Stevert Texas Zepher: wyldmanr8cer: how does DCC work? A command signal is sent through the rails. Each locomotive has its own processor (generically called a decoder) programmed for a certain channel number. The decoder looks for signals on its channel and controls the locomotive accordingly. Similarly throttles are set to a locomotive channel so that signals they send are translated to commands and sent out to the layout. Close, but not quite right. DCC has only one "channel", which is the output from the booster, so all the locos receive all the data packets that the booster puts on the rails. But part of the NMRA DCC standard also specifies that each packet of data contain an address. So when the decoder parses a packet, it checks the packet's address against it's own address. If it matches, the decoder executes the commands it contains. If it doesn't match, the decoder ignores that packet. It's actually more complex than that (long vs. short addresses, mobile vs. stationary addresses, etc), but the bottom line is that there's only one "channel" of data packets on the rails, with the addresses within those packets determining who responds to them.
Texas Zepher: wyldmanr8cer: how does DCC work? A command signal is sent through the rails. Each locomotive has its own processor (generically called a decoder) programmed for a certain channel number. The decoder looks for signals on its channel and controls the locomotive accordingly. Similarly throttles are set to a locomotive channel so that signals they send are translated to commands and sent out to the layout.
wyldmanr8cer: how does DCC work?
A command signal is sent through the rails. Each locomotive has its own processor (generically called a decoder) programmed for a certain channel number. The decoder looks for signals on its channel and controls the locomotive accordingly. Similarly throttles are set to a locomotive channel so that signals they send are translated to commands and sent out to the layout.
Close, but not quite right. DCC has only one "channel", which is the output from the booster, so all the locos receive all the data packets that the booster puts on the rails.
But part of the NMRA DCC standard also specifies that each packet of data contain an address. So when the decoder parses a packet, it checks the packet's address against it's own address. If it matches, the decoder executes the commands it contains. If it doesn't match, the decoder ignores that packet.
It's actually more complex than that (long vs. short addresses, mobile vs. stationary addresses, etc), but the bottom line is that there's only one "channel" of data packets on the rails, with the addresses within those packets determining who responds to them.
And it is even more complex than that when one gets into the decoder transmission stuff RP-9.3.1 and 9.3.2. I did not think the original poster cared any about that level of detail.
And you may deduce that you'd have to set up each locomotive to run with the "pack" first. If you had two F2A's, tail-to-tail, but one was from Company A and the other from Company B, no interchangeable parts, different factories, three years apart in issue, you would probably find they move at different speeds with the very same throttle setting, say a speed step of "20" showing on the LCD display on your hand-held throttle. If that's the case, which one will be doing the lion's share of the train lifting and the up-hill slogging? Not good. So, you individually fiddle with the CV's of each decoder that control low speed, acceleration rate, momentum, mid-range speed, and max voltage speed so that the drives work quite closely, not perfectly, in concert. Then you would form the consist.
Crandell
Yes,
There are a couple of types of consist but basically when you set up a consist, all of the loco's respond to the consist address.
One type of consist is maintained by the DCC system. The system knows which loco's belong to a consist. If you send a command to the consist the system sends the same command to each loco included.
The other type of consist is called an advanced consist. In this case each loco has the same consist address programmed into the DCC decoder. It also has settings based on where it is located so that a rear facing loco doesn't blow it's horn or light it's headlight. On this type the command station only broadcasts a single message for each command and the loco's on that address respond.
Springfield PA
The exact detailed steps to MU locos together will depend on the system, but once MUd, command sent to the 'consist address', which doesn;t have to be the address of one fo the locos, it can be a dummy number - like a train number. AN example would be a crack passenger train, timetable #1, the Limited Flyer, which happens to be assigned locos 853 and 871 for today's run. You could use 1 as the consist address which would be an MU containing addresse 853 and 871.
There are multiple ways to consist, but the two main ones use by the commonly available systems either set a CV on each decoder to the consist number - so that those decoders all respond to command sent to that sepcific address, or else they handle it int he command statio, which 'remembers' which locos are in a consist so when a command is sent to the consist address, it gets sent to each loco known to be in the consist.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
So when you program multiple locomotives with their addresses when you send a command is it easy to send one command that all the units in a given consist understand for example I have a 2 unit head-end consist with a helper on the rear I can give one command that all three will understand since they have been MU'd together regardless of which way they face, etc.? Im sure it depends on what type of DCC system & controller you have, correct?
That is the way I have thought about it. Sometimes I get things about DCC wrong, and it is good to be corrected, if not for my own eduction, then at least for the person asking the question and not knowing him/herself either.
I like to think of it as, "You...yeah..you...accelerate your butt to 20 scale mph!" One decoder knows who "you" is, but so do all of the other decoders unless you programme them to only recognize a numerical address other than "you". So, if all decoders are brand new, on powered rails, and they are set to factory defaults, when you dial in address "03" and dial speed into the throttle, guess what? Every single locomotive is going to obey because they all think they are "Hey you!" Change them to unique addresses and when the info packets come down the rails to them, only one decoder should obey the commands with its unique address code included in the packet(s).
This is somewhat more important than at first meets the eye. The reason is that any new locomotive with a new factory-defaulted decoder added to the rails will want to respond on address "03". When you dial that in and want to test the new locomotive, it should be the only one to respond. Also, in the right circumstances, say in Ops Mode out on the main rails, if you were to acquire that new address of "03" and want to change its other CV's or even its address, none of the other decoders would pay more than passing attention to the details because they are not being addressed. And they won't change their CV's to those values inadvertently.
It is a bit more involved, and there are other issues, of course, but that's a good way of orienting oneself to the way DCC should be imagined as one uses it without getting too far into the weeds...yet.
Texas Zepher wyldmanr8cer: how does DCC work? A command signal is sent through the rails. Each locomotive has its own processor (generically called a decoder) programmed for a certain channel number. The decoder looks for signals on its channel and controls the locomotive accordingly. Similarly throttles are set to a locomotive channel so that signals they send are translated to commands and sent out to the layout.
There are also DCC basics books available on the main site. Recommended reading if you're new to it.
Also Google DCC. There are several excellent articles and sites with plenty of free info.
One of the main advantages of DCC is that you can get mismatched loco's from different manufacturers to behave alike so they can be MU'ed to run together. Most loco's can be speed matched by adjusting configuration variables (CV's) until they run at the same speeds, or close enough, at the same throttle setting. This is easily done.
Athearn makes good loco's and rolling stock. But do not overlook Atlas, Walthers Proto series, and Bachmann Spectrum series. Athearn has trouble with the MRC decoders and is now using Soundtrax Tsunami sound decoders.
wyldmanr8cerhow does DCC work?
What I am most curious about is how a person runs the multiple unit consist and is it easy to program the locos for that?
Ten years ago I didnt really know DCC existed but wow I am excited by all the possibilities that lie ahead!!
I mainly stick with Athearn because of the solid detail
Crandell has done a very nice to the point summary of MUing and I would only like to add that the actual mechanics of MUing locos is system dependent. That is, each DCC control system (not the decoders) does it a little differently (which buttons to push and when). I would suggest that you download the manuals for a couple of the DCC starter systems (Digitrax, NCE) to get an idea of what is involved.
Joe
This is a great place to start:
http://www.tonystrains.com/tonystips/dccprimer/index.htm
MUing means telling each decoder to play to a given command. You only send the one command, and all the slave locomotives will receive that command and work in concert. The caveat is that if they have mismatched or defective drives, they won't work well together. With some decoders that use BEMF to read what the locomotive is doing, it can result in a constant battle of wills between the locomotives.
The nice thing about DCC is that you don't need to flip any toggles or have automatic relays. If you want to nudge a locomotive up behind another until just before they close knuckles, and then have the lead one accelerate away from the one that you just parked, you don't need to have a gap under them. Because each motor responds only to the decoders, you must tell each decoder what to do and when, and how quickly. It's all done easily and quickly via the hand-held throttle. When MUing in DCC, you must match the drives first so that they work at least closely with the same throttle settings, and then you couple them and tell them to respond to one address. When you acquire that address by punching in the numbers and tell it to accelerate in the forward direction with lights on, all engines will respond, but you can tell the hind engines to keep their lights off.
Pretty nifty, really.
After a decade away from the hobby due to military service I am diving head first into a large layout that I have decided will be controlled with DCC. The last layout I built was strictly DC, how does DCC work? I know that with DCC I can run multiple unit consist including DPU's and I can have the loco's facing any way I want and so forth. What I am most curious about is how a person runs the multiple unit consist and is it easy to program the locos for that? Ten years ago I didnt really know DCC existed but wow I am excited by all the possibilities that lie ahead!! I see that a lot of locomotives you can purchase (I mainly stick with Athearn because of the solid detail) are DCC capable with the pin plug in feature and some even come DCC ready! Thanks in advance for everyone's help I am honored to join in the discussion on this great site!