How to realize 485 wireless communication between multiple sensors and Siemens PLC?

With the continuous intelligent upgrading of traditional industry , Smart meters 、 Sensors are used more and more widely , An important condition for many enterprises in instrument selection is that they must have a network communication interface . The initial operation is to let the data analog signal output simple process quantity , Later, I began to use RS232 Interface as instrument interface , Although this interface can realize point-to-point communication , But it can't realize networking , And then RS485 emerge as the times require , That solved the problem . At present, in industrial control ,RS485/MODBUS It is a popular way of network distribution , It is characterized by simple and convenient implementation , Support RS485 There are many instruments , Especially industrial control PLC in RS485/MODBUS Is particularly widely used .

In this paper, analog signals from multiple sensors are transmitted wirelessly to Siemens PLC For example , To explain the sensor and PLC How to build 485 telecommunications . We can use Siemens S7-1200 PLC Be the master station ,DTD433F As a slave station to collect sensor analog signals ,DTD433F It has the function of inputting and outputting analog signals , The direction of signal transmission is determined by the functions realized by the master-slave equipment of the user's original system . So essentially , We only need wireless analog signal measurement and control terminal DTD433F European and American Department PLC Wireless communication terminal DTD434MC, As a hardware device to realize wireless communication , Build a system based on Modbus RTU Implemented under the agreement 1 The wireless communication of master-slave ad hoc network can solve the problem .

1. Hardware environment construction ：

● master device ： Siemens S7-1200

● Slave devices ：DTD433FC *4 platform

● Wireless data terminal （ master device ）DTD434MC*1 block

2. Test parameters ：

● Communication protocol ：Modbus RTU agreement

● Master-slave relationship ：1 Lord 4 from

● Master station communication interface ：Rs485 Interface

● Slave interface ： analog signal （AI/AO）

● Power supply ：9-24VDC

● transmission distance ：100 rice ,500 rice ,1KM,3KM,20KM

3. Main features of wireless analog signal measurement and control terminal :

wireless Modbus Analog measurement and control terminal DTD433F Provide analog signal input and output interfaces , accord with MODBUS RTU agreement , It can be used as a slave , Acquisition sensors 、PLC、DCS、 Data of intelligent instruments and other equipment , And master station PC、PLC、 Configuration software 、 Touch screen 、 The man-machine interface constitutes the wireless ad hoc network communication system .

◆ Analog input ：1-8 passageway AI Input ,0~5V Voltage signal or 4~20mA Current signal input ;

◆ Analog output ：1-8 passageway AO Output ,4~20mA Current signal output ;

◆ It can directly replace wired transmitter , Realize wireless sensor cluster networking ;

◆ transport ： All digital wireless encrypted transmission ;

◆ Support standard serial port protocol ： Datai free serial port agreement 、MODBUS RTU agreement

◆ DC wide voltage 9~24VDC Power supply , The average operating current is less than 50mA

4. Specific construction method :

New project , add to 1 Group devices ; Open the project to configure the equipment ; choice CPU：CPU 1211C AC/DC/Rly Under the 6ES7 211-1BE40-0XB0; Add communication module ： Under communication module, select Point to point —— Re selection CM1241（RS422/485）—— The final choice 6ES7 241-1CH32-0XB0 model ; Check the device configuration and set parameters ： Set parameters as needed , We use default values here ; Add a new block under the program block , choice DB（ Data blocks ）, And automatically generate background data ; Add data group , In the new data block DB1 Add data groups ; Program the configuration of the master station , After completion , Load master PLC You can talk to the slave station DTD433FC Conduct wireless Modbus Communications .