in loop, use next zone polarity)

Error condition 1 HIGH HIGH HIGH ---- Set Relay=LOW (you have a short or a detection problem, or a train too long, but you cant control it anyhow)

As you see, logic does not really care about status of relay, rather where the train came from and where it is headed to. Now loop zone polarity is set to the zone polarity from which the train entered and immediately changes to the polarity of the exiting zone once zone transition is complete.

Jim
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Hi Jim, it has been a while since I kept busy with this subject; I think my current software takes all your scenarios except the last one into account. Or am I wrong?

Paulo Correia · Mar 2, 2018

Hi.

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DCC++ and auto-reverse question

Erik84750 TrainBoard Member

Erik84750 TrainBoard Member

Paulo Correia New Member

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