# DCC speed steps



## Greg Elmassian (Jan 3, 2008)

There seems to be a little confusion on DCC speed steps.

A DCC decoder is "commanded" to a particular speed by receiving an instruction, but there are different "speed steps" that are the increments or granularity of speed attainable between your start speed (CV2) and your top speed (CV 5).

Originally, a long time ago, there were 14 speed steps. I know there must be more than LGB as manufacturers, but most of that stuff has been thrown away now. It was a very coarse granularity.

Every modern decoder uses 28/128 speed steps. In a smart move, the decoder can automatically recognize 28 or 128 SS mode and work with it.

But nothing can automatically switch between 14 and the 28/128 mode, you have to set a CV in the decoder: CV29, and to make it more fun, it's only one of the 8 bits in the CV.


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## Greg Elmassian (Jan 3, 2008)

I will be doing a thread on "bits and bytes", this base 2 system is what makes most people go nuts.

It does actually mirror what is actually stored in memory, in terms of 1's and 0's.

Most modern DCC systems give you a menu and prompt you to select options, and then "put the bits together" for the proper parameter in a CV.

Greg


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## Cougar Rock Rail (Jan 2, 2008)

There is also a misconception that you need 128 steps for smooth control. Even when set to 14 or 28 speed steps a modern decoder interpolates between the steps and the difference is almost impossible to notice (at least with Zimo or Massoth decoders).


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## Greg Elmassian (Jan 3, 2008)

Indeed the decoders often interpolate between speed steps, as they are moving to the next step, but you cannot "stay" at one of those interpolated speed steps.

Most of the time this is just fine... but for switching or slow running, I find 28 too coarse of control, and 14 is definitely a joke.

Greg


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## Paul Burch (Jan 2, 2008)

Ah yes, manually figuring out and setting CV bits. That was fun with the old Sierra DSX sound decoders.


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## Dennis Cherry (Feb 16, 2008)

Been using Decoder Pro for setting all my decoder functions, eliminates the CV counting. Simple user interface with check boxes and pull down menus. If you hover over a box with a number it will display a test box explaining your options.

DecoderPro has so many decoders already in the data base and when new decoders come out they have them ready for you to update.

This is free software, built and maintained by model railroaders.

It installs on Windows, Mac OS, and Linux.

www.jmri.org

It does install two programs, DecoderPro and PanelPro.

Dennis in Tennessee


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## toddalin (Jan 4, 2008)

Greg Elmassian said:


> Indeed the decoders often interpolate between speed steps, as they are moving to the next step, but you cannot "stay" at one of those interpolated speed steps.
> 
> Most of the time this is just fine... but for switching or slow running, I find 28 too coarse of control, and 14 is definitely a joke.
> 
> Greg



But isn't the idea to strive for reality. 


It is my recollection that diesels only had 8 notches of run speed. I also recall seeing EPA testing of diesel locomotives for emissions and they test at 8 notches.


Anything more..., well...


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## Cougar Rock Rail (Jan 2, 2008)

> Most of the time this is just fine... but for switching or slow running, I find 28 too coarse of control, and 14 is definitely a joke.


 If you properly adjust the accel/decal, as well as the speed curve so that more of the speed steps take place in the switching range, I have found that it works very well--certainly not in the "joke" range. I guarantee you that if you watched the slow speed performance of the last switcher I put a Zimo 696 decoder in, using either 14 or 28 speed steps the difference between that and 128 steps would be negligible. I'm not saying there isn't a difference, but it certainly can be worked. I tested this exact comparison the last time I borrowed a central station that could do 128 steps compared to the 28 of my MTSIII, and I could not see any difference in performance.
Maybe the NCE system you're using doesn't do the interpolation the same way...


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## Greg Elmassian (Jan 3, 2008)

Well, from a practical perspective, it's a joke from how I have seen people try to operate. I guess I should not say practical, but prototypical.

You are missing the point about interpolation, it only is in effect going BETWEEN speed steps.

Now (and to answer back to Todd too), if you indeed dial in prototypical acceleration and deceleration, and you have a brake to stop the loco, indeed 8 speed steps is more than enough for switching. Absolutely.

But, how many people have you seen ever use prototypical accel and decel? I've been using DCC for a very long time, and I can count on the fingers of 1 hand anyone that used prototypical settings.

A very few people use accel and decel at all.

(remember I am talking G scale now, outdoors... there's plenty of HO and N guys running prototypically).

So, if you are switching, and like the majority of DCC users, have NO accel and decel, even 14 speed steps is a joke if you want to do switching without crashing cars.

If 14 was great, why was 28/128 invented? And if you look at the basic NMRA CV's, they have proven to be the basics for years. There was a lot of thought that has withstood the test of time.

I prefer 128 steps, but most of my friends use 28 on throttles with knobs or wheels... mostly to be able to throttle down quickly.

Regards, Greg


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## CliffyJ (Apr 29, 2009)

Greg Elmassian said:


> I will be doing a thread on "bits and bytes", this base 2 system is what makes most people go nuts. It does actually mirror what is actually stored in memory, in terms of 1's and 0's.


I for one would like to know more about it, so thanks Greg.


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## Dan Pierce (Jan 2, 2008)

And some systems will do half speed where the lower half of the speed steps is expanded to the full range. Great for having an engine run between main line and yard work.
On my Zimo system the MN key does this as well as programming function 4 to do this (or change it to another function key for other systems).


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## Greg Elmassian (Jan 3, 2008)

That is nice. Also some throttles have "yard mode", for example my NCE throttle in yard mode changes the thumbwheel from 0 to full speed to full backwards, to zero to full forwards, i.e. you only need the thumbwheel for moving, not even the direction switch, allows complete concentration on moving the loco back and forth.

(someday Axel will allow me to buy a Zimo system so I can try what you described out ha ha!)

(In fact you probably have MY MX10 !!)

Greg


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## toddalin (Jan 4, 2008)

Have you ever tried to set up the speed table in accordance with how a real locomotive is "notched" to see how this affects the operation?

The data are available through EPA

For example a 3,000 hp EMD-16 uses 17, 105, 395, 686, 1,034, 1,461, 1,971, 2,651, and 3,159 hp at idle then Notches 1-8, respectively.

You could calculate the voltage equivelent using power as square of the voltage and enter that in the speed table.

http://www.epa.gov/otaq/documents/420r98101.pdf


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## Greg Elmassian (Jan 3, 2008)

Yes, I have, but our trains are so powerful that when set to a particular notch, they will definitely achieve that speed, whereas a real train may be in notch 8 but will never achieve unloaded speed for that notch.

This is because of the load, and there is no direct connection between the diesel crankshaft and the axles.

So, at best you could only map the notches to unloaded speed. 

Therefore we need to have speed steps in between.

But, sound cards (at least some) can be set up for notches, and I have one set up that way, i.e. you hear the motor's rpm stay pretty constant as the speed increases.

I don't really want to get into this aspect since it's very advanced, only works on some decoders, and there's a lot more basic information on speed steps to be presented.

Greg


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## Cougar Rock Rail (Jan 2, 2008)

Massoth decoders also have the switching speed function but I find it is unnecessary most of the time. You can program Decoders to do pretty much anything you want when it comes to how the sound is coordinated to load, speed etc....digital is great! The beauty of it is that you can run it as simply or as complex as you want.


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## Greg Elmassian (Jan 3, 2008)

Agreed, cannot emphasize that often enough. So many times the "DCC haters" use scare tactics like too complicated, have to learn all the CV's, can't do it without binary math.

I would state that switching does demand greater "resolution" in speed steps.

If you want to try it like a real engineer, put some realistic momentum in and try it out, you can "adjust your challenge". ;-)

Greg


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## East Broad Top (Dec 29, 2007)

For me, dialing in even a modicum of momentum (15 - 20%) pretty much negates any advantages 128 steps might give over 28 in terms of fine control over speed of the loco. Most of my locos run between 30 - 60% momentum. My QSI and Tsunami decoders are programmed for prototypical braking, so deceleration is even more gradual without applying the brakes. I've toggled between 28 and 128 steps just to see if there's a noticeable difference in performance, but I've yet to notice any. I prefer 28 steps because with the Airwire throttles I use, as it's less spinning of the knob. 

One thing with running locos with a good deal of momentum dialed in; the knob itself becomes much less about a proportional relationship between position and speed as we're used to from our Lionel days. Instead, the knob becomes more of a gas pedal. When you want to start, you jack the throttle up; it doesn't really matter to which speed step--run it all the way up if you want. The train will accelerate at the programmed acceleration rate regardless. Once your train reaches the speed you want to travel, back the throttle down to where it maintains that speed. When you want to stop, you close the throttle down, and the train drifts to a stop based on your deceleration parameter. (If you've got a decoder that allows for separate braking, then you close the throttle down, then you have to apply the brake to actually slow down.) 

This kind of operation is greatly enhanced with motor/sound decoders or combinations which allow for audible changes in the diesel motor or chuff sound as it's working hard or coasting. You find yourself running your train more by listening to the how hard the locomotive is working from the sound coming from the speaker and by watching the speed of your train itself as opposed to using the numerical display to tell you how fast you're going. 

Switching with momentum takes some getting used to, and switching with momentum and prototypical braking takes a _lot_ of getting used to. Having trained as a motorman in college, it's pretty close to "the real thing." Just make sure you have extra couplers. 

Later,

K


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## Greg Elmassian (Jan 3, 2008)

Question Kevin, exactly what settings are you using? There is really no such thing as "momentum" in a DCC decoder, it is broken up into acceleration momentum and deceleration momentum.

You may indeed have a controller with a single momentum button, but it would be helpful to understand your comments to know what the decoder is actually set to, so others could try your settings or compare directly.

Yes, as I stated on this thread several times, with momentum, the resolution BETWEEN the beginning speed and the ending speed does not matter since most decoders interpolate even more steps.

I would strongly suggest you get a setup that allows even more prototypical action, i.e. a brake function. I use this, and it allows me to run the loco like a real one, so I don't have to rely on an artificial deceleration that is much higher than the prototype.

It's also fun because most decoders with the brake function will also have some brake squeal (programmable).

Greg


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## ewarhol (Mar 3, 2014)

What systems/decoders allow for prototypical braking? This is something I'd be interested in. 

If I am remembering correctly from when I spoke with Josh at QSI, the Titan decoders with Q3 sound file can have break squeals automatically come on when stopping. If they do I haven't figured it out yet. I assume it's set up in the CV Manager program.


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## Greg Elmassian (Jan 3, 2008)

I believe the Zimo can do it. I know the QSI can be set up with brake function mapped to a function key.

Dan might chime in here on the Zimo, and perhaps CRR knows if the Massoth can have a function key for braking.

To be clear, we are talking about a function key that can be used as a brake, so that if you don't use it, and you leave the throttle at zero, the locomotive costs like a real train, very slowly reducing speed.

Greg


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## ewarhol (Mar 3, 2014)

Clear on that. 

Currently using the F7 (brake function key) for sound effect only. 

But using it as the actual break, now that sounds cool.


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## East Broad Top (Dec 29, 2007)

Greg Elmassian said:


> Question Kevin, exactly what settings are you using? There is really no such thing as "momentum" in a DCC decoder, it is broken up into acceleration momentum and deceleration momentum.


When I write of "momentum," I am referring to _both _acceleration and deceleration settings together (CV3 and CV4.) One usually doesn't set the one without the other, so I speak of them within that combined context. They needn't be the same value, and mine often are not. My deceleration value is often greater than acceleration, because I want slower stops. 



> I would strongly suggest you get a setup that allows even more prototypical action, i.e. a brake function. I use this, and it allows me to run the loco like a real one, so I don't have to rely on an artificial deceleration that is much higher than the prototype.


Perhaps you missed the third sentence in my first paragraph in my post above:_ "My QSI and Tsunami decoders are programmed for prototypical braking, so deceleration is even more gradual without applying the brakes."_ 

For the benefit of those who might not know how this functionality works, when I close the throttle on a locomotive programmed for this, the loco does not really slow down, at least not at all quickly. Think of it as just taking your foot off the gas pedal of your car. It's not unusual for a loco to travel 150' or more with the throttle set to 0 before it finally comes to a stop. (The greater the speed when the throttle is closed, the greater the distance it takes to stop.) This allows me to "coast" my locomotive down hill by dropping the throttle back to zero, which either quiets the chuff sound or drops the motor sound to idle. Because the rate of actual deceleration is pretty low, the train doesn't really slow down noticeably over say 30 - 40' of run. By then I'm at the bottom of the hill, and I can give the loco some throttle, hear the motor rev up or the chuffs get louder, and continue on. 

If I want to actually stop at a station or siding, I've got to close the throttle, then separately apply the brake via a function button (in my case, F7). On the QSI decoder, this alters the rate of deceleration proportional to how long I hold the button down. The longer I hold it, the more brake is applied, the faster the train stops. It's still far from instantaneous, and I can tell you that pressing harder on the F7 button does _not _make things stop any faster when a hard object is fast approaching in front of your loco. If you've got this set on your throttle, you_ do not_ want to go fast when switching cars. It also helps to have a "stop NOW!!!" button on your controller just in case. Alas, Airwire does not, so I've crashed into more than a few freight cars, which is also why all my spur-end sidings now have end blocks. 

(The Tsunami braking function is similar, but not identical in operation.) 

Again, comparing this operation to my time running a 1:1 trolley, it's pretty similar. Fortunately when running the trolley, I was always a little heavier on the brake than I needed to be. 

Later,

K


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## ewarhol (Mar 3, 2014)

Kevin-

What QSI decoder and sound version are you using? I have Titans with the Q3 EMD 645 sound file. Do the QSI decoders automatically have this function or do you need to program something using the CV Manager? My guess for one thing to program would be the deceleration rate.


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## East Broad Top (Dec 29, 2007)

The Q2 and Q3 firmware both do this on the Titan. I currently have it set up on a Q3 steam file, Q3 EMD 567, and Q3 Alco 244. I had it set up with the older Q2 firmware as well, but upgraded to the new sounds when they became available. 

It is keyed off of CV4. The greater the value for CV4, the longer it takes to slow down, and also the more "play" you have with respect to applying the brakes. With low values for CV4, the locos will decelerate fairly quickly, and even a quick tap of the F7 key will apply the brakes fully. With higher values, your stop times are longer, and you have more control over the amount of braking. A quick press applies just a little brake, a longer press applies more. There does seem to be a point where it's full on, though I don't know how all that is computed. 

I don't recall off the top of my head what my CV4 values are; I can look them up on my laptop later if you're interested. 

Later,

K


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## ewarhol (Mar 3, 2014)

Thanks Kevin, I would appreciate if you could look those up. In the mean time I'm going to play around with it and give it a whirl.


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## East Broad Top (Dec 29, 2007)

Just remember that your throttle has to turned to 0 for the braking to work. I was never so thankful for Airwire to put their "set speed = 0" * button on their latest throttle, as turning (and turning and turning) the knob on the T-9000 throttle never guaranteed you were actually at 0 to engage the brake. 

* Airwire calls it a "stop" button, but the train only stops condition to the settings for CV4.

Have fun, and practice with foam couplers. 

Later,

K


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## East Broad Top (Dec 29, 2007)

I checked my CVManager files for my Climax and center cab; On the Climax, CV4 = 245. On the center cab, one file has it at 200, another has it at 64. I forget which file is the most recent one I used to program it, and I seem to recall changing it recently anyway because I needed faster response for my workshop switching layout given how short it is. On the NW2 I just did for my dad, I have CV4 = 37, but his regular operating crew are more "traditional" operators, and I got complaints when I jacked up the CV3 and CV4 values on dad's engines one year. 

Later,

K


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## Greg Elmassian (Jan 3, 2008)

I have to smile at your post Kevin.

Many people profess to operate prototypically, but when it comes to the acceleration settings (NMRA terms) very few can "handle" realistic settings, especially stopping as you have stated.

Gives a lot of respect to the actual people running actual locomotives!

Greg


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## Gary Armitstead (Jan 2, 2008)

Greg Elmassian said:


> I have to smile at your post Kevin.
> 
> Many people profess to operate prototypically, but when it comes to the acceleration settings (NMRA terms) very few can "handle" realistic settings, especially stopping as you have stated.
> 
> ...


Greg,

I don't want to "derail" here.....just a funny little sidenote regarding running actual locomotives....... a couple of years ago when Tommy Mejia (MLS member) and I were running my 1-1/2 inch scale Baldwin electric on the LALS track in Griffith Park.........Tommy made a comment to me saying that running these larger models, you really "feel" the weight of the train and starting and stopping for just the simple things like a signal or coupling and uncoupling a car, was a great feeling for him. Just made it more fun. AND this is just a 750-1000 pound train! 

Off my derail now.


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## ewarhol (Mar 3, 2014)

Set my SD40-2 with QSI Titan to CV3=60, CV4=130. Was really cool to use the F7 brake for stopping. Using the brake is a lot of fun. 

Stopped in time for a rock on the track. I chuckled thinking of what Kevin said regarding pressing the brake button harder won't make the train stop sooner, he's right on that


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