AC vs DC vs DC with HO

[MikeL]

We've got Bachmann tracks and Bachmann DCC locomotives. We're also about to get some non-DCC stuff for my 4-year old (our excuse for getting into this...).

Some questions:

* Is all HO stuff DC powered? (vs. AC)?

* Will a non-DCC power unit/controller also work if we put DCC locomotives on it? i.e. will they work or will I burn something out? I assume they will not be able to run "separately" but will all go at the same speed setting etc.

* When the term "DC" is used, as opposed to "DCC", does this assume a difference in how it will react to the controller/power unit, and not the type of electrical power (AC vs. DC)?

I'm obviously new to this (since 40 years ago), and want to make sure I get things right and don't hurt anything when learning....

Any additional thoughts and explanations around the questions above and the things I'm forgetting to ask would be great!

Thanks.

 

[hamltnblue]

Any Bachmann unit you've bought will run DC.
DCC is Digital Command Control which basically runs a computer signal through the tracks. A DCC engine picks up those signals and converts them to functions such as Light on/off, forward, reverse, speed in pre defined steps etc.
Most DCC engines will also run on DC, but DC engines will not run on DCC.
The DCC decoders usually have a dual function which allows them to run on either. DC engines lack the decoder board to pick up and act on the digital signals.
The great thing about DCC is that you can have more than one loco running at any time and controlled separately. This includes different speeds, directions etc. Sound is also present on some which adds a whole dimension to running trains.
I suggest you spend time looking over the forums. There's a lot of info here.
Model Railroad Magazine also has a good forum with plenty of info.
Good Luck and welcome back into the hobby.

 

[Grant F]

We've got Bachmann tracks and Bachmann DCC locomotives. We're also about to get some non-DCC stuff for my 4-year old (our excuse for getting into this...).

Some questions:

* Is all HO stuff DC powered? (vs. AC)?

* Will a non-DCC power unit/controller also work if we put DCC locomotives on it? i.e. will they work or will I burn something out? I assume they will not be able to run "separately" but will all go at the same speed setting etc.

* When the term "DC" is used, as opposed to "DCC", does this assume a difference in how it will react to the controller/power unit, and not the type of electrical power (AC vs. DC)?

I'm obviously new to this (since 40 years ago), and want to make sure I get things right and don't hurt anything when learning....

Any additional thoughts and explanations around the questions above and the things I'm forgetting to ask would be great!

Thanks.

-HO items are both dc and ac, if its dcc controlled it will be ac and if its not dcc it will be dc.

-dcc stands for digital command control, and dc stands for direct current.

the way dc trains run is the controller has a variable resister inside it and as you turn up the speed it allows more current to flow to the tracks and the train will go faster.

dcc the whole track has an ac current and each train runs off the ac current, the signal is sent through the tracks to each train and the motherboard inside the trains receives the signal and then changes speed, direction and lighting etc

 

[MikeL]

Thanks for the replies. This tells me that the DCC system I bought will allow me to run once we get my son's Thomas and Friends non-DCC stuff at the same time with the Thomas controller. It will then run direct current, but the two trains - the Thomas trains (non-DCC) and the DCC engine/trains for the other Bachmann set will both run at the same time on the same tracks but will not be separately controllable for speed, etc. Did I get that right?

If so, since the Bachmann EZ-Command controller will allow 1 DC engine to run along with the several DCC engines, will it be running direct current or alternating current?

Just trying to make sure I understand both combinations and won't ruin anything.

Thanks.

 

[julienjj]

Thanks for the replies. This tells me that the DCC system I bought will allow me to run once we get my son's Thomas and Friends non-DCC stuff at the same time with the Thomas controller. It will then run direct current, but the two trains - the Thomas trains (non-DCC) and the DCC engine/trains for the other Bachmann set will both run at the same time on the same tracks but will not be separately controllable for speed, etc. Did I get that right?

If so, since the Bachmann EZ-Command controller will allow 1 DC engine to run along with the several DCC engines, will it be running direct current or alternating current?

Just trying to make sure I understand both combinations and won't ruin anything.

Thanks.

it will be using alternating current, BUT in a tricky way. the dcc throttle will ,use something called extented square wave. it will stretch one of the AC (+,-) wave to the maximum and shorten the other wave to the minimum (-,+)
due to the speed of the alternating, the DC engine wont have the time to react to the opposite current, and will keep going forward, wave wil return to normal when you issue the command to stop moving, and invert when going reverse. however, it not good for dc loco to stay iddle on the layout, you will notice their engine will "sing" due to the ac current, this, over long time, can burn motors

Because the current keep being AC all other dcc loco wont be affected in any way

 

[UP2CSX]

All good answers, especially Julien's answer about how AC current is tricked into being seen as DC by a DC motor. The E-Z Command will run one DC engine while you're running DCC engines at the same time. You will be able to control the speed of the DC engine by selecting zero on the controller and that of the DCC engines by selecting their number on the controller.

It sounded for a bit like you were asking if you could have a DC powerpack and a DCC controller both hooked up to the tracks and active at the same time. For anyone else who may be thinking of doing this - Don't. The DC current will feed back into the DCC controller and there's a good chance you could destroy the innards in a few minutes. Once you hook up a DCC controller, only use the DCC controller for power supply to the tracks.

The E-Z Command is a little different than other DCC systems since it has a plug on the back that allows you to use a Bachmann standard DC powerpack to give you speed and direction control of a DC engine without having to select it. You can pick one up on e-bay for around $20, and it might be a worthwhile investment since you are planning on running DC engines.

 

[CSX Robert]

-HO items are both dc and ac, if its dcc controlled it will be ac and if its not dcc it will be dc...

This can be a little misleading because there is a such thing as HO AC, which is NOT DCC. While the DCC signal is AC, it is very different from what most people think of when they hear AC. AC is usually a 50 or 60 HZ sine wave, whereas DCC is a square wave with a varying frequency normally in the 4000 - 9000 HZ range(it can vary even more when running a DC locomotive). This is important because you can not buy an HO AC locomotive and run it on a normal 2-rail DCC layout, in fact, it will short out because HO AC is "3-rail," so the wheels on each side are electrically common. I put 3-rail in quotes because the third "rail" is a row of studs in the middle of the track. The studs are on the ties and are not very noticeable, so it looks much better than an actual third rail. Many current HO AC locomotives are digital and will actually run on DCC, but it still has to be 3-rail

HO AC is not common in the US, but it is fairly common in Europe. None of the US or Japanese manufacturers make any HO AC equipment that I know of, but several of the European manufacturers do.

 

[MikeL]

It sounded for a bit like you were asking if you could have a DC powerpack and a DCC controller both hooked up to the tracks and active at the same time. For anyone else who may be thinking of doing this - Don't. The DC current will feed back into the DCC controller and there's a good chance you could destroy the innards in a few minutes. Once you hook up a DCC controller, only use the DCC controller for power supply to the tracks.

Actually, Jim, I was really looking to see if the non-DCC controller could be used with DCC locomotives/engines as well as non-DCC trains at the same time or not at the same time - I wanted to make sure that if I put a DCC engine on the tracks when I had the non-DCC power pack connected that I wouldn't burn either out....

But thanks for looking out for my possible mistakes - they will be many!

 

[Selector]

Actually, Jim, I was really looking to see if the non-DCC controller could be used with DCC locomotives/engines as well as non-DCC trains at the same time or not at the same time - I wanted to make sure that if I put a DCC engine on the tracks when I had the non-DCC power pack connected that I wouldn't burn either out....

But thanks for looking out for my possible mistakes - they will be many!

If the decoder is a modern one, it is likely to be what is known commonly as "Dual Mode", meaning it comes to you from the factory set to sense which current it is being presented at the rails. It will behave somewhat differently, but it will move and you can control such things as the bell and whistle with some switch throwing....at least, that was the case with the QSI brand of decoders a few years back.

Sound equipped engines will begin to make sound as you dial in DC voltage from your power pack, and near 6 volts they will then begin to move. This can be awkward because any DC engines you have placed on the same powered rails will want to move as soon as they get 3 volts or so.

I hope it is clear to you that DC current is variable and controlled by yourself. The DCC signal is imprinted on non-variable square wave AC current that is usually very close to a constant 16 volts or so. The decoder is what meters out pulsed DC voltage to the can motors in either case. In a way, the decoder rectifies the AC current and distributes it to the various thingies that need current on the engine....lights, motor, speaker...

-Crandell

 

[MikeL]

Thanks - this makes sense - I really appreciate everyone's help!

 

[RexHea]

CSX Roberts:
This is somewhat beyond the original question but in addition: Refining what you posted just a bit, technically DCC is not an alternating current (AC) at all, but a bi-polar square wave. The one major distinction is that while both change from a "0" reference (grd) to an above and below value, the AC value is constantly varying and dependent in time during the alternation (sinusoidal or other wave form); DCC (bi-polar square wave) is either positive or negative that is ideally near instantaneous in change from one to the other. (The DCC signal is always a maximum value: either max negative or max positive.) Simply, a signal that uses both negative and positive values with ground reference does not automatically classify it as AC.

Keep in mind that the amplitude of the DCC signal is not what controls the motor, bells and whistles, but the signal packet of data information being sent by the controller. Amplitude is important to ensure this information is received across the layout with usable and the least undistorted signal possible. Motor power uses PWM (pulse width modulation) from the decoder getting power from the track. PWM varies the width of square waves to give an average DC value to the motor, the wider the more power.

 

[MikeL]

CSX Roberts:
This is somewhat beyond the original question but in addition: Refining what you posted just a bit, technically DCC is not an alternating current (AC) at all, but a bi-polar square wave. The one major distinction is that while both change from a "0" reference (grd) to an above and below value, the AC value is constantly varying and dependent in time during the alternation (sinusoidal or other wave form); DCC (bi-polar square wave) is either positive or negative that is ideally near instantaneous in change from one to the other. (The DCC signal is always a maximum value: either max negative or max positive.) Simply, a signal that uses both negative and positive values with ground reference does not automatically classify it as AC.

This proves that I have a lot to learn technically, which, of course, always happens when I get into a new hobby, so I appreciate the information and the distinctions.

Being a lifetime-recovering New Yorker, I can't help making at least myself laugh by pointing out that the bi-polar issue and the sinusoidal issue sound like problems that need to be examined by a psychologist or a ENT specialist - you'd think that these kinds of issues wouldn't occur in technology, and only in humans, but I guess it goes to show that I may need to wear rubber gloves and a mask when using my trains....

OK - I'll apologize in advance to all for that. But I did make me laugh....

 

[CSX Robert]

...technically DCC is not an alternating current (AC) at all, but a bi-polar square wave. The one major distinction is that while both change from a "0" reference (grd) to an above and below value, the AC value is constantly varying and dependent in time during the alternation (sinusoidal or other wave form); DCC (bi-polar square wave) is either positive or negative that is ideally near instantaneous in change from one to the other. (The DCC signal is always a maximum value: either max negative or max positive.)...

I figured someone would probably make a post disagreeing with the assertion that DCC is AC. I even started to say something about it, but decided not to muddy the waters unless someone did post as such. Many people say that DCC is not AC for one of two reasons: it is a square wave and it's frequency is constantly changing. I have never seen a technical reference to AC that says that it cannot be a square wave, and in fact have seen many references to AC that list square wave as one of the possible wave forms. I also have never seen a technical reference to AC that says it has to be a constant frequency. In other fields there are references to an alternating polarity square wave as being AC - AC square wave welding and square wave DC-AC inverter(although any decent inverter would not produce a square wave) to name a couple. There are also references to an alternating polarity voltage source with a varying frequency as being AC - variable frequency AC motor drive controllers for one, and audio signals are often referred to as AC.

I don't want to turn this into an "Is DCC AC thread?" so I will leave it at this: Some people do not consider DCC to be AC, but I do not see anything about the DCC signal that would preclude it from being called AC.

 

[UP2CSX]

I'll just say that both Rex and Robert are right. Technically, AC can have several wave forms, including square and sine. My brain is still scambled from all the electronic theory I had to learn to get my amateur radio license so there's no point in scarmbling model railroader brains with the same thing. It's close enough, as a distinction, to say that standard DC trains run on variable DC, with the voltage levels controlled by the rheostat in the powerpack. DCC trains run on constant AC-like current and the trains are controlled by data packets sent and received through the DCC controller and the DCC decoder. The one thing I'll say is don't put your tongue on a powered DCC track - don't ask me how I know this.

 

[RexHea]

Mike, don't worry about all this techie stuff. Its irrelevant to your inquiry. It is mostly just background jibberish.

Yes Robert, this is not the place and the argument does goes on. We could even go back to the old school and before switching circuitry, when the development of a squarewave was dependent on multiples of harmonics...AC. I did not say anything about varying frequency (different poster), but varying amplitude and distinct differences being alternating vs. switching (there has to be some distinction.) Where you could technically say alternating in polarity makes it AC, the DCC type of this waveform must be considered as a bi-polar squarewave. There: compromise! Another thing to consider: the decoder only needs one-half of this signal: upper or lower depending on direction.
Ref: VF Drives. Was taught (Allen-Bradley) and I taught that the delivered power is pulsating DC, not AC. AC supply is converted to this type of waveform and varied by different methods so the the motor recognizes it as frequency varied AC.




Mike, I apologize for getting carried away and way out'yonder. I'm out of here.

 

[MikeL]

Mike, I apologize for getting carried away and way out'yonder. I'm out of here.

Not a problem from my perspective - I appreciate the learning.....

But:

A. I should have paid a whole lot more attention at Bronx High School of Science (I remember a lot of these words from the few times I went to class)...... and

B. I won't make UP2CSX's mistake about what body parts NOT to place on the tracks. And I'll watch my 4-year-old so we don't have a problem there either..... OUCH is all I can say.