I have been playing with CV 3 and have tried 60 and 50 as values. (I am new to this so I hope I am using the right terms). I want a slow acceleration rate, problem is the engine sits there still for a few seconds then starts to go. It starts moving just a little to fast, after it starts to move. I like the effect, but I want it to start at a craw, not like I dumped the clutch.
Is there another CV I can change to get it moving quicker but at a slower rate? Engine in question is a HO Athearn RTR SD40-2 with a Digitrax DH 163 pulling 21 cars. I running a Digitrax SEB.
I have finally got my Digitrax PR 3 to night at 9:45 PM so yet to be hooked up.
Thanks for the coming answers.
Cuda Ken
I hate Rust
A possible solution, Ken, would be to kick your starting voltage upstairs, and that would be via CV2, or what we call V-Start. I don't believe it will get you underway less quickly, but it will get you underway sooner, even immediately. The very slow acceleration from a bare crawl, as I understand it, is controlled through BEMF settiings and maybe 'dither', both of which should be covered in the decoder's manual. But an engine that sits for a couple of seconds after you wind in speed step "30", say, and then lurches into motion, is not getting the correct start voltage. The decoder is slowly raising the voltage per your CV3 setting, but the engine motor won't be able to get the axles turning until it can over come all the internal and external resistances and friction in the drive. When the voltage exceeds that necessary to make the engine commence moving, it does it with a jerk. No, not you...I mean the engine...it jerks into...oh, you know what I mean.
-Crandell
I agree. I would start by putting CV3 (and CV4) back to zero. Then set CV2 so that the engine just barely moves at speed step 1. I find I want a number like 2 to10 for this in most engines. Next, try 10 in CV3. That's a good starting point. Make it higher if the engine still starts too fast, or lower if it starts too slow. Once you're happy with CV3, adjust CV4 for deceleration.
A LokSound decoder, by the way, has a built-in "spin up" delay before the engine will start to move. I found I had to set CV3 to zero, or else I needed another beer by the time the engine got moving.
It takes an iron man to play with a toy iron horse.
A custom speed table might be the best option. When you get the PR3 hooked up with JMRI you can adjust the sliders for each step exactly how you want them. These are CVs65-95. Check out page 52-56 in the Digitrax decoder manual.
Engineer Jeff NS Nut Visit my layout at: http://www.thebinks.com/trains/
I will try playing CV 2, I was reading about it in the Digitrax book, but want to run it by you folks here first. This morning the SD 40-2 will not move, I have control of the lights and that is it? When I get home tonight I will resit the default and start over.
Thank again, Ken
This is exactly what you should do. And it's quite easy with the DT400 because it's obvious when you are on speed step 1. Using Ops Mode programming, you can just keep upping CV2 until the loco moves at the slowest speed it can sustain. You will probably notice this is more reliable on the decoders that have BEMF vs ones that don't (DH123 series do not). Once you have CV2 buttoned down, now it's tiem to play with CV3 and 4 and get the momentum set. There's no 'best' value, it really is a personal preference, but you can guide yourself somewhat by the intended function of the loco. Switchers tend to 'load' quickly in real life, which is good - switching with a lot of momentum programmed in can be tough! A passenger loco on a short train will take off quickly as well - part of the reason CNJ used big Trainmasters to pull 3 car commuter trains, they could get up and go when leavign a station stop (of which there are many on a local). For freight trains, it's going to depend on the consist of the train, a heavy ore train will take a lot longer to get up to speed than a train full of empty hoppers going back to the mine. The nice withing with DCC is you have two seperate settings, one for accelertationa nd one for deceleration, so you can have a train that takea a while to get up to speed, but slows down quickly when you shut off to prevent a disaster. This is the fun part where you play, and since you're only adjusting one CV at a time, you can switch it back
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
This is beside the point, but a nice thing about QSI decoders is that if you want the engine to stop quickly, but not use the emergency function (you have some time, it isn't an emergency, but it will soon be an emergency...), you press F7 and the engine brakes hard. If you had CV4 set so that it would have taken, say, 4 feet to come to a halt under momentum, pressing F7 makes the brake squeal sound and it grinds the engine to a halt in about 15-18". A nifty feature.
selectorpressing F7 makes the brake squeal sound and it grinds the engine to a halt in about 15-18". A nifty feature.
Crandell, I will have to give that a try, I know F 7 makes the brake squeal, but never held it down long enough to see any braking action.
Randy, this is a dumb question. How can I tell if a decoder has BEMF and what does it stand for and do? I have manily used Digitrax DH 123 and 163. I know the 1 means one amp and 2 or 6 is the number of fuctions. I want to try NCE and Total Train Control (is that the right name) decoders and will still use Digitrax as well.
Thank Folks, you are all great help. Now, are you sorry you got me to finally Digitrax, going to be a lot of CV questions coming!
Your friend, Cuda Ken
selector you press F7 and the engine brakes hard.
Just fired up the BLI M1a with QSI, train did not brake.
Ken, there are some locos that you just can't make behave using only CV3 and CV4. I call them jackrabbits and they are really noticeable when trying to speed match locos. Even seemingly identical locos may have a jackrabbit in the set.
It is good that you now have the PR3 because you will need to set a custom speed table to slow down a jackrabbit loco that starts too fast even with CV3 set to 0 or 1 (or the Vstart setting at 0 if you are looking at the motor control panel on Decoder Pro....which I imagine you will be using.....and man, it is so much easier to play with CV settings using Decoder Pro).
I have at least a half dozen locos that "race off" relative to others even with zero'd acceleration settings.
Learning about speed tables is part of the fun, I think. Some decoders will have preset slow start tables that you can enter in CV25 for example (called exponential curves which is a fancy term for a series of settings of speed CVs that have very low values for the first half of the throttle settings and then rises at an increasingly faster rate to reach the final top speed [sorry to go on if this is all something you perhaps already know].
But with your PR3/Decoder Pro you can just set this curve yourself easily in the graphical speed table panel by pushing the slider buttons to values you want....which for some of my locos is a value of 0 for several of the first half dozen speed steps just to slow them down and extend that beginning crawl to match other locos which don't need a speed table at all to do this.
cudaken selectorpressing F7 makes the brake squeal sound and it grinds the engine to a halt in about 15-18". A nifty feature. Crandell, I will have to give that a try, I know F 7 makes the brake squeal, but never held it down long enough to see any braking action. Randy, this is a dumb question. How can I tell if a decoder has BEMF and what does it stand for and do? I have manily used Digitrax DH 123 and 163. I know the 1 means one amp and 2 or 6 is the number of fuctions. I want to try NCE and Total Train Control (is that the right name) decoders and will still use Digitrax as well. Thank Folks, you are all great help. Now, are you sorry you got me to finally Digitrax, going to be a lot of CV questions coming! Your friend, Cuda Ken
Ken,
There are a couple of ways. The 123 series do not and the 163 and 165 series do have BEMF. This is hidden in the manuals, unless you are looking closely for it. They also call is Scalable Speed Stabilization in some decoder manuals. It is controlled by CV55-57. You'll note in JMPRI when you are working on a 123 series you won't see these CVs nor the settings on the Tab.
Here's what is in the basic decoder manual:
Scaleable Speed Stabilization (Back EMF)
Ciso, I seen the speed graph at Simon 1966 house and was sold on the spot. I just got mine this Thursday and have not had the time to hook it up yet. Hope to have it up and running Sunday.
jbinkley60Scaleable Speed Stabilization
Ok Binkley, that term I have seen listed when reading about the 163's. Need to look at the NCE decoder site and see which of there decoders have the setting.
Thanks again, Ken
Someone else mentioned internal friction. This is often a problem with new or very seldom run engines, including if they have sat on the store shelf for several years, that can be overcome by a few hours of judicious breaking-in at varying speeds both forward and reverse. Some people use Pearl Drops toothpaste in the gear trains as a burnishing/lapping compound to remove any flash or rough spots an polish the gears. Be sure to flush it out and re-lube when finished. John Colley, Port Townsend, WA
Ken, I just realized that I forgot an important element in the F7 braking. You have to reduce the throttle setting, maybe even to zero before you will get the braking. I apologize for that oversight. Also, I do not really know if reducing the speed from, say, 40-30 will have it braking when you press F7 and it will fall to 30 and continue at that new speed....never tested it because I had never wanted to use the feature that way...I have always wanted to get the train to stop, but had some time and didn't need to use the emergency button.
So, try your engine(s) again. Get them up to a scale speed, quickly zero your DT400 speed on the throttle, and assuming you have a fair bit of momentum in CV4, the engine should make the brake sounds and begin to slow very quickly. It will stop in less than half the distance it normally would for your CV4 setting.
FWIW, I usually set CV4 on my steamers up in the 60-120 range. In that case, pressing F7 any time after I have zeroed the throttle brings my trains to a safe, non-abrupt, halt. I wonder about the effects of repeated emergency stops on the driveshaft and such with a brass weight spinning on it, so I use emergency as seldom as possible.
cudakenjbinkley60Scaleable Speed Stabilization Ok Binkley, that term I have seen listed when reading about the 163's. Need to look at the NCE decoder site and see which of there decoders have the setting. Thanks again, Ken
NCE decoders don't have Back-EMF at this time. The Digtrax BEMF will have you pulling your hair out trying to get it to work with other engines, lots of adjustments.
The TCS BEMF works great, and can be programmed to turn off at a set speed, or you can use a function button to turn it off (default is F6). At low speeds a P2K GP60 will run with a Genesis MP15AC or an Athearn SD40-2 or an Atlas most anything, as long as they all have TCS BEMF in use. And they all start moving on speed step one, no monking around with CV2.
Mike WSOR engineer | HO scale since 1988 | Visit our club www.WCGandyDancers.com
Yup, none of the NCE decoders has BEMF. ANd I am really digging the implementation in the TCS decoders. None of the 'jump' I had to work around that the Digitrax decoders have. And since I've found TCS T-1 decoders as low as $17, I haven't hurt my bottom line too much using them instead of $12 NCE D13SRJ's.
I set up so that on speed step 1 the loco will move slowly as I almost always stop about 10 feet out, pause, then come up to the cars. I can just bunch or pull out the slack to test control. I have CV3 set at 10 and CV4 set at 5. At a friend's Operating sessions I have had people ask "what's up with that? as they didn't have a clue about momentum so they just cranked up the throttle then were surprised at the runaway. I know my engines and work up through the notches with no problems. My own feeling is that if one is going to the trouble to operate realistically then that should include engine control as well as car card control. John Colley, Port Townsend, WA
Hi Cuda Ken.
Most decoders use only a linear acceleration factor (momentum). That is, the factor remains the same over the whole speed range according to the value you entered in CV #3 and #4. The problem is that when you add a high value in CV #3 to have a nice slow acceleration indicating a heavy train it also takes longer for it to actually start to move from a stand still. Plus the whole acceleration process using CV #3 and #4 as it is, is in most cases not really prototypical either. When you watch a heavy train start up you'll notice that its acceleration at first is very slow because it has to overcome a lot of friction. Once it reaches a certain minimum speed most trains begin to accelerate faster. Likewise, when decelerating many trains ease up on the brake a little shortly before coming to a full stop; maybe more so on passenger trains to give the passengers a smooth ride. This is where CV #121 and #122 comes in on ZIMO decoders. These CV's "stretch" the momentum in the lower speed step range and thereby create a non-linear acceleration/deceleration rate. The two CV's let you chose the speed step range from 0 up that should be included in that process as well as the "stretch" factor.
Regards,Art LuescherZIMO Agency of North Americahttp://www.mrsonline.net/
cudaken I have been playing with CV 3 and have tried 60 and 50 as values. (I am new to this so I hope I am using the right terms). I want a slow acceleration rate, problem is the engine sits there still for a few seconds then starts to go. It starts moving just a little to fast, after it starts to move. I like the effect, but I want it to start at a craw, not like I dumped the clutch. Is there another CV I can change to get it moving quicker but at a slower rate? Engine in question is a HO Athearn RTR SD40-2 with a Digitrax DH 163 pulling 21 cars. I running a Digitrax SEB. I have finally got my Digitrax PR 3 to night at 9:45 PM so yet to be hooked up. Thanks for the coming answers. Cuda Ken
Back EMF is Back Electro-Motive Force. When an electric motor turns, it generates a small amount of electricity. You can measure this and use it to control the motor's speed to a very precise measurement. In our trains, if the train starts going up hill and the motor spin rate slows down, the amount of current it produces drops, and a decoder with BEMF detects that and gives more power to the motor so it spins at the rate it was spinning before - to the train goes uphill and downhill the same speed it goes over flat terrain.
CV 3 and CV4 affect the amount of time between speed steps. The amount of time increase for each increase in the CV setting is determined by the manufacturer so it isn't a set rate, but let's say on your decoder each number in CV3 adds 1/10th of a second between speed steps. If you have CV3 at 20 and you set your throttle at speed step 10 it will take the decoder 2 seconds to get up to speed step 10 for example.
Some decoders are set so when you turn the throttle up, it first applies enough power to get the engine moving, then applies the momentum to provide a smooth transition to the speed step you set the throttle to. With most of them, it just applies power starting at speed step one and pays no attention to whether that actually makes the engine move or not.
So...let's say from the above example you have set CV3 to 60. If you set your throttle to speed step 10, it will take the decoder 6 seconds to get to speed step 10. That's fine, but what if your engine's motor won't start turnng until speed step 8 ?? Then your engine is just going to sit there until it gets up to speed step 8, which will take around 4 seconds.
That's where you can adjust CV2 up a little to get the engine to start moving a little quicker, it increases the power the engine gets at the start.
cudaken selector you press F7 and the engine brakes hard. Just fired up the BLI M1a with QSI, train did not brake.
You have to be going over a certain speed step for it to work/be noticeable. Try it with speed step 32 and compare the stopping distances.
Set CV4 to something large like 120. Go up to speed step 32. Go to speed 0. Observe the distance
Go back up to speed step 32. Go to speed 0. Hit F7. Distance should be shortened.
I believe there is also a CV which affects the breaking rate.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
Thanks folks for all the great answers, so I am guessing I don't want NCE. To bad, I have 6 toasted decoders to send them, 6 decoders for $62.00 seems like a good deal.
I have been sick, and have not messed with CV 2, nor have I messed with the PR 3 yet. Decoders I have for now are DH 123's and 163's. What is the stock CV 2 setting? Going up will increase the starting voltage just to make sure. Reason I ask is till I feel better and learn to use the PR 3 I cannot read what the CV's are before I start.
On a funny side note, I finally tried setting CV's in OP mode. Seems I confused PO with PG and now all my engines CV 3 is sat at 40. Even my Blue Line's.
Sick again, Cuda Ken
cudakenOn a funny side note, I finally tried setting CV's in OP mode. Seems I confused PO with PG and now all my engines CV 3 is sat at 40.
NCE does sell a product called Auto-Switch which can prevent that problem. It senses Service Mode programming commands and automatically shuts off the output to the main layout. It was designed for the Power Cab but works with any DCC system that uses the main track outputs for Service Mode programming. Something to note, however, is it only breaks the connection between the track outputs and the layout, so, for example, if you have an Empire Builder command station plus an additional booster, the booster will still output the programming commands to it's section of the layout(unless you have an additional Auto-Switch on the booster) because it will get the programming commands from Loconet.
I guess in a way I agree. Then again, I am happy that the SEB can spank any decoder out there....certainly any of the several types I have.
Ken, I have done what you did several times. I have learned, at along last, to make it a point to look at the screen and make darned sure the number of presses I make on the "program" button corresponds to the displayed mode.
One thing about setting a CV like #3 to 40 and having all decoders comply is that you can undo it the same way. Then, of course, you must go back and configure that CV for each engine if you don't want the new value, but you can take a second the next time you go to use it and set CV3 for something appropriate for that engine. It helps to keep a record for each engine so that you don't have to go through a bunch of trial programming sequences.
cudaken Thanks folks for all the great answers, so I am guessing I don't want NCE. To bad, I have 6 toasted decoders to send them, 6 decoders for $62.00 seems like a good deal. I have been sick, and have not messed with CV 2, nor have I messed with the PR 3 yet. Decoders I have for now are DH 123's and 163's. What is the stock CV 2 setting? Going up will increase the starting voltage just to make sure. Reason I ask is till I feel better and learn to use the PR 3 I cannot read what the CV's are before I start. On a funny side note, I finally tried setting CV's in OP mode. Seems I confused PO with PG and now all my engines CV 3 is sat at 40. Even my Blue Line's. Sick again, Cuda Ken
I hope you feel better soon. Digitrax sets CV2-CV4 all to 0 from the factory. Here's something from their manual:
Speed Tables-How the Loco Responds to the Throttle
With Digitrax LocoMotion™, there are two types of speed tables: 3 Step Tables and High Resolution 28 Step Tables. Please see your Digitrax Decoder Manual for a discussion of the 28 Step Tables. The 3 Step Tables are set up by programming 3 CVs: Start Voltage (CV02), Mid point Voltage (CV06) and Max Voltage (CV05). These values are set at 000/x00 at the factory. All have a range of values from 000/x00 to 255/xFF. We recommend the following CV values as a starting point for experimenting with speed tables.
Felt a little better tonight and started playing with the CV's. Odd thing happened with the SD 40-2 the other night, it stopped running but I could control the lights. Pulled it and tonight I reset the DH 163 CV 8 to 8. could control the light, but still would not move. Did it again and still nothing? I was controlling the lights as cab 3, the default setting and SEB said decoder reset was good.
Wheels where nasty looking, so I hooked up the Kadee Wheel Cleaning Brush to a MRC 2500 and had at it. At first nothing, but I rubbed the brush against a pair of wheels and it finally started running. Sat it on the programing track, sat the cab back to 40, CV 2 to 1, CV 3 to 40 and for the fun of it, CV 4 to 70! Got the sucker up to spied steep 82 and backed off the power. Good thing the DT 400 has a Panic stop! After 40 feet it was still cooking and it was sharing the line with a 30 car grain train.
Setting CV 2 to 1 has helped but it was just dragging some track cleaning cars.
jbinkley60 Loco Type V Start CV02 V Mid CV96 V Max CV05 Switcher Concentrated low speed. Limited top speed 002/x02 038/x26 064/x50 Road Switcher Prototypical top speed w/evenly distributed curve from 0 to top speed 002/x02 048/x30 098/x62 Mainline Loco Quick increase to cruising speed then levels off to prototypical top speed. 002/x02 128/x80 154/x9A
Now for not as dumb questions because Simon 1966 could not answer it about CV's. Using the chart above. I under stand CV 02 an then the 002, that is the value you want to set CV 2 to. But what the heck does the / X 02 mean?
Then lets throw in the Mainline Loco, CV 5 is sat to 154, but what the heck does / x 9A mean? Like I said, Simon did not know when I asked him and he is my last hope! OK, just had a Star Wars flash back.
Having fun again, cough, Cuda Ken
cudaken Now for not as dumb questions because Simon 1966 could not answer it about CV's. Using the chart above. I under stand CV 02 an then the 002, that is the value you want to set CV 2 to. But what the heck does the / X 02 mean? Then lets throw in the Mainline Loco, CV 5 is sat to 154, but what the heck does / x 9A mean? Like I said, Simon did not know when I asked him and he is my last hope! OK, just had a Star Wars flash back.
Ok, that I understand.
On the SD 40-2, it is pulling a 15 car train and I do like what CV 2 has done. It starts moving with in a second or so, not long at all. No jerk when it starts to move. It all so seemed to help its low speed as well.
And here I thought I would not like playing with CV's.
CSX Robertcudaken Now for not as dumb questions because Simon 1966 could not answer it about CV's. Using the chart above. I under stand CV 02 an then the 002, that is the value you want to set CV 2 to. But what the heck does the / X 02 mean? Then lets throw in the Mainline Loco, CV 5 is sat to 154, but what the heck does / x 9A mean? Like I said, Simon did not know when I asked him and he is my last hope! OK, just had a Star Wars flash back. Each number is listed in the chart as decimal value/hexadecimal value, for example decimal 154 = hexadecimal 9A(0x is a short hand way of writing hexadecimal). Digitrax lists the hexadecimal equivalents because with the old DT100 throttles you had to program in hexadecimal(it used hexadecimal for programming because the maximum value you can program a CV to (255) can be represented with only two digits in hexadecimal(0xFF). With the DT400 throttle(or DT300 or Zephyr) you do not have to worry about the hexadecimal values.
Thank you for that explanation CSX Robert.
I was left scratching my head, when I saw that chart in the Digitrax decoder manual.
Don't know why Digitrax couldn't put a paragraph is their manual that says exactly what you said in your post. They assume that all of us know this stuff-- I know of two of us who didn't.
I'm sure the decoder manual is due for an update since it makes no mention of the new 165 series decoders with built-in current limiters - although as far as I know there are no actual programming changes. But the latest revision is now 5 years old. Also not on Page 26 where it starts to talk about programming CVs it mentions that some throttles use hex and some do not, and refers you to Appendix B which explains how the 'pseudo hex' works on the DT100, mentions that hex numbers have an 'x' in front of them, and also includes a complete hex to decimal conversion chart.
I won't give up posting explanatory posts on why hex is actually EASIER for bitmapped CVs (those like CV29 where the instructions say things like "set bit 3 to 1 to make this happen, set bit 3 to 0 to make that happen") because the binary bits convert into hex in a much more straighforward fashion than converting to decimal. Of course the absolute easiest way is to avoid hex AND decimal numbers altogether and just use DecoderPro and click the check boxes for the features you want and let it handle any numeric values.
cudaken Ok, that I understand. On the SD 40-2, it is pulling a 15 car train and I do like what CV 2 has done. It starts moving with in a second or so, not long at all. No jerk when it starts to move. It all so seemed to help its low speed as well. And here I thought I would not like playing with CV's. Cuda Ken
What value did you end up setting for CV2 to get this response ?