gapping track

[eric halpin]

Just for clarification: my dog bone layout is going to be divided into two DCC power sub-sections protected by two Digitrax PM42 short circuit relays. Therefore, it is necessary for me to double gap each set of rails to isolate each section from the other...correct?

Further, is it correct that the Digitrax booster DB150 puts out both AC and DC waves to the rails?

Thanks fellas
Eric

 

[baldwinjl]

Just for clarification: my dog bone layout is going to be divided into two DCC power sub-sections protected by two Digitrax PM42 short circuit relays. Therefore, it is necessary for me to double gap each set of rails to isolate each section from the other...correct?
Yes.

Further, is it correct that the Digitrax booster DB150 puts out both AC and DC waves to the rails?
Not really. The DCC signal is in a way an AC signal, but it is not as sine wave as 'normal' AC is. The rails alternate between plus voltage and ground, with one always high and one always low. Normally the total time for each state is the same, this is why a DC loco hums, it is switching direction quickly enough back and forth that it never goes anywhere. Now, if you have a system that allows operation of a single DC loco (such as digitrax), when this is selected the pulses in one direction or the other are stretched, so that the train can move.

If you really want to know more, you can find it here: http://www.nmra.org/standards/DCC/standards_rps/S-91-2004-07.pdf

Thanks fellas
Eric

Jeff
Vail and Southwestern

 

[60103]

Eric: I think that double gapping is probably the simplest way to do it. The instructions may give you a way to do it with common rail. I think that something has to be common for trains to pass between blocks -- sometimes a wire between the controllers.

 

[baldwinjl]

Eric: I think that double gapping is probably the simplest way to do it. The instructions may give you a way to do it with common rail. I think that something has to be common for trains to pass between blocks -- sometimes a wire between the controllers.

It might be possible to use common rail in this application in DCC (I haven't thought about it enough to say for sure), but it is only going to make things more difficult to troubleshoot later, and adds no value that I can think of.

In this case the source to both breakers/relays is the same. When it is separate boosters the input to the boosters is common (you do need to make sure the polarities match at the track). There is no need, or reason to use a common rail.

Jeff

 

[railwaybob]

Double gap both rails. Common rail refers to the days of analog.

As to whether it's AC or DC really doesn't matter. If you're familiar with the signals in a Local Area Network, then you're well on your way to understanding the signals used in Digitrax DCC. However, this is a study that is separate from running the trains. If you really want to get involved in this aspect, then lurk around the LocoNet Hackers@yahoogroups discussion forum.

Bob M.

 

[eric halpin]

Thanks again to all. Will keep you posted as we progress.

 

[eric halpin]

DCC success

After double gapping the tracks, we had success! Hooked up our track feeders to the DCC terminal strip and low and behold our 0-6-0 switcher ran like a charm on DCC. Between the three of us building this layout (Algoma and Rideau RR) we figured out the hook up process. I must say I find the Digitrax start-up manual to be a bit lacking. The competent operation of the throttles is still a bit of a mystery but one step at a time. Tomorrow the reverse loops should get wired through the PM42 device. Thanks again fellas for your comments.

 

[railwaybob]

Yes, the Digitrax manuals are a bit lacking. However, if you lurk at the digtrax@yahoogroups discussion forum, you can pick up quite a lot. Don't get too frustrated about how things all work. Give yourself some time. Take 15 minutes a day to learn something new about DCC and Digitrax. Recognize that, while operating the trains with DCC is simply, this is really sophisticated stuff with unlimited potential. After a month or two of operating the trains with DCC, you'll wonder what you ever did without it.

Bob M.