Another communication example for our blog library.
The easy one, should be do it only one HMI and one PLC. But to do it more interesting we are going to set up a Modbus ASCII network of one HMI(master) with 3 PLC’s(slaves).

To setup any system I always divide the problem in two basic parts, Hardware and Software.

Hardware (physical level):
Take a look to the pinout of all the devices to connect, in our case the PLC is easy, and for the HMI, take a look to the next image extracted from the instruction manual.

Software (Protocol):
An old trick that I learn after a couple of communication challenges is write in a post it the communication protocol that you are going to use. Basically, because you will need it so many times, and is very easy to make mistakes!!

Protocol used:
7,N,2 (Modbus, ASCII), 9600 bps

Network configuration:
HMI Address: 0 (master)
PLC1 Address: 1 (Slave)
PLC2 Address: 2 (Slave)
PLC3 Address: 3 (Slave)

Software (Computer level):
And finally, to show you how to configure the communication with the ScreenEditor and WPLSoft, I’ll ask you to download the next file, where you can file the programming examples, and some video file with the exe extension, to follow all the process.

HMI – 3 PLC communication example