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Power Controller Problem

  • Bajers (3 posts) , 886 days ago 18:26 13 November 2011

    Hi Guys,

    Wonder if you can help.

    I am building a layout roughly based on the latest Hornby Trackmat system on an 8' x 4' base for my grandson (me as well!) and basically, it has got two loops connected together by points and a third inner section for sidings with points etc.

    I am presently using 2 standard Hornby 12v DC power controllers connected at each loop corner and all works fine until the points are set to move a loco from one loop to another. Depending on each controllers switch position and presumably DC polarity, depends on whether the loco just stops (and you get a flashing red light on the controller you are operating) or keeps going when the 2 loops are connected. It's easy enough just to throw the switch on the other controller to correct polarity and then the loco runs again and moves across the points.

    Problem now is that one of the controllers has failed, DC input ok, but definetly no DC output and I am wondering if it is because of the way it is set up? I can't see any other way really to have 2 seperate DC feeds on 2 seperate tracks without at some point, the 2 are connected together.

    Don't want to go down the DCC route at the moment as I have spent enough!

    Any ideas?



  • poliss (4615 posts) , 886 days ago 18:43 13 November 2011

    Did you use isolating (plastic) fishplates at the point where the loops met?

    Get off the line Bobby.

  • Rog (RJ) (797 posts) , 886 days ago 18:49 13 November 2011

    It is usual to fit insulated fishplates (AKA Insulated Rail Joiners - IRJs) in the crossover between the two loops. On the old R965 controller this wasn't absolutely necessary because there was an "Off" position on the reversing switch to prevent the two controllers interacting.

    It may be that the thermal cutout has operated in the faulty controller. Leaving it to cool down for a while may be all that's required. Avoid having both controllers turned up when the crossover is "open".

    Rog :-)
    I don't model anything in particular, I just play trains

  • Gregd99 (960 posts) , 886 days ago 22:43 13 November 2011

    You need to ensure that you do not connect two controllers to the same piece of track. when the points are set to run locos between the two loops this is exactly what happens.

    assuming a dc output from your controller (many are pwm) the worst case is that you could have +12VDC (more or less) from one controller connected to -12VDC from the other. Ohms law tells us that V=IR. if V=24 and R is small then I will be big! Controllers have various protection mechanisms but in the end such a set up is not going to lead to a happy life!

    I am not the expert on dc ops but I would think that you need to :-
    1. fit the insulated joiners
    2. connect each controller to each loop with a double pole switch.
    3. when going from one loop to another you switch off (disconnect with switch above) one controller (you need to be disciplined here and not connect two controllers to the same loop)
    4. use the switches to connect the other controller to both loops and then
    5. throw the points and drive the train through....
    6. once the train is on the other loop set the points back to straight ahead and
    7. set the switches to connect controllers as required.

    all that sounds a bit complex but if you sketch out some circuit diagrams the ideas are pretty straightforward.

    Others will straighten out any mistakes above.


  • Bajers (3 posts) , 886 days ago 23:20 13 November 2011

    Thanks for the prompt replies guys.

    I think the IRJ's might be the answer then! Never heard of them before, problem now is the track is nailed down and ballasted so it's going to be a bit difficult to fit them.

    I presume I will have to fit these in the bit of track where the loops connect to each other which is two sets of points connected together? I have checked with my meter and I have continuity when the points are set to move a loco from one loop to another. I can see now if one of the controllers is set different to another, then I will have a full short. I bought the standard Hornby points.

    I did leave it overnight Rog as it had cut out before like this but it was still faulty when I checked it again. My main concern was that by shorting the two controllers I have blown one of them. Do you think this could have happened?

    Once again, thanks for your help and it's off to buy some IRJ's.



  • Bajers (3 posts) , 886 days ago 23:26 13 November 2011

    Thanks Greg, just read your reply.

    Makes emminent sense!

    I'll get onto it.

  • poliss (4615 posts) , 886 days ago 23:50 13 November 2011

    Flashbang is the expert on this subject. I don't think you need the DPDT switch, just have the controllers set to the same speed as the loco crosses the insulated joiners. You must ensure the polarity is the same of course. There's one other thing needed, but I can't remember exactly what it is.
    I don't have these problems because I use DCC.

    Get off the line Bobby.

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