摘要针对近年来城市交通的拥挤现象，特别是驾驶员违章严重、交通事故频发、车辆尾气污染等问题，介绍集计算机、信息、电子及通讯等众多高新技术手段于一体的智能交通指挥中心控制系统。该系统的安装及使用，大大缓解了城市道路堵塞现象、提高了道路的通行能力。减少了驾驶员违章的次数，抑制了交通事故的发生、同时能够减轻车辆尾气排放，从而对降低环境污染起到了不可低估的作用[1]。分析现代城市交通控制与管理问题的现状，结合城乡交通的实际情况阐述了交通灯控制系统的工作原理，给出了一种简单实用的城市交通灯控制系统的硬件电路设计方案。关键词:交通控制；交通灯；PLCABSTRACTInrecentyears,forurbantrafficcongestion,especiallydriversofseriousviolations,thefrequenttrafficaccidents,vehicleexhaustpollution,introducedthesmall-computer,information,electronicsandcommunicationsandotherhigh-techmeansinoneoftheintelligenttrafficcontrolcenterSystem.Thesystem,andtheuseofandgreatlyeasetheurbanroadcongestion,increasedroadcapacity.Toreducethenumberofillegaldriverstocurbtheoccurrenceoftrafficaccidentsandatthesametimetoreducevehicleemissions,thusreducingenvironmentalpollutionHaveplayedaroleshouldnotbeunderestimated.Analysisofthemodernurbantrafficcontrolandmanagementofthestatusquo,combinedwiththeactualsituationofurbanandruraltransportonthetrafficlightcontrolsystemworkingprinciple,givenasimpleandpracticalurbantrafficlightcontrolsystemhardwaredesign.Keywords:trafficcontrol；trafficlights；PLC目录1绪论.................................................................32PLC概述.............................................................42.1PLC的发展现状..................................................42.2PLC的发展趋势..................................................52.2.1在产品规模方面，向两极发展。..............................52.2.2向通信网络化发展..........................................52.2.3向模块化、智能化发展......................................52.2.4编程语言和编程工具的多样化和标准化........................52.2.5PLC应用中存在的问题......................................52.3PLC的特点......................................................62.3.1可靠性高，抗干扰能力强....................................62.3.2控制系统结构简单，通用性强................................62.3.3编程方便，易于使用........................................62.3.4功能完善..................................................72.3.5设计、施工、调试的周期短..................................72.3.6体积小，维护操作方便......................................72.4PLC的结构和工作原理............................................72.4.1PLC的基本结构............................................72.4.2PLC循环采样的3个工作阶段.................................93十字路口交通灯PLC系统设计方案......................................103.1十字路口交通灯设计背景和意义..................................103.1.1设计背景.................................................103.1.2研究目的和意义............................................113.2十字路口交通灯总体方案设计....................................123.2.1单片机的控制方案.........................................123.2.2微机的控制方案...........................................123.2.3PLC的控制方案...........................................133.3显示方式......................................................143.3.1LED显示方式.............................................143.3.2LED+数码管显示方式.......................................143.3.3LCD液晶显...