Just because it is the positive side of the circuit doesn't mean it can't be a common. Common just means it is something connected to every load, and the blue positive common on a decoder is indeed just that.
Way back when, a lot of cars used to 'ground' the positive side of the battery to the frame, instead of the now universal negative. Come across one of those classics and try to jump start them and you might be in for a surprise.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
richg1998Notice the ouput of decoders, common is used for the postive voltage as used by the different functions.
in many cases, it is preferrable to close a circuit by turning on a transitor and grounding (negative) the one side of the circuit rather than providing power to the circuit. This allows the controlling device to control various circuit requiring different voltages.
Decoders functions are controlled similarly, the output grounds the signal. A positive voltage source is needed for these functions. I wouldn't read too much into whether a particular decoder manufacturer describes the postive voltage source as "common". It certainly isn't textbook.
greg - Philadelphia & Reading / Reading
The Brits have it right, when it's a GROUND they call it Earth. A common is a common. You can have an earthed common, but not all commons are earth.
Ground and common are often used interchangeably in the US, and it's not really correct.
richhotrain zstripe Rich, https://www.youtube.com/watch?v=BcIDRet787k Take Care! Frank Frank, thanks for the link, but I understand the difference between AC and DC. What I was asking, was how do others use the terms neutral, common and ground. I believe that I use the terms correctly. Rich
zstripe Rich, https://www.youtube.com/watch?v=BcIDRet787k Take Care! Frank
Rich,
https://www.youtube.com/watch?v=BcIDRet787k
Take Care!
Frank
Frank, thanks for the link, but I understand the difference between AC and DC. What I was asking, was how do others use the terms neutral, common and ground. I believe that I use the terms correctly.
Rich
I have seen over the many years some use the terms differently.
Notice the ouput of decoders, common is used for the postive voltage as used by the different functions.
I have seen in circuits for many years, common was a negative voltage and not always ground or considered earth ground.
Common also a point all other voltages are measured from.
I remember some years ago I worked on a circuit assembly and the positive voltage was common or ground and all other points in the circuit were negative.
Generaly ground is considerd an earth ground like the connection in your house at the water pipe entrance.
Wikipedia will have very good info if you search.
You can also search for DCC wiring.
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.
Deleted <off topic per the subject of the thread>
"The true sign of intelligence is not knowledge but imagination."-Albert Einstein
http://gearedsteam.blogspot.com/
Alton Junction
Phoebe Vet,
Dave You sound like My Physics II teacher.....LOL.
I slipped in My own advice...''Too many cooks in the kitchen spoil the soup''.
Size of wire matters with DC same as with DCC. Voltage drop occurs no matter the type of power supply. Difference is that with DC it can be more easily "fixed" by simply turning up the throttle (voltage) when the train slows down due to voltage drop. Just because it can be fixed with a throttle change does not mean the wiring is not deficient. Also there is no signal being sent with DC so that the voltage does not cause glitches in commands to the engine. DCC supplies full voltage to the track at all times. The decoder rectifies it to DC and runs the motor at the selected speed and direction. What comes out of a decoder's motor wires is dependant on what goes in its track supply wires. It can't make voltage that isn't there.
But, voltage drop is voltage drop. If you train is running on DC at full throttle near the power pack, it will run slower as it gets further from that power supply. How much slower will depend on the size of the wire and number of feeders. Since it was already at full throttle, turning the speed up won't work.
Martin Myers
Or A rail and B rail.
in house wiring (at least my house) the neutral wire on the common bar in the box is connected to a water pipe, literally ground. And there are 2 wires coming in from the street: "hot", in laymans terms, not "+". These two are out of phase (I think 120 degrees) and can be use together for 3-phase 220V.
When power drills had metal cases, it made sense that if there was a short inside the case that the metal case is connected to neutral with the same voltage potential as the earth the worker may be standing on.
richhotrainIn DCC, I use the same terminology as in DC, that is, positive and negative. What do others say and use as a matter of terminology?
What do others say and use as a matter of terminology?
A pair of connections designated + and - typically implies that the + connection is more positive than the - connection.
Ethernet is also an alternating signal, one lead goes more positive while the other goes more negative and designates its signals as +/-. In ethernet, a 1 is represented when the + signal is more positive than the - signal and a 0 is transmited when the + signal is more negative than the - signal.
DCC transmits digital data (1s and 0s) differently. It uses time. The polarity reverses twice for each bit being transmitted, returning to its original polarity after each bit is transmitted. The duration between determines the bit value: 0 or 1.
Unlike Etherenet which will not work correctly if the signals are incorrect, a DCC decoder can communcate regardless which rail is connected to the terminals on the command station.
In the oscilloscope trace of a DCC signal below, the 1-> on the y-axis (vertical) indicates where the signal being measured is equal to the ground reference of the scope. The DCC signal is never at ground, either more positive or more negative.
It important to label the DCC connections so that the rails aren't reversed when the shouldn't be to avoid shorts. Labeling them as + and - isn't technically correct. Neither is hot and common/neutral. red/blue, or whatever wire color is being used might be clearer.
The difference in wiring between DC and DCC is how it is implemented.
With direct current, you typically have mulitiple power sources, one per train, to operate the layout. Since the current draw isn't very high, heavy wiring isn't really needed. Power flows from the source to the throttle, and is routed to the train by switches.
DCC is the opposite: One central power source for all the trains. Since the power flows directly from the source to the load, you have more loads and a larger current draw, which demands heavier wire. There are no switches routing power an individual train in a specific block.
With both systems, you must pay attention to polarity.
Dave, that's a good point on writing content.
Too much info and/or "run on" paragraphs typically confuses and may even chase away the reader.
When trying to convey multiple ideas or remarks, the use of "bullet points" is often an excellent way to go.
And to address the OP's questions...... wiring for DC and DCC is primarily the same - with hook ups being the bulk of the differences.
ENJOY !
Mobilman44
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
zstripe I would just like to clarify one point...there is no neutral wire in DC/DCC....Direct current, DC one wire is hot + and one wire is ground-...that remains absolute. Normally people choose Red + Black - or which color You choose, but remains constant. Polarity is changed by the reversing switch on Your DC power pack to make Your engine motor go forward/reverse...DCC is basically the same main wiring for track, one rail + Red, other rail - Black or the color of Your choosing, that also remains constant through out. Your DCC controller sends a Digital command through the rails to Your Decoder equipped engine to change it's motor control functions...forward/reverse, speed....there is no polarity reversal of the rails to change engine functions like in DC. The decoder does that....but the main wiring for the two are the same constant. Take Care! Frank
I would just like to clarify one point...there is no neutral wire in DC/DCC....Direct current, DC one wire is hot + and one wire is ground-...that remains absolute. Normally people choose Red + Black - or which color You choose, but remains constant. Polarity is changed by the reversing switch on Your DC power pack to make Your engine motor go forward/reverse...DCC is basically the same main wiring for track, one rail + Red, other rail - Black or the color of Your choosing, that also remains constant through out. Your DCC controller sends a Digital command through the rails to Your Decoder equipped engine to change it's motor control functions...forward/reverse, speed....there is no polarity reversal of the rails to change engine functions like in DC. The decoder does that....but the main wiring for the two are the same constant.
This is not a criticism, just an observation from someone who used to teach.
Too much information, while correct, confuses people when it isn't needed to answer the original question.
The OP asked if the wiring rules are the same for DC & DCC. The answer is "Yes". Crossing the wires is a short circuit in either. Color coding is the best way to remember which is "rail A" in both.
Dave
Lackawanna Route of the Phoebe Snow
zstripe Richg1998, Technically You're correct, positive+, negative-. Then of course, you have positive+ ground and negative- ground vehicles. From the 40's/50's era, running on 6volts, positive ground. You just don't use the term neutral with Direct Current. Take Care! Frank
Richg1998,
Technically You're correct, positive+, negative-. Then of course, you have positive+ ground and negative- ground vehicles. From the 40's/50's era, running on 6volts, positive ground. You just don't use the term neutral with Direct Current.
So, the correct terminology is important to me. When do you refer to that "second" wire as neutral, common, ground?
For household electrical projects around here in the Chicago area, we are required to use metal conduit, so that green ground wire is less critical than the white wire which I refer to as neutral (or common). All neutral wire connects to a common bar in the service box which is grounded.
In areas of the country that use plastic cable such as Romex, the white wire is still referred to as neutral (or common) and the green wire is the ground wire, taking the place and function of metal conduit. In, household wiring, the black (or red) wire is the HOT wire.
In DC, whether it is used in an automobile or on a model railroad, the two wires are referred to as positive and negative. At least, that is how I have been taught to use the terms.
In DCC, I use the same terminology as in DC, that is, positive and negative.
There is no ground either with DCC. I see that term used sometimes.
I also see the term ground sometimes used for decoders. Decoders have positive and negative for the DC operating power.
I worked in industrial maintence for many years. There is hot, neutral and ground.
One thing that can't be overstated, no matter if it's DC or DCC, is the importance of keeping the wire color code, size & placement constant. In 5 or 10 years (or more), you won't remember exactly how you wired the layout. Once you do it and stop looking at it, it will fade from memory. This has happened to me on my club layout when I was doing a lot of wiring from 2000 to 2006.
What saves me when I go back to look at a problem is that I was consistant in what I did. I always wired the same way, over and over. The 14AWG track bus in black nylon loops right under the mainline track; the 14AWG detection bus ran along the front edge of the layout in white loops; the 10AWG main power bus runs along the back; Tortoise wire is a 22AWG 8-cond. gray cable, the stationary switch machine power is a 14AWG blue/gray pair, green is always system ground, and so on.
Under my club's old DC layout that stood from 1953 to 1998, the wiring was done with whatever was on hand. When we took in apart, there was everything from TelCo. wire to lamp cords under the layout. It was a total horror show whenever you tried to chase down a problem.
So keep it constant. No momentary rush is worth it.
Thanks all for the responses and good ideas! -Sully
Sometimes it is easy to get confused as to which rail is which. I mark the layout next to each rail with two different colored tapes. Then I put a flat car on the track at that point and put the colored tape on each side of the flat car to match the layout. By moving the car around the track as you wire, you can keep the polarity correct. Knock the car off the track? just put it back at the layout markers and start over.
Maintaining a consistent color code for your under-layout wiring is always a good idea. It just makes repairs and changes so much easier. I like to label my wires, too, either with tags or just by writing on the underside of the layout with black markers.
It takes an iron man to play with a toy iron horse.
Makes (common) sense. Thanks MFM!
Ya, that's kind of what I expected. Thanks Rich!
Yes, the same convention holds true. A short circuit is a short circuit no matter what the type of power is.
Generally speaking, the same wiring protocol holds true for DCC. Even if the DCC layout is divided into separate power districts, sub-buses should be wired in phase with one another. On my DCC layout, I added a second booster and, even in that case, I needed to make sure that the bus wiring was in phase to avoid pauses as locos crossed from one booster district to another.
One exception would be reversing sections where it doesn't matter whether the input side is in phase since the function of the reversing switch (auto-reverser or DPDT toggle) is to match polarities inside the reversing section.
Been awhile since being here. Always enjoyable reading/learning from here. Simple, silly ques. Answer should be obvious to me, but....
In terms of basic layout wiring, I know (for DC) you match one of your two bus wires for the inside rail (e.g. black (hot)), the other for the outside (white (neutral)). My bus wire is 14awg. From there, occasional feeder wires (22 guage) to connect bus wire to rail. Once you choose which rail is 'black', and which is 'white', you must stick with that convention throughout the layout (maybe not for block wiring, don't know). But does the same hold true for DCC? I mean, I cannot mix 'n match here, once I have started it one way, right? Thank you. -Frank
PS I've got the MRR wiring books, and a copy of the big book of DCC. I know - overkill. But I haven't really seen this question answered. If I had a better understanding of how things work, electrically, I'd probably have my answer.