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Author Topic: Loopback + Block detection + Automatic Switch Control (BXPA1 + DS64 + Tortoise?)  (Read 241 times)

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Offline chrispix

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I had an old post that did not have enough detail, so hopefully this adds the missing detail. I am wanting to switch to the loop back when there is a train present in the loopback section which is managed with an auto-reverser BXPA1. I am hoping one of two things can be controlled, just not sure how they can be done (or maybe this is where the computer control comes in)..

If the point is not set for the loopback to reverse, then halt the train near the points.  If the loopback is set then allow the train to proceed..

Alternatively (which was my thought on how to solve this), if a train enters the loopback section, to change the points automatically. I just am not sure how to do that between the BXPA1, DS64 and Tortoise.  I have a BD4, but would rather use that on another area of the track, and since I need an auto reversing section, this (BXPA1) seemed like the right solution.


Online Nigel Cliffe

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Lets start with "Digitrax manuals are crap",  and in this case its "the manuals are really crap".   The BPX1 says it can report occupancy, but the manual is really opaque on that detail.   Suspect you can't do anything with the occupancy data without a computer in the mix, to receive and then act upon the occupancy information.     
But maybe there is something presented to one of the not-described screw terminals which is the occupancy signal ?   And maybe that can be used to trigger something else on another device ?    Maybe the Digitrax forum on Groups.IO could answer what those terminals are for.



Auto-stopping the train in the loop.  Possible, depends on the decoders in use.   

In order of cost, rising....

Cheap, nasty, crude, but works.   Have a dead section before the end of loop, which is only energised if the turnout is set correctly.   Section switched through contacts on tortoise motor switch gear.   Locos run into dead section and just stop (or come to stop on their stay-alive if fitted).   Its nasty, but it will work. 

If you're using modern European decoders (eg. Lenz, Zimo, newer ESU, and a few others), they support Asymmetric DCC Braking.  Which means you can stop trains in a section, following their deceleration curves, easily using a 50cent circuit (six rectifier diodes), using the switch circuits in the tortoise to bring it into and out of action (assuming there is a spare switch circuit).   Switching is almost the same as the crude "no power" option, but the diode circuit ensures things stop smoothly, keep the sound running, keep their lights on, etc..

If using a larger range of decoders (including many US brands), there is an option to do "stop on DC", which can bring the locos to a stop.    That requires a DC stop signal generator, of which there are several, some of which are simple to wire into track and don't have external power supplies (so no need to worry about voltage paths, etc.. ). 

Then costs start to go much much higher, and gets into computer software to track trains, and bring them to a stop. 




Offline chrispix

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Thanks Nigel. Yes the Digitrax Manual for the BPX1 is really crap. I like the idea of an additional section, but that means if a train does approach and points not set, it will short when the rails bridge, and drop the entire section of track, including the train going over the points that has the right of way.

I think I may have to do something like a Asymmetric braking section which I believe should be able to be powered with my auto reversing section.. I will give that a try, will be going with computer control, but still a way out from doing that..

And to think my loop back seemed like the easiest piece of my layout to start with because of auto reverser.. ha!

Online Nigel Cliffe

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If you can get asymmetric DCC working for all the decoders in your locos, its probably the easiest solution.   It should work fine within the auto-reverser, as that's just swapping the phase of the DCC, its not altering which rail is "right" or "left" w.r.t. the locomotive.     You might need a brake zone of most of your loop, depends how long the track section really is, but so long as there is a short (loco length) of track before the brake zone, it really should work. 

In asymmetric DCC, the loco detects a drop in voltage on one rail, and treats that as a "brake" instruction.  Bypass the diodes (brake module) with a switch (spare contact on tortoise?), and there is normal DCC voltage, so no longer brake and run normally. 


 

Offline chrispix

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Awesome, I have a couple dapol factory fitted decoders, but also ordered a Zimo MX64 from youchoos, which I believe should work.. Guess I will be updating my decoders.. To your point, it looks like I will need to replace a small section of track & isolate it so the diodes can do their thing.

Online Nigel Cliffe

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Do you mean a MX64 ?   That's really ancient, and its also quite big, doubt it would fit anything N gauge!

- Nigel

Offline chrispix

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Crap will look into it.. Thought I ordered something else, but that was the receipt.. :/

Offline chrispix

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Looks like it was a MX649N

Online Nigel Cliffe

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Totally different beast to MX64.    MX649N is a small sound decoder.   

Nigel

Offline ahellary

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hi there

witha multi meeter and a little time you should be able to work out what pins go high or low on the bxp1a ...i have one but its under the railway but from what i see there is a terminal marcked com so  suspect thats common and from that you should be able to see whci pin goes high when the section is occupide  didgrats states it can do this may be a qustion io groups or direct to the support desk at digtrax

Offline ahellary

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heres the connection info

Additional Connections

Connections between the ON and OP terminals of the BXPA1 allow for external triggers when the detection section of the BXPA1 is active.


The XR and XG outputs can be connected to and External Bi-Color LED to indicate the status of the reversing section.


NOTE: RS, COM, MO, and P are not used at this time and reserved for later implementation.



Offline chrispix

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So what it looks like is ON/OP is just a switch that gets closed when there is something occupying the track.. I need to do some more research on it, but it did not seem to get triggered all the time (was using just a single coach with lights). it shows it as occupied light... I guess I will mess around with it a bit.. hopefully I can figure this thing out.. Appreciate it.

Offline ahellary

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So what it looks like is ON/OP is just a switch that gets closed when there is something occupying the track.. I need to do some more research on it, but it did not seem to get triggered all the time (was using just a single coach with lights). it shows it as occupied light... I guess I will mess around with it a bit.. hopefully I can figure this thing out.. Appreciate it.

no worries ... i just asked the q on the digitrax io group ... im a long time digitrax user and have used the group for ages  there a lot  of nery knowledgeable people on it its just the sort of place to go for that sort of question

an old boss of mine once said  dont remember everything .. just know where to look it up .... a very wise man i still live by that code to this day

Anthony
« Last Edit: April 10, 2020, 08:39:06 PM by ahellary »

 

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