无协议通信在空调系统监控中的应用

Application of Non-protocol Communication in Supervision of Air-conditioning System

MODBUS是用于控制设备的一种通用串行通信协议。简要介绍MODBUS协议以及PLC与变频器之间进行无协议通信的方法;讨论循环冗余校验码(CRC16)的生成方法,并设计PLC计算CRC16的子程序。给出了一台欧姆龙小型PLC,使用RS-422A总线,通过无协议通信的方式集中监控空调系统多台分散变频器的工程实例。实际应用表明,该方法简单易行、可靠性高、控制效果良好、经济实用。

MODBUS is a universal serial communication protocol used in controlling devices. The MODBUS protocol and the method of non-protocol communication between PLC and inverter are introduced. The creation method of cyclic redundancy check code （ CRC16 ） was discussed and the calculation subroutine of CRC16 by PLC was designed. An example of application that several distributed inverters in air-conditioning system monitored by one OMRON pocket PLC through non-protocol communication via RS-422A bus was given. The practice indicates that this method is convenient, reliable and economical.