I have very new to DCC. From visiting club layouts I have observed that the digitrax brand is the defacto standard, sort of like Kadee is to couplers. I know that there are four basic components, the handheld controller, the command station, the universal receiver and the decoder. I am trying to understand all of the basic components and how they interact. I am guessing that the handheld controller talks to the command station, which in turn, relays instructions to the locomotive’s on board controller. What does the universal receiver do in this process?
I assume that the track voltage remains constant all the time.The voltage is varied to each locomotive’s motor by the decoder. Is that right? What is the best track voltage for this system?
Is the command signal impressed on the track voltage? Is it then filtered out by the decoder? Or is it a radio signal sent through the air and picked up by an antenna on the locomotive?
I understand I am late getting to the party. Thanks for your help and patience.
George
SO yes Digitrax is one of the biggest brands (it's what I use) but NCE is a good option too. I would look hard at both and see what you like.
Simply put the command station is control central in the DCC world. Everything has to go through it. Track voltage is a constant and signal is sent through the track and picked up by the DCC decoder in the engine.
Digitrax now offers duplex wireless control which allows the hand held controller to both receive and send signals where the older style wireless could just send signals. This means you hardly ever have to plug your controller into the command station or loconet. You do have to have a duplex antenna for this to work however it comes with any of the duplex sets.
The DCC controller can also control turnouts and other accessories which is a big advantage in my opinion.
Late to the part or not you will definitely enjoy it once there so welcome aboard the DCC train, pun intended.
George,
Digitrax makes a very good product but so does NCE, Lenz, and CVP (EasyDCC). If you want the Cadillac of DCC systems, look into Zimo.
If you are just learning about DCC, here's a good DCC primer from Tony's Train Exchange web site. You can either read it online or download it onto your computer as a .pdf file.
Hope that helps...
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
Which system is the "defacto standard" is probably more related to the preferences of a geographic area than anything else. All the major brands have their following.
You are correct in that the throttle talks to the command station, which talks to the decoders. The UR (universal receiver) is the name Digitrax uses for their wireless receivers - The UR90 receives IR signals, the UR91 receives simplex (one-way) radio, and the UR92 is for Duplex (two-way) radio. Note that for either radio option you need the appropriately-equipped throttles - One with an "R" suffix such as the UT4R for simplex, and one with the "D" suffix, such as the DT402D for duplex. All recent Digitrax throttles have IR abilities. Of course, other manufacturers use different types of wireless throttle setups, and have their own nomenclature for them.
Yes, the track voltage remains constant (see below). The voltage you use depends on the scale, but I do think the NMRA has either Standards or RP's that cover that.
The track voltage is actually a square-wave AC, and the signal is imposed by varying the duration of those square waves. The decoders "read" the 1's and zero's from that square wave to receive their commands. They also rectify it for the motor and function outputs, and to power the sound if the decoder is so equipped.
Finally, although there are radio control systems that transmit directly to the loco, I am not aware of any that can actually be considered DCC systems.
Below are some links about DCC. Store the links in Favorites. You will need them. The Internet is loaded with DCC info.
http://www.nmra.org/standards/DCC/
http://www.members.optusnet.com.au/nswmn/index.htm
http://www.wiringfordcc.com/intro2dcc.htm
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Your universal receiver I'm guessing is really a booster.
It goes like this
Cab <custom communication language> -> Command Station -> Booster <dcc language> -> Track
The "language" used between the command station and your cab (throttle) is unique to the manufacturer of the system. For example you can't mix a Lenz cab throttle with a digitrax command station. However everything after the command station uses the same language DCC.
What the command station does is takes the commands from your throttle and translates them to the DCC standard. However this is very low voltage and not enough to run your trains. This would be akin to trying to run your big big stereo system off a little handheld music player.
The booster raises the command station signal to track level voltages the decoder can run on. Typically ~14 Volts for HO scale.
With DCC one rail is always hot (14 Volts) while the other acts as ground (0 volts) This swaps back and forth very quickly. For example below let the top row be the left rail. The second row = right rail. 14 = high voltage 0 = ground
Left Rail: 0 0 0 14 14 0 14 0 14
Right Rail: 14 14 14 0 0 14 0 14 0
You could translate this to:
Left Rail: 0 0 0 1 1 0 1 0 1 Right Rail: 1 1 1 0 0 1 0 1 0
Left Rail: 0 0 0 1 1 0 1 0 1
Right Rail: 1 1 1 0 0 1 0 1 0
See how the rails are always opposite each other? It's the length of the High voltage vs. low voltage that determines if it's a one or zero in binary (the language of computers)
This way the signal does not have to be superimposed and can run at full voltage reducing teh likelyhood of signal corruption.
There is no defacto standard far as systems go. In Europe Lenz is popular. Here in the states Digitax has the largest user base, followed by NCE. NCE is quickly catching up however.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
It's important to remember that that NMRA standards apply to the voltage and encoded signals on the track, and everything that goes to the locomotives. So, any NMRA-compliant system, which includes all the major ones, will be compatible with any DCC decoder. So, you can take any manufacturer's decoders and run them on any manufacturer's DCC system. Everything that's covered by the NMRA standards is sometimes referred to as "trackside." Some of the "extra" equipment, like stationary decoders (for running turnouts, if you wish) or automatic reversing modules (for reverse loops) are also considered "trackside" devices.
Everything else is up to the manufacturers themselves, and typically these can NOT be mixed and matched. Command stations and throttles, in particular, pretty much tie you to a single company. For this reason, I always advise people to try out throttles as part of the selection process. The throttle will be your interface to the system, and you need to be comfortable with it. Personally, I like the Lenz throttle with its big buttons, but others prefer the Digitrax throttles with smaller buttons, but more of them.
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