I am experiencing issues with RS 485 communication between the FX 5U-32 MT and the FOTEK temperature controller slave device. The RD LED is currently on, despite correctly configuring parameters on the PLC side. What could be causing this failure? Any help would be greatly appreciated.
The product specifications indicate compatibility with either Modbus RTU or Modbus ASCII communication protocols. It is important to ensure that the serial settings, such as baud rate, word size, number of stop bits, and parity, are the same on both ends of the connection. Additionally, a unique slave node ID number must be assigned to the controller. Default values for these settings are not predetermined, so it is recommended to verify and adjust them accordingly. The register/address table can be found on page 2. It is worth noting that there is no standard labeling convention for RS-485 drive lines. If all settings are correct but there is still no connection, try swapping the two driver lines on one end to troubleshoot the issue.
In the spec sheet provided, it states that the device is compatible with both Modbus RTU and Modbus ASCII protocols. It is crucial that the serial settings match on both ends, including the baud rate, word size (8 bits for RTU, 7 bits for ASCII), number of stop bits, and parity. Additionally, a slave node ID number is required for the controller. Default settings for any of the mentioned parameters are not specified, so it's essential to verify them. The register/address table can be found on page 2, with PV located at address (4)0065 (one-based). Keep in mind that there is no standard labeling for the drive lines on RS-485. If all settings are correct and there is no connection, try swapping the two driver lines on one end to check for any issues. I also have the manual attached for reference. I have successfully communicated via RS-485 with this model of temperature controller two months ago. While I'm unsure if there are any malfunctions in the new temperature controller, I have also tested it with another one.
From your description, it sounds like your issue might be due to a wiring issue or the slave address could be wrongly set. RS 485 communication can be quite sensitive to incorrect wiring and termination. Make sure your line termination, signal polarity, and grounding are correct. Additionally, do double check the slave address on the FOTEK temperature controller and ensure it matches with the configured address on the PLC side.
From your question, it sounds like a wiring issue could be a possible reason for this setback, particularly dislocations or breakages in the RS485 data lines, as the RD LED remains on. Ensure that the cable and terminals are in good condition with no damages or misconnections. Also check on your termination resistances, baud rates, data bits and stop bits configuration. These factors need to be similar between devices to allow effective communication.
Hi there! Often, troubleshooting RS485 communications starts by ensuring that the wiring is executed correctly, including the termination resistors. However, since you have configured the parameters correctly on the PLC side and the RD LED is still on, it sounds like your messaging might not be set up correctly. Do ensure to check your message instruction between the PLC and the slave device, also the right Modbus address might not be called. Additionally, don't overlook baud rate and parity, these must match on both devices. Let's hope this provides a starting point for you. Good luck!
While your issue could be stemming from a number of factors, one potential culprit might be the wiring. Incorrectly wired RS 485 ports often result in communication failures. Make sure your A and B lines match between your PLC and temperature controller. Also, don't forget to check if the FOTEK temperature controller’s settings match those of the FX 5U-32 MT. If all parameters are installed correctly and your wiring checks out, there might be a hardware issue at play, so checking these areas would be a good starting point.
It sounds like you're dealing with a tricky RS-485 issue! The fact that the RD LED is on suggests that the RX (receive) side is active, but it might not be receiving the expected data from the FOTEK device. Make sure to check your wiring connections, especially the polarity and termination resistors, as incorrect connections or reflections can disrupt communication. Additionally, verify that the baud rates and other communication settings match between both devices; sometimes even slight mismatches can lead to no data transmission. It might also be worth checking for any ground potential differences or noise in the line, as those can severely impact RS-485 communication.
It sounds like you’ve already put in some solid work on the configuration, but the RD LED being on could indicate that the PLC is receiving data but not interpreting it correctly. Check if the baud rate, stop bits, and parity settings match exactly between both devices, as even a small mismatch can cause communication failures. Also, ensure that your wiring is secure; any loose connections can lead to intermittent communication issues. If everything looks right, consider using a logic analyzer or RS-485 sniffer to see if you can spot any anomalies in the data packets being sent. Good luck!
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Answer: 1. Why is the RD LED on despite correct parameter configuration for RS 485 communication between FX5U PLC and FOTEK temperature controller? - The RD LED being on could indicate a communication failure or incorrect settings. Check the wiring, baud rate, parity, and address settings to ensure they match on both devices.
Answer: - Start by verifying the wiring connections, baud rate settings, parity settings, and address configurations on both the PLC and the temperature controller. Ensure there are no conflicts in the settings.
Answer: - Common reasons for communication failures include incorrect wiring connections, mismatched baud rates, parity settings, or address configurations, faulty hardware, or communication protocol discrepancies.
Answer: - Ensure that both devices are using the same communication protocol and follow the manufacturer's guidelines for setting up RS 485 communication between the FX5U PLC and FOTEK temperature controller.
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