The PLC controlled model elevator (often called a lift by our friends in the UK) allows the student to apply his Programmable Logic Controller (PLC) operating skills to a real world application. Built by Stig Johansson of the AE department, and Nick King (SDSU '98) the elevator consists of a steel base with six supporting columns approximately 4 feet high. The upper portion of the model has a 5 volts DC motor (donated by the Pittman Company) and its associated sprocket chain drive assembly used to lift the car. A counter weight system is used to keep the hoisting chain taught. The weight assembly is fitted with a optical sensor that communicates the position of the car to the PLC (see pics). The sensor parts, consisting of an LED emitter and photo diode, were donated by Hewlett-Packard. The electrical signal of the sensors is connected to a Seimens PLC. There is a myriad of programs that can be written for the model. Depending on the PLC program, the car can be simply operated up and down, or include service routines for selective passenger movement. These can include skipping calls as the elevator goes up to a higher floor to pick up a passengers, demand strategies for servicing lower or higher floors while avoiding others, etc. Future plans for the model include the addition of a network interface to allow students from around the world to control elevator via the web.