I've decided to build a model railroad having never done it before (not even the old way). Sounds like DCC is the future so I want to start with that. Decided on Athearn Genesis locos (which I believe are DCC Ready?) and the Atlas Master DCC system (cheapest). I've laid my track out(Atlas TrueTrack) but now am scared to death of all this talk about shorts, wiring switches, etc. I want to run three locomotives at once on my track. Do I need to design my track so that it doesn't short out? I thought this was the problem with the old AC/DC? way. With DCC I shouldn't have to worry about this... right? Is there any recommended decoders for Athearn loco's using Atlas DCC equipment? Athearn told me their Genesis units were DCC ready but didn't recommend a decoder. Should Athearn recommend one or should I talk with Atlas? In other words does this mean that I should always use Atlas decoders because I'm using Atlas DCC system? Thanks

-- Ken Varble (kvarble@tekord.com), July 14, 2003

Answers

Hi Ken,

Welcome to the great hobby of model railroading. I also welcome you to the Wiring for DCC question and answer forum. Lets get answering your questions.

Regarding your True-Track Switches, The track is made separated from the road bed with some gentel prying. If you have not laid your track yet, I reccomend doing that and modifying the switches as per Mr. Gartners instructions on the Turnouts Page on the main "Wiring for DCC" site. I reccomend reading the first couple sections as they explain some facets that are nice to know concerning Turnouts and DCC. I find the modifications easy to perform and can be acomplished with some simple soldering skills. Doing this will prevent that annoying stalling at the frog. (Explained further on the turnouts page)

As for the track shorting out, what we are trying to do is not lay track in what is known as a "reversing" Section. This is where the track is laid in such a fashion that the train can reverse its physical direction. If electrical isolation is not maintained the track will move back with an opposite polarity of what it was when it entered the reversing section and thus cause a short. Reversing sections in their most common form are loops and Wyes. A loop obviously is where the train travels in a loop and goes back the way it came. A wye is kind of like a tri-angular shaped arangment of track that allows a locomotive to reverse direction. I would carefully check your track plan and see if you cant find any routings of track that accomplish this. In reversing sections the section must be longer than the train navigating it. This prevents the system from getting confused and potentially "detecting" the train at both ends of the reversing section at once. If you feel you must have one, isolate both rails of the reversing section at both ends. I do not know what the capabiliies of the Atlas System are (Its a very low featured system so isn't very popular), but with most DCC systems you can isolate the section of track in which the "reversing" is being done and power it off a separate booster. The power boosters will then be connected to one another and when one booster detects a short caused by the train going over the insulated joint. It will automaticly swap polarity. Its this automatic polarity swap that you dont have to worry about with a booster powering the reverse loop. (Thats about as clear as mud right? :) )

Now about decoders. When the NMRA developed the common standards for DCC, It defined that any NMRA standard decoder had to be compatiable with any NMRA standard DCC system. This allows you to use any decoder from any manufacture on any DCC system. The decoders needed for Athearn Genisis engines are ones equipped with an "NMRA Standard 8 pin Harness" This allows for for a direct plug and play instillation of the decoder. I have a couple Athearn Genisis my self and use Digitrax DH-121 Decoders with the afore mentioned harness. The DH-121 has since been discontinued and the Digitrax DH-141 is the present equivilent. It has more features and special effects than the DH-121 has. Visit your local DCC supplier and they can most likely supply you with the said Decoders and Harnesses. I noticed a peculiar thing with their 2-8-2 though. That the DCC plug is configured to plug stright into a Digitrax Decoder thus bypassing the NMRA Harness.

Glad I could be of assistance. Feel free to ask more questions and we here at Wiring for DCC will do what we can to assist you. Again welcome to Model Railroading and have fun.

Sincerely

James R. Mitich Forum Moderator

-- James R. Mitich. (Challenger@hrp.every1.net), July 14, 2003.