Aspro648 writes -

A more functional train microcontroller… Power is coming from a 12V wall transformer which powers both the Arduino (at 5V), and the shield(at 12V). The shield provides pulse-width modulated DC to the rails. The microcontroller is programmed to control direction, maximum speed, and rate of change. I am using a momentary toggle switch with center off to increase or decrease speed. The computer is reading the current settings from the controller over a USB connection. Hitting the reset button automatically stops the train.

Holy smokes. That was easy. In one evening I soldered the kit and had my model train doing the “PWM-boogie”. Thanks to Lady Ada for making it possible for wantabe hacks like me to do cool stuff! [and] Added a toggle switch and more code, and now it is a functional train controller. I can set the max speed and max rate of change to simulate a real engine while keeping is easy enough for my 7yo daughter to run. All I need is some positional sensing and I can do some auto reversing, ect. I’m amazed how easy you made this for us! Many thanks Lady Ada!