two voltages on dual gauge track : LUSENET : Wiring for DCC : One Thread

i"m looking to use DCC on my N/Nn3 dual gauge layout. The problem is the narrow gauge engines can withstand 12VDC only and the standard gauge uses 18VDC. My question is can boosters with different max voltages be wired with a common wire as it would be with dual gauge (3 rail)trackage?

I haven't put this question to any of the manufactures yet, I thought that I would ask the experts first.

Thank You Milt Perkins San Diego, CA

-- Milton Perkins (, May 07, 2003


I'm sure someone will correct me if I am wrong, but the track voltage - be it 18 or 12 - goes to the decoder, not the motor, the decoder would then regulate how much voltage reaches the motor. To be honest I think your major problem will be three rail operation - I am not sure how you would wire dual guage switches, crossings, the devices used to change which side of the standard guage is shared with the narrow guage, etc. Good luck. I will be interested in your success - I have never done any narrow guage, but you never know ...

-- Charles Lewis (, May 07, 2003.

I would hesistate trying to connect two different boosters and use a common rail. That might work with some manufacturers, but definitely not all of them.

Besides, I have a simple solution for you!

Decoders have speed tables and a CV called Vmax. READ YOUR INSTRUCTION MANUAL FOR YOUR DECODER CAREFULLY. Depending on what step mode you are in, which is used.

By setting these at say 2/3 of their max value, when you have your throttle at max, it will only send 2/3 of full power to your motor. So if you had 18V, a decoder with these settings, would send 12V AVERAGE. You would set all your narrow gauge locos to these lowered settings. Now you only need to use one booster and no exotic wiring to power both your narrow gauge and standard gauge trains!

Note on voltages: You mentioned 18V. Power supplies usually put this out. Most boosters set to HO or N, regulate down to something lower, like 14V. Then there is a fixed voltage drop inside your decoder that lowers it to about 12V - which is the max the motor sees. You may not have a problem at all! Usually only O and G use 18V. Not even most HO locos would like 18V - DCC or regular DC. So I doubt your standard gauge N uses 18. I am not an N person, so I could be wrong.

Go to my track wiring page and make the super simple voltage measuring circuit if you have any doubts about what your booster is putting out. Or buy the meter from Tonys Train Exchange. Lastly, you can measure the voltage across a motor with a regular DC meter. Make you don't try to measure the output of a decoder without a motor, or if you are afraid you will burn it up, at least a 12V or 14V bulb from Radio Shack.

-- Allan Gartner (, May 07, 2003.

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