Author Topic: Dcc versus Dc running characteristics  (Read 1114 times)

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kgreen

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Dcc versus Dc running characteristics
« on: October 25, 2017, 11:55:45 AM »
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For those who changed to dcc did you find better operation of engines or much the same.  Thanks  Kirk

peteski

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Re: Dcc versus Dc running characteristics
« Reply #1 on: October 25, 2017, 12:20:47 PM »
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Are you comparing straight DC (no decoder installed) locos vs. DCC locos, or ones with decoders installed running in DC and then DCC?

If it is the former then IMO DCC (with its PWM pulsed motor control and BEMF) gives much better and smoother slow speed than what a pure DC loco can do with DC throttle.  There are fancy DC throttles out there (Like TAT-4 which provide very good slow speed), but most average DC throttles are not that advanced). Also speed matching of multiple unit lash-ups is easier and better with DCC.

But having said all that, there are still plenty of modelers who use (and like) DC control. It has been a standard for many decades and many great layouts out there are or were operated on DC.

There is also more to this. DC has the block control issues (where you can run a block) where this is not a problem with DCC. But DCC is more complex to set up and just like with all computer-based equipment - it can have glitches and mysterious faults which have to be troubleshot.  DCC of course is much more flexible.
« Last Edit: October 25, 2017, 12:26:25 PM by peteski »
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mightypurdue22

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Re: Dcc versus Dc running characteristics
« Reply #2 on: October 30, 2017, 08:58:29 AM »
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I think my engines run smoother at slower speeds with DCC.  It's been years since I switched to it, so my memory may be a little foggy.  Since then, locomotive quality has gotten better.  For sure, I like controlling my trains with DCC than controlling my track power with DC.  I'm using JMRI's DecoderPro.  With it, I can easily manipulate the "handling" of all my locos.  It can be a bit cumbersome getting started with it and learning it, but the upside is way too much for me to live without at this point.

Dave

DKS

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Re: Dcc versus Dc running characteristics
« Reply #3 on: October 30, 2017, 10:06:48 AM »
+1
As Peteski notes, the question can't be answered simply. There are multiple factors to consider beyond simply "DC vs. DCC."

While I use DCC on occasion, I personally don't like it. But as a lone wolf modeler who is not into operations, I have no need for it. So switching would, for me, be an unnecessary added cost.

But preferences aside, there are multiple factors to consider for just the DC side. Peteski's remarks about throttles is pretty much on the mark, i.e. better performance necessitates better throttles.

There's an added twist, however: I've found one of the best DC throttles I've ever used isn't even a throttle. It's a brightness control for LEDs, which is available on the Bay for as little as $5. The reason it makes such a great throttle is that it's a PWM (pulse width modulation) circuit. It does require a bit of modification to use as a throttle--you need to add a reversing switch, and provide a filtered DC power source. But even after that, it can still wind up costing less than $10.

So there's no "binary" answer to your question. It depends on many factors, such as the locomotives (DCC, DCC on DC, or pure DC), the throttle, and your personal preferences.

Point353

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Re: Dcc versus Dc running characteristics
« Reply #4 on: October 30, 2017, 11:03:28 AM »
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There's an added twist, however: I've found one of the best DC throttles I've ever used isn't even a throttle. It's a brightness control for LEDs, which is available on the Bay for as little as $5. The reason it makes such a great throttle is that it's a PWM (pulse width modulation) circuit. It does require a bit of modification to use as a throttle--you need to add a reversing switch, and provide a filtered DC power source. But even after that, it can still wind up costing less than $10.
Have you ever tried this PWM throttle?
http://www3.sympatico.ca/kstapleton3/851.HTM

DKS

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Re: Dcc versus Dc running characteristics
« Reply #5 on: October 30, 2017, 11:37:47 AM »
+1
Have you ever tried this PWM throttle?
http://www3.sympatico.ca/kstapleton3/851.HTM

I considered it, but with a $20-30 price difference, I couldn't justify it, especially since my little kludges work so well.

craigolio1

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Re: Dcc versus Dc running characteristics
« Reply #6 on: November 04, 2017, 01:23:31 PM »
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As Peteski notes, the question can't be answered simply. There are multiple factors to consider beyond simply "DC vs. DCC."

While I use DCC on occasion, I personally don't like it. But as a lone wolf modeler who is not into operations, I have no need for it. So switching would, for me, be an unnecessary added cost.

But preferences aside, there are multiple factors to consider for just the DC side. Peteski's remarks about throttles is pretty much on the mark, i.e. better performance necessitates better throttles.

There's an added twist, however: I've found one of the best DC throttles I've ever used isn't even a throttle. It's a brightness control for LEDs, which is available on the Bay for as little as $5. The reason it makes such a great throttle is that it's a PWM (pulse width modulation) circuit. It does require a bit of modification to use as a throttle--you need to add a reversing switch, and provide a filtered DC power source. But even after that, it can still wind up costing less than $10.

So there's no "binary" answer to your question. It depends on many factors, such as the locomotives (DCC, DCC on DC, or pure DC), the throttle, and your personal preferences.

Would you mind providing a link to said controller and power supply?  This is very interesting to me.

Thanks.

Craig

jagged ben

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Re: Dcc versus Dc running characteristics
« Reply #7 on: November 04, 2017, 05:47:30 PM »
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Would you mind providing a link to said controller and power supply?  This is very interesting to me.

Thanks.

Craig

I'm guessing something like this:
https://www.ebay.com/itm/DC-12V-8A-LED-Light-Protect-Strip-Dimmer-Adjustable-Brightness-Controller/222246410337
(nothing special about that one, there are dozens of similar results if you search eBay for 'LED brightness controller.')

I'm curious though that DKS didn't mention overcurrent protection.

mmagliaro

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Re: Dcc versus Dc running characteristics
« Reply #8 on: November 09, 2017, 03:45:49 PM »
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Reducing the problem so we can compare apples to apples:
Let's assume on your DC layout, you are running only one engine.
And lets's assume that on your DC layout, you are using DC-only engines and a DC throttle,
and on your DCC layout, you are using DCC equipped engines.

(In other words, no "hybrid" cases of trying to run a DC engine on a DCC system).

As others have noted, decoders use PWM output to drive the motor, which is da bomb for getting motors to
spin smoothly at low speed without stalling.  So if you use a PWM DC throttle, you should get the same
impressive results you would get from a DCC engine.

Except....
If your decoder has the back emf feature enabled, it has another advantage.  It is continuously sensing the
speed of the motor and adjusting the output to compensate.  When this is tuned right, it can keep a motor
moving at lower speeds than it would ordinarily be capable of on smooth DC, or even PWM DC.

There *have* been DC throttle with back emf features, but they are rare.    That TAT IV or V that Peteski mentioned
was one, and the Radio Shack throttle, which was a TAT in sheep's clothing, are two that I know of.

Complicating things:
If you put two engines on the track, there isn't much a back-emf DC throttle can do because it cannot accurately
sense the speeds of two different motors on the track at the same time.  Whereas a decoder, remember, only has
to measure the one motor in its own engine. 

DCC is like carrying around a really nice PWM back-emf enabled throttle inside each engine, dedicated to only that
engine.
-------------------------------------------------------------------------------

So even though I use only DC, it's obvious that you should be able to get better motor performance
in a DCC-equipped engine running on a DCC system. *



* unless, of course, you use coreless motors and gearheads and get the mechanical capabilities of the engine
so good that it doesn't make a rat's hind quarters worth of difference what the throttle is.   :)


ek2000

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Re: Dcc versus Dc running characteristics
« Reply #9 on: November 09, 2017, 08:00:58 PM »
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I know the question is more on running characteristics but I would also like to weigh in with the operational characteristics/flexibility that you get with DCC. When I entered the hobby, like many before me, I had a DC set up. While the running characteristics were generally very good especially with manufacturers like KATO, the ability to control locomotives and their functions independently was a huge driver for me to move to DCC. With DCC, the joy of running trains is compounded many times, in my opinion.

With DCC, I have observed that some locomotives lose power in spots where with my DC set up (same track and the same locomotive) there are no issues.
DC is like the pick up trucks of past - reliable but not with a lot of bells and whistles. DCC to me is more akin to newer cars with all fancy gadgets, the more gadgets there are, the more that can go wrong, but once you get used to them, hard to live without..

I digress, but long story short, there is no dearth of good DCC models that perform reliably in DCC set up, great slow speed, reliable pickup plus all the great benefits you get with DCC. My experience with running characteristics, while mixed depending on the manufacturer, is much more positive with DCC.

peteski

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Re: Dcc versus Dc running characteristics
« Reply #10 on: November 09, 2017, 09:55:53 PM »
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DCC locos have problems in certain spots? That sounds like your track-work needs some work.  I have operated on many N scale DCC layouts where there are no such issues.

If your track-work is not optimal then yes, DC locos (especially with low-friction mechanism and flywheels) are much more forgiving. Same goes for turnouts which are not what we call "DCC friendly". DC locos glide right though those where a DCC loco might stall after it shorts out on it.  After all, a DCC decoder is actually a tiny computer (processor, RAM, ROM, I/O devices) and it does need a reliable power source. If the power is lost it needs to "reboot".

To me the benefits of DCC greatly outweigh the simplicity of DC models. Making the track-work good enough for smooth DCC operation is well worth the effort - if not for anything else, just for the ability of freely controlling multiple locos without the dreaded (to me) block control.  Also, the keep-alive circuits are getting smaller and smaller. Those can lessen the problems caused by poor track-work.
--- Peteski de Snarkski

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ek2000

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Re: Dcc versus Dc running characteristics
« Reply #11 on: November 09, 2017, 11:15:27 PM »
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I should have added that other DCC locomotives have no issues over the same spots even with DCC. The emphasis there was on "some" (e.g. BLI) DCC locomotives showing finickiness or  hyper sensitivity to track power and yes of course, turnouts are even trickier. It could be that this may also exist in DC, but I think your're more probable to notice this with DCC.

Somebody here rightly said that it should be illegal to sell DCC sound locomotives without keep alives. I saw a HO scale locomotive (ST GEVO's ) with keep alive circuitry that keeps the locomotive sounding for 2-3 seconds even after the locomotive is completely off-track. Boy would I love to see that in N!

peteski

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Re: Dcc versus Dc running characteristics
« Reply #12 on: November 10, 2017, 12:57:37 AM »
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Somebody here rightly said that it should be illegal to sell DCC sound locomotives without keep alives. I saw a HO scale locomotive (ST GEVO's ) with keep alive circuitry that keeps the locomotive sounding for 2-3 seconds even after the locomotive is completely off-track. Boy would I love to see that in N!

Depending on which locomotive, you can, even in N scale.  There are keep-alive modules available which are small enough to fit alongside of a decoder (even a sound decoder) in a steam loco's tender  Same goes for any wide body diesels, although some frame milling will be required.
--- Peteski de Snarkski

-"Look at me, I'm satirical!!!"
-"Look at me, I'm anal retentive!!!"
-"Look at me, I have the most posts evahhhh!!!"
-"Look at me, I'm snarky!!!!"
-"Look at me, I have OCD!!!"
-"Look at me, I'm a curmudgeon!!!!"
-"Look at me, I'm not negative, just blunt and honest!!!"