1．设计一个十字路口的交通灯控制电路，要求甲车道和乙车道两条交叉道路上的车辆交替运行，每次通行时间都设为25秒；

2．要求黄灯先亮5秒，才能变换运行车道； 3.根据交通灯控制系统框图，画出完整的电路图。

3.设计出PCB图

-1. Design a crossroads, the traffic lights control circuit, A request lane motorway and two B crossover vehicles on the road alternate operation, each time as the passage of 25 seconds; 2. Asked yellow first-five seconds, can transform running lane; 3. According to the traffic light control system block diagram, paint a complete circuit. 3. PCB design plans