"Carl M. Kadie" <carlk@msn.com> wrote in message news:FnHCMC.KzF@lugnet.com... (...) Thanks for all the suggestions. I've refined my goals a bit: I'd like to use just Lego parts. I don't mind of the sensor is conspicuous. I don't mind modifying the (...) (25 years ago, 29-Dec-99, to lugnet.robotics, lugnet.trains)