Programmable Logic Controller simulation: A door showing how PLC's work.
This is a video showing a simple garage door being run by a servo motor. To the right is the ladder logic.Ladder logic is the program that makes the simulated Allen Bradley PLC-500 tell the motor to stop, to go up or down (provided it has not hit a limit switch in either position), to stop at any point, and a set of lights showing the doors state. It is sort of unnecessary to use PLC for this simple operation in most cases, but it is a good start to learning how to actually program them.