GridLock
General Description
Automatic traffic lights are a typical engineering invention that made the lives of common people safer and more convenient. For the development of the future SustainCity, its design inevitably appears in the agenda of the city master plan and becomes the essential task of this game module. The game invites students to investigate solutions to automatic traffic light control that better fits the future traffic flow of a 4-way intersection. With the capability of invoking MultiSim by National Instruments (NI) – a powerful circuit design and teaching software environment to aid in visualizing the simulation results as the responses of traffic lights, the game naturally transforms the digital logic fundamentals to lively concepts that students can associate. This game is devoted to sequential circuit design, involving the concepts of finite state machine, state minimization for optimization, as well as the design procedures.
Problem Statement
A traffic light which controls the traffic at an intersection with a North-South direction street and an East-West direction street is presented to the students as shown in the first image on the right. The sequence of lights turning green, yellow and red are given in a table as shown in the second image on the right. The North-South direction light directs the flow of traffic arriving at both the North and South intersections while the East-West direction light directs flow of traffic arriving at both the East and West intersections. The sequence contains a state where both lights are red to provide a safety margin for design. The outputs of the controller to the signals can be seen in a table as the third image on the right. The traffic light also has a timing requirement. The design task is to allow the green light to stay on for 16 clock cycles, then the yellow light for 16 clock cycles, and then the red light for 16 clock cycles as specified by the customer. The lights will be repeatedly following the previously given sequence of turning specific lights on or off without modification.
