# DCC BEGINNERS: BASIC INFO



## time warp

I wanted to start this thread due to some mis information and confusing theories being posted lately, and in response to others' suggestion to do so. Simple, helpful comments welcome.

I do not have any Model Railroad DCC experience, which is why I feel I can comment without partiality and with a naïve viewpoint. Based SOLELY on information learned on this forum, here is my take.

All model trains require control of some sort, unless static models. Power pack or transformer control has been around for decades, whether AC or DC. The object being to control the speed and direction of the model train. The subject at hand is currently available DCC control- DIGITAL COMMAND CONTROL.
The BASIC idea is that the train (locomotive) direction and speed control is accomplished by powering the motor through a circuit board (decoder) which responds to command signals generated from a Command station. 
For the sake of discussion, the subject example will use a dc motor. The following list is deliberately basic.
ITEM #1. The supplied power to the rails, thence to the Decoder, is AC voltage. The power supplied to the locomotive motor is DC, Rectified through circuitry in the Decoder circuit board.
ITEM #2. The AC supply voltage remains constant to provide power to the decoder, the Digital CONTROL SIGNAL is "carried" by the AC signal to affect various DC outputs from the Decoder.
ITEM #3. Due to the fact that Digital control signals are used to command the decoder functions, excellent wheel to rail contact is necessary. The AC power supply to the decoder board is equally important.
ITEM #4. While the object is to control speed and direction of the locomotive motor and many different systems exist, quality of course will vary. Decoder quality and performance will differ as well. Things like motor hum, programming difficulties, erratic performance and sporadic activation do occur.
ITEM #5. A benefit of the digital control is the ability to add "functions", such as sound and lighting effects. 
ITEM #6. Programming. Decoders must react to specific commands for the aforementioned speed and direction, but also the sound and lighting effects. Additionally, multiple locomotives and therefore multiple decoders,must be able to respond to specific individual commands. Each decoder must therefore be programmed to respond to its specific desired control via the address assigned to it from the command station.
I may be way off on some of these points, but look forward to commentary in any case.


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## fcwilt

Hi,

You have the essentials correct.

One item that you might find interesting is the a digital control system like this does not need to use AC as the power on the rails.

A system could have been devised that worked fine with just DC power on the rails. Of course you still need to impose the command information on the DC power but that is not difficult.

One advantage of the DCC approach is that the average DC voltage on the rails is zero - so when you put a DC loco on the rails it just sits there and hums/buzzes rather then runs away down the track at full speed - which is what would happen in a DC power based design.

Also the DCC approach allows varying the waveform so that the average DC voltage is other then zero allowing control of a single DC loco. I have heard that this feature doesn't work well with all DC locos. I don't know if all command stations implement it and I don't know if it is used very much.

Frederick


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## Bwells

Time warp: sounds good to me and easy to understand.
Fcwilt: I just assumed that AC was chosen as possibly carrying the digital signal better. Never thought about the run-away effect DC would cause.


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## time warp

Is the "general" industry standard AC power with DC signal? Makers like Digitrax or MRC for example.
Is the control signal typically square wave "bits"? I'm thinking the decoder must receive it's signaling in the form of data, rather than FM. Hence "D" CC.


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## wvgca

the signal can be roughly described as alternating square wave [ideally] , with changes in the duration of each portion of the full square being the data ..if you increase the length of the top, or 'positive' portion relative to the lower, or 'negative' unchanged portion, you basically get a DC offset, which can drive a non decoder equipped DC loco ...
all of your post looks good ... i'm glad to see the lack of the term 'fact' ...


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## Bwells

Warren, I'm assuming the "packets" of information are sent in a 1 and 0 sequence possibly 8 or 16 digits long. If so, are these "packets" read at the top and bottom of the square wave?


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## time warp

My knowledge of this material is testimony to the helpfulness of members here, so thanks to all of you.
So fcwilt, you and W are saying the same thing; the frequency of the control waveform influences the decoder functions. Noting that it is of constant amplitude.
It seems inevitable that there is a likelihood of motor heating. I used to have trouble with transistor power packs overheating my old 3 pole Motors at lower voltages. Looks like a somewhat similar problem( potentially) here.


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## Mark VerMurlen

Bwells said:


> Warren, I'm assuming the "packets" of information are sent in a 1 and 0 sequence possibly 8 or 16 digits long. If so, are these "packets" read at the top and bottom of the square wave?


You are correct that data is transmitted in packets of 1s and 0s. The NMRA has the full DCC specification on its website. Packet definition is at http://www.nmra.org/sites/default/files/s-92-2004-07.pdf. It's very technical of course, but interesting to skim through. A simpler description is available on Wikipedia at https://en.wikipedia.org/wiki/Digital_Command_Control.

Mark


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## Bwells

Thanks Mark for the links. I looked at the wiki one and was afraid to go to the NMRA one.

Opps, it looks like we veered off the beginner DCC format!


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## wvgca

Bwells said:


> Warren, I'm assuming the "packets" of information are sent in a 1 and 0 sequence possibly 8 or 16 digits long. If so, are these "packets" read at the top and bottom of the square wave?



Yes, binary zero at 58us for each half [positive & negative], with a zero bit each half being 100us or longer ..

I have no idea on read, but I assume zero crossing with a positive read , but have nothing to base that on ..

As far as frequency, roughly seven to ten Khz, more One bits, higher frequency ... it changes continuously .. 

Also, packet length, I know there is a [roughly] fixed preamble of ten [or more] One bits, and an end bit, depends on the data between those ..

there is some good information on the OpenDCC web site also ..


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## time warp

Bwells said:


> Warren, I'm assuming the "packets" of information are sent in a 1 and 0 sequence possibly 8 or 16 digits long. If so, are these "packets" read at the top and bottom of the square wave?


 This is what I was thinking, you worded it better than I.
The point is the commands are sent as data.
That data does not control the motor or lighting/ sound directly. The decoder receives the data commands as an input,
The motor and lighting/ sound are controlled as an output from the decoder.

Here is what I'm driving to:
Decoder outputs are DC.


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## mopac

Here is what I'm driving to:
Decoder outputs are DC. 

100% correct. The neatest thing I like about DCC is that only the decoder addressed
reacts to the data commands. That's what makes DCC wiring easier.


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## time warp

Thanks, Mopac. I wanted to clarify that point based on some earlier misinformation from other threads.

Okay, so if locomotives are run in multiple, are they assigned the same address?
I can see where mismatched power would need individual control, but what about similar units?


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## Mark VerMurlen

Bwells said:


> Thanks Mark for the links. I looked at the wiki one and was afraid to go to the NMRA one.


Don't be afraid to go to the NMRA spec. The spec is broken up into multiple parts, so the above link is just to the packet definition pages of which there are just a couple. Skimming through the document you'll see there are provisions for error detection and that commands are sent multiple times. So the designers took into account dirty rails and other real life problems.

Mark


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## highvoltage

Mark VerMurlen said:


> You are correct that data is transmitted in packets of 1s and 0s. The NMRA has the full DCC specification on its website. Packet definition is at http://www.nmra.org/sites/default/files/s-92-2004-07.pdf. It's very technical of course, but interesting to skim through. A simpler description is available on Wikipedia at https://en.wikipedia.org/wiki/Digital_Command_Control.
> 
> Mark


So looking at those two links, it looks like Pulse Width Modulation. Am I correct?


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## mopac

Multiple locos are programmed into a "consist".
The consist has an address. So all locos in consist
receive the same command. Pretty neat. When removing
one or more of the multiple locos they must be removed
from the consist by programming and given their
unique address back.


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## CTValleyRR

Good thread. I hope a certain individual stays away from it...


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## fcwilt

mopac said:


> Multiple locos are programmed into a "consist".
> The consist has an address. So all locos in consist
> receive the same command. Pretty neat. When removing
> one or more of the multiple locos they must be removed
> from the consist by programming and given their
> unique address back.


Just in the interest of clarity when removing a loco from an consist setup using CV19 you only need to set CV19 back to zero and the loco will then respond to its normal address, either the short address in CV1 or the long address in CV17/CV18, depending on the setting of the long address bit in CV29.

These values are not changed when setting/clearing the consist address in CV19 so there is no actual need to set them again.

Frederick


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## fcwilt

mopac said:


> The neatest thing I like about DCC is that only the decoder addressed
> reacts to the data commands.


It may be of interest to know that DCC address zero is unique in that all locos must respond to a command sent to address zero.

These feature is used, for example, to allow the command station to stop all locos with one command.

Frederick


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## Bwells

Interesting, I take it that is what the "emergency stop" button does?


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## fcwilt

Bwells said:


> Interesting, I take it that is what the "emergency stop" button does?


While I cannot say for sure what any given system may do I think it is quite likely they would use address zero for this purpose.

Frederick


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## DonR

My Bachmann EZ DCC controller emergency STOP button cuts
the power to the tracks. Since it is NMRA compliant,
I assume that all (or most) DCC controller makes
would do the same.

This is a much needed thread and the information
has been very correctly presented.

I would add, however, that most of the various
DCC makes are much the same, some are
easier to use, some are limited in the number
of locos they can have in their database and
some, like my Bachmann, cannot change
the individual CVs that the decoder uses
to control the motor, lights and sound.
However, in general, you can run any make DCC loco
with any make DCC controller.

Don


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## wvgca

Bwells said:


> Interesting, I take it that is what the "emergency stop" button does?


Some systems send a stop command out, others, like my MRC Prodigy, just shut off track power completely at the controller ..and all loco's stop dead, well, except for those running that have any type of keep alive installed ..


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## gregc

time warp said:


> Here is what I'm driving to:
> Decoder outputs are DC.


If by DC you mean a constant voltage as with DC systems, then the Decoder output is not DC.

It's a pulse width modulated signal that has an average DC voltage between zero and the max.

the advantage is it efficient in term of little wasted power and therefore requires not higher power components or heat sinks.


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## wvgca

yes, gregc is correct ..
in the last decade or more, what has been termed 'silent drive' or similar, is simply an increase in the operating frequency of the PWM signal to the motor .. and got rid of that annoying audible whine that older decoders may have had in some cases..


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## gregc

wvgca said:


> Yes, binary zero at 58us for each half [positive & negative], with a zero bit each half being 100us or longer ..
> 
> I have no idea on read, but I assume zero crossing with a positive read , but have nothing to base that on ..
> 
> As far as frequency, roughly seven to ten Khz, more One bits, higher frequency ... it changes continuously ..
> 
> Also, packet length, I know there is a [roughly] fixed preamble of ten [or more] One bits, and an end bit, depends on the data between those ..
> 
> there is some good information on the OpenDCC web site also ..


to clarify what Warren said, each data bit is represented by a cycle of the DCC signal transmitted over the rails where the period of both half-cycles are roughly the same, 52-64 usec and 116 usec total for a data value of 1 and a half period ~100 usec for a data value of 0. (S9.1 spec)

The cycle can start with the first half cycle either being positive or negative. It's strictly time that determines if the bit is a 1 or zero.


The following figure illustrates the format of a DCC command. The number of bits in the command is a constant. The average frequency varies with the density of 1s and 0s (as Warren said). (S9.2 spec)


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## gregc

time warp said:


> ITEM #3. Due to the fact that Digital control signals are used to command the decoder functions, excellent wheel to rail contact is necessary. The AC power supply to the decoder board is equally important.


momentum allows a locomotive to continue to run despite temporary loss of power due to dirty track. (obviously keep alive circuits allow longer losses in power).

capacitance in the decoder circuit allows it to maintain operation during temporary loss of power, as well as continue to perform the last commanded operation

dirty track will corrupt transmission of commands, but they are sent periodically, so many can be lost. Error detection bits sent in the command allow corrupted commands to be ignored.


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## gregc

time warp said:


> ITEM #5. A benefit of the digital control is the ability to add "functions", such as sound and lighting effects.


i don't think digital control is necessary for sound, but a steady source of power is.

A sound module on a DC locomotive could only start operating once the DC voltage is above some level to provide sufficient power to the sound module.


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## time warp

The "items" as listed are based on my impressions formed by information I've read in several different threads here, so I'm glad that these things are being clarified.
My impression is(was) that the command signals were not dependant on a return signal or feedback. I'm still not sure about this in light of the previously mentioned error codes. Are error codes read by the command station via feedback?

Also, I was aware of sound equipped DC locomotives, but thought perhaps DCC control with sound was different.
Now I see that output from the decoder would be for direction and speed , plus lighting. Sound isn't activated with control bits, It is merely incorporated into the decoder board. Or at least can be.


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## gregc

time warp said:


> My impression is(was) that the command signals were not dependant on a return signal or feedback. I'm still not sure about this in light of the previously mentioned error codes. Are error codes read by the command station via feedback?


there is no standard mechanism for a decoder to transmit information back to the command station in normal operation. (S9.3.2 is proposed, by I'm not familiar with it).

The NCE PowerCab is able to read back CV values from a single decoder/locomotive on a programming track because the decoder momentarily applies power to the motor, momentarily increasing the current, which the PowerCab can measure. The decoder transmits CV values by modulating the current.

The error detection bits I mentioned earlier are transmitted in the command. These are the last group of data in the command along with preamble, address and instruction. These bits are used to verify that the DCC command is not corrupted. The command is ignored if it is corrupted. The command station is unaware that a command is corrupted. The command station will repeat the command periodically.


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## time warp

Perfect, thank you. That confirms my initial thinking that the transmitted commands were sent regardless of whether or not a decoder received it.

Regarding rail/wheel contact, the impression I've had was that DCC was far more sensitive to dirty track than DC. While track certainly needs to be clean, the presence of redundant control signals would lead me to believe that it's not as critical as I thought.
In other words DCC will work in the real, imperfect world.


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## ncrc5315

What I have found, was that DCC was less sensitive to dirty track due to a consistent voltage applied to the track, instead of variable voltage to the track.


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## time warp

ncrc5315 said:


> What I have found, was that DCC was less sensitive to dirty track due to a consistent voltage applied to the track, instead of variable voltage to the track.


 Seems logical to me, and you are talking about actual experience, not theory!


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## DavefromMD

Reference Emergency Stop Button.

On the NCE Power Cab the emergency stop button stopped ONLY THE CURRENTLY SELECTED LOCOMOTIVE. All others will keep running. Trust me, I know. I don't know why they make it like that.


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## time warp

What good is that? I would assume the emergency stop button is there in case there's a derailment or something and you want to stop the show immediately.


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## fcwilt

DavefromMD said:


> Reference Emergency Stop Button.
> 
> On the NCE Power Cab the emergency stop button stopped ONLY THE CURRENTLY SELECTED LOCOMOTIVE. All others will keep running. Trust me, I know. I don't know why they make it like that.


What if you press it a second time?

I know some systems work like that. First press current loco, second press all locos.

Frederick


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## DavefromMD

NCE Power Cab:
Nope. Press the emergency stop until the cows come home and it will only stop the selected locomotive. The only way to stop them all quickly is to disconnect the throttle. You learn how to do that in a hurry.


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## fcwilt

DavefromMD said:


> NCE Power Cab:
> Nope. Press the emergency stop until the cows come home and it will only stop the selected locomotive. The only way to stop them all quickly is to disconnect the throttle. You learn how to do that in a hurry.


That is rather amazing given the simplicity of implementing a second press to send out the command to stop all locos.

NCE does things I don't understand.

Frederick


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## Lemonhawk

I have a switch on my panel that removes all track power. But now I'm curious what the EMRG OFF button on my DT402D does.


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## time warp

Next question: compatibility.
One would assume that most brands of DCC equipment that is NMRA compliant would be compatible. So a certain brand of command station should communicate reliably with other brands of decoders, and perform reasonably well.
Also, is there evidence of performance problems associated with a lower priced decoder that you wouldn't experience with higher priced units? Comparing cost to quality.
The problems of excessive hum or buzz and sporadic performance are things I've read and heard about. Maybe these problems were more evident in older equipment?
The focus of these comparisons should naturally be on currently available components.


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## Mark R.

time warp said:


> Next question: compatibility.
> One would assume that most brands of DCC equipment that is NMRA compliant would be compatible. So a certain brand of command station should communicate reliably with other brands of decoders, and perform reasonably well.
> Also, is there evidence of performance problems associated with a lower priced decoder that you wouldn't experience with higher priced units? Comparing cost to quality.
> The problems of excessive hum or buzz and sporadic performance are things I've read and heard about. Maybe these problems were more evident in older equipment?
> The focus of these comparisons should naturally be on currently available components.


Lot of truth in that statement. For example, I purchased a number of Bachmann engines that came with a (non sound) decoder. They ran "ok", but not all that great. I ripped out the decoders and installed a comparable TCS decoder and the difference was night and day. They were now actually running as well as my Atlas engines !

The same rule applies as always .... you get what you pay for ....

Mark.


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## DonR

I seldom use the Emergency Stop button on my
Bachmann EZ DCC controller or hand held. But
what I've discovered is that the STOP button
on the main controller shuts off the power to
the tracks, but the STOP button on the hand
held stops only the loco it is set for. The
others continue running.

Is it possible that the NCE Main controller STOP
kills the power and the hand held stops only
the loco it is set for?

Don


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## Bwells

Don: My NCE Power Cab has a wall wart type transformer, a PCP fascia mounted panel and the handheld unit. There is no main external controller and must be housed in the handheld. In fact, there isn't even a power switch to turn it off!


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## Chip

I moved up to the NCE SB5 and the power switch on THAT is my "KILL IT!" go-to when I need to STOP everybody in those "OH, $H!T!" moments! I would think that JANKIN the plug out of the wall would also work in an emergency with any DCC system.


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## Chip

I've run as many as 4-5 different manufacturers Loco's at once with the decoders that came in em with my NCE Powercab and then on my SB5 system and they all did just fine together. I have only had one of my BLI's "take a dump"(it just "DIED"!) on me and putting it through the "reprogramming dance" on the program track took care of whatever was wrong with it and it plays nice now.


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## time warp

From what I can see, the 2 things that can cause the most problems are current path from rail to decoder, and decoder issues.
I don't hear about too many issues with command stations generally.


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## gregc

time warp said:


> From what I can see, the 2 things that can cause the most problems are current path from rail to decoder, and decoder issues.
> I don't hear about too many issues with command stations generally.


rail connections and decoder installations are two things outside of the manufacturers control. I doubt a decoder design is tested with all possible locomotives. The CVs allow customization of the decoder for locomotives that may need it.

Another example of issues outside the manufacturers control are wireless throttles. The club I'm in had to give up due to an interfering signal that operates on the ISM band.

DCC works very well considering all the possible applications and environments.


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## time warp

Without getting into personal preference, are there any advantages to using one brand of command station over another?
Maybe it's comparing apples to apples?


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## fcwilt

time warp said:


> Without getting into personal preference, are there any advantages to using one brand of command station over another?
> Maybe it's comparing apples to apples?


Most all command stations will allow you to run trains and program decoders.

But when it comes to controlling other things like turnouts, signals, etc or doing occupancy detection there can be significant differences.

Check out the Roco Z21 or the Digikeijs DR5000

http://www.z21.eu/en/Z21

http://www.digikeijs.com/

Each has support for a number of different control buses.

Frederick


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## Cycleops

I guess it's' horses for courses'. I don't know what the Digikejis philosopy is as its not apparent from their site. I wasn't aware of their products. I imagine it might be a basic system best suited to an enthusiast who knows how to add to it to get the best from it. What's your reading fcwilt? 

I have the Z21 and I'm very happy with it, you can be up and running in a few minutes. I'd say it's not a 'beginners' system and although it looks very complex in actuality it's very simple and easy to use but would best suit someone who understands the basics. What could be easier than flicking a turnout on a screen to the desired direction? Their z21 (white unit) would be better for a first time user who probably wouldnt use the 'bells and whistles' of the more expensive set up, perhaps why they only sell it with train sets and not as a stand alone unit.


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## Cycleops

DonR said:


> Is it possible that the NCE Main controller STOP
> kills the power and the hand held stops only
> the loco it is set for?
> 
> Don


Correct.


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## time warp

As far as programming the locomotive decoder goes, are any command stations more user friendly than others?


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## mopac

I only know about digitrax. But I think all would work the same. Hit the program button.
Select the CV number. Select the value number. And hit "enter". And done.


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## CTValleyRR

mopac said:


> I only know about digitrax. But I think all would work the same. Hit the program button.
> Select the CV number. Select the value number. And hit "enter". And done.


MRC functions identically. With the exception of the loco address, it can be done either on the main or a programming track. Older Prodigy Express units require the use of the programming track.


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## fcwilt

Cycleops said:


> I guess it's' horses for courses'. I don't know what the Digikejis philosopy is as its not apparent from their site. I wasn't aware of their products. I imagine it might be a basic system best suited to an enthusiast who knows how to add to it to get the best from it. What's your reading fcwilt?


The DR5000 is an amazing unit particularly for the price.

It's still a work in progress to a degree as indicated by the most recent firmware being marked as BETA.

Digikejis currently doesn't have any handheld throttles BUT this may be intentional as you can use other brands like Digitrax or Roco.

The DR5000 has WiFi but no Apple/Android throttle application as of yet.

Aside from those issues it is certainly a versatile unit having more control buses than even the Z21.


On my layout I use the Z21 but I have a DR5000 on the bench. 

Frederick


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## mopac

Great thread time warp. Very good for the beginner. Sorry, but I have not read every
post here so I don't know if this has all ready been addressed. I must admit that when
I first thought about DCC I was intimidated with all the talk about CVs and CV values.
Don't be intimidated !!! It is very easy. Its like anything else, after once or twice you
know how to do it. You don't need to be a computer whiz. A decoder may have 200 or
more or less CVs. All you need to know is each CV controls something. How do you know what each CV controls? Usually with a new DCC locomotive or decoder purchase
you will get a CV chart. The chart tells you what each CV controls. And the chart will
tell you the range of CV values. Some values may be 1 through 7 or 1 through 255.
Each will fine tune your locomotive. Example, most decoders will come with several
different horns, you have a choice. The chart will tell you which CV does the horns. The chart will give the vale range. Lets say 1 through 5. Each value 1 through 5 is a different
horn. Try each one and go with the one you like. I like all my engines to start creeping 
on throttle setting of 1. They don't do this out of the box. There is a CV for that. I like my trains to have momentum (sp). On DC you shut the throttle down and train stops 
pretty quick. I like mine to to travel a bit after shutting throttle down. Not too much but 
some. There is a CV for that. You don't need to know what a CV is, just what it controls.
Hope this made some sense.


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## time warp

Absolutely makes sense, MoPac. In the OP I stated that my aim here was to discuss the ins and outs of DCC based primarily on the experiences and knowledge of the members here. 
Very informative discussion, speaks well of all.


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## mopac

A little more. Every DCC user needs to know how to reset their decoder. At sometime or
another there will be the need to reset. Sometimes they just get goofy. 90% of problems
with DCC engines can be corrected with a reset. Resets are great but there is one problem. All those CVs you changed will revert to factory settings. It is a smart thing to do is to make a card for each engine and list CV number and the value number of the
CVs you changed from factory setting. I only change maybe 10 CV values on each
engine. Some CVs I am not sure what they do, don't change a CV unless you know
what it controls. If you screw up, and you will, no biggie. Just reset.

Resets are easy. On most decoders just select CV8 and give it a value of 8. Your chart will
tell you the reset CV.


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## time warp

Actually, I had planned to bring up CV's soon, so I'm glad you posted about the subject. I am immersed in PLC controls a lot of the time so I do understand parameter assignment. 
Doesn't look to me like it matters too much whether a particular system requires a programming track or not, and a rough understanding of CV values should be enough to get someone started. Learning through experience looks like the way to go on this particular subject although I can see where some frustration could creep in.
Glad you brought up the reset/ default point. That could catch a person off guard easy enough.


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## redman88

There are some decoders out there that can be locked. If a reset doesn't work you might have to look up the decoder manufacturer and see how to unlock it.


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## mopac

I have heard of decoders that can be locked. I have no experience with them.

Programming on the main is fine but you have to make sure there are no other 
locos on there also. You will change their CVs.

After a reset your address will be 03. That's why it is good to have your changes written down somewhere so you can quickly give the engine its road number back. That is done with CVs. Many of the CV changes are by trial and error till you get the loco to do what you want. You don't want to do the trial and error thing every time you reset. You can't
remember all the values you like. Write it down. I guess some of these JRM programs can remember the values.
I my self don't care about my PC running things. Some do.


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## time warp

I need to clarify a remark I made in post 59. I was referencing as to whether or not a specific manufacturer might REQUIRE a programming track.

I believe, however, that it is best to use a dedicated programming track.


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## Chip

time warp said:


> I need to clarify a remark I made in post 59. I was referencing as to whether or not a specific manufacturer might REQUIRE a programming track.
> 
> I believe, however, that it is best to use a dedicated programming track.


AMEN!

I use NCE and have had MUCH better results with a dedicated program track than "programming on the main"!


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## fcwilt

mopac said:


> Programming on the main is fine but you have to make sure there are no other
> locos on there also. You will change their CVs.


That is incorrect.

POM requires specifying the address of the loco you wish to program.

However POM will not allow reading of the current settings - in most cases.


The mode used with a programming track WILL program whatever loco is on the programming track regardless of the locos current address.

Also you will be able to read the current loco settings.


Frederick


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## CTValleyRR

time warp said:


> I need to clarify a remark I made in post 59. I was referencing as to whether or not a specific manufacturer might REQUIRE a programming track.
> 
> I believe, however, that it is best to use a dedicated programming track.


Older MRC units (the ones without the 2 or "Squared" in the name) do not have the ability to POM.

That said, I agree. It's a function I rarely use. It works ok for "set cv x yo y" situations, nut not for "add 1 to the value of cv x", unless you already know what that value is.


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## wvgca

CTValleyRR said:


> Older MRC units (the ones without the 2 or "Squared" in the name) do not have the ability to POM.
> 
> That said, I agree. It's a function I rarely use. It works ok for "set cv x yo y" situations, nut not for "add 1 to the value of cv x", unless you already know what that value is.


I have two of the MRC Prodigy handhelds, an older Express [ non squared], and a new Advance squared unit ..
The older non squared handheld will program on the main as well as program track, but only the newer Advance one will read back CV values, but only on the program track .. 
It may be that different production versions may possibly have different capabilities or limits, but don't know if there is any way to tell before it's bought?
The MRC units seem to contain most of the 'brains' inside the handheld itself, there is very little inside the express 'controller box' other than a couple pair of final driver transistors, I blew mine up once and had the controller box apart for repair ..


----------



## CTValleyRR

You're definitely right about the brains being in the handheld unit. The "Wireless Upgrade kit" is nothing more than an upgraded handheld and a dongle (a wireless antenna that plugs into the jack where the handheld formerly went).

At some point, they must have upgraded the older (non-squared) version. My original Prodigy Express DEFINITELY wouldn't, and the glossy "Which MRC System Should I Choose?" that I picked up at the MRC booth when I was shopping for sets doesn't list it as a feature. That was right after the "Advance Squared" came out. Maybe just an oversight by the Marketing folks?


----------



## CTValleyRR

Capacitor said:


> Hello time warp.
> 
> I see that you are just starting to think about converting your model train layout to Digital Command Control.


Well, actually, that wasn't why he started this thread. He started it because, when he did it, we had a member who was posting utter nonsense about DCC, and much of what was posted was not valuable to people with lack of experience.

And while I think you're really making a genuine effort to contribute to the discussion, much of what you posted is perpetuating some of these same myths.

Using a DCC system with brass track certainly requires more care than nickel silver track with regard to track cleanliness, but it's hardly a show stopper. When I returned to the hobby in 2001, I built a "practice" 4x8 layout using mostly items I had on hand (read: brass), and only nickel silver for new acquisitions, perhaps a third of the track, all told. My track cleaning regimen has never changed: a bright boy after major construction work, and a weekly wipe down with a rag and denatured alcohol. When I converted to DCC 3 years later, I disconnected the feeder wires from my DC power pack and connected them to the DCC command station. It took a little longer to convert my Loco fleet, but my DCC system worked out of the box. There were no more stalls and hesitations than there had been under DC.

Also, you do not need Walthers DCC Friendly turnouts. That's a marketing gimmick. My initial turnouts were Atlas Snap Switches with plastic frogs, and I rarely had trouble, even when stopping locos directly on the points. Granted, metal, powered and isolated frogs work better, but those from Atlas (Custom Line), Peco, and MicroEngineering work just as well as Walthers. Some older powered frogs may require some surgery to work properly, but you can simply insulate those frogs to make them dead, and you can run DCC -- again, not as well, but there'should no show stopper about it.


----------



## time warp

I haven't used brass track since around '92.
The purpose of this thread is to carefully discuss DCC basics based on members' experiences.


----------



## time warp

Back to the subject: 
Would it be correct to say that most, if not all, currently available systems favor or require using a programming track?
I don't want this thread trashed.


----------



## wvgca

time warp said:


> Back to the subject:
> Would it be correct to say that most, if not all, currently available systems favor or require using a programming track?


I have some experience with only two systems, MRC and Arduino based DCC++ ..

The MRC can do some programming on the main, but reading CV values with the Advance2 handheld requires the program track ..
and the DCC++ [as far as I know] requires the program track to read back or write CV values


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## CTValleyRR

I would say favor vice require.

MRC makes a stand alone decoder programmer, which at least in theory makes a programming track unnecessary, as do 3rd party systems like JMRI.


----------



## time warp

Sorry, I know that may have seemed a bit redundant, but I was specifically reference current equipment.
Looks like this to me in a nutshell: DCC basically isn't difficult or complicated. The popular systems apparently are user friendly and work fine "out of the box".
You can add many features if you want, but there's no magic. Its really simple.


----------



## mopac

I would say within an hour or less you will have a good feel of your system,
no matter which one you choose. I went with digitrax (which is supposedly
hard to understand). I really had no problem. Yes, I had to read sections of
the manual twice. But no biggie. I do keep my manual close.


----------



## CTValleyRR

You can see my story above. I disconnected one box and connected another, then systematically pulled the shells from my locos and installed decoders.

Well, OK, I actually had one installed before I made the switch, so I could test it right away, and a couple of my older locos gave me fits, so I paid someone to do the install. 

But basically, it was just a plug and play. Didn't even have to crack the manual until I got a second handset and had to figure out how to give it a unique identification.

My personal opinion is that, while I don't really see any compelling need to go DCC, especially if you already have a DC layout that you're happy with, I also have yet to see a good reason not to use it. Cost, complexity, time to install decoders, "can't do this in DCC", all just minor issues, and most not valid anyway.


----------



## time warp

Things follow trends, just like when clockwork was standard or live steam. Once electricity was more widespread clockwork went away. So is DC to a certain extent.
I think DCC shows strongest in switching, but like has been said, I have a relatively complex DC system and it works well.I don't need DCC, but little man will probably push that direction. That means bye bye to most Tyco engines because you can't isolate the Motor.


----------



## mopac

That means bye bye to most Tyco engines because you can't isolate the Motor. 

Well kinda, if you go just DCC. Have both !!! You can have your DC transformer
sitting right next to your DCC command station and just a switch to select DC
or DCC. I know a few guys on the forum does have both. It is not hard at all. You
just CAN NOT have power from each at the same time. One or the other. It works.


----------



## time warp

Thanks mopac, I'd forgotten that. 
So now, the wiring. Perfect scenario undoubtedly would be a twisted pair buss, and nickel silver rail with powered frog switches.
But from other postings I see that a system could be up and running just connecting two wires with existing trackwork.
I'm kind of asking a question here that may be a concern to those just starting out.


----------



## DonR

Considering that you have some DC locos you likely
won't convert to DC, simply use a Double Pole, Double
throw switch in the main buss from your DCC controller
and DC power pack. When you want DC trains toggle
to DC on the switch, or the other way for DCC. No
need to do any additional wiring. 

If however, you have a number of blocks or capability
of running more than one DC power pack, you would
need to set all of those switches to take power from
either DC or DCC controller. When in DCC mode they
would all be ON for the SAME source.

There is no requirement that your DCC turnouts have
powered frogs. I have more than 20 Peco Insulfrogs
on my DCC layout and do not have any power pickup
problems.

Don


----------



## mopac

Ok, the wiring. Your layout works great on DC. If you got DCC you would take the
2 wires from your DC transformer and hook the 2 wires to your DCC unit. You can now 
run DCC that quick. I don't know but you might have switches to cut power to
sidings to park DC trains. Most on DCC will just flip all those switches to powered. You
would not have to remove them. What you will probably have to do is remove locos
from the layout depending which power you are running. Really I guess you could
park them in sidings and switch power off to those sidings. If that makes any sense.
You don't want your DC engines getting DCC power.


----------



## mopac

I think DON and I are saying the same thing. He posted while I was writing mine.


----------



## time warp

It wouldn't be difficult to gang the DC inputs, and all the blocks would be turned on for DCC.
I appreciate the turnout info, that goes directly contrary to an earlier posting. Your comments make perfect sense.


----------



## time warp

Were overlapping, but you both are spot on in my opinion


----------



## CTValleyRR

DonR said:


> Considering that you have some DC locos you likely
> won't convert to DC, simply use a Double Pole, Double
> throw switch in the main buss from your DCC controller
> and DC power pack. When you want DC trains toggle
> to DC on the switch, or the other way for DCC. No
> need to do any additional wiring.
> 
> If however, you have a number of blocks or capability
> of running more than one DC power pack, you would
> need to set all of those switches to take power from
> either DC or DCC controller. When in DCC mode they
> would all be ON for the SAME source.
> 
> There is no requirement that your DCC turnouts have
> powered frogs. I have more than 20 Peco Insulfrogs
> on my DCC layout and do not have any power pickup
> problems.
> 
> Don


I'm quoting this, but MOPAC is essentially saying the same thing. This is absolutely correct.

I actually did install a DPDT switch for a few months once I realized I wouldn't be able to convert all my locos at once. One word of caution, since you do not, EVER, want DCC and DC outputs going to the rails simultaneously, for even a fraction of a second, make sure the DPDT switch is a "break before make" design; either that or a "center off" switch (which is really just another form of break before make). 

And yes, I think we've thoroughly debunked the "must have DCC friendly powered frogs" myth. Never mind what I've done in the past: my son's layout is working just fine with an MRC Prodigy Express2 DCC system and 14 Atlas TrueTrack turnouts with plastic frogs.


----------



## CTValleyRR

Deleted in it's entirety. The post I quoted, and any like it, has no place on this forum.

Now perhaps we can have an intelligent give and take which will actually be helpful to beginners.


----------



## time warp

Anyway, Point being that any individual should be able to to succesfully set up and operate with DCC without a lot of unnecessary expense or modification. There are always better methods or improvements that can be made, not to mention expanding controls for lighting and other effects.


----------



## Lemonhawk

While its a matter of only having 1 switch that converts between DC and DCC, I think the possibility of doing damage to DC only engines would make me think twice about installing such a switch. That DC only engine might hum loud enough to warn you or it might just set there and burn out the motor, only smoking when its too late to save it. Convert to DCC and don't look back.


----------



## time warp

If someone is going to operate with DCC, I agree that you're going to need to commit. There's no arguing that a can type Motor is going to respond much better to DCC control, so converting older equipment may be a crap shoot. Might be better just to add a DC loop for older engines.
What's the general consensus on the buss wiring?


----------



## Lemonhawk

Certainly safer to have a DC only loop that has no physical connection to the DCC part. One could still get confused but the chances are less. What do you mean about bus wiring? Loconet bus or rail power bus? If your converting a DC layout, that's virtually your rail power bus.


----------



## time warp

Rail power buss. I know it's been a back and forth issue for years, even in DC. Yes the rails are in fact a power buss, but I've heard differing opinions on the subject


----------



## Mark R.

time warp said:


> Rail power buss. I know it's been a back and forth issue for years, even in DC. Yes the rails are in fact a power buss, but I've heard differing opinions on the subject


The rails themselves should not be considered a bus - for two reasons ....

First is the fact they are not a solid continuous run. Rail joiners (unless soldered) are purely a mechanical connection and should not be relied upon for indefinite electrical contact. Turnouts and other types of trackwork can also interrupt contact in the run.

Second is the fact nickel silver rail isn't as good of a conductor as copper wire - running distance referenced.

A run of 14 gauge wire under your layout as a bus will ensure good signal and voltage along the run. Drop feeds from solid track sections to the buss will ensure the track gets the best connectivity. All my track is soldered to optimize electrical flow in the rails. Whether it's two feet or twenty feet, a soldered length of rail will receive a pair of drop feeds. I never rely on turnouts to flow through, so drop feeds are installed on all three legs of the turnout.

Basically, I install drop feeds to every SECTION of track between two turnouts and sidings.

Mark.


----------



## time warp

Are you using twisted pair?


----------



## Mark R.

time warp said:


> Are you using twisted pair?


Nope. For the most part, they are running parallel about three inches apart. That being side, there are some places due to space restrictions they are running right together (broken rule number 1)

I also looped my bus around the room and tied it right back in where it came from (broken rule number 2).

And guess what ? After more than twelve years I've never had any problems. I installed it all this way back before there were "rules" and before I knew any different. Never had any problems, so I've never gone back and changed it.

All these "rules" are legitimate as there is the potential for things to happen if you don't, but I don't honestly think it is all as fussy as we are lead to believe ....

Maybe mine works as flawlessly as it does because at the time, I didn't know it shouldn't. 

Mark.


----------



## time warp

I believe a person can over think things, but experience is the best teacher.
General rule of thumb: if it's working correctly, it's right.


----------



## Lemonhawk

The track bus (and it is a bus) can loop around and get connected to its self, although there is no reason to do that. It would be best if cut at the point farthest from the command system. The loconet bus is not something I would loop around and connect to its self, my guess is that would cause some spurious problems.


----------



## CTValleyRR

time warp said:


> I believe a person can over think things, but experience is the best teacher.
> General rule of thumb: if it's working correctly, it's right.


Which, I think, shows the value of this thread. We want to demystify DCC for beginners, and especially show them that installing DCC isn't rocket science, and things don't have to be perfectly according to one set of specs. This is illustrated by the garbage that ED-RRR / Capacitor posted here, which has fortunately disappeared. I keep hearing "No brass", "use live frogs", "put feeders every 3 nanometers" (ok, slight exaggeration there), but I've been violating those "rules" for 15+ years on 3 different layouts, and I have yet to experience the disaster that everyone keeps warning me about. The possibility of it being blind, dumb luck is zero.

Perhaps inventing rules where there really aren't any is just the human brain's way of making order out of chaos; providing a path to navigate the wealth of information (some of it conflicting) available in the Information Age.


----------



## time warp

I'd rather learn it from "doers" than talk about it with theorists, CTV. There is relevance to the use of bussed feeders, originally to overcome rail resistance on long runs, but also continuity problems through rail joiners. You are correct however in saying they aren't absolutely necessary. A good idea though
I've got to plead ignorance on the Loco net bussing.


----------



## CTValleyRR

Well, you're agreeing with me. What I've DONE (am doing) disagrees somewhat with the accepted theory, and still works fine. Much of the theory is far too conservative. And I'm not talking about relying on rail joiners to carry current, but on how often to add feeders. I solder most of my joints.


----------



## mopac

My opinion. If it wasn't for rail joiners one set of feeders would do it. The track rails are large enough that you would not have resistance loss. I soldered my joints on first layout.
I don't think I will on my next layout. I filled the track gaps with solder and sanded
it smooth. Worked great and no power loss. But I lost my clickety clack from the
metal wheels. And its not easy to make track changes. I do not want to rely on rail
joiners to carry current so I will be putting feeders to 99% of the track pieces.
Daunting task for sure, but it will be bullet proof. I don't mind the task.


----------



## time warp

I would favor feeders (buss) over soldering rail joints myself (copper wire is a better conductor), but others are doing fine either way. I too like the clickety clack, but you could still file or notch your rails here and there if they're soldered, that would add the sound.


----------



## CTValleyRR

Just to be clear, I make the solder joint to the joiner, not to the rails themselves. Since unless I get sloppy, most of the solder is on the side of the rail, not the top, I still get the clickety clack. My typical run between feeders is about 8 feet.


----------



## time warp

With all the back and forth, the consensus obviously is that feeders, (buss) is the BETTER way to go.
So now the next question:
Say we've added a reverse loop into our railroad. DC control dictates that the reversing track must be insulated on both rails, at both ends of the section so the train can progress through the reverse loop while the mainline polarity is reversed. Then allowing the train to continue in its now reversed path.
What I gather from discussions regarding DCC reverse loops is that the insulated section is still required but a switching unit can be added, which affects the control signal through the detection of the momentary short circuits as the locomotive crosses the gap.
I confess that I'm not clear on what exactly transpires here.


----------



## gregc

as you said, the reverse section must be fully isolated (2 gaps at each end).

an auto-reverser is connected to both mainline and the reverse section. It has the capability to reverse the polarity of the track connections to the reverse section and the ability to detect an excessive current.

when it detects an excessive current, it can disconnect power to the reverse section, giving it time (5ms) to reverse the polarity of the track connections using either a mechanical relay or mosfet switches and then restores power.

there are problems if the train is longer than the reverse section

an auto-reverser may also be needed at a crossing.


----------



## time warp

Do you mean but there are problems if the train is longer than the reversing section or if the locomotive is longer than the reversing section?


----------



## gregc

when there are metal wheels spanning the gaps at both ends of the reversing section


----------



## DonR

The DCC reverse loop controller reacts when the
loco wheels short across the entrance insulated joiners. It
reverses phase (Polarity) in the isolated section. 
When the loco wheels
span the exit insulated joiners there is another
short that causes the controller to again reverse
phase of the isolated section. (the main never
reverses). If the loco is over the exit joiners
and a lighted car or metal wheels span the entrance
joiners at the same time there is a short
circuit. 

You can avoid the metal wheels short by either using
a small sliver of styrene over the insulated joiners
which would lift the car wheels so they cannot span
the joiners, or you can use a tiny dab of clear
finger nail polish which would do the same. The
isolated section should be long enough to fit your
longest lighted passenger train to avoid a short
caused by the cars.

Note: The input to the reverse loop controller is
from your main DCC buss. The output goes to the
isolated section. It is totally automatic and never
needs attention once set up. It is usually under
the table near the isolated section it powers.

Don


----------



## wvgca

When the loco's pickup wheels touch both the main track, and the reversing section, the auto reversing module will see a current surge if the sections are not in phase, and switch phase.. and all is good ..
However, a metal wheel on a piece of rolling stock will do the same, as DonR and gregc have indicated .. a styrene insert bump will work, or finger nail polish, as will creating a small dead section, the loco will not be affected by a half inch dead section ..no different than going through a dead frog or insulfrog situation .. 
the only time a 'dead' section needs to be longer is where you have lights or other power pickup on rolling stock, as in most cases both wheel sets on a truck are used for the power pickup, and the dead area needs to be just a bit longer than the truck wheel base .. if you don't use power pickup, or metal wheel sets, this wouldn't matter


----------



## time warp

So guys, it's not so much a reverser as it is correcting phase error? Excellent discussion.


----------



## time warp

wvgca said:


> When the loco's pickup wheels touch both the main track, and the reversing section, the auto reversing module will see a current surge if the sections are not in phase, and switch phase.. and all is good ..
> However, a metal wheel on a piece of rolling stock will do the same, as DonR and gregc have indicated .. a styrene insert bump will work, or finger nail polish, as will creating a small dead section, the loco will not be affected by a half inch dead section ..no different than going through a dead frog or insulfrog situation ..
> the only time a 'dead' section needs to be longer is where you have lights or other power pickup on rolling stock, as in most cases both wheel sets on a truck are used for the power pickup, and the dead area needs to be just a bit longer than the truck wheel base .. if you don't use power pickup, or metal wheel sets, this wouldn't matter


 Those short ATLAS filler sections would be pretty handy for dead sections, at least in HO. Maybe they make them for N as well.
Gonna need a lot more than that for some steamers.


----------



## gunrunnerjohn

I removed the off-topic posts, all better now.


----------



## Fire21

DonR said:


> You can avoid the metal wheels short by either using
> a small sliver of styrene over the insulated joiners
> which would lift the car wheels so they cannot span
> the joiners, or you can use a tiny dab of clear
> finger nail polish which would do the same. The
> isolated section should be long enough to fit your
> longest lighted passenger train to avoid a short
> caused by the cars.
> 
> Don


I don't understand...if the styrene or nail polish keeps the metal car wheels from shorting, why does it allow the loco to "short" and activate the reverser?


----------



## gregc

metal trucks used for electrical pickup provide a conductive path between wheels. A short will occur when one wheel is on either side of the gap. Same is true for locomotives with wheels connected through a metal chassis.


----------



## wvgca

Fire21 said:


> I don't understand...if the styrene or nail polish keeps the metal car wheels from shorting, why does it allow the loco to "short" and activate the reverser?


As gregc noted .. depends on the length of the electrically connected section of the loco or rolling stock , a normal diesel is maybe four to six inches in HO, a big steamer can be double that, and will reliably trip the auto reverse module...
A metal wheel has only maybe 1 sixteenth of an inch conductive length, and a lighted passenger car can have maybe a inch and a half if both wheel sets on a single truck are power pickup wiper equipped ..


----------



## time warp

So is it the wheel shorting across the gap, or the wheels sharing common contacts, or wheel base that's the issue?
I thought the problem would be the surface of the wheel tread potentially bridging across the rail gap , shorting the reversing(transition?) section to the main trackwork? Maybe a compound problem aggravated by multiple sets of wheels in the circuit, like lighted rolling stock or pusher engines?


----------



## Mark R.

The better quality reversing modules like the Digi-trax AR1 have sensitivity adjustments on them. You can adjust them so a single wheel set won't trip the module, but a fully powered unit like an engine or lighted car will trip it.

Mark.


----------



## gregc

time warp said:


> So is it the wheel shorting across the gap, or the wheels sharing common contacts, or wheel base that's the issue?


anything resulting in a low resistance (metal) conductive path between the rails across a gap can result in a short if the rails are of opposite polarity.

this can be a single wheel touching both rails momentarily as is straddles the gap or can be through two wheels having metal contact with a metal truck or chassis.


not sure i understand mark's comment.

i'm told by one manufacturer that when it detects a short, it disconnects power, reverses the polarity and reapplies power. If a short is immediately detected, it acts like a circuit breaker and disconnects power for a longer period of time.

I've wondered if an AR that detects a short after reversing power couldn't try restoring polarity and checking one more time before acting like a circuit breaker. 

I think this would be helpful if cars with insulated wheels are causing shorts when a train is longer than the reverse section. Such an AR would tolerate short-term (msecs) shorts.


----------



## wvgca

I have probably one of the cheapest Auto Reverse Modules currently sold, the MRC AD520, it's non adjustable for current trip level, and is relay based so it's slow to switch compared to others .. 
I only have one reversing section, a Wye, and it works okay ... Initially I did see some flickering on the lit power switches as metal wheels ran over the joint that was at a different phase, but it didn't trip ... 
Inserting a small piece of styrene, maybe 1/16 inch or so, on all four insulated joint gaps took care of the flickering, I currently do not have any lit rolling stock, or and power pickup other than loco's


----------



## Lemonhawk

Here's an example of shorting across a truck that powers lighting in a passenger car. The part in focus you can see has wipers on both wheel flanges essentially shorting both the leading and trailing wheels, thus even if the short caused by the wheel crossing the gap does not trigger the reverser, the short cause by the leading wheel being on the other side of the gap from the trailing wheel will cause a long short that the reverser will respond to. The wheels out of focus on the other side also will cause the reverser to act (assuming the phase at the gap is not in-phase.)


----------



## time warp

This is interesting. A little confusing also, but again, experience is the best teacher.
I'm curious as to this "polarity" thing. Given that we have AC applied, I still tend to think it's a phasing issue as Don mentioned before. The AC waveform is carrying the control data bits, so if the phasing is correct so then should be the data as well.
It would be very interesting to see this on a dual trace scope. Maybe I'm thinking wrong here.


----------



## DonR

TW

Yer right. AC has phasing, not polarity. The AC actually
stands for alternating current, alternating the 'positive'
on red wire while black wire has negative, and reverse,
60 times a second, But never the
less, you can't allow it to be short circuited.

Think of it this way. If you have a pair of wires, red and
black. The red is plugged into the 'high' side of a wall outlet.
The black is to the 'ground' side. If you also had another
pair plugged into another outlet with the Black on the high
side and red on the ground side they would be out of phase
to each other. If you touched the two reds you would get
a very bright spark. However, if you reversed one plug
they would be back in phase and you could touch the red
wires without a spark. That is what the reverse loop controller
does. It has nothing to do with the digital information carried
by the track current.

The whole 'wheel' short thing is very simple. You
have a gap or insulated joiner separating the main
from the isolated section. After the loco has entered
that section the reverse loop controller puts it in phase to the main but when the
loco spans the EXIT gap or insulated joiners the
isolated section phase is again reversed. Thus A metal
wheel spanning the ENTRY gap or insulated joiner 
causes a short circuit. That can be avoided by the
tiny dab of finger nail polish or a splinter of styrene
to prevent the metal wheels from touching isolated
rails and main rails at the same instant.

Don


----------



## gregc

time warp said:


> It would be very interesting to see this on a dual trace scope. Maybe I'm thinking wrong here.


where would your ground be ...

we all know if you put an ac voltmeter across the rails it will indicate around 14V. And of course, it you put both probes on the same rail it will indicate zero. Because it indicates the difference in voltage.

if you put the probes on the rails on opposite sides of a reversing section gap, you would measure either ~14V or 0 depending on whether the track voltage in the reverse section has been reversed or not. Again, the meter indicates the difference in voltage and if a metal wheel bridging the gap sees a difference, there is a short


... assuming the ground in the negative terminal of the (nominal 14+V) DC power supply to the command station, each channel of the scope would show a pulsing positive voltage of ~14V.

if you used a single channel and ground to a rail you would see a pulsing signal + and - 14V, 28V pk to pk, because the rail being used as the ground reference is changing voltage relative to the ground of the power supply ... but there is only ever a 14V difference between the rails



have you ever seen a video of the guys working on the high voltage lines that carry power across the country? The ones i've seen show a guy in a helicopter. First he drops a metal conductor from the frame of the helicopter to the cable that is at 10s thousands of volts. This brings the helicopter to the same voltage potential as the cable. Then the guy climbs onto the cable and does maintenance. He of course is at the same potential as the cable - alternating 10s 000 V.

there's no problem (excessive current flow) because everything (cable, helicopter, guy) are at the same voltage.

it's the difference that causes current flow


----------



## time warp

I'm with you on the ground reference and potential. I was curious about the phase mismatch.
A moot point really.
Like I said, maybe I'm thinking wrong.

If your using lighted pass cars or caboose, is it still a good idea to have a short dead section, say 1 1/2 inch, or not?


----------



## gregc

time warp said:


> I was curious about the phase mismatch.


i think it's fair to describe the potential mismatch between the rails across the gaps of a reversing section as a polarity mismatch -- the wires are crossed. The same would happen if you wired feeders to your track and mis-wired the feeders which would probably cause a short.

phase mismatch is not so simple. The figure below is of an h-bridge used for controlling a motor with a pulse width modulated voltage in both directions. 

Only 1 transistor (mosfet) is needed if you only drove the motor in one direction. the PWM signal controls the transistor and the other motor lead is grounded. You need four to control it in both directions because you need to reverse polarity. 

Two of the 4 transistors are used in one direction and the other 2 in the opposite direction. Regardless of direction, one of the 2 transistor can be held on and the other transistor is controlled by the PWM signal.










i assume the same type of circuit is used to create a DCC voltage across the track. In this case however, two transistor are turned on and then the other two paired on the diagnals.

but what if you only switched one transistor at a time. Assume top left and bottom right transistor are on. then simultaneously turn off the bottom right and turn on the top right and an instant later simultaneously turned off the top left and turned on the bottom left.

during that instant when both top transistor are both on, the motor would see the same voltage. This would be an example of the voltages on each motor terminal changing out of phase.




another example is that you normally get two power lines from the road. both are ~110VAC. But they are out of phase by 120 degrees. And because they are out of phase, there is a difference in voltage between both of them as well as a difference between each of them and ground. Both power lines are used in 220V AC circuits.

it would be misleading to say the reverse section is out of phase.


----------



## time warp

Thanks Greg, I get it now. Explaining the signal source answered my question. I am digging in a little here to help me and others understand better. So much of what you guys are providing goes contrary to some of the half brained remarks that were posted in the past. I appreciate it, and your patience.


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## Suncat2000

DonR is sort of right on AC, but it's a "technically" right http://www.modeltrainforum.com/images/smilies/stroke.gif. The DCC power and signal are alternating current by the fact that the voltage difference between the rails is switching between positive and negative voltage thousands of times per second. The length of time it takes to switch indicates a "1" or a "0" bit that make up the commands. Because the voltage difference (regardless of polarity) is practically constant, the decoder rectifies it to provide DC power. Timing of the switching carries the command data. Depending on the decoder, lighting effects make be fully-rectified (both polarities are used to provide power) or half-rectified (polarity only in one direction is used). The decoder powers the motor from fully-rectified power, but pulses it to control the speed and direction of the motor; in other words, power to the motor is controlled completely by the decoder, which is why the motor and track must be insulated from each other.

What is traditionally thought of as AC, like the 60-cycle electricity from your house outlets, is a smoothly changing voltage from positive to negative in the form of a sine wave - the length from a point where the signal crosses a certain voltage until it crosses it again is term the phase. The DCC "AC" is a square wave. Square waves cause more heat in a motor because of resistance to abruptly changing the current, which is why it is possible to burn out a DC motor by leaving it on a DCC-powered track; but, some DCC systems can modify the switching so as to control the average voltage on the track and safely operate a single DC locomotive.

An automatic reverser detects the short circuit caused by a metal wheel (or entire train) crossing from the main line to the isolated section (assuming the polarity is different when it enters). It then reverses the polarity of the section so the signals on both the main and isolated section are the same, until the train leaves the isolated section and returns to the main, at which point it reverses again to match polarity. In this regard, DCC and DC are the same: polarity between the rails of both sections must be the same for the train to move forward and not short out the system. A reversing section must be isolated and its polarity matched to the main or it causes a short. The nail polish or styrene makes it so the short that is detected is not from a single wheel.


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## Lemonhawk

The normal house is supplied by a center tap transformer so the 110 ac is 180 out of phase with the other 110. 3 phase power is at 120 deg. the reverse in DCC makes sure that things are in phase by detecting the short and changing the phase to remove the short.


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## time warp

Sorry this got a little complicated, a perfect example of something that may be harder to explain than demonstrate.

The devil looks to be in any bridged gaps, like some crossings as was mentioned before.


----------



## Suncat2000

*Re: automatic reversing*

Sorry, time warp. Let me rephrase the reversing loop. The primary fact about the reversing loop is that the rails at one end are physically connected to the opposite rails at the other. If nothing were done, this causes the polarities of voltage in each section to be opposite, essentially a short circuit. By electrically isolating the loop (or wye or whatever reversing structure you have) with gaps, the polarity of the loop can be changed to match the main at whatever end the train is at.

An automatic reverser (AR) detects the polarity difference as a momentary short when the train first crosses from the main into the loop. The same thing happens when it crosses out of the loop back to the main. The AR reverses the polarity of the loop so it matches the main and removes the short. You could do the same thing with a manual switch (same as DC), but with the AR, you never need to worry about forgetting to flip the switch.

This is why the loop should be longer than your longest train: so both ends of the train are not triggering the reversing while the train is bridging both gaps. A smart AR would act as a circuit breaker in that case and shut down all power until all shorts are removed.


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## time warp

I appreciate your input, Suncat, but you should really read through from the first post. The question at hand was not the mechanics of reverse loop isolation but the actual behavior of a given DCC Reverser.

This is not a scale specific discussion either.
That being said, are there any particular difficulties that any of you have experienced with larger scale equipment? How about 3 rail?


----------



## wvgca

All two rail track systems will give the same problem in a reverse loop wiring situation, doesn't matter if they run on DCC, DC, or AC .. and no different rules for size or scale of any system using the track to feed power to the locomotives. In three rail systems, the center rail is commonly referred to as the 'power' rail, and will always be the center of the three rails, no reverse loop problems ..
In DC and AC two rail types, a DPDT switch is commonly used to control the isolated portion of a reverse loop. and can also be used for DCC operation ...however, the total wattage available in a DCC system is larger than normal operating wattage in an equivalent size DC or AC system, and an automatic reverser [either relay or transistor switching styles], is much faster to react , and is also more convenient..


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## Suncat2000

That was unnecessarily harsh. I read the entire thread. Sorry I missed your question about a specific brand of reverser. I was merely trying to simplify some previous remarks that would confuse someone unfamiliar with DCC and stick to the spirit of the thread.


time warp said:


> I appreciate your input, Suncat, but you should really read through from the first post. The question at hand was not the mechanics of reverse loop isolation but the actual behavior of a given DCC Reverser.
> 
> This is not a scale specific discussion either.
> That being said, are there any particular difficulties that any of you have experienced with larger scale equipment? How about 3 rail?



Sent from my SM-G930V using Tapatalk


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## time warp

Sorry, no harshness intended. Weren't talking about a brand of reverser, though.
Rather the behavior, or specific operation of a reverser.
I don't intend to specifically condemn or recommend any particular brands of equipment here, rather to outline what a beginner in DCC might expect in setting up and using their own system. Completely based on forum members experiences.


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## time warp

*Motor Isolation*

We know that the locomotive motor must be electrically isolated from the rails with DCC. Newer locomotives in any scale shouldn't be a problem in this respect as most are DCC ready or DCC equipped.
Older locomotives obviously can be a problem, with many having the motor attached to a metal frame which is part of the electrical circuit, or any number of brands over the years using metal cased self contained power trucks, which use the truck assembly as part of the circuit.
Looking at N scale diesels for example: the common use of split frame construction could be insurmountable in some cases. Likewise the old HO Tyco MU2 power trucks. 
Some older equipment may not be able to be converted to DCC because of these issues.


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## wvgca

In my personal experience, I have found no problems with a DCC decoder installation where the motor housing was not isolated from the frame, provided that both motor brushes are isolated from the motor housing ...Even the older three pole Mantua motors that have one brush isolated, and the other directly connected to the motor housing, and then the frame, are easily converted simply by isolating the second brush with a piece of spaghetti tube or shrink tube ..
Admittedly, some take more work to convert, a good [or bad] example is the older Bachmann 44 ton with two motors ..
To me the only reason to silicone mount a motor is to possibly reduce vibration and / or transmitted noise from metal to metal contact


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## time warp

Makes perfect sense to me, There again is an assumtion I'd made, from years of hearing that the entire motor had to be isolated.


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## gregc

time warp said:


> Older locomotives obviously can be a problem, with many having the motor attached to a metal frame which is part of the electrical circuit, ...
> 
> Some older equipment may not be able to be converted to DCC because of these issues.


it seems pretty conventional that a metal motor case will be mounted to a metal frame with a metal screw. As already said, the issue is the brushes.

in several conversions, there was a wire soldered to motor frame and attached to a brush. It was trivia to unsolder and remove the wire.

in another case, I put cardboard between the motor and frame and used a plastic screw.

even if you used silicone, i think you need to make sure there is no metal to metal contact.


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## time warp

My remarks were taking into account plastic framed locomotives, as well as isolated motor mount situations like Athearn blue box. I have seen some cast metal frames where the motor had no leads at all, there were tabs on the brush assembles that contacted each side of the two insulated frame parts. 
Die cast metal steamers, and some diesels like the old Pennline midget come to mind, the entire locomotive was part of the circuit because of the metal body.
Just saying, and as Warren mentioned, some could be tough to convert.


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## DonR

Time Warp

One of my Bachmann Spectrum GP 40 locos used
that split frame electrical system. As originally
produced there was not one wire in the loco. 

It was, however, easy to isolate the motor and
the lights, and
attach the decoder wires. The existing truck power pickup
worked well so I didn't have to rewire that. The input
to the decoder is a styrene piece that wedges the
input wires against the 2 frame sides. Works perfect.

Don


----------



## gregc

time warp said:


> Die cast metal steamers, and some diesels like the old Pennline midget come to mind, the entire locomotive was part of the circuit because of the metal body.


my experience is solely with metal chassis and metal open frame motors. What do you mean by entire locomotive (i.e. beyond a metal chassis)?

i'm curious to know of an example where the only recourse is to replace the motor?

The image below is presumably of the Penn Line midget and a comment in another forum post suggests it wouldn't be hard to convert to DCC and is consistent with my experience with similar motors.


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## time warp

Gregc, I don't think I was implying that the motor would have to be replaced, I can't see where that would be required. 
The example I gave of the Pennline is correct, two insulated wheels wired to one side of the motor( a Pittman) and the other side of the motor wired to the frame. Since the frame is now part of the circuit through the uninsulated wheels to the opposite rail, and the metal body is screwed to the frame, the body is now part of the circuit. In series with the motor but parallel with frame.
Moot point though if you isolate the brushes via the connections. Might be worth noting however that any locomotive having this arrangement, if modified for DCC, is going to have the metal body casting energized with track power. Shouldn't the inside of the body casting be taped or insulated to prevent the possibility of unwanted short circuits to the decoder?
Bowser locos, Brass, Arbour, ETC.
You would be the go to guy as far as the metal frame conversions because you have the experience.


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## DonR

Some of the motors in early HO locos drew more
current than available decoders could handle. I had
one such, an old Yougoslavian SW 1. It looked like
a fireworks display as it moved. The decoder popped
in a puff of smoke and that's all she wrote. I replaced
it with a very efficient can motor.

One should always do a stall test on old locos before
attaching a decoder. Thankfully, tho, many decoders
now can handle 1.5 amps.

Don


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## gregc

i'm familiar with the motor shown in the figure. It is pretty common. The design of the motor does not electrically tie either brush to the frame of the motor. Extra connection are required and depend on the locomotive. I believe these can easily be removed.

i think it's misleading to suggest any motor with a metal frame making contact with the chassis will be difficult. I described one that is. I think most aren't.

another thing about this particular motor, again a common one, is that the magnet can easily be replaced with neodymium magnets which reduce the motor current and increase its strength.


----------



## time warp

I agree with you 100% Greg, I believe I noted several times that some of these MAY be difficult.


----------



## tr1

*Choosing A DCC operating system?*

With DCC being out for awhile now.One question remains.....
Which system is superior over the other?NCE or Gigitrax?
Thank you in advance for your opinions provided here!
My regards,Tr1
( I may be leaning toward NCE, I just do not know for sure):dunno:
(Which one is more cost effective??) For instance.


----------



## fcwilt

tr1 said:


> With DCC being out for awhile now.One question remains.....
> Which system is superior over the other?NCE or Gigitrax?
> Thank you in advance for your opinions provided here!
> My regards,Tr1
> ( I may be leaning toward NCE, I just do not know for sure):dunno:
> (Which one is more cost effective??) For instance.


In my opinion? Neither one. 

Not that they are bad, just that there are systems out there with more features.

BUT these features may not be of interest to folks just looking to run trains.

I have a NCE PH-Pro (5 amp) and a Digitrax DCS100 and a Digitrax DCS200 which I used to use at one time but no longer.

Currently I use a Roco Z21 

I am also testing a Digikeijs DR5000.

Frederick


----------



## Fire21

Just do some research on DCC systems and decide for yourself. We have a lot of people here who will tell you why they prefer one or the other, but it all comes down to what you want, can afford, plan to do with your layout in the future, etc. 

This is a decision you yourself have to make. You can accept info from others, but don't rely on them to decide for you.


----------



## Cycleops

As tr1 rightly points out DCC has been out for a long time with Lenz developing it but no more, leaving Digitrax MRC and NCE the front runners but they really haven't done as much as they could with it. Digitrax have just come out with a new starter system i see but it still has the same tired old remote with those dreadful 'pegs'. I've had a NCE system and excellent it is too but I'm now running a Roco Z21 like Frederick. Its a world away from the others but because it uses more up to date unfamiliar ( in model railway terms) technology potential users may shy away from it. That's a shame because its a very capable system and very easy to operate and understand.


----------



## fcwilt

Cycleops said:


> but it still has the same tired old remote with those dreadful 'pegs'.


That is a perfect way to describe them.

I like the NCE throttle but wish the NCE would update their tech some.

I run my layout with TrainController and the NCE protocol used for computer connections is missing a important bit that allows TC to know what exactly what the NCE system is doing.

With the Z21 (and others) I can pick up a handheld and start running a train and TC knows what I have done.

With NCE you have to manually inform TC that you are going to be using a handheld.

And it would be such a simple thing to fix.


Happy with the Z21. 

Waiting on the new Roco Wifi multiMAUS which is supposed to be out next month.

Just enough buttons on the multiMAUS to keep me happy.


The DR5000 is an amazing unit - just about every control bus you would ever need.

Frederick


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## CTValleyRR

tr1 said:


> With DCC being out for awhile now.One question remains.....
> Which system is superior over the other?NCE or Gigitrax?
> Thank you in advance for your opinions provided here!
> My regards,Tr1
> ( I may be leaning toward NCE, I just do not know for sure):dunno:
> (Which one is more cost effective??) For instance.


Others may have a different opinion, but I would say the differences between the big boys (Digitrax, NCE, and I'll throw in MRC for good measure) is largely a matter of personal preference. It's especially your opinion of the ergonomic, interface, and user-friendliness, all of which are very subjective.


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## CTValleyRR

And if you remember how this thread got started in the first place, isn't it interesting how these useful threads keep popping back up organically, because they ARE useful. 

No one has to make them sticky to avoid consigning them to history, as another (now-departed) user insisted that someone do with his....


----------



## deedub35

If you are buying a new truck will it be Chevy, Ford, Dodge, or an import? They are all capable and will do what needs to be done. 

Same thing with a DCC setup. Everyone here will have an opinion in terms of ergonomics, manuals, price, availability, ease of use, etc.

Best thing to do is test drive as many as you can and decide for yourself.


----------



## CTValleyRR

deedub35 said:


> If you are buying a new truck will it be Chevy, Ford, Dodge, or an import? They are all capable and will do what needs to be done.
> 
> Same thing with a DCC setup. Everyone here will have an opinion in terms of ergonomics, manuals, price, availability, ease of use, etc.
> 
> Best thing to do is test drive as many as you can and decide for yourself.


Funny. I almost said exactly the same thing.


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## ExONRcarman

I'm late, but i got here! love this thread! thanks guys.
I have a basic understanding of the Digitrax and NCE "power cabs" but what i cant seem to find info on is whether components of these two are interchangeable. For instance i found someone willing to sell me their Nce power cab and a digitrax PR3. ( i have no idea what the pr3 does) Are they compatible? i like the digitax controllers but the nce seems more suited to me, can i swap them?


----------



## fcwilt

ExONRcarman said:


> I'm late, but i got here! love this thread! thanks guys.
> I have a basic understanding of the Digitrax and NCE "power cabs" but what i cant seem to find info on is whether components of these two are interchangeable. For instance i found someone willing to sell me their Nce power cab and a digitrax PR3. ( i have no idea what the pr3 does) Are they compatible? i like the digitax controllers but the nce seems more suited to me, can i swap them?


The PR3 is used (among other things) to connect a computer to the Digitrax DCS100/DCS200 command stations.

The newest command station from Digitrax, the DCS240, has the functionality of the PR3 built-in.

You DO NOT use a PR3 with a NCE.


What NCE unit are you looking at? The older NCE units had a built-in serial port for connecting to a computer.


When it comes to running trains the both will do very much the same thing.

There may be a few advanced features that one may have and not the other but I don't know them well enough to answer that question off the top of my head.

Frederick

P.S. I have both but no longer use them. I now use a Roco Z1 (black)


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## ExONRcarman

fcwilt said:


> P.S. I have both but no longer use them. I now use a Roco Z1 (black)


thanks frederick, you just saved me some money. Since you have had both in the past wich did you prefer?

And why did you change to the roco unit?


----------



## CTValleyRR

ExONRcarman said:


> I'm late, but i got here! love this thread! thanks guys.
> I have a basic understanding of the Digitrax and NCE "power cabs" but what i cant seem to find info on is whether components of these two are interchangeable. For instance i found someone willing to sell me their Nce power cab and a digitrax PR3. ( i have no idea what the pr3 does) Are they compatible? i like the digitax controllers but the nce seems more suited to me, can i swap them?


A good guideline is that everything between the wall socket and the rails must be from the same manufacturer (that is, all Digitrax, NCE, MRC, etc.). Not hard and fast, but a good starting assumption. Stationary decoders and reverse loop controllers are the exceptions to this rule.


----------



## fcwilt

ExONRcarman said:


> thanks frederick, you just saved me some money. Since you have had both in the past wich did you prefer?
> 
> And why did you change to the roco unit?


My layout is computer controlled

I preferred the NCE handhelds BUT the NCE command station was missing a feature that was desirable for the best computer controlled experience.

The Digitrax unit has this feature BUT I really don't like their handhelds.

The Roco Z1 is a much more "state of the art" design then either, had all the required features for computer control, including a built-in network interface, was LocoNet compatible and gave me a choice of handhelds.

While nobody I know supports the NCE handheld but NCE the Z1 can use a Digitrax handheld and several others.

I went with the Roco handheld because it was simple, comfortable, did what I wanted and came in both wired and WiFi versions.

Plus the Z1 can use a tablet/smartphone app if your prefer a colorful touch screen experience.

Roco has certain locos with a built-in camera which can be viewed right on the tablet/smartphone which is kind of fun to show foiks.

European products are different but most are more advanced than the US offerings.

Frederick


----------



## JerryH

Since I went to TCG, my hand helds have sat in a box ever since. I like the point and click with TCG. I should go to W10 with a touch screen:sly:


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## ExONRcarman

TCG? im not up to speed with all the terminology yet. sorry


----------



## JerryH

TCG = Train Controller "GOLD" is computer software used on a PC to automate a layout.
see post 420
http://www.modeltrainforum.com/showthread.php?t=14852&page=42


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## Cycleops

When I buy something be it a food blender or a model rail control system I expect it to be well designed, have user options and easy to use and operate in a way you like. That's why I and I think Frederick bought the Z21.

The Digitrax stuff is technically excellent but the user interface is lamentably lacking and looks like it was designed in the last century. All those odd pegs with little to differentiate them and the muddled display. And why use radio for remote? There are better options now. And if you do choose their radio throttle you have to take the battery and turn it around to turn it off, couldn't they have installed a switch? You can straight away see from the design of the handsets from NCE, MRC and others that a lot more thought has gone into the design and user interface. If you don't like using a smartphone to control your Z21 you can use a multitude of other manufactures throttles including Digitrax.

Model railroading is all about having fun and imho for my money Roco with all its features gives the most bangs per buck at present.


----------



## CTValleyRR

Cycleops said:


> When I buy something be it a food blender or a model rail control system I expect it to be well designed, have user options and easy to use and operate in a way you like. That's why I and I think Frederick bought the Z21.
> 
> The Digitrax stuff is technically excellent but the user interface is lamentably lacking and looks like it was designed in the last century. All those odd pegs with little to differentiate them and the muddled display. And why use radio for remote? There are better options now. And if you do choose their radio throttle you have to take the battery and turn it around to turn it off, couldn't they have installed a switch? You can straight away see from the design of the handsets from NCE, MRC and others that a lot more thought has gone into the design and user interface. If you don't like using a smartphone to control your Z21 you can use a multitude of other manufactures throttles including Digitrax.
> 
> Model railroading is all about having fun and imho for my money Roco with all its features gives the most bangs per buck at present.


You've hit on exactly the things that I found wrong with Digitrax. Not that it isn't right for others, but it certainly wasn't for me. In my book, it completely fails the "human engineering" test -- that is, how the user interacts with the product.

I went with MRC and have been extremely happy.


----------



## J.Albert1949

Adding to an older thread...
Very general questions on DCC if anyone cares to answer.

For HO scale, is there an "optimum voltage setting" for track power?
If so, what would it be?
15vac?
Higher?
Lower?
Is there an acceptable range?
At what setting would voltage become "too high"?

Considering a Roco z21 (white)...


----------



## Cycleops

Most systems put 18v on the track and a few less for programming track. This is set by the command station. I have the black Z21 and it’s an excellent system. All you miss out on with the white are a couple less amps and a few less connections which probably won’t worry you. Just a breeze to program and operate. I used an iPad mini and a Huawei smartphone to operate. Loads of cool features.
The white units are split from train sets so are available at a bargain price. You won’t be disappointed J.Albert.


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## katytexasnscaler

*DCC for beginers*

So if this is for new people to DCC, I am truly at a loss....Can someone direct me to thread for DCC for morons ?


----------



## Fire21

katytexasnscaler said:


> So if this is for new people to DCC, I am truly at a loss....Can someone direct me to thread for DCC for morons ?


I understand your confusion. Part of the problem is that there is SO much info available that it begins to jumble in our minds. I suggest you google "DCC for beginners". 
That will give you a big selection of articles to read and begin to build your understanding.

Don't be discouraged. I'm still an infant in the learning process, but it does come together after a short time. DCC is way easier than DC, and the benefits of enjoyment in your layout are immense. Take your time and you'll find things falling into place. 
:smilie_daumenpos:


----------



## DonR

KatyTexas

Actually DCC is very simple for the modeller
and operator.

You have a 'Controller' (in place of a DC power pack
or transformer). It produces a constant track
modified AC current of around 14 volts. (the
lights don't dim or go out as they do with DC).
You connect 2 wires from the controller to your
track. There are no blocks, complicated switches
or rats nest of wiring. 

The 'Controller' has buttons (like a TV remote).
By pressing them you select which loco on your
layout you wish to run. You push a button for
FW or RV. There is also a 'speed' control knob.
Turning it determines the speed of your loco. As
you push the buttons the controller is sending DIGITAL 
signals to the locos through the track.

Each loco on your layout has a decoder with a distinct 'address'
which is either 2 or 4 digits. Many use the loco's
number. The decoder interprets the digital signals from
the controller and sends
DC power to the motor and lights as directed. Locos
can be purchased with decoders installed or you can
add them to existing DC locos.
Decoders cost around 20.00 or less each. Decoders
that also produce sound such as the prime mover,
horns, bells and other effects are also available at
higher cost.

You can run 3, 4 or even more locos at the same
time with your one controller. 

If you can use a TV remote you can run a DCC
train right out of the box.

Don


----------



## katytexasnscaler

Thanks for the info, I do have a grasp of the DCC system and its benefits over dc, I am 64 yrs old and can wire a dc layout front to back with out even thinking of what I am doing, however, understanding the complex amout of stuff to run a DCC layout is what throws me,
off track.....I have read and watched a lot of video's of this but still do not grasp it all, and would never want my layout computer controlled, cause I could care less if my computer has fun running trains...So a basic good DCC system starts getting cloudy when I see reversing loops, Circuit protection, boosters, and six or seven other things daisy chained together, after viewing a mans 30x50 layout and all the electronics under it, I knew it was way out of my league understanding it all.


----------



## CTValleyRR

katytexasnscaler said:


> Thanks for the info, I do have a grasp of the DCC system and its benefits over dc, I am 64 yrs old and can wire a dc layout front to back with out even thinking of what I am doing, however, understanding the complex amout of stuff to run a DCC layout is what throws me,
> off track.....I have read and watched a lot of video's of this but still do not grasp it all, and would never want my layout computer controlled, cause I could care less if my computer has fun running trains...So a basic good DCC system starts getting cloudy when I see reversing loops, Circuit protection, boosters, and six or seven other things daisy chained together, after viewing a mans 30x50 layout and all the electronics under it, I knew it was way out of my league understanding it all.


If you can wire a DC layout, then you will have no trouble with DCC. Yes, DCC allows you to get VERY complicated, but you don't have to (and I'm with you: I just don't see the attraction of having a computer control my layout). At it's simplest, DCC works like this: disconnect your DC power pack. Connect your DCC controller. Punch in the locomotive's ID number. Increase the throttle and watch the train run.

If you didn't bother with reversing loops, circuit protection, boosters, and six or seven other things daisy-chained together with DC, then you don't with DCC either.

You have to understand one fundamental concept: in DC, you make the train go by increasing the voltage applied to the track, and switch directions by changing the polarity of the rails. DCC uses a constant track voltage, and uses a small circuit board / microchip (called a decoder) in the loco to regulate the voltage and polarity sent to the motor. My son's 8x8 layout runs just fine from a DCC controller and a single pair of AWG22 feeders, with 3 places around the perimeter to plug in a throttle or two.

It gets SLIGHTLY more complicated, because DCC allows you to run multiple locomotives in the same block of track at the same time, so you do have to make sure you have enough amperage for all of them (that's where boosters come in), and you generally want to have one throttle per operating locomotive (multiple connected devices), but again, you may not need or want any of these enhancements. Reverse loops are reverse loops no matter whether you're in DC or DCC, and DCC actually makes them EASIER to handle.

Do yourself a favor and stay away from all these folks who are showing you all the amazing things you CAN do with DCC and focus on what you NEED to do, and how you do it with DCC. The 30'x50' computer controlled, fully signaled layouts of the world are not the place to learn about the basics of DCC. Larger layouts may want things like power districts and extra circuit protection in case of shorts, but you don't NEED them, especially on a small layout. I've never used either, and I'm still alive to talk about it (but in fairness, you'd want these things in a large DC layout, too).


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## CTValleyRR

Also, a brief history of this thread: it wasn't supposed to be "DCC for Dummies". Rather, we had a member here for a while who thought he know everything and posted a lot of misleading or downright incorrect information. This thread was intended to set the record straight on those topics.


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## DonR

Katytexan

Hey, at 64 you're just a kid. I'm 88.

I can sure understand how you could be confused by the posts of modellers who enjoy the exotic digital electronics. Forget all that.

As I said in my previous post...all you need is the
basic DCC controller, 2 wires to your track and at
least one DCC decoder equipped loco to run even
a very large complex layout. The devices
in your list of concerns are not used by most of us.

The one exception is one you could have run into
with your DC layout...a reverse loop; which is simply
an ability to turn a loco around so it will run the opposite
direction. The difficulty with this is that the track
and turnout connections result in a short circuit. On 
a DC layout you would need a complex switch
arrangement and wiring, but
here again, DCC makes that simple. A special device
automatically corrects the reverse loop polarity and
you need do nothing. No complex wiring either. And
again, you won't need such if your layout does not
have a capability to turn a loco around.

As one with the wiring experience of an old fashioned
DC layout you will be pleasantly surprised at the
ease of DCC installation. Two wires to the track.

I have a room size DCC layout with a single track
main that basically follows the walls. It has passing
sidings so I can run one train clockwise and another
counter clockwise on the same track. Something
impossible with DC. The difference is that DCC
lets you control the individual locos where DC controls the
track. I use the ultra simple Bachmann EZ DCC
system yet I have 10 locos on my tracks and 
often run 3 or 4 of them at the same time.

Don


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## katytexasnscaler

Don

Thank you for this information, I think I will not wory about it and probably just post any areas that may need special attention where there is a potential for short....I do plan on a reversing loop, as well....One more question is it important to stick with same manufacture
for all parts of the DCC system ?

terry


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## gregc

katytexasnscaler said:


> So a basic good DCC system starts getting cloudy when I see reversing loops, Circuit protection, boosters, and six or seven other things daisy chained together,


a DCC system is composed of

 cab/throttle used by the operator to control one or more locomotives by sending commands to a command station
 a booster the that provides power to the track with the polarity determined by the command station
command station that receives requests from one or more cabs and generates DCC commands to all the locomotives by controlling the track voltage polarity 

an NCE PowerCab is all three of these things in one unit and is more than adequate for a small layout. An NCE PowerPro has a separate command-station/booster unit and throttle. any other cab/throttles need to be from NCE

decoders are needed for each locomotive. The decoders don't have to be from the same manufacturer as the command station

if the layout has a reversing section, an auto-reverser is used rather than reversing switches. It monitors the current being drawn, and reverses the track polarity either with a relay or electronic means (power MosFets) to correct the short condition when the wheels bridge the gaps at either end of the reversing section. An auto reverser can be from any manufacturer


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## ncrc5315

CTValleyRR said:


> If you can wire a DC layout, then you will have no trouble with DCC. Yes, DCC allows you to get VERY complicated, but you don't have to (and I'm with you: I just don't see the attraction of having a computer control my layout).


I hope to be able to start my next layout, next summer. I intend to have some computer control, but more for animation. I think it would be neat to automate/simulate, the loading of a grain train, for instance. Or to have trains running by, while I'm working industries., having to duck into a siding, while the manifest freight goes by on the main.


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## CTValleyRR

ncrc5315 said:


> I hope to be able to start my next layout, next summer. I intend to have some computer control, but more for animation. I think it would be neat to automate/simulate, the loading of a grain train, for instance. Or to have trains running by, while I'm working industries., having to duck into a siding, while the manifest freight goes by on the main.


You can do this without computer control, provided you have multiple operators.

What we typically do on my layout is set a passenger train to travel slowly around the main track (just call it up, dial in speed step 6, and let it run). Since it is a passenger train, it has priority over freights, so all the freight operators ("manned" trains) have to clear the main and reline all turnouts before the passenger train arrives. Having to hit the "master stop" button to prevent a collision is admitting failure, as is having to take control of the passenger train to get it back on the proper "schedule".


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## DonR

Terry

We can all be thankful for the NMRA standards. 
The major DCC makers comply with these so you
can use a controller from Brand A, locos with decoders
from Brand B and Brand C and a reverse loop controller
from Brand D. Basically, if you like a product, and
find it affordable, buy it. It will work with whatever
system you select.

Let us know when you get your track design and we'll
help you with the 'reverse loop'. It's not complex, but
there are some 'rules' that make for smoother
operations.

Track has not been mentioned. Many of us prefer
flex track over the track on base type offered by
several makers. The reason is that flex works with
any turnout or other track accessory, while the
proprietary track is designed to be used with track
accessories made by that same manufacturer.
Atlas flex is perhaps the most popular brand. 
But, a lot of us shy away from Atlas turnouts. Some
prefer Peco or other quality makes.

Don


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## flyboy2610

katytexasnscaler said:


> Don
> 
> Thank you for this information, I think I will not wory about it and probably just post any areas that may need special attention where there is a potential for short....I do plan on a reversing loop, as well....One more question is it important to stick with same manufacture
> for all parts of the DCC system ?
> 
> terry


You can use or install a decoder from any manufacturer you choose, and any DCC system will operate them. This is due to manufacturers complying with NMRA recommended practices.
For the hardware of the system itself, I would recommend sticking with one manufacturer. By hardware I mean things such as the system controller, any additional throttles you may add, boosters, reversing units, and anything else you may someday choose to daisy-chain together. I recommend this for the simple reason that manufacturers have designed their components to work together properly. If you have problems, the manufacturer of your system components can help you out, IF all the components are of the same brand.
That's just my two cents.


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## MichaelE

I am new to DCC too. After reading around the web and watching videos about various systems NCE Powercab has to be most idiot-proof system offered today.

I have always wanted painfully slow, imperceptible starts, momentum, and realistic stopping on my railroads, but my current railroad under construction is the first to have all of that and more.

Brake squeal, compressor blow-off, brake release, turbocharger sounds along with the diesel engine, full lighting contol front and back, even station arrival announcements, coupler latching, on and on.

And that is just the capability of a DCC sound locomotive. :smilie_daumenpos:

You can also control turnouts and automate signaling using DCC, but for the turnouts I will probably be sticking to old school operation.

I know you can hook up two wires, so I know you will be able to operate a DCC railroad. It's easier than DC. You don't need to know how a computer operates to use one and tge same for DCC.


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