CCIB-157 ARDUINO INTERFACE BOARD (ships only to continental US states)
This board connects any Arduino board to any of the following:
2 - servos
2 - sensors
4 - LED's
It has a 5 vdc pin and GND pin which is common with the Arduino.
Write your own program to use them as you see fit.
One idea is to use it for a model train crossing signals and gate operation. Get some Adafruit IR breakbeam sensors (product# 2168) to detect the train when the first car brakes the beam and when the last car leaves the second sensor. Use two Tower Pro micro servo 9g to raise and lower the gates. There are enough LED connections to make two complete signal flashers to operate with the gates.
Or how about the servos providing some animation around the track, while the sensors turn on some signs or building lights as the train goes by. The ideas are endless. Connect with your Arduino board the easy way.