3 Rail DCC O vs 2 Rail DCC O

@NW posted:

Are there any feature or functionality differences between the two?  I understand there are differences in DC.

Thanks!   

Nope. I have Digitrax DCC along with DCS and Legacy. I ran the wiring through a toggle switch to select between DCC and DCS/Legacy.

Joe Shipbaugh

The original poster asked an all DCC question; are there any differences between 3-rail and 2-rail DCC?  To answer this question, someone would have to be running both types of layouts.  I'm not sure how big that "pool" is, but I hope you get a decent answer.

Chuck

I have 2 rail DCC, my firend has a 3 rail layout with DCC.   there is no difference in functionality.

@prrjim, I'm curious; is your friend only running MTH engines with PS3 electronics?  If so, there may be no "functional" differences, but "feature-wise" he has a somewhat limited (less than the entire universe) pool of locomotives to run.  If your friend is running other 3-rail (non-PS3) MTH engines, Lionel engines, Atlas engines, etc., didn't he have to modify the engine electronics and/or motor to install DCC in those engines?

Chuck

I think the OP has to be clearer with the question. As it's asked, I too, think there's no difference.

How can the engine(s) know what rails they're on? (As long as they get power and signal)

I've been wrong plenty of times. So let's see how this one unfolds.

DCC has a wide open platform supported by dozens of vendors.  Not subject to any one company's solvency, availability,  limited sound files,  price gouging, service or longevity.

The only difference is how reverse loops and wye's are handled.  3-rail doesn't require any extra wiring, where as even with DCC, 2-rail requires an auto-reverse circuit or toggle switches to flip the phase of the DCC pulses.

Rusty

I do wish that ESU had created a Lok Sound 5L that supported two motors.

Some confusion may be due to my lack of knowledge on the subject.  I (perhaps incorrectly) used the "DCC" term to cover all digital systems and "DC" to pertain to analog systems.  I'll try to rephrase:

My understanding is that with analog (DC?) three rail, the outer rails are always the same polarity and the inner rail is always opposite in polarity.  This functionality facilitated the "toy" segment (whistle, uncoupling, etc.).

Since digital systems function with two rail layouts, does the center rail still offer any functional or feature advantages over two rail?

Hope this makes sense.

To That question,  I can't think of any other than the wiring issue for reverse loops. 

With 3 rail, one side of the circuit (AC or DC) is on the center rail and one side is on the outside rails.    You only need one outside rail for a complete circuit, so many modelers use the other for signaling and detection and whatnot

A Wells. I have ESU decoders in some of my two rail O both ver 4 and 5 are good for 8 amps. should be more than enough for any two motored O scale loco.

@Rick Rubino posted:

A Wells. I have ESU decoders in some of my two rail O both ver 4 and 5 are good for 8 amps. should be more than enough for any two motored O scale loco.

Rick - I assume you have the motors hooked up in parallel.  No issues at low speeds or other spurious problems then esp. during speed changes?  (Not particularly worried about the amperage output.)  Most full bridge ICs are adamant that you only connect one motor per channel, so that's where my concern comes in.  Anthony

I've got 24 Atlas locos with LokSound Version 4's & 5's (L's & XL's) with the motors wired in parallel. They run superbly at slow speeds (speed step 6 which translates to about 3 smph).

Some will buck or hesitate at speed steps < than 6 but putting a few cars behind them solves that. Others are smooth at speed step 2 or 3. This discrepancy is more a reflection of the cheap DC can motors than the decoder.

I have wired a couple of the ones with china drives in series to slow them down a bit. ESU also has a nice feature CV54 that sets up the motor to function with the decoder. in programing on the main you set CV54 to 0 then exit program on the main and hit F1, the loco will take off at full speed for a coupe of feet then stop. after that it will run much better , it will probably fix catnap's bucking problem on starting or stopping. Rick

@Rick Rubino posted:

I have wired a couple of the ones with china drives in series to slow them down a bit. ESU also has a nice feature CV54 that sets up the motor to function with the decoder. in programing on the main you set CV54 to 0 then exit program on the main and hit F1, the loco will take off at full speed for a coupe of feet then stop. after that it will run much better , it will probably fix catnap's bucking problem on starting or stopping. Rick

Since you two aren't having any detrimental issues, that does make me feel better about installing the LokSound 5L in two motor locomotives...should that come to pass.  I did see where some had issues when using the auto feature that you mention that it would set the maximum voltage CV too low and it was necessary to manually adjust.

Anthony

@A. Wells posted:

I do wish that ESU had created a Lok Sound 5L that supported two motors.

Like a few others have posted previously, I also have Loksound decoders in numerous makes and models of two motor engines (MTH, Atlas, Williams). All perform superbly.

My recent experience with wireless DCC sytems in OGauge was quite informative. Although DCC has basic standards, each manufacturer (there are many) has added some unique features to their product. Overall, there are a lot of very useful capabilities in the DCC system. The decoders I have tested had no problem handling two motors either in parallel or series. In overall capability, DCC is equivalent to any of the current OGauge track signal based systems.

@BOB WALKER posted:

My recent experience with wireless DCC sytems in OGauge was quite informative. Although DCC has basic standards, each manufacturer (there are many) has added some unique features to their product. Overall, there are a lot of very useful capabilities in the DCC system. The decoders I have tested had no problem handling two motors either in parallel or series. In overall capability, DCC is equivalent to any of the current OGauge track signal based systems.

Do you feel like one unique feature is getting more precedence over others?  There is one in particular that comes to mind.

@NW posted:

Some confusion may be due to my lack of knowledge on the subject.  I (perhaps incorrectly) used the "DCC" term to cover all digital systems and "DC" to pertain to analog systems.  I'll try to rephrase:

My understanding is that with analog (DC?) three rail, the outer rails are always the same polarity and the inner rail is always opposite in polarity.  This functionality facilitated the "toy" segment (whistle, uncoupling, etc.).

Since digital systems function with two rail layouts, does the center rail still offer any functional or feature advantages over two rail?

Hope this makes sense.

In most 3 rail, even command (digital systems), the center rail is a different polarity than the outside rails (Outside rails are tied together electrically in most track systems.).  The center rail allows for simple powering of return loops and other complex track layouts.  I don't know about the "toy" segment you speak of.  By keeping 3 rail by going to command (Like DCC.) you still keep the ability for simple powering.  Instead of wiring a left and right rail, you are wiring center and outer rails.  The command systems don't care if you have 2 rails or 100 rails, as long as you have a total of 2 polarities.

DCC can run on either DC or AC power. Under AC the power is rectified to drive DC motors.

As long as the motor is isolated from the track power. Running DCC on 2 or 3 rails is the same. (assuming the outside rails in 3 rail are isolated from the center one)

@NW posted:

Some confusion may be due to my lack of knowledge on the subject.  I (perhaps incorrectly) used the "DCC" term to cover all digital systems and "DC" to pertain to analog systems.  I'll try to rephrase:

My understanding is that with analog (DC?) three rail, the outer rails are always the same polarity and the inner rail is always opposite in polarity.  This functionality facilitated the "toy" segment (whistle, uncoupling, etc.).

Since digital systems function with two rail layouts, does the center rail still offer any functional or feature advantages over two rail?

Hope this makes sense.

Traditional Lionel and other 3-rail trains ran on AC power. In the mid-20th century, Lionel worked out how to send a DC power burst through the rails to activate a horn or whistle in the engine. You could run an AC engine on DC power, but if it had a horn, it blew all the time there was power on the track! You could add a bridge rectifier to the engine to replace the Lionel mechanical reverse unit, so on DC reversing track polarity changed the engine's direction, but horns and whistles had to be disconnected.

As noted, the three-rail track allows you to build layouts with reverse loops without needing to isolate the loop and add some way to reverse polarity like you have to do with two-rail track. In two-rail, one rail is positive, the other negative. In a two-rail reverse loop, the positive rail turns around and connects to the negative rail, which would cause a short-circuit. In three-rail, if the center rail is positive, then the two running rails are negative. Even going around a reverse loop, the center rail is still positive and the outer rails negative, so no special wiring is needed. But this works the same whether you're running AC, DC, DCC, or other systems like Legacy etc.

In an analog system, how much power is on the track determines how fast the engines on the track go - all engines in the same block will respond to the power. In a command control system, each engine has a unique ID and receives an individual signal from the controller telling it what to do, so one engine in a block can move while another stays still. In DCC, there is a constant AC power fed to the tracks, and the decoder in the engine picks up the instructions from the controller and converts the AC to DC to feed the engine's DC motor, lights, sounds, etc.

DCC is a DC powered system.

Bob Walker.   DCC power supplies are 5 or 10 amp 15 volt AC and that's what's on the track. the AC is rectified by the decoder in each loco to power DC motors.

The DCC track signal is not a standard AC sine wave but a variable pulse width coded signal.

Being new to all this I am confused?  I come from HO (2R DC).

Do they actually make DCC systems designed for 3R which is traditionally uses AC?

Or is this only for equipment (Locos) that has DC motors (like everything I have bought so Far)?  Do you then "gut" the existing Loco electronics and install a DCC Decoder upstream of the center pick-up side of the motor.  Then take the other motor lead and Direct attach it to the chassis.  Then it would work and use the same system as 2R DC/DCC (pulse width modulated)?

Some one please let me know?  Thank you!

There is only one DCC system, it is the same for HO, O, N 3 rail, 2 rail, etc.

You can get different rated boosters (some built into command stations) to handle different amperage loads.   You need less AMPS for N than HO, and you need more O.  

With DCC, you use one Command STation, and as many Boosters as you need to support the amperage your layout needs.    For example, I have a friend with a very large HO layout who has 20 boosters.   He says because of the originally wiring it was much eaiser to add more boosters than rewire, and he doesn't really need that many.     I have 3, 8 amp boosters on my system.    I use Digitrax and 8 amps is the highest rated.    

It would be hard to run an AC motor with DCC but not impossible..    You would just have to put something between the decoder and the motor to control direction.

My friend who runs 3 rail DCC does replace the electronics in the locos with his preferred DCC decoder.

PRRJim - Thanks for the answer!

It is correct that there is only one basic DCC control system format. What varies is the origin of the DCC control signal and the method by which the DCC decoder control signal is handed over to the loco. Traditional track signal based DCC layouts use various trackside encoders. More recently, wireless DCC systems have come on board which create the DCC control signal in the PC module onboard the loco. For a modeler considering DCC, this might be a more convenient approach as it avoids any modifications to the track power arrangement.

BTW, wireless DCC is about to get much more interesting.  Stay tuned.

@BOB WALKER posted:

BTW, wireless DCC is about to get much more interesting.  Stay tuned.

Hmmmm... Could this be what you are referring to?  Can't wait for Tuesday.

Ron. You hit it right on. Can't wait for Tuesday!

Blue tooth.  bluenami decoders