braking sections using a digitrax chiefgreenspun.com : LUSENET : Wiring for DCC : One Thread
I've read many books & articles that mention "braking sections". All you have to do is put D.C. power on a section of track and, depending on the polarity, the engine will either stop, slow down (if D.C. is lower voltage), or cruise right through. The next thing you read is that running trains from a DCC section to a D.C. section can really mess things up without light bulbs or special circuit breakers!!! I have a buried 4 track staging yard (double ended) where this would really be nice to use, but I don't know how to wire it up!! HELP!!!
-- phil bode (firstname.lastname@example.org), June 18, 2004
I have always thought DC braking was a neat feature, but I have yet to find a need for it. You mention some features of DC braking that I am not aware of. I only know it can do one thing: When you put DC on the track, the locomotive will slow to a stop based the deceleration CV setting. When DCC is put back on the track it will return to its previous speed according to the acceleration CV setting. I know nothing about varying DC voltages nor changing polarity. Therefore my advice is limited to the one feature I know about.
To wire up for DC braking, I would do the following. On either side of the section of track where you will have DC braking, make a section of track at least as long as your longest locomotive or lighted passenger car. Call these sections, buffer sections. Connect each rail to your bus wires through 1156 automotive taillight bulbs.
To the section of track that will use DC braking, connect a DPDT switch or relay. This switch or relay will select either DCC power or DC power from a power pack.
Note that the Chief has a way of using the programming output terminals to generate a DC braking voltage. I don't know how much current you can get out of it. I think I would just leave the programming track outputs alone and use a DC power pack to generate the DC you need.
Note also that not all decoders support DC braking. Check with your manufacturer. I know that the Digitrax FX decoders support this feature. Also, with the Digitrax FX decoders, you can program the lighting to stay on while the locomotive is stopped.
-- Allan Gartner (email@example.com), June 19, 2004.
Since you are using DG-380's and talk about needing 2.5 amp decoders, I assume you are not running HO. The light bulb can only be used for HO and smaller. You will need to use an electronic circuit breaker, such as the PM-42 in the buffer sections leading to your DC braking sections.
Yes, you should be able to have the train run into a DC braking section. You will definitely need the electronic circuit breaker.
As I mentioned previously, I have not actually used DC braking. My advice to you is based on what I know about how it is supposed to work. I suggest you find a website where someone has experience with it just in case there is something else you should know.
-- Allan Gartner (firstname.lastname@example.org), June 21, 2004.
Please see a new section on my webpage that has been written by Fred Hughes of DCC-BitSwitch. http://www.WiringForDCC.com/blockdet.htm#a10
You have the option of commanding the locomotive to a speed of 0. That would eliminate the need to use bulbs and provide a buffer section.
-- Allan Gartner (email@example.com), June 23, 2004.
DC braking requires that you turn off analog conversion for your decoders by changing CV29. For this simly subtract 4 from the current value and set CV29 to this (for 2-digit addressing the usual value is 6, for 4-digits 38). The light bulbs in the DC circuit have two purposes. First they protect the DC powerpack from the possible high current that can flow in DCC settings, secondly it makes DCC dominant over DC in case both power supplies feed the braking section simutaneously, e.g. while additional engines, lighted cars etc cross the gap.
The best use I see for DC braking is to have a train come smoothly to a stop in front of a red signal, and then accelerate nicely.
-- Ulrich Albrecht (firstname.lastname@example.org), August 18, 2004.