I finished a small project the other day. It's an Arduino circuit that uses phototransistors to detect a train coming into turnouts and uses geared motors to align the turnout with the train. I'm sharing it here in case anyone needs an excuse to play with an Arduino.
https://i.imgur.com/MTmETuk.mp4
A single Pro Mini with a circuit like this can move up to four turnouts and monitor eight sensors. All the parts (including the four motors) add up to less than the cost of a single Tortoise.
The version in the next pictures can operate two turnouts. The remaining five pins will be used for signals. It's not as complicated as it may appear at a glance. The four transistors in the bottom left make a pair of motor drivers, two transistors per motor. The IC in the bottom right is a RS485 interface, because my homemade controller uses a RS485 bus to send data to/from layouts. The IC in the top right is a trusty old L7805 because the onboard regulator can't supply enough power for motors. The remaining blocks of pin headers are for attaching sensors, signals, etc.
And here's an up close of the phototransistor (the little guy between the rails). It's so tiny it'll be basically invisible once surrounded by ballast.
Well that's basically it... I can post a detailed circuit schematic and the Arduino code to run it if anyone is interested in replicating this project or something like it
Very neat. I used photoresistors, which are bigger. I may have to try some of these sometime.
Thanks for posting this.
York1 John