Hello,
I am pretty new to the rs-485 serial world. And I have a customer that has an RS-485 network that links a PLC with a VFD and several power meters. The PLC is a Unitronics V570 and the drive is a Lenze ESV. I did not write the plc program, but I do have access to the code. The issue is that always at a certain time in the start sequence of this machine, the modbus write status will faill to the drive. And this prevents the machine from starting. But if you exit the start sequence and start over, chances are it will work just fine. The PLC pulls in a contactor that powers up the drive, then in 10 seconds, the plc starts sending commands to the drive and it is somewhere in that interval where it usually errors.
Please help. Does this sound like a program problem. I set my timeout settings around 3 seconds and 3 retries and it still happened. Or does it sounds like a hardware issue or network installation problem? I think it has been doing it about since new, but former contractor didn't fix it.
I am pretty new to the rs-485 serial world. And I have a customer that has an RS-485 network that links a PLC with a VFD and several power meters. The PLC is a Unitronics V570 and the drive is a Lenze ESV. I did not write the plc program, but I do have access to the code. The issue is that always at a certain time in the start sequence of this machine, the modbus write status will faill to the drive. And this prevents the machine from starting. But if you exit the start sequence and start over, chances are it will work just fine. The PLC pulls in a contactor that powers up the drive, then in 10 seconds, the plc starts sending commands to the drive and it is somewhere in that interval where it usually errors.
Please help. Does this sound like a program problem. I set my timeout settings around 3 seconds and 3 retries and it still happened. Or does it sounds like a hardware issue or network installation problem? I think it has been doing it about since new, but former contractor didn't fix it.