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OK, where is this coming from?

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  • Member since
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  • From: Reading, PA
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OK, where is this coming from?
Posted by rrinker on Monday, August 07, 2017 7:04 PM

 In the past few days we've had people saying the reason for odd operation is that the system is sending 28 speed steps and the decoder is set for 128, or the system is sending 128 speed steps and the decoder is set for 28. Where is this information coming from that so many people think this is a possibility? There is no decoder setting for 128 speed steps. The only decoder options are 14 or 28 steps, defined in CV29. The decoder does nothign to store a setting that i is expecting 128 speed steps - 128 speed steps is generated by the command station using NMRA DCC extended format packets. The structure of this DCC packet is completely different from a 14 step of 29 step packet, and in addition to controlling 128 speed step operation, is responsible for all the extra functions past F8. When a decoder that recognizes extended format packets gets one, it acts on it. There is no setting to make it not. Most any decoder outside of the earliest can recognize extended format packets - but not all can recognize the most recent change - there are plenty of decoders in use that can run at 128 speed steps but can't map functions up to F29.

                              --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by rrinker on Monday, August 07, 2017 8:07 PM

 Which exactly supports what I've been saying - there is no bit to set 128 speed steps in the decoder (direct quote).

 If the system is delivering 14 steps and the decoder is set to 28 - there will be issues. If the system is set to deliver 28 steps and the decoder is set to 14 steps - there will be a problem. There is no setting in the decoder for 128. All driven fromt he command station side. 

                                     --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by BATMAN on Monday, August 07, 2017 11:14 PM

The electronics side of the hobby is my weakest part. I was reading about what people were saying about speed steps and decoders and thinking I'm dumber than I thought. Thanks for letting me have a little self-redemption, Randy.Laugh

Brent

It's not the age honey, it's the mileage.

https://www.youtube.com/user/BATTRAIN1

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Posted by gdelmoro on Wednesday, August 09, 2017 7:14 AM

Thanks Randy, and thanks for the responses to my posts asking about holding 128 the next time the Loco is powered up. 

So based on your explaination (if I even am able to understand it)    1. There is no memory setting in a locomotive decoder.                   

2. The control station (in my case the NCE PH Pro) retains the speed step information ??

3. The next time the particular loco is selected the control station knows to apply 128 to it ??

OR

None of the above is true and I need to make sure the loco decoder is set in CV29 for Advanced 28/128 speed step control and select 128 on the controller when I want it?

Gary

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Posted by rrinker on Wednesday, August 09, 2017 7:41 AM

 The first 3. You should not have to keep hitting the 28/128 button. I have no idea what BLI could be doing differently that makes you need to keep hitting the 28/128 button to switch it. I would think that once the system is sending on an extended format 128 step control packet, it would just always do so and the decoder would respond accordingly. I have no idea what NCE could even be sending out when you press the 28/128 button - it shouldn;t be sending anything on the rails, just change the packet that gets sent when you change speed or direction. Pressing the button on a loco that is selected but just standing still shouldn't change a thing - there's nothing in the decoder to change.

                                          --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by gdelmoro on Wednesday, August 09, 2017 8:38 AM

Thanks

Gary

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Posted by 7j43k on Wednesday, August 09, 2017 9:26 AM

Randy,

Thanks for explaining.  Sometimes info has to be "inserted" several times into my head before it sticks.  And, even then, it tends to evaporate over time.

I just finished installing decoders (soundless Soundtraxx) into three identical Athearn RS-3's.  This included changes in the speed table.  When I put them on the layout, first and third ran on 128.  Number two ran on 28.  I don't THINK I pushed any wrong buttons (but who does?).  I used Power Pro for programming.  And I turned it off and on quite a number of times as I worked.

So, I understand that the throttle is s'posed to stick on 28 or 128.  But it looks like it's possible maybe sometimes it's got something on its mind.

I noticed the problem when #2 decided to go really fast way too soon.

 

On another note, as I slowly pick up this DCC thing, I'm seeing rewards.  I didn't like how the locos were running when I dropped in the new decoders.  And I found an article on fixin' them up a bit:

http://www.trainweb.org/gnw/BEMF%20Tuning.htm

 

Sure did work.  With doing the above plus redoing the speed table, they run beautifully.  Wish they had sound, but that's for another day.  Far in the future.

 

With that bit of new knowledge, I have started on my new Walthers Plymouth switcher.  Which had sorta similar problems as the Athearn Alcos with THEIR new decoders (kinda poor stuttery slow speed, and way too fast way too soon), and results are promising.  Top speed is gonna come way down, 'cause right now it kind of emulates the Athearn Hustler.

 

 

Ed

 

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Posted by maxman on Wednesday, August 09, 2017 9:42 AM

rrinker
Pressing the button on a loco that is selected but just standing still shouldn't change a thing - there's nothing in the decoder to change.

I'm not sure this is correct.  I always change the speed step setting while the loco is standing still.

I just did an experiment.  I had a loco set to run on 28.  While it was running I changed the setting to 128.  There was not an immediate change in speed.  However, when I tweaked the speed control up a notch, then the loco immediately dropped speed to where it would have been if the loco had been set to 128 in the first place.

So something is telling the decoder to react differently.

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Posted by 7j43k on Wednesday, August 09, 2017 10:01 AM

maxman

 

I just did an experiment.  I had a loco set to run on 28.  While it was running I changed the setting to 128.  There was not an immediate change in speed.  However, when I tweaked the speed control up a notch, then the loco immediately dropped speed to where it would have been if the loco had been set to 128 in the first place.

So something is telling the decoder to react differently.

 

 

I'm a newby on this.  

 

But.

 

You pressed the 28/128 button, expecting a speed change.  But the throttle hadn't sent a new speed on the 128 setting yet.  It only changed what WOULD be sent WHEN the throttle again transmitted.  So the decoder just kept going on whatever the last input was.  Which was a "28".  As soon as you CHANGED the throttle setting, the throttle sent out a NEW instruction, which would have been based on the "128".  Which it did.

So it looks like your experiment demonstrates exactly what Randy said.

Sorry about the caps, but I wanted to do emphasis.

 

Ed

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Posted by rrinker on Wednesday, August 09, 2017 12:07 PM

 Exactly. Pressing the button sends nothign to the decoder. After switching to 128, then you move the throttle or press the direction button, the packet sent to the decoder will be compeltely different than the packet send when it was set on 28 step mode. Hmm, maybe there is a use for a DCC packet sniffer after all.

 Want more proof? Set your system to 128 step mode. Run the loco. Then take it to a friend's hosue who has never changed to 128 step mode for that partcualr address. If they just aquire the loco and run it without pressing the 28/128 button, the loco will respond to 28 steps.

 Or another one - my Digitrax system always does 128 steps unless I configure it otherwise. I can give you one of my locos and it will work on NCE just fine without you having to press any buttons besides selecting the loco address. They will run with 28 steps unless you press the 28/128 button.

                          --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    February, 2008
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Posted by maxman on Wednesday, August 09, 2017 1:04 PM

7j43k
You pressed the 28/128 button, expecting a speed change. But the throttle hadn't sent a new speed on the 128 setting yet. It only changed what WOULD be sent WHEN the throttle again transmitted.

Yes, I agree.  But my point was that Randy said something about doing the speed setting change after the loco was running.  My thought was that any speed change setting from 28 to 128 should be done with the loco at stop.  Otherwise the loco will potentially have a sudden drastic speed change which can lead to other operational problems.

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Posted by rrinker on Wednesday, August 09, 2017 1:19 PM

I said if you change it on a loco sitting still, nothing will happen. hat it ould do if you had a loco running in step 14 or 28 then pressed the button - I have no idea. Either the loco will jerk and then be running at step 14 out of 128, or if it will figure out that 14/28 is 64/128 and adjust accordingly. Probably not something you would want to try with your favorite loco running.

                                             --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    January, 2015
  • 147 posts
Posted by RR Baron on Monday, August 14, 2017 5:32 PM

 

Some of the DCC speed steps misinformation has come from ill-trained manufacturer’s staff.

 

A company whose DCC command station only supports 28 speed steps was advising how to use 128 speed steps inquirers they had to buy 128 speed step decoders in order to run a DCC decoder equipped locomotive using their DCC command system.  

 

RR Baron

 

 

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