VFD Update: Well I spent two hour reading the 20 pages in this topic yet again, looking for some grain in data that I might have overlooked on how to establish communcations with the VFD.
I am using the 3KW VFD and Spindle which I purchased probably close to two years ago. It works on the bench fine and just got busy with other projects so it never got installed on the mill.
I am using a USB to RS485 converter which uses the Prolific PL-2303HX chip, just like the one with photos and details at this link.
http://cgi.ebay.com/USB-RS-485-Converter-Adapter-RS485-New-17-/180612321384?pt=LH_DefaultDomain_0&hash=item2a0d555068My cable between the converter and the VFD is connected in the following manner:
VFD RS- >>> T+/B (DB9-2) and VFD RS+ >>> T-/A (DB9-1)
I have tried ground, no ground, and no difference. One note when I measure the voltage on the TI 75176B differential chip on the VFD it measure 5VDC as expected, if I measure VCC to DCM on the VFD which is suppose to be DC Common I only get about 3.4VDC with respect to Pin 8 (vcc) of the 75176B chip. However, if you measure between V0 and Pin 8 you get the full 5VDC. DCM is not really the common DC side with respect to the IC's on the upper VFD pc board. Anyway I tried to use the V0 ground as a reference back to the PC usb RS485 converter again the same responses.
At this point I am not sure if the USB to RS485 converter I am using has been successfully used to control the VFD. Hope this info helps someone else or highligths something that someone else has noticed that might point me to a solution. I might blow another $30 on a different USB to RS485 converter.
I did noticed after reading these 20 pages of posts several times that Bryan "Bolingerbe" had the exact same issue and responces from his VFD but he disappeared and had not posted in a long time. I know he was also frustrated and talked about get a different VFD fully modbus compliant. I hate to go that route until this one dies because I already spent the money.
Comments or Suggestions are welcome. Thanks
Russ