Changing Polaraity in PCM E-7

[Bob Bufkin]

I'm new to DCC and have been trying to change the polarity of an N scale PCM E-7 A unit.  Have followed all directions and have not been able to change the polarity.  I have a dummy A unit I can use but would like to be able to use 2 powered units in the near future.  Any help would be appreciated.
Bob

[wcfn100]

??????????

What exactly are you needing?

This is a consisting question, yes?


Jason

[Bob Bufkin]

I'm using a MRC Prodigy Express I just received.  Followed directions on changing polarity but so far no luck. Want to run the A units back to back.
Bob

[wcfn100]

OK, no more polarity talk, that's so DC. ;D


I'm going to take a guess that you have given both locomotives the same address, yes?

So what you need to do is change what direction is forward for one of the locos.

This operation shouldn't have anything to do with the type of DCC system unless you're just doing it wrong. It should just be about the decoder installed and picking the right values for the right CVs.

We can figure out either one.

edit: Almost forgot, some sound decoders have a hard time getting programmed with some systems, anyone know if the MRC is one?



Jason

[Bob Bufkin]

Yes, I'm trying to get one loco to change direction (MRC manual and PCM manual use the term polarity).  I have changed direction on some Atlas with no problem.  Which CV-29 code to I use.  Send PCM a e-mail asking them.  Their directions say to use 0 or 1, but no go.
Bob

[wcfn100]

OK, yeah, CV29 is the one.  The default is 4 for analog operation.  But changing it to '1' should work just as described. 

I don't know what to say.

Have you been able to change any CV's?  If not, it could be because the sound decoder is requiring more juice than a regular decoder for programming.  The only think I could think to to is try using the programming track output instead of the regular track (or vica versa).


Good luck,


Jason

[Bob Bufkin]

I've changed CV's in Atlas locos but not the PCM one.  Will work on it some more tomorrow.  I'm too darn tired now.  Thanks for your help.
Bob

[Bob Bufkin]

Jason.

Thanks for the info on using programing track.  It worked.  My units are not running the way I want. 
Bob

[wm3798]

Bob,
It's easier to just address each loco individually, then change the direction of the trailing unit when you consist them.
All you have to do is select "consist", give the consist a number (I usually use the last two digits of the lead engine) then input the loco numbers.  When you type in the trailing unit, simply push the direction button to reverse it before you hit "enter".  No need to fool with CV's.  That's how it works on my Prodigy Advance.  I'm assuming the Express supports advance consisting the same way.

On all my Digitrax decoders, I set cv29 to "35" to reverse the normal direction of travel.  Not sure what PCM uses...

Lee

[Bob Bufkin]

They use either 00 or 01 for their sound equipped locomotives.  Just beginning to understand some of the capabilities of DCC.  Read about consist and will try it when I redo some Atlas locos I have.
Bob

[cv_acr]

Bob,
It's easier to just address each loco individually, then change the direction of the trailing unit when you consist them.
All you have to do is select "consist", give the consist a number (I usually use the last two digits of the lead engine) then input the loco numbers.  When you type in the trailing unit, simply push the direction button to reverse it before you hit "enter".  No need to fool with CV's.  That's how it works on my Prodigy Advance.  I'm assuming the Express supports advance consisting the same way.

The advantage being you can set up and delete consists in about 30 seconds without directly programming data values on each decoder. And you can consist anything, in any order you want.

Why would you want to "hard code" the normal direction of the engine to only use those two in one configuration. DCC is way more flexible than that.

[cv_acr]

They use either 00 or 01 for their sound equipped locomotives.  Just beginning to understand some of the capabilities of DCC.  Read about consist and will try it when I redo some Atlas locos I have.
Bob

The "standard" default decoder address is 03. Some DCC systems allow you to run non-DCCed engines using address 0, but most people suggest that's not very good for the engine's motor (haven't bothered to try that myself).

Any decent DCC system should allow you to give your engines 4-digit address numbers, so the best/easiest thing to do is assign each engine the actual road number as it's DCC address. No need to remember what any addresses are then, they're all printed on the side of the engine already.

Your system will allow you to consist engines; you set up a consist and enter the numbers & direction of all the engines you want to have in the consist. You then tell the entire consist to go forward, and all the engines go the same direction regardless of what the "front" end of each individual loco is. My club uses the NCE system, and consisting is very easy & intuitive, and you can address the consist by the lead loco number. You don't even need to know the consist number to select it. (Although when creating consists it helps to know which ones have been used already or you might clear an older consist using the same number)

[Bob Bufkin]

I thank everybody for the info so far.  As I said, I'm new to DCC and just learning the ins and outs.  Intend to try consists shortly.
Bob

[mmyers]

To reverse the direction of any NMRA compliant decoder add 1 to the current value in CV29.
Default Normal Direction Of Travel is always an even number. "Reversed NDOT" is an odd number.

Martin Myers