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Is it safe to run a DC locomotive on Digitrax DCC?

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Posted by rrebell on Thursday, November 5, 2020 7:24 PM

railroady

I have a Kato NW2 ho scale that I put a decoder in, under the fuel tank, and I removed an old decoder to do it, no metal removed. 

 

Never heard of that. I guess the fuel tank is just empty space? How did you run the wires?

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Posted by railroady on Thursday, November 5, 2020 3:50 PM

I have a Kato NW2 ho scale that I put a decoder in, under the fuel tank, and I removed an old decoder to do it, no metal removed. 

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Posted by rrebell on Wednesday, October 28, 2020 8:15 PM

I should have said of the current RTR, must have been thinking of my Kato NW2's. Haven't seen one yet converted to DCC without removing metal, especialy if with sound.

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Posted by rrinker on Wednesday, October 28, 2020 4:45 PM

 I don't have a single loco I converted to DCC that is lighter than the same loco as a DC loco - I've ADDED weight if anything (not that decoders are heavy) because all I did was add the decoder - none of the existing weight was removed. 

 In SOME cases (although with the latest speaker designs, it's less of an issue) you might have to mill some weight away to fit the speaker for a SOUND decoder, which of course will result in a loco being lighter than the DC only counterpart. 

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Posted by rrebell on Wednesday, October 28, 2020 4:16 PM

No the question of dc on a dcc can be relivent to anyone, it is to me. DCC engines are generaly lighter and have less tractive force and with todays wheel sets and trucks unless you run really long trans or very hilly is a moot point. But as in my case you want to run track cleaner cars like the CMX or some who run muliple track cleaner cars, it is quite importaint and it can give a use to those engines you may never convert like my small fleet of Kato NW2's

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Posted by ATLANTIC CENTRAL on Wednesday, October 28, 2020 11:30 AM

Mike,

I understand your point and experiences, but others have different goals.

Many want wireless throttles.

Many do not want to have to assign blocks to throttles.

I am a DC operator, I understand your points now. Again I think you should learn how to just say your main point, in stead of dancing around it for others to "figure out".

I will offer more thoughts later when I am not working, possibly in a separate thread.

Sheldon

    

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Posted by richg1998 on Wednesday, October 28, 2020 9:16 AM

At least the OP got his answer and bought some decoders.

I switched to DCC because I liked electronics since 1954.

Rich

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Posted by ATLANTIC CENTRAL on Wednesday, October 28, 2020 6:22 AM

betamax

Somehow the question of "can I use a locomotive without a decoder on a DCC powered layout" has become the equivalent of those silly arguments about CD audio in the 1980s.

Those arguments were along the lines of "Vinyl is superior as it captures all of the sound versus digital, which only captures some of the sound." 

The same people now tout the superiority of high priced speaker wires with electrons optimized at the atomic level via treatment with liquid nitrogen during the application of a 10 kV DC de-polarising voltage. Your MP3s will never sound better!

Revisiting the original question:

Yes, you can run an analog (decoder-less) locomotive with a DCC system. But why bother?

Decoders are not that expensive today, and DCC offers so many advantages.

 

But the best vinyl is better, and those speaker wires are BS - just my opinion, been collecting vinyl and building HiFi speakers since the 70's.

DC and DCC - yes, do one or the other, even if you do it with a DPDT switch on the same layout..........

Sheldon

    

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Posted by betamax on Wednesday, October 28, 2020 6:16 AM

Somehow the question of "can I use a locomotive without a decoder on a DCC powered layout" has become the equivalent of those silly arguments about CD audio in the 1980s.

Those arguments were along the lines of "Vinyl is superior as it captures all of the sound versus digital, which only captures some of the sound." 

The same people now tout the superiority of high priced speaker wires with electrons optimized at the atomic level via treatment with liquid nitrogen during the application of a 10 kV DC de-polarising voltage. Your MP3s will never sound better!

Revisiting the original question:

Yes, you can run an analog (decoder-less) locomotive with a DCC system. But why bother?

Decoders are not that expensive today, and DCC offers so many advantages.

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Posted by Mark R. on Wednesday, October 28, 2020 12:20 AM

You guys are expending way too much energy on a troll ....

Mark.

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Posted by rrinker on Tuesday, October 27, 2020 5:08 PM

 You still don;t grasp how putting the control and signal in one is SUPERIOR to the way it was done before DCC. A tiny, easily lost and/or corrupted AC signal sumperimposed on a steady DC voltage - that's how many pre-DCC command control systems worked, and it was not nearly as robust - that tiny signal could easily get lost int he noise, and if they made it any bigger, there would be enough of an AC component to create issues. Such sumperimposed signals has been used for ages to allow power companies to remotely control substations, and consumers got a version of it witht he X10 home control stuff that more or less started the home automation craze. But those systems inject a short burst at the zero crossing of sine wave AC. The model train controls put a steady DC on the track, and then superimposed a small AC control signal. The CTC-16 was one like this, and very well documented in MR. In fact, I was about to start building one (actually the improved CTC-16e version) when word came out about the NMRA working on a standard.

 ANd the technology used for the signal distribution etc. has nothing to do with ergonomics.

 Digitrax throttles have 2 knobs, so yes, one person can CONTROL two locos at the same time. And there's still an advantage with DCC even with just one person running trains - you can pull one in to the station, stop it, and just by selecting a different address, start up a second train. Yes, one at a time, but no toggles, no cab assignment.

 The only way yo get what you want is if all the direct radio locos were battery powered, AND completely isolated from the rails. The the track could have DCC on it to run DCC locos, or DC to run DC locos - but you'd still have the same issue running DC and DCC. So pick 2 - direct radio and DCC at the same time, or direct radio and DC at the same time. The concept of a fixed track voltage and DC locos just don't join. Either the track voltage varies to control loco speed as in DC< or the track coltage is fixed and a control signal determines loco speed and direction. You CAN combione DCC and rail-powered direct wireless easily enough, but there still no DC option. There just can't be. Every command control system fromt eh very first, up to the latest direct radio (wifi and bluetooth) systems control the loco in the loco, DC (and hi rail O with AC) are the last systems where the speed and direction are controlled at the controller and vary the voltage on the rails. 

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Posted by ATLANTIC CENTRAL on Tuesday, October 27, 2020 5:00 PM

selector

Someone please hand him a DT throttle and let him play with three or four locomotives, each separated by a scale mile of track, no two locos the same, and say that DCC doesn’t offer me more utility than a DC locomotive.

 

I have to say I don't completely understand this example? A scale mile of track is about 60'. Interestingly the typical block length on my DC layout will be between 40-60 feet, with the average freight train being 20-25 feet.

What am I going to do with these randomly placed locos? Are they going to be moving at the same time?

Even if I had DCC, I personally would only "operate" one "train" at a time.

Now, Like Tom describes, I may have a train running in "display" mode on the mainline while I work the yard.

My layout is designed so that DCC offers no real advantage for that function. I have blocks, signals, and dedicated routes that "display" mode trains can on with no real attention. We were doing that in DC long before DCC was thought of.

I'm not discounting those who want to "control" two trains at once, I'm just admitting I'm not up for that task. A train is either on a dedicated safe continious route, or it is the only train I am operating. 

But none of this negates the virtues of DCC for multiple operators.

Although, with good planning there are a number of DC control schemes tha come very close to the same streamlined operation of multiple trains, some with ergonomic advantages over DCC.

Sheldon

    

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Posted by richhotrain on Tuesday, October 27, 2020 3:31 PM

tstage
 
Lastspikemike
As for the remainder of the DCC operating, controlling and running distinctions I will just rely in my trusty dictionary.

You all can remain clinging to your favourite illusions about how capable and useful DCC is...for a single operator. 

aka I don't have a good argument to present to keep this discussion going. 

Spike is quite an outlier to saay the least.

Rich

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Posted by tstage on Tuesday, October 27, 2020 2:47 PM

Lastspikemike
As for the remainder of the DCC operating, controlling and running distinctions I will just rely in my trusty dictionary.

You all can remain clinging to your favourite illusions about how capable and useful DCC is...for a single operator.

aka I don't have a good argument to present to keep this discussion going.

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Posted by selector on Tuesday, October 27, 2020 2:02 PM

Someone please hand him a DT throttle and let him play with three or four locomotives, each separated by a scale mile of track, no two locos the same, and say that DCC doesn’t offer me more utility than a DC locomotive.

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Posted by ATLANTIC CENTRAL on Tuesday, October 27, 2020 9:54 AM

Mike, you still seem to miss the point.

I agree, direct radio would be a better system if we were starting today.

The point of DCC is not one person controlling multiple trains, the point is multiple people each controlling their own train, sometimes in close proximity to each other without the need for separate control blocks, and a method of assignment for those control blocks.

So yes, lone operators don't need that aspect of DCC.

Most people in this hobby are simply not going to change large investments in infrastructure, that's why it has taken DCC 25 years to reach 60% usage and finally become the deffacto starting point for most new people.

Sheldon

    

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Posted by tstage on Tuesday, October 27, 2020 9:36 AM

Lastspikemike
indeed, my biggest objection to DCC is that one operator can only operate one locomotive at a time anyway so why bother with multiple controls that can only be controlled one at a time?

Nope - A DCC operator can operate more than one locomotive at a time.  However, I guess it depends how you want to define the word "operate".

If I have one train out on the mainline and another locomotive switching cars in the yard then I call that operating two locomotives.  The switcher preoccupies my attention; the train on the mainline can run with less supervision.  Both locomotives are controlled with my Power Cab throttle and both can be accessed by it at any given moment.

Tom

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Posted by rrinker on Tuesday, October 27, 2020 8:11 AM

 In DCC, the short pulse is a 1 bit, the longer pulse is a 0 bit. There is a minimum and a maximum for the short 1 bit pulse, then a dead area where the pulse is neither a 1 or a 0 and so you should never see one with a duration in that window, then there is a minumum length for a 0 bit, and a VERY large maximim. Since the 0 is already a longer pulse, making it longer for one side or the other half of the wavefor makes a net non-zero DC voltage in the track and doesn't prevent decoder equipped locos from understanding the data signal part of it. However, since you are making ever 0 bit transmitted take longer to transmit, it does reduce the bandwidth available for signalling. For the intended use - smaller layouts where you haven't converted every loco yet - the effect is not even noticable. But in a club setting, running 50 decoder equipped locos and one person tries running on address 00 - yes, response to commands for the DCC locos will be slowed. Especially noticeable with sound decoders, press the horn button and there's a very obvious delay until the horn souinds on the loco.

 But you are 'running; as many DC loco as the system can handle. The same exact way you cna put 4 or more locos on the rails and use an ordinary DC power pack. It is EXACTLY the same. If you had sidings that were isolated and had toggles to kill the power, you could park one DC loco, kill the power (so it's safe sitting there - no power = it won;t heat up) and run a different one on address 00. Just like you would on a DC layout with only one power pack.

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Posted by Overmod on Monday, October 26, 2020 10:41 PM

Lastspikemike
Which locomotive are you operating?

Both or more.

Obviously how you turn the voltage up and down affects how fast they all go.  Were you expecting a single control to give you independent modulation of different functions?  Doesn't work that way.

Now if you had a yard goat that ran much more slowly at "7 volts" than the locomotives on main lines, it wouldn't get into trouble as fast as the others, and you could 'wait longer' before mashing the reverse to make it go the other way for a while.

As noted, the principal use of 'more than one locomotive' on a single DC throttle control is double- or multiple-heading.  Sheldon has summarized it pretty well.  More amps at the 'commanded' PWM voltage level will run additional engines on or in the same train just fine.

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Posted by ATLANTIC CENTRAL on Monday, October 26, 2020 10:39 PM

Mike, You can only "control" one "train" on address 00, that train can have more than one locomotive.

The average train on my layout is powered by two steam locos or 3-4 diesel locos, and that will work on a DCC layout, with address 00.

But I would never subject my locomotives to that signal......

Sheldon

    

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Posted by ATLANTIC CENTRAL on Monday, October 26, 2020 10:32 PM

Lastspikemike

Let us say you are "operating" two or more DC locomotives using address 00.

One is running through your yard while the other(s) are running on various points of main lines.

Which locomotive are you operating?

 

What part of this is so hard to understand. You are controlling both of them, just like putting two DC locos randomly on a DC layout with no blocks and turning up the throttle.

Most of the people in this conversation referring to operating two locos on address 00 are referring to double headed/MU operation, not two seperate trains.

Sheldon

    

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Posted by ATLANTIC CENTRAL on Monday, October 26, 2020 10:20 PM

Lastspikemike

 

 
Lakeshore Sub

Mike,

You're not assigning an address to anything when you use address 00.  It's just putting a DC like voltage to the tracks instead of the DCC signals so any DC locomotive on the tracks will respond.  Just for giggles I put a B&O dockside on the tracks with the chassis of an Athearn SD40-T2 for my Cary E-7 which are both DC locomotive and turned up the throttle on my DCS-50 with address 00.  Both of them moved in opposite directions and when I reversed the direction,  they ran towards each other.

Could have run more but I only have 2 DC locomotives.

Scott Sonntag

 

 

 

Well, digitrax seens to disagree. 

 

Why? Because you don't understand the term "zero stretching"?

The DCC signal is a pulsed AC signal, address 00 alters that pulse so a DC motor sees part of it as a PWM DC voltage. If they shift the pulse foward on the right hand rail, the DC loco moves "forward", if the shift the pulse forward on the left hand rail, the loco moves in "reverse".

The farther forward they shift the pulse, the higher effective voltage the DC motor sees, so it goes faster.

Mean while, the rest of the DCC AC signal is bouncing around overheating the motor...........which they warn you about.......

Sheldon

    

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Posted by Overmod on Monday, October 26, 2020 10:18 PM

Lakeshore Sub
You're not assigning an address to anything when you use address 00.  It's just putting a DC like voltage to the tracks instead of the DCC signals so any DC locomotive on the tracks will respond. 

It's more complicated than that, and probably far more interesting.

When address "OO" is active, what has to be happening is that the entire DCC voltage is being modulated in such a way that it approximates PWM DC at the appropriate chosen polarity (that term now being used advisedly, in the DC context) for whichever direction is currently toggled.  We know this in part because Digitrax advises that there is massive bandwidth consumption in this mode, meaning that there may be latency in control recognition for 'other' DCC signals being sent to decoder-equipped locomotives.  Presumably the modulation is accomplished so that regular DC motors 'see' only a complexly-modulated voltage (unfortunately some parts respond to the quickly-pulsed combination of logic and PWM and start to buzz and heat up...)

Don't ask me how decoder functions requiring relatively high minimum voltage continue to work when the commanded voltage for 00 drops the aggregate 'track voltage' below that level.  Perhaps they don't.

DCS51 documentation specifically references that you can run (so there!) more than one DC locomotive at once.  (Of course you can't control them 'separately' but if you're wanting multiple trains going around and around at the same time, that could be done.)

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Posted by rrinker on Monday, October 26, 2020 8:12 PM

 Already covered, you don't 'assign' address 0 to anything. But even if it did - I can 'assign' any valid DCC address to any number of locos - and they will all run at the same time that address is selected. The difference is, a DCC loco, when commanded to forward, move 'forward' regardless of which way they are facing, unless the motor wires are swapped or CV29 set for reverse direction of movement. 

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Posted by PC101 on Monday, October 26, 2020 7:27 PM

ATLANTIC CENTRAL
 
rrinker

 What do you mean "you're not running them"? If I put 4 DC locos on the tracks, dial up address 0 on my Zephyr, and increase the throttle, they will all move. If they are the same brand, with the same motor, they might even move together, at the same speed, like they would on actual DC power. I have speed control and direction control. Unless one is wired backwards, they will all move the same direction. I could keep adding more locos, as long as I don't exceed the 2.5 amps the system can supply. Or I could power the track through my DB150 booster and run up to 5 amps of DC locos simultaneously.

 Exactly the same as using a regular DC power pack, or the same as having multiple DCC locos all set for the same address - select that shared address and all locos using that address will move at the same time. Same direction, same speed (if they are similar locos). 

                                      --Randy

 

 

 

And, let's reinforce an important point for a poster a few posts back.

They will all move in the same direction (left or right), without regard for which way the locos are "facing". A pair of back to back units will move togther just like they do on real DC.

 

Sheldon

 

Yep my oversight. Thank you Sheldon.

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Posted by selector on Monday, October 26, 2020 4:15 PM

If using Add 00, any DC loco on the rails will move at the speed it’s engineered/geared to run at the voltage currently imparted to the rails for 00. This could be a single locomotive or 12, assuming their need for motive power severally does not exceed the output of the system, and that their individual and unique drive ‘stickiness’ gets them underway as voltage rises in discrete steps per setup of speed steps.

The manual may not mention it, but the logical inference ought to be that any DC locos will respond commensurate to the configuration of the voltage if Add 00 is enabled.

I have learned something new today. Sheldon doesn’t ‘run’ his trains because they move when he manipulates his DC throttles.Confused 

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Posted by richg1998 on Monday, October 26, 2020 3:19 PM

You can run more than one DC loco but there will be a current limit. No idea what it is one that controlller.

Some years ago I had an MR Command 2000 DCC controller with five throttles which had a one amp limit. Three on the main panel and two on a hand held controller. Number one on the panel was for a DCC or DC loco.

You can still find it on ebay last I knew.

I think the Bachmann EZ Command has a one amp limit.

 Rich.

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Posted by jjdamnit on Monday, October 26, 2020 3:09 PM

"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"

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Posted by Lakeshore Sub on Monday, October 26, 2020 2:45 PM

Mike,

You're not assigning an address to anything when you use address 00.  It's just putting a DC like voltage to the tracks instead of the DCC signals so any DC locomotive on the tracks will respond.  Just for giggles I put a B&O dockside on the tracks with the chassis of an Athearn SD40-T2 for my Cary E-7 which are both DC locomotive and turned up the throttle on my DCS-50 with address 00.  Both of them moved in opposite directions and when I reversed the direction,  they ran towards each other.

Could have run more but I only have 2 DC locomotives.

Scott Sonntag

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