Connect a Do-more PLC to a GS4 VFD via Modbus TCP

We want a Do-more PLC to talk to a GS4 Drive over Modbus TCP. For this video, we’ll be using this network setup . You will also need the GS4 Drive’s optional Modbus TCP com Card to communicate using Modbus TCP. To configure the Do-more enabled PLC for Modbus TCP, you just go to the system configuration and setup the IP Address to be compatible with the network the GS4 Drive is on, which in this example is this. There is a separate video showing how to configure the GS4 for Modbus TCP and I’ve already done that. So, all we need to do now sends commands. Let’s have contact C10 do a Modbus write. We need the built-in Modbus TCP Client, our GS4 Drive is at address, and we are writing to a single location. In appendix B of the GS4 user manual we see that Modbus TCP frequency commands need to be sent to address 8194 and since this chart uses the plus 1 addressing convention for the decimal addresses and that’s exactly what the Do-more PLC expects, so we put that … here. The Do-more pre-pends the 4 for us. And let’s set the frequency to 60 hz. Let’s copy and paste that rung and modify it so C11 changes the frequency to 45 Hz. Copy and Paste again and let’s have C12 run forward which we know from that appendix B table is done at this address … and this binary value which is this in hex. Copy and paste again. And let’s have C13 …. write to the same control Modbus address but set the bits to run in reverse. Copy and paste again and have C14 write to the same control Modbus Control Address but set the bits to stop the drive. And let’s add the END Let’s give each of these control bits a name so they are easier to read in the data view. Great. Accept that, and write it to the Do-more PLC. Let’s bring up a Data View and add those control bits. The drive is configured for Modbus TCP and it is in REMOTE mode so it’s ready to go. The PLC is running so if we activate the 45 Hz instruction, sure enough the drive changes frequency. If we activate the 60 Hz instruction – the drive reacts accordingly. If we toggle the run instruction the motor starts turning and we see it is in the forward direction. Toggle the reverse contact and the motor changes direction and toggle the stop contact and the motor ramps to a stop. Exactly what we expected. Click here to learn more about the GS4 Drive. Click here to learn about AutomationDirect’s free support options, and click here to subscribe to our YouTube channel so you will be notified when we publish new videos.