Does Dither help in N scale?

kmcsjr Feb 27, 2014

  1. kmcsjr

    kmcsjr TrainBoard Member

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    I'm programming my locos. Some have dithering. Is it ever helpful? And then more specifically does any gain decrease for great runners like Kato E8s? I'm going to play with it, but I'm not sure what I'm looking to judge.

    Thanks
     
  2. retsignalmtr

    retsignalmtr TrainBoard Member

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    Dithering? Explain please.
     
  3. Kenneth L. Anthony

    Kenneth L. Anthony TrainBoard Member

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    I have an idea what dithering MIGHT mean. Back 20 years when I had a 286 computer that was not strong enough to display jpg images, it displayed some kind of images in 16 solid colors. Lots of colors it could not make, and could not make an even shaded gradient. But it could simulate that shading a range of dots- one area solid color, then a few dots of different color among mostly the background, then equal dots of both colors, then mostly the second color with just a few dots of the original color and finally solid the second color. This is called dithering in graphic arts.

    The old DC "pulse power", ie. half-wave rectification might be considered a kind of dithering in power. Under "pulse power", only one polarity of the AC plus-and-minus wave would be delivered to track and engine so power would in effect be turned on and off 60 times a second. This could have a micro-jolting effect on an old-time motor, too fast to see but it could allow it to run slower than otherwise possible without stalling. It caused many motors to overheat, and if you switched from pulse power to normal power while running, the loco would jump forward.
    Some "advanced transistor throttles" for DC could switch gradually from pulse-power to normal power and avoid that jumping forward. This might be considered an analogy of "dithering" though I never heard the term used that way.

    I suppose there might be a DCC program that conceivably could do something similar, and again, this might be what "dithering" means in this context. Just guessing...
     
  4. Flashwave

    Flashwave TrainBoard Member

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    Lifted from the TCS website. http://www.tcsdcc.com/public_html/Customer_Content/Technical_Info/Tech_Info/FAQPage.php?q=21
     
  5. retsignalmtr

    retsignalmtr TrainBoard Member

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    Sorry I asked.
     
  6. lexon

    lexon TrainBoard Member

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    What power pack are you using?
    I have never heard of dithering in model railroading.

    Rich
     
  7. kmcsjr

    kmcsjr TrainBoard Member

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    Rich,
    I'm using an NCE powercab. Dithering is a function of the decoder. Flashwave described it (Thanks :) ). I am wondering if anyone is USING it. When I play, I don't know if my performance is improving because of "dithering" or break in. Since I'm getting mostly more questions, I'm guessing it isn't used much. I will be sticking to decoders with BEMF, going forward, which (I think), has replaced dithering and seems to run well.
     
  8. ppuinn

    ppuinn Staff Member

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    Marty:
    Two weeks ago, I bought a cable, downloaded the free jmri software (which includes DecoderPro for conveniently programming decoders), and connected my computer to my n-scale layout (Digitrax Loconet). When speed matching some locos this week, some blind trial and error produced improved low speed performance when DecoderPro gave me the option of tweaking the loco's dithering CVs. Adjusting the dither on this loco definitely helped me match its slow speed performance to its sister loco with a different brand of decoder (for which DecoderPro did NOT show dither adjustment options)...but the improvement was by luck rather than by design.

    After looking through my 2003 editions of the Digitrax mobile decoder manual and Super Chief manual, to my definitely limited and possibly faulty understanding, it seems like adjusting CV02 (VStart voltage), CV56 (dither/pulse frequency), and CV57 (dither/pulse amplitude) provide 3 different ways to "boost" power in some way to solve problems with a loco's low speed performance...but I'm not clear yet on which CV needs to be adjusted in what precise way to achieve specific types of improvements.

    For those of you with experience tweaking starting voltage and/or dithering CVs (and with apologies to Marty for drifting a little from his original question about whether anyone is adjusting dither to improve loco performance), what loco performance symptoms or issues would be best addressed by tweaking VStart voltage with CV02, and what symptoms or issues are best addressed by adjusting loco dithering with CV56 and/or CV57?
     
  9. Flashwave

    Flashwave TrainBoard Member

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    You're welcome.

    I think you've pretty well answered your own question. What I know about pulse is that DCC decoders don't like it, something to the tune of trying to jump rope and someone keeps playing with the cord. With Dithering its the decoder doing it itself, and so isn't as hard on the decoder as it can predict its own actions, but yes, Dithering appears to be largely out-modded.

    As to whether or not Dither will help with N scale...

    250px-DeepTrouble_Helper_Bot.jpg
    Hoow could you say no to him?

    (Sorry, I am a bit of a nerd...)
     
  10. kmcsjr

    kmcsjr TrainBoard Member

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    Ppuin.. something to consider, when i start matching speeds.

    Flashwave.. the model train world has plenty of room for nerds. Or, the nerd world had plenty of room for model trains....

    Sent from my SCH-I545 using Tapatalk
     
  11. lexon

    lexon TrainBoard Member

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    Did a little research about this issue and came up with the below link. Most of you are probably familiar with this issue. I was not. TCS is really improving decoders.


    http://www.tcsdcc.com/BEMF.pdf

    Rich
     
  12. DCESharkman

    DCESharkman TrainBoard Member

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    Dithering is only a TCS decoder function. Digitrax has no such functionality. Digitrax uses those CVs for BEMF.
     

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