I have a couple of Athearn GP40-2 locos that I remotored about 20 years ago using "Helix Humper" motors. I am about to add Digitrax DH123 decoders to these locos. I can't find the data sheets that came with the Helix motors that would probably identify the attached wires. They have motor wires attached.....one on the bottom, and one on top at one end. They don't have the NMRA color code of today. The bottom wire is black, and the top one is yellow. I am wondering if the black wire is indeed the negative wire.
My question is this: Is there a standard that says all motors will have the positive (+) lead on the upper side, and the negative (-) on the bottom? Now, with the NMRA standard, the gray wire goes to the negative side, and the orange wire goes to the positive side. I realize that if you wire pos and neg backward, all that is going to happen is that the loco will run backwards when it is supposed to go forward.......not that that is serious, I just don't want to unsolder and resolder to make it correct. I'd rather do it right the first time! Hence, my question about there maybe being a standard on all locomotive motors.
Thanks. -Al
Al,
The NMRA 'standard' for DC is that if positive power is applied to the RH rail - the engine should go forward. If you get the wrong direction with a motor, you reverse the leads.
For DCC, you follow the same basic rule - but it is from your throttle. If you are set for forward, and the engine goes in reverse - swap the motor leads OR set the direction of travel in CV29 to the opposite direction.
I think you will need a little 'trial & eror' testing. Remember, this motor came out long before DCC was invented!
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
So your basic starting point should be, whichever wire is connected to the right rail when the loco is facing forward (as if you were sitting on the loco - so this works even if the factory wiring is backwards as to "long hood forwar" or "short hood forward", if that applies at all) is the red wire from the decoder. Even if that happens to be the black wire on the motor. It's a pretty good chance it will run in the proper direction when the decoder is installed. If not, you can either redo the motor wires or set CV29 and reverse it.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
One thing to watch is the current draw of that motor. The DH123 is 1.5 A and you would think that would cover it, but it could burn the decoder.
I agree with everybody here that has already posted. If you do find that the loco runs backwards, CV 29 can just be programmed to switch the motor polarity.
FURX NS CSX in HO
The RED and BLACK wires from the decoder can go to either the right rail or the left rail pick-ups. It doesn't matter because the track power is basically AC.
The GRAY and ORANGE wires from the decoder go to the DC motor in the locomotive. It is these wires that determine which way the locomotive travels when you select forward.
Yes, you can change the direction by setting CV 29 appropriately, but I think you would also have to change the way the lights work by remapping some other CV's in the decoder. If you have Decoder Pro on a computer with a computer interface set up to your DCC system, it is easy. If not, swapping the gray and orange wires may be easier. After all, you have a 50-50 chance of getting it right at the beginning.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
FURXandNORX I agree with everybody here that has already posted. If you do find that the loco runs backwards, CV 29 can just be programmed to switch the motor polarity.
It would be my recommendation to take the time to determine which wire is which and re-configure if necessary so that you don't have to adjust CV 29 to adjust for direction. This is because some day you may want to program the decoder in ops mode with the loco moving. Such as when adjusting speeds or installing speed tables.
I have found that some motors want to surge or jump as they are being programmed. I have also found that the decoder wants to surge in the normal direction of forward travel, and this direction is normal forward regardless of how CV 29 is set. So if you have forgotten that you adjusted CV 29 to get the engine moving in the new forward direction and try to make a moving adjustment, you'll get a nasty surprise when the engine locks its gears to go from one forward to the other.
Connect the orange decoder wire to whichever motor brush you want to be positive. Determine that by testing the motor's rotation before starting. Grey goes to the other brush. Hook up the function wires per the instructions and everything should work as advertised.
Martin Myers
With any motor of some age........... test the + and - leads with an Ohm meter and check for continuity to ground. There MUST be no conection. That is.... the armature is fully controlled by the decoder.
With Digitrax decoders you have a curious safety feature in some DZ models and perhaps others, I don't have that much experience with Digitrax. If the decoder sees a short to ground across the motor it goes to a fail safe mode and does nothing. It will make no attempt to turn the motor. I have no idea how they accomplish this but they do.
I wired up an early Lindsay motor and the DZ tripped out giving no indication that it was making some decision. It just seemed to do nothing. When I examined stuff more carefully I discovered the short on one brush carrier and solved it. After that the DZ operated correctly and is still running.
As noted above...... gray and orange wires may be swapped for forward operation or done with the decoder by reprogramming. Depends on what you are comfortable or able to do.
I Have found that not all can motors go in the same direction just because of what is marked +.
see ya
Bob