As part of my journey looking for new projects for the club layout, I just finished a book called Arduino Model Railroad Animation. It covers using servos to operate semaphores, water tank, cranes and other trackside accessories. This is a good practical guide to electro-mechanical automation using an Arduino as the brain. The authors (Paul and David Bradt) have a few other Arduino books as well that are equally good. We are working on a project using servos to actuate turnouts and microswitches.
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Arduino Model Railroad Animation
Arduino Model Railroad Signals
Arduino Force, Pressure, Friction and Acceleration Science Fair Projects