Serial interface

[cghaba 0]

Hi, I try to use an FX1S PLC with the serial interface FX1N-485-BD to control an inverter. I am not sure that the interface is working well. The transmitter is working, LED is flashing and I also verified it connecting it to a PC and read signals with a terminal program (Hyper Terminal or TeraTerm). I am not sure that the receiver of the interface is also working, the receive flash doesn't flash. How can I test if the receiver of the interface is also working? I do not have another PLC with serial interface to connect them, for example, in a parallel link mode. Cristian

[swimmy67 9]

What brand of inverter are you using? Attached is a communication troubleshooting page that I made up for a Mitsubishi PLC and inverter. I use a FX2N with the FX2N-485-BD. swimmy67 485BD_Comm_Check.doc Edited 7 Jun 2006 by swimmy67

[cghaba 0]

I use a Mitsubishi FR-E520 inverter. Unfortunately the troubleshooting page doesn't help me so much. My problem is to find if the receiver part of the FX1N-485-BD interface is working. The inverter is working when controlled through the communication port. I have tested it by connecting it to the PC and using the VFD setup software. Cristian

[Crossbow 296]

Is the VFD sending any data back to the PLC? If not, there's nothing to receive. Instead of sending data like a speed command, try to read something from the VFD. See if you can read data and if the VFD sends and the PLC receive operates.

[cghaba 0]

I said I have connected the VFD to the computer and using the VFD setup software I could sent forward and reverse commands and I could also read all the parameters set in the VFD. So, I guess the VFD knows how to send data back (if the request is well formed). The program in the PLC has to send the forward command to the VFD and it seems it sends it in the correct format (Data format A' explained in the VFD manual, chapter 4.2.36) as I verified connecting the PLC to the PC (serial port using a RS485/232 converter) and reading data received from the PLC in a Terminal window. Cristian

[cghaba 0]

The question is (PLC+FX1N-485-BD connected to the PC running a terminal window and sending the forward command), if I type some garbage in the terminal window (not the acknoledge replay that VFD would send and which should be in format C - see VFD manual) in this way sending something to the PLC, the receive led should flicker or not? If not, does it means the receive part of the FX1N-485-BD interface is not functioning? Cristian

[swimmy67 9]

Have you checked the cable from the PLC to the Inverter? Have you written the code for the communications? I see that you can communicate with your PC because you are using a different cable. You need to verify that the cable from the PLC to the Inverter is good. The code has to initiate the communication and receive a responce. The Inverter will not try and communicate with the PLC. I have attached a working program that I use on my machines. I am communicating with 4 inverters. 1 FR-A540, and 3 FR-E540 drives. The attachment is in a pdf format. Pay attention to the RS command and the timing of the communication logic. I hope this will help you. swimmy67 FX2N_to_FR_A540_and_FR_E520.pdf

[swimmy67 9]

Cristian Were you successful in establishing communication from the PLC to the Inverter? We are just courious to see how things worked out. swimmy67