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Simple Signal Circuit for Model Trains

Basic Bi-Directional Signaling



Signals are operational necessities on the mainlines, but they also add a lot of visual interest and excitement as well.

®2010 Ryan C Kunkle, licensed to About.com, Inc.

Signals are an important part of railroad operations, keeping trains safe as they share the rails. A working signal system can add a lot of operational and visual interest to our model railroads as well. A fully functional signal system is not an easy undertaking. Although more products are coming on the market every day to make it more manageable, you must still invest a lot of time and money to make sure everything works properly.

What if you don't want or need a complete system, but want your signals to do a little more than your street lights? This simple wiring circuit will do just that. The idea for this project was submitted by Bernard Zalewski, and the attached pdf was drawn by Mark Hannah. It provides an easy way to signal a track for bi-directional running. In other words, if an eastbound train has a clear signal, the westbound signal will read "stop" and vice versa.

How it Works

The wiring diagram for the two signals is very similar to a circuit for wiring reverse loops. As shown, it works with conventional DC power supplies - the standard in Z-S and G scales. This logic will not work with DCC track power. Crossing the leads to the LED's in each signal will cause the opposite indication display.

With the signals wired directly to the track (with the addition of a resistor), signal indication changes with the change in track polarity. In other words, the signal indicationn will match the direction of travel as you have it set on the power pack. If your signals are backwards, just switch the leads at the track.

Although this system does not detect the trains, or interact with switches, even this basic indication can be helpful for a quick reference as to the direction setting on your throttle. This can be very helpful at clubs, working with children or other applications.

Since the LED's draw very little current, you could install multiple signals around the layout for added visibility and still not place too much of an electrical load on the system.

A Platform to Build On

The system seen here is simple, but it is a good start to something more involved. The basic 2-LED signals shown here can be used as signals in their own right. They are available at moreleds.com. You could use the same wiring diagram with more realistic signals as well.

With the signals in place, you can always add in more layers of control later. Even a complete signal system and DCC control can be tied in without changing the signals on the layout.

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