Help me w/ DCC Specialties Auto Reverse Module

Discussion in 'DCC & Electronics' started by TrainNut, Oct 16, 2007.

  1. woodone

    woodone Member

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    After doing some thinking ( not allways good in my case). :confused:I am asking how does this thing work? We are working with AC voltage here, so if we make a loop and connect the wires we make a short, OK I got that. Now we insulate the loop at both ends so we have a section (center) that is powered by the reverse detector. When we go across the gaps into the loop we could go in with the rails being powered up with out a short because the center section is the same polarity as the section we just left. Ok now we leave the center section and enter into the first section, now we have the center section and the first section that are no longer the same polarity. This is were the reverse detector must switch the polarity so we don't have a short. How does the reverse dector switch your main power, as this power is comming from your main buss? It seams to me there must be somthing in the DCC power supply or booster that would change the polarity.
    Or I would guess that when we make the short when we leave the center section and go into the first section the detector changes the center section so we now have the same polarity. The same would apply if we reverse the wires at the first section- now when we enter the center section, the dectector sees a short and switches the polarity so they match
    Any input--

    Not to highjack TrainNut's post, but just trying to understand what is going on .
  2. baldwinjl

    baldwinjl Member

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    Alright, I'll have a go!
    Firstly, don't worry about whether it is AC, DC, or BC. Out of the booster there are two lines going to the track, we'll just call them A and B. These got to the autoreverser, which conceptually has a DPDT switch that controls the output to the reversing section. It puts A on track one and B on track 2 in one position, and B on track one and A on track 2 in the other. So, as a train crosses the boundary between the main and the reversing section there is either not a short (the rails in the reverse section match the rails in the main section), or there is a short. If there is a short, the autoreverser detects it (there will be a lot of current going through the rails through the reverse section), and throws its 'switch' to eliminate the short. When the train gets to the other end of the reverse section there will be another short, so the reverser will switch again to eliminate it. Remember, one of the 'rules' for a reverse section is that you can't be crossing both boundaries at the same time, as you then can't get rid of the short. Except when the reverse section is being entered or exited it is isolated from the main at either end, so it doesn't matter what polarity it is. Also remember that for DCCwhich ril is A and which is B does not matter, that's why you don't have to change the direction of the locomotive when the polarity on the track changes, the way you do with DC.

    Jeff
  3. woodone

    woodone Member

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    Thanks Baldwinjl.
    I do understand that the digital information is what makes the locomotive move forward of reverse. And the decoder does not care how it gets its information.
    It seems that TrainNuts problem is the reverse loop module is not switching and the short of the locomotive is shorting out his main power supply. The trip amps are too high (on the reverse module) to make the switch, so the main power supply shuts down.
    Is it possable that the reverse module is not correct for his system ?Trip set point can't be set low enough.
    I am not sure what system he is using, I know that it is Digitrax system, not sure if it is Zephyr- Chief or Empire.:confused:. Also would a booster make any differance?
    Hope that we can resolve the problem, as you have stated, you have three of these units.
  4. baldwinjl

    baldwinjl Member

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    All (or at least most) the the autoreversers I know of have some means of setting the trip current. The lowest setting on this one is well below the output available on the Zephyr, I think that's what he's using, so assuming he is getting it set it should work. It sounds like he was able to sense the short in one path, but not the other, so I am suspicious of the unit (though I didn't start out that way). Now that he's talked to Bruce, I imagine it will sort itself out pretty quickly.

    I've been in contact with Bruce, as well, since an e-mail I sent to DCC Specialties bounced, mostly to point out to them that the unit's delivered configuration makes it impossible for some people to use it since they can't get to the CVs, and the defaut trip level is too high. But anyone that the unit will work for without programming has a system that will program it. Catch 22!

    Jeff
  5. TrainNut

    TrainNut Ditat Deus

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    I received an MRC reverse unit today from another member to see if we couldn't figure this out. I hooked it up to the loop on my layout and No go. I then did the same thing as I did before and isolated it on a single piece of track with varying polarities (picture above) and I get the same problem as the DCC Specialties reverse unit. To me, this points to the DCC controller. Is anyone else using a Digitrax Zephyr system having any luck with a reverse unit? My next step is to contact Digitrax. Sheesh if I can't figure this out, I may have to resort to doing this the old fashioned way - DPDT.
  6. Nazgul

    Nazgul Active Member

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    TN....I have a Zephyr and reversing unit. It is one of the reversing units that Tony's Trains used to sell (I don't know about their new one).
    There has been no trouble with it at all. I have had 3 trains running around on my layout at the same time and it has always worked flawlessly. I don't know how much that helps you.
  7. TrainNut

    TrainNut Ditat Deus

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    As you eluded to, Tony's trains no longer sells that one and the one they are now selling is either the same as DCC Specialties or a spinoff. :confused:
  8. woodone

    woodone Member

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    Is there something (CV )to set the trip point of you cab, and or booster?
    If not I will bring my Power Cab set up with me this weekend- stop by after the swap meet, we can hook it up to your layout and see what happens.
  9. TrainNut

    TrainNut Ditat Deus

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    At this point, I dunno. I'm digging ever deeper into the manual to see what I can find. I am currently typing an email to Digitrax and will share what I learn from them. At this point, I'm suspecting it may be my Zephyr (for lack of not knowing what else to suspect). I'll keep in touch as I may take you up on that offer.
  10. baldwinjl

    baldwinjl Member

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    Hmmm, I can't (yet) find any documentation on the MRC version. I did hook up one of my DCC specialties versions to my old Prodigy this morning to see whether the Prodigy could trip it as it comes. Suprisingly, it did! The Prodigy is rated for 3A, which is more than I expected. I hooked the inputs to my DCC bus and just out wires on the outputs. At power up, the two power LEDs were lit. When I touched output wires to inputs, I was able to get the flashing LED flashing, and then by shorting the other way, I got it to stop flashing. Now I just need to get my double crossover control in, and see if it works in real life!
  11. TrainNut

    TrainNut Ditat Deus

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    Just found this in the manual on page 40...
    The way the text in the box is worded is confusing but I think it pertains to the issue I am having.

    [​IMG]
    [​IMG]
  12. baldwinjl

    baldwinjl Member

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    Mr. Nut,
    I think you are on the wrong track, here. Your Zephyr is your command station, you are not trying to use it as a booster for another command station, and you are not trying to have it do autoreversing. You might want to check the Option switches to make sure they are not in a contradictory position, make sure that switch 3 is open and switch 2 is open.

    As far as the Zephyr is concerned it should not even be aware that someone is performing a reversing function. The autoreverser is conceptually just a DPDT switch that throws when it senses a short. It needs to sense the short before the Zephyr does. What's in the MRC reverser docs? I'm going to have a look for them online, as well.

    Jeff
  13. baldwinjl

    baldwinjl Member

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    I did not find a manual for the MRC reverser, but I found several references to it as a 2 Amp unit, so your Zephyr should throw it. But the MRC unit is a slower relay driven unit, so perhaps the Zephyr sees the short too soon. This you can change by stting option switch 18 to 't', see page 46 in the manual.

    Jeff
  14. TrainNut

    TrainNut Ditat Deus

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    It has been suggested that I update this thread in case anybody was wondering...
    After exhaustive testing, we believe the fault of this whole thing lies with the Zephyr controller. We switched out controllers and used an MRC unit that controlled the reverse loop in the layout perfectly. We then tested the reverse loop modulator with a different Zephyr and it worked perfectly. I have since sent the defective Zephyr controller back to Digitrax where they hopefully will find a problem and return it to me in pristine working order.
    - I just received an email from them stating receipt of my Zephyr and for me to expect something back in 10-14 working days.
  15. jesso

    jesso Member

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    Hope things work for you when it gets back. 10-14 days?! I hope you have some other way to run trains in the interim.
  16. TrainNut

    TrainNut Ditat Deus

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    Well, I could always go back and hook up my DC controller and run things that way I guess. Mr. DCC (Bruce of Litchfield Station) also offered to let me borrow another Zephyr he's got lying around until then. So far I've been using the 5DC control with some success and I've managed to hold off any withdrawl symptoms. I've also taken this opportunity to dive into that pile of unbuilt building boxes underneath the layout. I think I'll be okay.
  17. BigJim

    BigJim Member

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    Am I missing something here? Seems to me you could set the polarity of the loop based on the position of the first "loop" turnout. I don't like using the Tortoise switch points for this but you can use them to power a reversing relay so it turns on when the Tortoise / turnout is in the "reverse" direction.

    Auto reversing is a great concept but detecting the need to reverse by shorting the output of DCC unit seems to be a bad idea. Can't be good for the DCC unit or the wheels.

    It takes a little thought but I think most "Y"s & loops can have their polarity set by the turnout direction. The single direction crossing inside a loop is a little harder but most of us should avoid these since they only allow you to turn the train once and then you cantturn it back.
  18. baldwinjl

    baldwinjl Member

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    I thought this at first, but the more I see and read the less I think this is true. The reverser acts before the DCC unit senses the short and shuts down itself, so the impact there is less that the impact of a short. As far as the wheels go, I expect that as much damage due to dirty track and just normal operation as there is form this. In theory, the DCC Specialties reverser that started this thread switches quickly enough that there is little or no spark at the wheels. It is actually one of the 'neat' things about DCC that you can detect the short and reverse the polarity before anything on the layout notices it.

    My layout will have three autoreversers, I have two reversing sections that are effectively cutoffs on opposite directions (the way the layout is you have to really think about it to see that they are reversing sections. The very situation where using switch points to determine polarity won't work. The third reverser will by controlling part of the track in a double crossover (the throw mechanism controls the other part). Again, the position of the switch can't set these, you need to also know which track you are using). So for me, the autoreversers are very handy.

    Jeff
  19. BigJim

    BigJim Member

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    I knowwhat you mean about the double crossover issue with solid frogs. I have four of them I built with a fast-tracks jig. I plan on building current sensing devices to detect the train direction at the four entry points tos et the internal polarity.

    If your loop looks like this
    [​IMG]
    you might want to consider having the center track be the directly connected one and set the polarity of the two loops based on the two turnout positions. If you have the entire outside loop set at the same polarity you could have a problem with a train longer than the crossing track if the wheels short out both isolation cuts at the same time.

    ...Jim
  20. baldwinjl

    baldwinjl Member

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    The reverse sections look like this:
    [​IMG]
    [​IMG]

    They are in red, except for the tiny bit on the upper level I missed.