American Flyer Arduino 769 Rotary Beacon Controller
This is based on an Arduino chip. I laid out a circuit board for it and orderd them. This is a description of how they work and some assembly tips.
The control board is designed to work with a standard AC powered American Flyer train layout. For more realistic effect, the 769 Rotary Beacon needs to be modified. I actually built mine out of scrap parts from some towers in my junkbox that were beyond original restoration. At some point I will try to add some detailed photos of the hardware modification to this page. The YouTube video gives you some idea how it is made.
The circuit description is a s follows:
Power from the 16 volts of the train transformer is rectified by a bridge rectifier where it becomes about 22 volts DC. It is fed to the buck converter module which is adjusted to provide 5 volts DC for the ATmega 328 processor chip.
The processor chip is programmed to drive a small stepper motor through a ULN 2003 driver chip. The stepper motor and driver board are often found on places like Amazon or eBay for as little as $3.00. They are made by the hundreds of thousands to drive the louvers in many air conditioning units, therefore they are inexpensive. I salvage the driver chip from the supplied board to use in my Arduino based board.
The buck convertor is about $1.45 which is cheaper than trying to use a linear regulator like an LM7805 and it's associated support components.
A short YouTube video showing the board and beacon in operation can be seen https://www.youtube.com/watch?v=ZJTCgxkEQyU&t=68s
Code for Arduino chip
Source for PC boards