Abstract
At present, traffic pressure in many large and medium-sized cities in China is very great. Some traffic lights’s working hours is unreasonable, violation and records of the incident is inaccurate too. Therefore, to improve and enhance the existing transport system's efficiency and strengthen the control of traffic lights and monitoring the security situation is very important.
The main idea of design is to achieve the control of traffic lights at crossroads and monitoring by PLC. Through the host at control centre to control the various crossroads PLC according to the specific needs of the junction of the city,to control the change of traffic lights at the crossroads,and to monitor the security situation at crossroads, whether the vehicle violate regulations,whether cause incident， and to record The results. then, storage, upload and processing.
This design's superior machine uses PC, uses the VB higher order language to make the monitoring contact surface. Through installs in the intersection monitoring equipment as well as the mobile electron monitoring equipment, carries on the monitoring to each intersection's safe condition. The lower position machine uses German Simens's S7-200 series CPU226 to make the main engine, matches expands module EM222. In the design uses S7-200 programming software STEP 7 - Micro/WIN3.2 to carry on the programming. Uses methods design procedure which the smooth functional diagram and the trapezoidal chart unify. Realizes to the city intersection reasonable control and the monitoring.
Key words：PLC controlling system；Trapezoidal diagram；Traffic Light
