I have an engine with a Cannon motor and want to wire it for DCC. What is typically considered the pole that is wired to the frame? When connecting the motor leads to the decoder, what happens if you get the + and the - swapped? I tried a search but had no luck.
Don't think there is a typical. If you get them backwards it no big deal. the locomotive will just go the opposite direction from expected.
To fix just swap the wires or change CV 29 to reverse the direction in the decoder.
Peter
Wondered about that. Thanks for the help.
I'm not sure about other brands, but for Athearn diesel locomotives I always consider the left rail and bottom motor brush as the negative side and the right rail and top motor brush as positive, because that's their polarity if the engine is running forward on DC control.
One other thing. You MUST isolate the motor. If it is connected to the frame, you should isolate it from the frame as well. If you don't, it COULD cause you problems. You don't have to isolate the motor housing, just the electrical connections (motor brushes).
When you are finished, the motor should have two wires connected to it, an only two wires. Usually one to one side and one to the other side. (Or top and bottom.)
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.
Get your ohm meter out and place the loco on the track. With the DCC system on. Clip one lead to the right rail and touch the other lead to the motor wires. Whichever one gives you a signal should be the positive pole unless they were connected wrong. Most motors I've seen have the positive pole on top.
Dr. Frankendiesel aka Scott Running BearSpace Mouse for president!15 year veteran fire fighterCollector of Apple //e'sRunning Bear EnterprisesHistory Channel Club life member.beatus homo qui invenit sapientiam
thanks to all for their help. Allow me to provide a status update. I have assumed that the right drivers are the pickup and the tender left wheels the other pickup. I have assumed the right side is positive. This has all turned out to be true. The motor has the connections on a horizontal orientation or 3 o'clock and 9 o'clock. I disconnected the motor leads from their connections to the engine and drawbar. I found the motor to then be isolated from the frame. I made all connections according to the directions and it is now working quite well with one exception. The light won't come on although I swear it was working when I started. I am going to start a new thread on that.
If you have a DC test track still, NMRA convention is that with the right rail positive, the loco moves forward. So set your DC controls so the loco moves in a forward direction, then measure the voltage across the motor, whichever side is + is the one the orange wire should go to. Or remove the loco fromt he track and check continuity from the right wheels to the motor, whichever one is connected to the right side when the loco is moving forward is the orange connection.
And should it still end up backwards, you cna always adjust CV29. I've done 5 Proto 2000 GP7's, and after the first one I kept remindign myself to switch the motor wires because Life Like wired them to run short hood forward and that is not the way they ran on my railroad. But every single one of them, I end up connecting like wire to like wire and then end up backwards on DCC until I reset CV29.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Polarity of the permanent magnet also determines the rotation direction of the motor. This is easily tested with an 'open frame' motor.
So, for the people that are using 'rare earth' (or similar) magnets to re-power old engines - magnet orientation is a consideration.
A member at our club has done this and on testing found the current draw to be much lower.
taildisk
GMILL47I have an engine with a Cannon motor and want to wire it for DCC. What is typically considered the pole that is wired to the frame?
I have been running it since I having the decoder installed but am about to open it up again, so will check.