Watlow F4 and Modbus

[Brian_Beal]

I also remember that the F4 is sensitive to the 485 converter, if that is what you are using.  I had F4's that wouldn't communicate using a converter that worked fine with Watlow Power Series SCR's and Eurotherm products.  There was something that the F4 didn't like.  A B&B Electronics converter with Send Data control is what got things to communicate.

[Joe_Gerhardstein]

unclebump:

I tried your "my modbus serial query" app, which uses the same LV7 modbus VIs I tried earlier.  I get the same "Error 6101 Timeout" error from the Read/Write block in the while loop. See attached screenshot.  Let me know if I configured something wrong on the front panel. 

The 19200 baud and COM1 are correct, as wel as the RTU mode and Slave Address = 1.  I tried parities of Even and None with all combinations of Flow Control, and could get none to talk.  Register 300 is the Set Point, which is marked as R/W in the manual for the controller.


Joe

[Joe_Gerhardstein]

Brian:

I'm talking RS-232 to the Watlow, so there is no RS-485 converter to cause problems.


Joe

[Joe_Gerhardstein]

unclebump:

Attached is a portmon log from a write and attempted read.  Line 53 shows the Write to register 300 for the set (which is accepted by the controller), and line 155 shows the query (Read) for register 300.  However there is no response received.

So this implies to me that I may have a bad controller.  Does this sound correct?


Joe

[unclebump]

See if there is an option in portmon that will let you see the hex code that was transmitted.

[Joe_Gerhardstein]

Hex version of portmon log.

[unclebump]

Only thing I could say now is try 9600 baud, 8 data bits,  even parity, and 1 stop bit in the controller. The data stream looks correct. 

[Joe_Gerhardstein]

unclebump:

Thanks.  I tried that yesterday, but got the same thing.  I think I may have a bum controller.

[unclebump]

Do you have anything else in the building that uses Modbus??

[Joe_Gerhardstein]

unclebump:

No, I think this is the only thing.  We have a Thermotron 2800 controller on our other chamber, but I don't think it does modbus (Thermotron has LabVIEW drivers for it, but they are just calls to a .dll, so it is hard to tell).  At this time, we are probably just going to run open-loop with the controller (e.g., no feedback to the PC, but controller itself runs closed loop).  We have thermocouples in the chamber anyway that measure temperatures of the DUT instead of just air temp, so these are better feedback mechanisms for us.  It would be nice to know that the controller accepted the setpoint and know when it thinks it had got there, but these are secondary to the overall solution.

Thanks for your help!