Isn't that the way it's supposed to be? I thought the standard was that the top of the motor is the + side and it gets the orange wire. I recently replaced the decoder in a Bachmann DCC equipped loco with a new decoder and it had the orange wire to the bottom of the motor. I read an article in Model Railroader about putting a sound decoder in a Bachmann 44 ton switcher and it also said to put the orange wire on the bottom. I read decoder install instructions on TCS Decoder's site for an Athearn non-dcc ready loco and those instructions also said to but the orange wire on the bottom of the motor. When I followed those instructions the loco ran the wrong way. What gives? Do I have the standard wrong? Why are so many saying to put the orange on the bottom? Thanks.
The orange wire goes to the motor terminal that was originally connected to the right rail. The grey goes to the terminal that was originally connected to the left rail. The standard doesn't mention whether the connection is to the top or bottom of the motor as that would require all manufacturers to mount their motors the same way. If you hook the motor leads up backwards you don't have to change the physical connections. You can logically reverse the direction of travel with CV 29 bit 0.
Inevitably, eventualy, you're gonna cross the polarity on an installation.. and if you discover it after your beautiful soldering and wire routing; there is a fix for most decoders.. it's CV29 for NDOT (normal direction of travel).. http://www.digitrax.com/v1/cV29 config register.htm Edit.. markwr touched on that
Thanks. I guess the short answer is, it doesn't matter as you can change the direction of travel anyway with a CV. Wish I'd understood that before I took it apart again and resoldered!
however changing the cv will only change the direction of travel, then the lights will be backwards...saw the loco is going forward, the rear headlight will be on
Ken, I do as you did. The gotcha with using the CV is that if you reset the decoder, or replace it even, you have to remember to change that CV again. OK, hardly a big thing, but I like my work to be as right as I can manage
On the locomotives that I've seen setting bit 0 of CV 29 causes the light functions to match the direction of travel. The front light is on when the locomotive moves forward.
Changing CV29 for NDOT will also make the yellow lead the forward light. If the white lead happens to be connected to the forward light, the lights will be reversed. CV's can be changed to correct that on many but not all decoders. Ideally, the orange lead goes to whichever brush on the motor that has the positive lead when traveling forward. Connect it that way and no Cv's will need to be changed to fix normal direction of travel. It's a good rule to follow especially when adding decoders to roads that ran the long hood forward. Martin Myers
yes, but only if the wires to the motor leads are correct. If the motor leads are backwards, the lights will be also.
This is correct. To be clear, if the motor is wired backwards, but the lights are wired correctly, then simply changing NDOT(Normal Direction Of Travel) will not correct it, you will also have to remap the lighting. If both the motor AND lights are backwards, such as would be the case with an 8 pin plug plugged in backwards, then changing NDOT would correct it. This makes sense if you consider what NDOT is for. It's purpose is not to correct miss-wired motors, it's purpose is for locos that have a different end as "front" on different railroads(such as locos that are run long hood forward on some railroads but short hood forward on others). To change the "normal direction of travel" the NDOT bit has to change the direction the motor turns and swap the headlights.
Compliments to the posters here, especially CSXBob whose summary gets it all done. As usual I'm non-plussed by CV's and wiring issues. Anyone recommend set of current sources that do all this? (Guess I should start a thread for this question, sorry.)
