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DCC Wiring vs. DC Wiring
Art models N scale and has this question for readers:
“I have watched many seemingly simple videos on DCC wiring and it seems to me that the only real difference from DC is the installation of a bus line and feeders at intermittent spots along the layout BUT the bus location line still has to be connected to the main power source, right? So why does running DCC necessitate installation of a the bus and feeders if ultimately the power is coming from th same main source? Sorry if this is a stupid question. I would love to go DCC to get all the sounds, horns, engines, etc but it just seems like an awful lot of work! I am using Kato unitrack by the way. Thanks in advance for any help!”
11 Responses to DCC Wiring vs. DC Wiring
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Because DCC is a higher power rating, the bus needs to be heavier wire (14-18 ga) and the feeders cab be finer wire (20 -22 ga).
Track-work is designed to be hard wearing so made of Nickel-silver or even steel. These materials are not particularly good conductors and so, over a long distance and at high current, can drop quite high voltages. Also fishplates (joiners) are normally made of spring-steel and good electrical connection can not be guaranteed. Point-work (switches) can cause all sorts of problems.
Copper laid in a continuous run provides a reliable supply to all areas and if you use, as many people do, ID (insulation displacement) connectors like Scotchblocks then the copper is truly continuous.
When laying Buses DO NOT close the loop. For reasons, beyond explanation here, but put simply signals going one way round the loop will be out of phase (time) with signals going the other
It’s all a matter of connectivity & voltage drop – in fact, the more connections, the merrier, even with DC or analogue systems. Unless you bond all the rails to each other (with solder) you apparently need to connect every piece of rail to its appropriate bus. A complex model railway should have more than one bus, each supplying a different electrical “district” from a separate controller, so that when something goes wrong, such as a short occurring, only part of the system drops out, not the whole thing; this also helps establish the physical location of the problem. Personally, I find the complexity of DC or analogue wiring much easier to deal with.
The power sources ARE NOT the same. DCC power sources also supply the signal to the decoders. DC power sources put out straight line DC only. Only the newest engines are capable of either/or power sources.
Jerry,
DCC power does not supply the signal to the decoder – the hand piece does. The power (between 16 and 18v AC) in the track only carries the signal to the decoder. When the decoder reads its own personal address, it does as it’s told and moves the engine, or toots its whistle in accordance with the instructions it receives – The voltage of the track does not fluctuate to change the speed of the loco. This is one of the misconceptions that people not interested in DCC use to put people of trying it.
In DC, the power is routed from the wall socket (240v AC) to a transformer which delivers 12v DC current, to a rheostat (there might be some fancy electronics like pulse mode as well). As you turn the knob, the voltage is altered and sent down the track to he loco motor which spins at the speed indicated by the volts available and moves the loco.
Both systems have their uses, but should not be mixed. Your final comment is about locos suitable for both systems. If a loco is a standard DC loco it will not work on a DCC layout unless fitted with a decoder and a switch which makes it the active system and visa versa. A DC Loco on a DCC layout will run like a scalded cat until it’s motor burns out, and a DCC loco on a DC layout will just sit there cooking its chip. Very expensive either way
The main difference between DC and DCC is that the engines, turnouts and ect. get their commands from the bus line. Basically the command station sends signals and power to the tracks. Trains get their information on where and what to do from the bus line. Basic DCC systems (starter) can run about 5 to 10 trains at one time. DC you would be hard pressed to run 3 trains at the same time. So how many trains do you plan on running at the same time?
Art, Not a dumb Question. Actually wiring a Dc system should have bus wires as an example through the rails the farther away your track gets from the power source the more power loss. also with switches the more they go through the more the power loss. In Dc your trains will run slower at the back of your layout verses the front near your power. due to voltage drop. (been there seen it) The same thing happens in DCC but usually because of the power drop you will loose control of your engines because the chips installed in the engines will drop too much in power to keep the chip going. Power need to be connected every 4 to 8 feet for good continuous full power. We should have been doing this on our old Dc layouts years ago too. Newman
The reason DCC has a power buss under the layout table is because DCC has more than ppwer for the locomotive. Lights and sound capabilities are also sent through the power buss.. The power is not usually run through the table top rail because the there are way too many sections of track that may cause a trouble spot. With DCC you want flauless operation of your locomotives. A bad track joint with DCC makes the sound go off then on again. I hope you understand this.
Now for the good news ! Most DCC locos will also run on DC and still produce their main sound effects automatically (engine, whistle, bell, horn, brakes etc).
I nave a (fairly basic) DCC with sound loco which, when running on DC, gives engine chuff proportional to speed, brake sound when seriously slowing, with the bell and whistle controlled by flicking the direction change switch on the DC controller.
I find these sound effects very satisfying, even without a DCC controller yet.
Guys,
See my comment to Jerry above
Please understand that the difference between DC and DCC is that in DCC to track voltage is constant and its role is to carry the address and instruction signal to the decoder.
Don’t over complicate the story. It’s simple – controller in the hand, signal sent down the rails, decoder receives and acts. All this talk about point or switch and signal management is irrelevant to most people’s “problems” understanding DCC.
We have over complicated tit. Get constant power to the track, make sure there are no short circuits, have locos with chips and you’re away. Simple.
When familiarity grows, and confidents lifts then get on with DCC signalling, point control, accessory control, animation. These are so much easier with DCC but are not what novices are concerned about.
Sorry if I sound a bit impatient
David
You MAY not need a BUS.
Most of my layout is four loops of track about 45 ft long all electrically joined together so that the power is distributed via 16 poor conductors (the rails wired as 4 ring mains) instead of 2 good conductors (a BUS wired as a recommended spur). Voltage drop at the furthest point, 23 ft from the power source, is 0.2 volts. That is insignificant and has no noticeable effect on any engine or any control signal even with 6 locos running at the same time. I would expect the voltage drop on a BUS to be very similar.
My sidings are all powered from the four main loops as are the points and signals. I have had no problems in the three years since I built this. I wired it in a way that I could easily add a BUS if it was necessary – it isn’t.
Unless you have a very long single loop of track I would suggest just trying DCC on your DC layout and see what happens. The DCC controller will have built in protection so you are unlikely to damage it. There is an awful lot of theoretical advice out there from people who have followed the instructions themselves without really understanding why.