How to realize wireless communication between human-machine interface and PLC

In a factory, a human-machine interface usually needs to establish communication with multiple PLCs, and the locations of the devices are different. If wiring is required, it needs to be constructed in multiple places, which is troublesome. In this case, it is more convenient to establish communication between the human-machine interface and the PLC wirelessly. Because the wireless PPI protocol has a fast response speed and does not require programming, only configuration is required, so the PPI protocol network has more advantages. However, a special wireless data terminal is required to realize wireless PPI communication, and the matching of the setting parameters must also be considered during configuration.

This solution takes the human-machine interface (Weluntong touch screen) as an example to introduce the wireless PPI communication implementation process between the Weluntong touch screen and two S7-200Smart PLCs. In this solution, the Siemens PLC dedicated wireless communication terminal DTD434M is used as the hardware device to realize wireless communication.

1. Overview of the Solution

Through the European and American PLC dedicated wireless communication terminal DTD434M, the wireless PPI network can be stably and conveniently realized without changing the network parameters or the original program, and directly replacing the wired RS485 communication.

Wireless network diagram▼

2. Test equipment and parameters

● Touch screen: TK6071IQ × 1 unit

● 200SMART model: CPU SR20 × 2 units

● Wireless communication terminal: European and American PLC dedicated wireless communication terminal - DTD434MC × 3 pieces

● Data line: Siemens PLC dedicated 485 line × 1

● Touch screen data cable: Touch screen dedicated RS485 data cable × 1

● Master-slave relationship: 1 master and 2 slaves

● Communication interface: RS485 interface (two-wire system)

● Communication parameters: 9600, 8, E, 1

● Power supply: 9-24VDC

● Transmission distance: 100m, 500m, 1KM, 3KM, 20KM

3. Detailed explanation of the functions of wireless communication terminals for European and American PLCs

Wireless data communication terminal DTD434M, with built-in RS232/RS485 dual interface, can directly replace traditional wired solutions such as RS232/RS485 without programming. It can form a wireless measurement and control network with Siemens PLC, configuration software, human-machine interface, touch screen, measurement and control terminal and other industrial control products.

■ Main features of DTD434M:

◆ Directly replace the wired RS485 solution to achieve wireless networking communication;

◆ Fully digital wireless encryption method ensures data security and reliability;

◆ Powered by DC 9~24V wide power supply voltage, average working current is less than 50mA;

◆ Communication interface: RS232/RS485;

◆ Support standard serial port protocols: Modbus RTU protocol, PPI protocol.

4. Wiring method

1. Wiring between touch screen and wireless device

Step 1: Connect the red wire of the touch screen RS485 data line to the A port of DTD434MC; connect the black wire of the touch screen RS485 data line to the B port of DTD434MC.

Step 2: Set the last digit (K8-8) of the wireless communication terminal switch to the top

Step 3: Connect the wireless communication terminal to the antenna

Step 4: After all wiring is completed, power the touch screen and wireless communication terminal

2. Wiring between PLC and wireless devices

5. Weiluntong touch screen realizes PPI master station

Open "Wei Lun Tong touch screen 1 master 2 slave PPI routine.emtp"

1. System parameter settings

2. Touch screen screen production

3. I point setting of slave station No. 1

4. Q point setting of slave station No. 1

5. I point setting of slave station No. 2

6. Q point setting of slave 2

7. Physical wiring diagram

6. Siemens PLC realizes PPI slave

1. PLC parameter setting

2. Set the PLC address

Set one PLC address to 1 and the other PLC address to 2

Select "Parameters - Module Parameters - 485 Serial Port"

3.CPU mode

Select: RUN to download the program to the PLC

4. Physical wiring diagram

7. Wireless communication test

1. Touch screen output signal

Use the button on the touch screen to give the Q point signal to slave station No. 1 and see if the Q point corresponding to 200SMART is lit. If it is lit, it means the communication is normal.

2. PLC input signal

Give a signal to slave station No. 1 externally to see if the corresponding point on the touch screen is lit. If it is lit, it means the communication is normal.