Getting slow speed on DCC

Model Railroader Electronics and DCC
21

I thought I’d try a test:

(remember, this is a Loksound decoder)

CV 67 was set at 1, CV 68 at 5. I changed both of them to 40, to see if there’s be a sudden bout of quickness on start. No noticeable change.

I DID see that CV67 did not accept the new value–it stayed at 1.

That would appear to endorse what Mark has said.

Well, there you are. Or, more correctly, here I am. I guess.

I do kinda get the point. Sorta. In particular, at least for Loksound, there isn’t straightforward choice between simple and complex speed curves. As Mark says, some of the data from the simple speed curve is incorporated into the output of the complex speed curve.

Thanks, Mark. I’ll have to think on this some more.

Ed

22

Thanks Paul.

I’ve got much more than that.

Ed

23

Ed,

I mentioned 3’ in my previous post. However, when I actually ran the automatic motor tuning feature with my H20-44 it didn’t even travel 12" before it came to an abrupt stop. I think 3’ should be plenty…unless you plan to run the feature using a 4-8-8-4 Big Boy.

To answer your other question: I think a decoder reset is what you’d need to perform an “undo” of the motor tuning feature.

Tom

24

More big fun (and confusion):

From page 21 of Loksound Users Manual:

"5.2.2.3. Speed curve

You may also define your own speed curve: simply enter the desired values in CV’s 67 to 94. The decoder will superimpose these 28 values onto the real speed steps."

To me, that sounds like what I’m hearing, here. The “real speed steps” would seem to be CV 2, 5, and 6.

But:

“When this mode is active, the settings in CV 2, CV 5, and CV 6 have no influence.”

THAT seems to be saying what I thought in the beginning: Simple and complex speed curve settings are unrelated.

The Loksound Manual is surely being unhelpful. As, indeed, many manuals are.

Ed

25

The “real speed steps” are the actual steps issued by the command station, not the steps from CV 2, 6, and 5.

–Randy

26

More experiment:

I checked some more CV’s (keep in mind that this decoder was reprogrammed by Litchfield Station from a 73800 to a 73836):

CV2 was 3, I changed it to 1

CV5 was 255, I changed it to 130

CV6 was 88, I changed it to 50

Keep in mind that I’ve (supposedly) got CV29 set for the complex speed curve.

Results: Speed step 1 went from 1.3 mph down to .2 mph. Uh, WOW!

I’ll note that you can see a bit of jerkiness from the motor cogging. And I suspect that’s fixable a bit, too. Not for me now, but I got a feelin’…

I also noted that, when I tried changing CV 25 from 0 to 16 (which I heard somewhere I should do), the decoder wouldn’t accept it, and stayed at zero.

But, I’ll tell ya, I am indeed happy at the improvement.

Thanks, all for helping out. And a couple of extra thanks for Mark.

Ed

PS: This little loco is a zebra stripe Santa Fe GP9 (P2K), destined for road switcher service. So she’ll run solo, mostly. Besides the decoder, there’s a speaker and “keep-alive”, all by Loksound. And as much lead as I could conveniently fit. A real sweety. And I ain’t even a Santa Fe guy. Well, a little, I guess.

27

I would try the CV54 procedure again. See where it runs slow better (not necessarily slowest), at CV2 set at 1 vs 2, with the Cv54 procedure done for each. You might have a choice to make; i.e., slower at CV2 equals 1 vs. smoother at CV2 = 2. Of course if it runs equally smooth at 1 or 2 value the choice is easy.

Would enjoy the answer if you don’t mind experimenting more. All this is informative as there’s a learning curve.

BTW, if you have not tried the Loksound Yahoo User Group it is worthwhile monitoring.

28

Paul,

I hadn’t tried the CV54 thing yet. So I did. After first recording the original number. Minimum speed dropped to .1MPH. And it was pretty smooth. Bad news was that the fella goes REAL SLOW now, at least according to the sound.

When I first put the loco on the track a couple of days ago, with sound, it felt like the loco was going way faster than the engine sound. Then when I changed the low number CV’s an hour ago or so, it felt like the engine sound matched pretty nicely the loco speed. Now it sounds like the sound is way up there, compared with the speed.

So the CV54 adjust was, all in all, anti-rewarding.

So it still needs work. I do wonder what would happen if I restored the low number CV’s and then did a CV54.

OK, I did restore the low number CV’s to “as delivered”. It’s “less negative”. Meaning it still seems like the loco is working way too hard (soundwise). But less than just awhile ago.

So, I’m pretty happy with things. Certainly enough to leave it for now.

DCC is SO neat. And SO much better than the olden days. Though a little intimidating.

Ed

29

You still didn’t answer whether or not you are using JMRI to do the speed step CV changes. Again, I think that the only two speed step settings that carry over are CV2 and CV5. I’ve not heard/read anyplace the the mid-speed CV (6?) carrys over. You said you are using the complex speed curve, but exactly what other CVs are you changing? Are you just picking the other speed curve values at random?

30

No, I’m not using JMRI to do the speed step CV changes. The CV’s 67 to 94 are whatever Litchfield Station installed. I haven’t changed them. I DID change CV2, 5, 6. And I have since changed them back, also to what was supplied by Litchfield. So, no, I’m not picking other speed curve values at random. I’m not picking them at all. The Litchfield folks picked them.

As far as I know, the only CV that is different from what they shipped is CV54 (which was shipped as 50 but self-adjusted to 96, and 29, which was 14 (??) and I changed it to 50.

Ed

I have to ask, why would you ever think to ask if someone would pick speed curve values at random? Do you really think anyone would do that? Do you really think I might? Do you see that a person might see that as insulting? Did you mean it that way?

31

I’ve found the CV54 Auto Tune always resulted in my engines running overall more slowly … no idea why, it’s just the way the decoder interpolates the BEFM from the motor and optimizes the settings. DO NOT ask me HOW it does that ! [swg]

As you discovered, having set your speed table to where you liked it, the Auto Tune now makes it run too slow. Going back in to CV5, you can pick up the pace again. If you have the speed table activated, CV6 has no bearing on it - just CV2 and CV5. If you have the speed table off, then you use the three point curve utilizing CV2, CV5 and CV6.

Mark.

32

Thank you, Mark.

I’ll go in and muck around a bit more, later.

Ed

33

Whoa, big guy, no insult was intended. The reason I asked the question was because you were speaking about a speed curve and changing speed curve step values but it wasn’t clear if you were changing only the CV’s for steps 1 and 28 or others also. It also seemed that you were not aware of the fact that the CV2 and CV5 values defined the end points of the “curve”, and that CV6 had no effect on the curve.

In addition, I have a strong suspicion that the “curve” installed by Litchfield was really nothing other than the curve that was the LokSound decoder default, unless you specifically asked them to do something other than just download the decoder files. And I also believe, although I haven’t looked, that the default “curve” is a straight line defined by whatever values were programmed into CVs 2 and 5.

When you make the changes to CV29 (if that is the one) that allows you to use speed curves, that usually means “user defined speed curves”. So if the only defined speed curve is a straight line, that’s what you’re going to get. Now in the case of a Soundtraxx decoder (yes I know that’s not what you have) there are a group of speed curves that you can pick from, including one that is a straight line. There is also a curve that can be totally owner generated. Thus you can pick any of the pre-loaded curves or the one that is owner generated by changing another CV value.

So anyway, that was why I asked my question. Again, no insult was intended. However, if you really do feel insulted, let me know and I’ll add you to my list of those to whom I should not offer any assistance.

Have

34

OK, then.[:)]

As has been hinted at by myself (and observed by others) I’m a beginner. The only other decoder I’ve messed with “extensively” has been a Soundtraxx. First, keep in mind that I had a “keep alive” installed, so I couldn’t read the CV’s (learned THAT one pretty quickly) (and, yes, I realized I could have temporarily disconnected the “keep alive”–with no small amount of work). Anyway, it was then obvious that I had to actually do some planning and record keeping.

As delivered, the Soundtraxx installation had far from ideal running traits (remember: gas electric). I had heard of the speed curve adjustment. And I figured (perhaps wrongly) that the pre-installed speed curve was dead linear. So I came up with numbers based on that and what I wanted, and input new CV’s for 67-94. And 29, etc. Worked BEAUTIFULLY right outa the box. For 67-94, I made a number column as if there was a linear array of increases (since that appeared to match how it was running). Then I made a number column that reflected how I thought the speed curve should be. And input my new numbers.

Hey, I’m a programming wizard!!

So my next one was an ESU equipped ATSF GP9. I approached the programming exactly the same way as the gas electric. Assuming, incorrectly, that DCC decoders had a standardized program. Seemed reasonable at the time.

And here I am. But enough about me…

Your comments have been and are helpful and useful. But the way ESU set up the various speed “choices” is not straightforward. To me. And I certainly don’t think they did a great job of explaining things in their official manual.

What it appears is so is that IF you wish

35

Loksound has five pre-set speed curves as well … Exponential1 / Exponential2 / Linear / Logarithmic1 / Logarithmic2 in addition to just creating your own.

Mark.

36

No, the Auto Tune does not reset ANY of the user-defined speed table settings. It adjusts the four CVs used in setting the BEMF performance. BEMF is most beneficial in the lower range speeds, so it is adjusting the parameters so the engine will perform optimally at lower speeds - hence you noted how much slower the engine would crawl. Since these parameters affect the entire speed range, it only makes sense that the upper levels would be affected as well. Again, that can easily be compensated for by increasing CV5 without affecting the speed curve you already created.

Starting to see the beauty of how Loksound does it yet ? [swg]

Mark.

37

Strictly speaking, I didn’t say “reset”. I said “rearranges the output”. The “output” being what gets sent to the motor.

So, I just wandered into the train room and checked: CV5 is currently at 255. So I don’t see CV5 being increased.

Actually, I cranker er up to full throttle, and the top speed looks just fine-ish.

I guess what I’m seeing is that a light engine is sounding like it’s working way too hard for the speed and acceleration I’m seeing.

Are there CV’s for that???

I did, by the way, change CV3 and 4 from 80 to 40, to see what would happen. Not much change, to me.

I am impressed with ESU decoders. Not so much some of their instructions. Which is an incredibly common problem with electronics. Instructions should be designed for people who DON’T get how something works just by touching it.

Ed

38

I personally don’t like using the Auto Tune feature (unless I HAVE to, to get an engine running right) for just the reasons you are experiencing. All my engines run just fine without having to resort to that.

I’m sure there are ways to tweak it manually with the four BEMF CVs, but I don’t understand them fully enough to actually KNOW what I’m adjusting.

There are no CVs for adjusting the sound transition points on the Select decoders. In the V4.0 decoders, you can go into the sound schedule and adjust the points.

Mark.

39

I will say that I am not at all unhappy with how this little guy runs. Now. And I appreciate both the advices and the learning opportunities provided by all.

What is really quite neat, as I run between the computer and the layout, is that the CV’s can be changed almost in an instant. Over and over and over. That is NOT true for a locomotive paint job. Or, for that matter, a DCC/sound install.

Ed

40

By “working too hard” do you mean it sounds like it’s revving up the prime mover way too much for alight engine move? Try reducing CV3 AND also turning up the throttle slower. Or just the latter. If you crank it open and rely on the momentum to accelerate slowly, the prime mover will run wide open like it’s startting a heavy train. If you don’t want it to go right into a high notch, you need to bump the throottle up slowly, like you are trying to accelerate slowly without the help of momentum. Part of what triggers the higher notch on the prime mover is the difference between commanded speed and actual speed. Dunno if that is still the case with the Full Throttle feature, I have no place to run anything and I haven’t loaded the updated sounds into any of my locos.

–Randy