jjdamnitIf you are lucky enough to have a large pike most DCC manufacturers recommend using powered facia panels to "extend" the DCC command signal for optimum signal flow and eliminate the "ringing" effect. These panels have auxiliary power supplies to help "boost" the DCC signal to the command station/boosters. Adding powered facia panels is a cheaper alternative to adding command/power boosters, if your aim is to strengthen the DCC signal over long distances to the power booster(s).
These panels have auxiliary power supplies to help "boost" the DCC signal to the command station/boosters.
Adding powered facia panels is a cheaper alternative to adding command/power boosters, if your aim is to strengthen the DCC signal over long distances to the power booster(s).
is this addressing ringing of the DCC signal on the track bus?
CSX Robert(in Loconet, Railsync is the DCC signal and is used to power throttles and other devices that are not powered separately).
huh? do they Railsync to connect the command station to boosters?
context?
greg - Philadelphia & Reading / Reading
I think you may be thinking of the Digitrax LNRP. While it is built into a fascia panel it is much more than just a powered fascia panel - it is a Loconet repeater module. Digitrax does sale powered fascia panels that are not Loconet repeaters (UP5, which can be powered or not depending on your needs), and they do nothing to boost the DCC signal. They can prevent devices from loading down the DCC signal because they can provide power to the devcies to keep it from drawing power from the DCC signal (in Loconet, Railsync is the DCC signaland is used to power throttles and other devices that are not powered separately).
Most other DCC systems don't even pass the DCC signal through the fascia panels in which case a powered fascia panel would have no effect on the DCC signal.
My obeservations on the topic(s):
1) How many folks start out with a loop of track and a single set of feeders, which is what pretty much all DCC manufacturers tout as "how easy it is to get started"? Those are basically a just a circular bus, although with the track forming that bus instead of copper wire. It isn't a problem.
As far as signal reflection, I saw once where someone (an EE) used the DCC signal frequency, etc, to calculate the size of a loop needed for it to be an issue. The resulting loop size was roughly large enough to encircle a (US NFL) football field. But due to wire resistance, a loop that large would require electrical sections with separate boosters anyway, making signal reflection moot.
2) Snubbers: It depends. The subject regularly comes up on the NCE list on groups.io, usually with lots of discussion. Some folks swear by them and insist everyone needs them, others say they've never used them and never had an issue, etc. It goes back and forth, sometimes comically. On the Digitrax list it only occasionally comes up, usually by someone saying "I saw this big discussion about snubbers on the NCE list. What's a snubber?" My personal opinion: Unless you have a specific problem that has been identified (by use of an o'scope) as ringing, you don't need snubbers.
One thing you should NOT ever do is loop your control (throttle) bus. Digitrax specifically mentions this in one of their KB articles, although after a quick search I was unable to find anything there one way or the other about looping the track bus.
When I built my first large layout back in 2004, it was a continuous loop, 162 foot double mainline, built in an L-shape. The bus wires were also continuous loop directly under the double mainline. I never had a problem with that wiring arrangement, and I had plenty of feeders to avoid voltage drop.
Then, along came the notion of DCC snubbers. I saw no reason to install them, but I did anyhow because it was all the fashion. Later, the consensus seemed to be that snubbers weren't really required on home layouts.
When I built my new layout in 2018, I again built a continuous loop double mainline. But, my dear friend, the late Randy Rinker, convinced me to use power districts, each with its own bus wires, none longer than 50 feet. I skipped the snubbers.
Rich
Alton Junction
gregcIt would reduce the wire resistance by half at the mid-point and presumably reduce reflections.
The DCC guru, and electrical engineer, I know has told me that on a large layout connecting the bus into a loop is advatageous for exactly the reasons Greg mentioned.
In actual application, I think Rich said it best. There will probably be no noticeable advatage.
-Kevin
Living the dream.
Hello All,
In the September 2021 National Model Railroad Association (NMRA) magazine "The Pulse Of DCC" column; pg. 38-45, focuses on bus wire size and amperage drop.
Secondarily it addresses DCC signal distortion.
On pg. 42-45 it talks about the phenomenon of DCC signal "ringing" and "snubbers" or "Signal Termination Devices"- -RC (Resistor-Capacitor) Filters- -at the terminus of the bus wires.
A DIY schematic of an RC Filter is shown, along with a screenshot of an oscilloscope capturing the "ringing" effect.
If you are lucky enough to have a large pike most DCC manufacturers recommend using powered facia panels to "extend" the DCC command signal for optimum signal flow and eliminate the "ringing" effect.
They do not provide more amperage to the system to power more locomotives, as additional boosters do, or create power districts.
DCC signal distortion- -"ringing"- -is different than the loss of power over longer bus runs.
If you need increased amperage to run additional motive power and current drawing cars or, large power districts, then additional power boosters would be the way to go.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
WilScarletMacaw Is there any advantage to connecting the ends of the bus lines for a continous run circle on a DCC layout, or should the terminal points just be left alone?
Is there any advantage to connecting the ends of the bus lines for a continous run circle on a DCC layout, or should the terminal points just be left alone?
If there is one absolute about this question, it is this:
Do NOT close the loops crossed. That is, do not connect the 'positive', left, or red wire issuing out of one output post on the base station to the other wire issuing from the opposite output.
You can fashion a loop back to the same output post, but do it with the same wire.
As to whether-or-not it's a good idea, that part has been debated at lenght at least once a year in my 15 years in the hobby. I don't recall there ever being a consensus.
Hi Wil,
Conventional DCC wisdom and some DCC vendors specify that the ends of a DCC bus should not be joined. Specifically, Digitrax specifies that each end should either just be left empty or terminated with a device called a snubber. Not sure about other vendors but I have not seen any examples of joining the ends.
Checking Allan Gartner's DCC site, it suggests snubbers for terminating the ends of the bus but not connecting them.
Scott Sonntag
it would reduce the wire resistance by half at the mid-point and presumably reduce reflections.
Hi there. What is the configuration of the layout? Can you post a plan?
Simon