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Possible volt drop using Digitrax causing lighting to dim

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  • Member since
    August, 2017
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Possible volt drop using Digitrax causing lighting to dim
Posted by Mikearm77 on Thursday, August 10, 2017 2:52 PM

Hi

I am new to this so please be kind. I am going to be building a rather large n scale layout using Digitrax control and zone detection feeding back to a computer for automatic operation and timetabling.

I am concerned that if the control gear uses voltage drop on the tracks to control the speed and separation between trains causing the lighting to dim in the trains,

Does anybody know about this type of system and can let me know the answer?

Oh by the way, I was considering using DC instead of DCC,

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Posted by betamax on Thursday, August 10, 2017 6:12 PM

DCC does not use track voltage to control speed.  The only way that can happen is if the voltage drops enough to reduce the voltage available to the motor from the decoder.  But you would need to be running your trains at full throttle too.

Did you follow the recommendations for DCC wiring, which is not the same as old direct current wiring methods.  Impedance in the power bus is very important, and has a direct effect on voltage drop. (See https://www.dccwiki.com/Wire_Sizes_and_Spacing for info on DCC wiring.)

What Digitrax devices are you using?

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Posted by Stevert on Thursday, August 10, 2017 10:19 PM

Mikearm77

Hi

 I am going to be building a rather large n scale layout using Digitrax control and zone detection feeding back to a computer for automatic operation and timetabling.

<snip>

Oh by the way, I was considering using DC instead of DCC,

Those two provisions would seem to be mutually exclusive - "Digitrax control and zone detection" IS DCC.

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Posted by RR_Mel on Friday, August 11, 2017 10:19 AM

Welcome

I would suggest you do a Google search of DCC 101 so that you will have a good understanding of DCC.  There are quite a few YouTube videos on startup DCC.
 
Here is a Text page.
 
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
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Posted by rrinker on Friday, August 11, 2017 11:09 AM

DCC presents a steady voltage on the rails. The speed and direction of the trains is not controlled by the voltage on the rails as it is with DC, but by commands that are part of the voltage on the rails being sent to decoders installed on each loco that regulate the motor speed. Train stops in DCC - full power still on the rails, car lights would stay on. Train stops on DC, track power is off, lights would go oout.

           --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by 7j43k on Friday, August 11, 2017 11:38 AM

Saying what everyone else said, kinda, but in a different way:

You don't want DC, because your control options will be much more limited than with DCC.  And, since you're talking about computer operations, I expect you'll benefit from having more options.

And, repeating others, DCC will provide a constant voltage on the track, so your lighting (which could possibly be controlled by DCC, too) would be at a constant brightness.  Even stopped.

I'm not familiar with the phrase "zone detection".  But I'm sure there are detection systems that you can use that will operate as you describe.  I use block detection (sounds similar to me).  It only controls signals, but I expect it could be used for train control, too.  Especially with a computer.

 

To me, it sounds like you're getting into something REALLY COMPLEX.  And you say you're kind of new at this.  Your goals are just fine, but I think getting there is going to be, uh, REALLY COMPLEX.  But attainable, if that's what you want.

 

I recommend patience and research.

 

 

Ed

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Posted by rrinker on Friday, August 11, 2017 12:16 PM

 Perhaps he means zone detection as something like a current sensor that says a train is in a given block, vs a point detection system such as IR beams that tell when a train is at a specific point.

                               --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by carl425 on Friday, August 11, 2017 2:28 PM

rrinker
Perhaps he means zone detection as something like a current sensor that says a train is in a given block

Of course he does.  That's why he's asking about the voltage drop (caused by Digitrax BDL occupancy detectors)

I have the right to remain silent.  By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.

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Posted by BigDaddy on Friday, August 11, 2017 3:25 PM

If he (she) meant they are new to model railroading, this is a very ambitious plan for a first build

Henry

COB Potomac & Northern

By the Chesapeake Bay

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Posted by rrinker on Friday, August 11, 2017 4:14 PM

carl425

 

 
rrinker
Perhaps he means zone detection as something like a current sensor that says a train is in a given block

 

Of course he does.  That's why he's asking about the voltage drop (caused by Digitrax BDL occupancy detectors)

 

 Reading it with that insight changes things a bit, but the question still makes little to no sense. Yes, the type of occupancy detectin used in the BDL168 is a diode drop type detector. But why woudl speed and or seperation of trains have anything to do with it, the voltage drop is the same everywhere. (within reason - diode drop DOES change with current draw if we need to be exactly technical here but it's extremely non-linear, so as long as you stay away from the maximum diode current the drop is the same if it's 1, 2, or 3 locos, or just a lighted car or two, the locomotives having moved intot he next block)

 There's more likely to be flickering from dirty track or poor contact than any perceivable brightness fluctuation caused by a changing load through a diode drop detector. Easily fixed with a capacitor circuit in each lighted car. Similar diodes can be added to non-detected blocks to keep the drop consistent everywhere. Or the superior current transformer type detection used, which has no voltage drop (ok technically, yes, there is a TINY bit but good luck seeing that without high quality meters). There are Loconet-compatible options for this from several vendors. There are a lot of commercial, as well as DIY, Loconet accessories available on the market. Never saw anything negative written about any of the commercial ones.

                                   --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
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Posted by Mikearm77 on Saturday, August 12, 2017 3:29 AM

Thanks for your reply.

I probably didn't express myself correctly in the sense that I do know the defference between DCC and DC and (as someone mentioned incorrectly) you can use zone detection with DC via a computer program to control the trains. The only question was, would the speed control be used by voltage control to the track in that zone and I think I've answerred my own question in doing this as it would have to be done this way using DC. Cheers to all and thanks for your replies.

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