Loco & switch troubles

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New Member
I have an HO scale pike---am going to install about 20 Twin COIL (NJ Int)
switch machines. I notice that they have (3) terminals all with blue colored
wire...anyone know how to hook them up to on/off button? Also have Penn RR 2-8-2 loco w/ tender attached and with a single wire entering it....EWngine is fine IF connected to tender-but once tender is set on track engine will NOT run! Anyone have clues? Franklyn Elliott, felliott@optonline.net


The 2 outside terminals on the switchmachines are for the specific direction you want it to throw while the center terminal is the common. You will need 2 momentary normally open (N.O.) pushbuttons for each switchmachine.

From the AC (desired) accessory terminals of the power pack you will use or the transformer, run one wire directly to the center terminal of each switchmachine. Then run a wire from the other AC terminal to one side of each of your pushbuttons. From the other side of your pushbuttons run a wire directly to the other terminals of the switchmachine.

As for the locomotive, check the wheel trucks on the tender. The tender only picks up power on one side and both trucks must be picking up from the same side. Look at the wheels in the truck. In older models one wheel might be brass and the other plastic. In newer models you might have to look for insulation where the axle connects to the wheel in order to determine which wheels are picking up power. Once you are sure the pick up wheels are all on the same side, put it on the track and see if there is a short. If there still is, then rotate both trucks so the pickup is on the other rail. This should clear up the problem.

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I use a Tortoise switch machine to control some crossing gates. I don't turn off power to the switch machine. It just "stalls" when it reaches the end of travel. I think the current is so small that it does not hurt the machine. The NJ machine could be the same way, eliminating the need for a pushbutton. A single pole double throw switch could then be used. Again, I'm not sure if NJ machines are stall motors, like Tortoise.


Red Oak & Western

Active Member
I'm sure. The NJI switch machines are "twin coil" and MUST use a pair of normally open momentary switches, typically single pole single throw (push button preferred). They can also be operated on DC as well as AC, though when using DC, you must be aware of "inrush current" and make sure the power supply you use can handle it. A "capacitor discharge" DC power supply is frequently used, especially if you will be operating the switch machines in succession, as in setting up a route in a yard ladder.

Hope this helps. If you are still confused, just ask for more info.

By the way, the wires on my NJI machines are all tan -- the color doesn't matter, so long as the center terminal is treated as the "common connection" and the other terminals are connected to the push buttons, as David illustrated.

You should also have a series of contacts (usually 6) on the left side (when the NJ Switch Machine lettering is right side up), as well as another set of 3 on the top. They are used for routing power to the various parts of the turnout (depending on the turnout manufacturer, style, etc.) to prevent shorts. More information can be found in How to Wire Your Model Railroad by Linn Westcott or Basic Electricity and Electronics for Model Railroaders by Don Fiehmann, both published by Kalmbach. You might be able to find a copy in your local library.



So these machines are like Atlas and Peco twin coil machines. I use capacitor discharge switches for my Peco machines. There are several designs out there that could be used if you don't like the idea of a pushbutton switch. Mine for example use an alternate action pushbutton that flips the turnout one way and then the other.


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