Running Model Trains Without Human Input

A Raspberry Pi Pico Controls Two Trains

- By Mike Christle

Running two model train sets on a single set of tracks without collisions is fun but exhausting. So Mike programmed a Raspberry Pi Pico and used a Digital Command Control signal, multiple turnout switches, sensors, and control software, to run two trains with no crashes—all without any human intervention. His code and related files are included.

Lately I have been playing with a model train set. To challenge myself, I bought two sets with two engines, four turnouts, and lots of track. My goal was to run both engines at the same time, without crashing. This was fun at first, but after a while I got tired of constantly adjusting speeds and throwing switches. So I finally thought, why should I do all this work, when I can just program a computer to do it all for me?

SYSTEM REQUIREMENTS

I want to run two trains—a fast passenger train and a slow freight train. Each will have its own schedule, coordinated with the other so there are no collisions.

To accomplish this, I need four elements. First, I need to drive the Digital Command Control (DCC) signal to power and control the engines. With DCC I can control the trains, control lights, toot the whistle, and have all sorts of fun. Second, I need to control the four turnout switches to control the trains’ routes. Third, I need four sensors to monitor where the trains are on the track. Fourth, I need control software to control the trains and turnouts.

The Raspberry Pi Pico is perfect for this project. I can program the PIO module to handle all the time-critical operations and implement the control software in a powerful, high-level language. I will use the PIO module to drive the DCC signal and pulse the turnout switches. The final PCB is shown in Figure 1.