Friday, October 22, 2010

Power Problems During Op Session

   The UPRR Geneva Sub hosted an operating session last Sunday afternoon.  I was looking forward to the session because it was going to be the first op session with signalling and a full dispatcher.  We had ten operators in attendence and the session was going real well.  I was dispatching, a couple of guys were working the Proviso/CLinton Yard, an operator was attending to Global III and everyone else was taking turns being road crews.  Trains were moving pretty efficiently and everyone was keeping busy for the most part.  It turns out however, that things were going a little too well.  With so many operators, there were at times up to four trains runing on the mainline along with two sets of yard switchers working Proviso Yard as well as the Global II sitcher and the BNSF local crew.  The Digitrax DCC system began to shut down under the strain.  At first we thought that there was a short problem somewhere on the layout.  However, nothing was ever found and and the shut downs were becoming more frequent as the session progressed.  Every time the system shut down, the PM4s went crazy with all 8 power districts tripping in a rythmically random fashion.  To get things going again, the system had to be shut off and restarted.  We got about 3 hours into the session and were to the point of just 4 or 5 trains left to complete the days work when the shut downs were to the point where I gave up and we ended the session.
   Throughout this week, I have been thinking about what may have caused the problems.  For a while I thought maybe the battery in the command station was dead. But, even though its been five years since its been replaced, it did not make sense that a bad CMOS battery would cause shut downs like that.  Especially since the layout works fine when I operate alone.  In thinking about the problem, I keep coming back to the fact that the layout works fine when its just me, but shut down when 10 of us were operating.  The difference has to do with load of all those engines running at the same time.  I sat down and figured that the shuts downs were occuring when we had around 15 locos running at the same time.  With a five amp system, that means that each loco had to draw 1/3 amp each in order to strain the system.  Looking at Kato reviews on MR, I saw that Kato locos draw less than .2 amps slipping, so at first that did not make sense.  But, then I got to thinking that my Katos have all seen quite a bit service over the years and have accumulated their fair share of gunk which likely has decreased their efficiency and increased their current draw.  Add to this the fact that I have a number of tunrouts connected to track power, there are 30 or so idle locos on the layout and there were 6 throttles plugged into the loconet and I think maybe we were straining the power limits of the system.  I have been able to recreate the problem, by running 7-8 mutliple consists at the same time.  When I recreated the problem, I discounected the PM4s and found out that, when it shuts down, the system makes continuous clicks which the manual says mean a drop in voltage.
   So, I have concluded that either I need to add a second 5 amp booster or my power supply is not providing enough volts.  Since I am using the Digitrtax 15 volt, 5 amp power supply, I doubt its the problem.  I'm leaning more toward not enough power.  I'm going to see if I can get a spare booster here so that I can test and see if that is indeed the issue.  If so, I will be in the market for an additional booster for the layout. 
   I'd be interested if anyone else out there has any ideas on what the problem might be.  I always try to keep an open mind about such things.


  1. I was surprised to read that you have only one 5 amp booster for all that you have there. Granted, on the DCC side, I'm used to providing power for HO engines w/sound, but still, the number of accessories you have is significant. For example, my UP5s/91s are powered by a PS12. When track power is off, my DT400 shows 10.x volts when it is plugged in (no battery), but when track power is on, it shows 14.0 volts. So it appears that the UPs are still pulling a little load from the track, even though I have a power supply hooked up. Considering all of the accessories that you have (with and w/o their own power supplies), that may even add up to half of your power usage. And despite properly gauged wire, on a layout your size, even the resistance of the amount of wiring and nickel-silver rail could add up to a very small, yet appreciable load.

    Of course, since I haven't looked over the system, there could be something that I'm missing altogether.


  2. Hi Daryl,

    Another great layout and I'm enjoying following your progress.

    In the Ntrak club that I belong to when we got up to about the number of engines and throttles that you mention running on your layout, we began to have problems with response time and also with enough power reaching locos furthest from the single DSC100 that we had.

    What our DCC system gurus did was to add a booster with its own PS515 power supply. Also, I do recall that the LocoNet between the DSC100 and the booster are separate from the LocoNet that runs the throttles. Since it's an Ntrak layout with the separate tracks and blocks for DC throttles, they also put in either PM42 or something similar at each booster with the outputs feeding the tracks.

    Hope this helps and thanks for sharing your layout with us.

  3. Thanks for your input guys. You are confirming what I finally came to realize... One booster is not enough power for the Geneva Subdivision. I do have seperate power supplies to almost all of the DCC accessories. But I think that If you add in all the wiring, 13 UP5s, 6 throttles, and all the idling locos you get an overloaded system. We were getting slow response times from turnouts when the system was geting close to shut down. So, I already ordered a power supply and have my eye on a couple of digitrax Boosters on ebay. I got the power supply on ebay as well. instead of paying $40 on the Digitrax PS515, I got a toshiba laptop charger for $12 with free shipping. It delivers 15 volts and 6A.


  4. Daryl,

    You should really be powering the UP5's off a separate bus, either using the power connectors on the UP5's, or as a parallel Loconet bus.

    Loconet can start behaving strangely if the voltage drops to low!




  5. Collin, Thanks for the input. I thought about powering my UP5s, but I was able to recreate the problem with all the throttles unpluged (using DecoderPro throttle via computer interface), so I did not think it played a key role. Do the UP5s draw power of their own? There is a lot of loconet wiring so that may be causing the voltage drop. I may just hook up some power to the UP5s to see if it makes a difference.


  6. You might also look at adding a power cutoff switch for staging yards and engine servicing facilities. I have built both versions of my railroad with the ability to cut the power to those tracks when locos are not being used.

  7. NS-CRE, Thanks for the input. I pulled all the locos in the staging tracks off the tracks and run the trains again. Instead of the system cutting out @ 15 locos, I was able to get it up to 18 locos before the system cut out. I also checks the loconet wiring and made some changes. Mainly, I made sure the back, side plug of the UP5s were not being used for daisy chaining. There were three instances where this was the case. That did not seem to make a difference. All assessories, with the exception of one DS44 powering four tortoise turnouts and the UP5s, have their own power supply. The only throttles I use are UT1s which draw little if any power. So, I'm not sure adding power to the UP5s is going to make that much difference, if any.

    I'm leaning toward a second booster as the solution. BTW, running 8 trains at one time if not easy, even on a big layout!