CV for direction change

[rrinker]

 I don;t rightly know who would only want 14 speed steps - someone with the old original MRC systm that can only do 14 speed steps? 14 speed steps would have been all we got had Digitrax and NCE not stepped in during the standards development. I even remember some of the discussion on the old CompuServe Railnet forums (they still exist, in a more modern format, actually). People were saying things like "real locos only have 8 notches, 14 should be plenty" - too bad physics doesn;t scale, and our models don;t keep rolling on momentum the way the real thing goes. And that discounts anyone runnign Baldwin diesels. Or many electrics. Or Steam.

 That old DH120 ought to do 14 speed steps fine, although it was either that one or the preceeding model that have a lot of known issues and were quickly replaced by a newer version. That goes way back before I even got my first DCC system.

                    --Randy

 

[maxman]

rrinker

CV29 = 0 would be short address, normal direction, 14 SS. CV29=1 would be the same, except reverse direction.

Yes, but 14 speed steps?  Who wants that?  I thought that I had also read where setting some decoders to 14 speed steps caused other problems.  But maybe I'm remembering incorrectly.  My opinion is that it would be better to set that decoder to a more valid value.  Or else the next question that gets posted will be why doesn't my loco do this or that and there will be multiple postings before it gets figured out that CV 29 is the real problem.

[jalajoie]

Thanks Randy.

[rrinker]

 It's valid though. In this case, 0 or 1 would also work, since indeed, that old decoder does not have Railcom. No Digitrax decoder does. Bit 3 just does nothing on this decoder.

CV29 = 0 would be short address, normal direction, 14 SS. CV29=1 would be the same, except reverse direction.

          --Randy

[jalajoie]

I agree with you maxman, I wonder how the loco run with such values. A value of 8 means only bit3 is on and a value of 9 indicates bit 3 and 0 are on. Normally bit 3 is for Railcom and not to be use if that feature is not supported by the decoder. I doubt a DH120 will support Railcom.

Something odd going on here.

[maxman]

Hooty

I have it!

My system is a DCS 100 with DT 400 controllers. I put the engine on the programing track, it has a digitrax 120 decoder. I brought up CV29 and put in the value of 9 the engine ran long hood forward. Value 8 lets the engine run short hood as forward.

I would like to thank you for responding to this ?

Hooty

 

Hooty, I don't know exactly what Digitrax decoder you have, but I believe that all of them use the same method of determining the value of CV 29.  I'm going out on a limb here, but I think the values you used are not necessarily the best choice, and might actually not be valid, even though you accomplished what you wanted to do.

 

Take a look at page 34 of a typical Digitrax manual, http://www.digitrax.com/static/apps/cms/media/documents/documentation/decodermanual.pdf.  There is a table of CV values where you can determine how you want CV 29 to function.  If you notice, values of 8 or 9 are not shown.

 

If you want 28/128 speed steps, speed tables disabled, analog (DC) operation disabled, 4 digit addressing, and reverse direction, the table suggests that you really want a value of 35 in CV 29.

[maxman]

jalajoie

I know it is an oversight Maxman but it is Bit 0 of CV29 not Bit 1. Just to make it clear.

 

Yes, it was.  Thanks for pointing that out.  I went back and made the correction.

[Hooty]

I have it!

My system is a DCS 100 with DT 400 controllers. I put the engine on the programing track, it has a digitrax 120 decoder. I brought up CV29 and put in the value of 9 the engine ran long hood forward. Value 8 lets the engine run short hood as forward.

I would like to thank you for responding to this ?

Hooty

[jalajoie]

I know it is an oversight Maxman but it is Bit 0 of CV29 not Bit 1. Just to make it clear.

[maxman]

gregc

is it bit-0 of CV29?

http://www.nmra.org/standards/DCC/standards_rps/rp922.html

Yes, it is bit 0 of CV29.  That is discussed here: http://www.allpointsnorthmrrc.org/files/tech/CV29Explained.pdf

But after you figure out that you want to add 1 to the value in CV 29, then the question would be what value do you have in CV 29 right now.  This is sometimes difficult to determine if you have a decoder where you can't easily read CVs.  Rather than going through all the investigation to determine the current value in CV 29, I think it is easier to use a CV 29 calculator.  An easy to use calculator is here: http://www.digitrax.com/support/cv/calculators/

{edit: corrected my oversight}

[Hooty]

Thanks

[gregc]

is it bit-0 of CV29?

http://www.nmra.org/standards/DCC/standards_rps/rp922.html

[Hooty]

Afternoon is there anybody out there can tell me which CV it is to change the direction of the loco travel without taken everything apart

Thanks

Hooty