Sk commander modbus RTU with PC

[fishin_fl]

I am having a heck of a time getting my PC to communicate to my sk Commander drive. I initially set the drive up via Sm-ethernet card because I had it. I recently needed to add Modbus TCP from my pc to my cnc software and it can only talk to one device, so I am told and understand.

So I am back trying to get the pin out correct for permenant termination from Serial on Pc to RJ45 on the Sk Drive.

I have looked at the advanced manual and I just must be missing something.
Any help would be greatly appreciated.
Thanks.

 

[sjohnson]

Are you using a Suitable RS232 to RS485 Converter Per Chapter 5 of the advance user guide?

An external EIA232 hardware interface such as a PC can be used with a suitable converter. This converter must have the hardware and software
support to tri-state the transmit buffer following the message transmission. Otherwise, the Commander SK EIA485 transmitter will not be successful
in transmitting a reply as the host transmitter will cause contention on the 2-wire interface.​

Examples of EIA232 to EIA485 converters (one to one)​

• CT Comms cable (CT part number 4500-0087)
• USB Comms cable (CT part number 4500-0096)
• Amplicon 485Fi
CT Comms cable is specifically designed to convert EIA232 to EIA485 with Control Techniques products.​

These converters are for one to one connection between a PC and the Commander SK drive, they do not have multi-drop capability.

 

[fishin_fl]

Converter

I had a converter that was RS-232 to RS485 but I guess it was not *EIA*.. A cheapy I suppose.

I do have on hand B&B Electronic Optically isolated RS-232 to RS-485.
Model 485LDRC9

http://www.bb-elec.com/Products/Quick-Start-Guides/8413_r003_485LDRC9_2512_qsg.aspx

Would this work? Never used it before. Thanks.

 

[sjohnson]

In all theory it should work I have had good Luck with B%B Stuff in fact some older B&B com 32 still out on the floor today. I used a weintek hmi to a SK Modbus it worked rather well.. Some Converters work where others will not but this B&B should and using the pinout in the advanced user guide.

 

[fishin_fl]

converter

Thanks... I will give it a try, I'll let you know what I come up with.

On the HMI side. I have been trying to build a pendant using an HMI but my issue on that side is that my cnc software ( MACH3) I use is Master and all the HMI's I know can not be ran in slave mode. Like C-more which is what I have. Uhhhhh. Does the weintek hmi allow for modbus slave? If so do you have any suggestions on setup..

Thanks again.

 

[Gene Bond]

From the UnidriveSP User Guide (note, all the current CT drives use the same configuration for the 485 port on the RJ45:

Table 6-26 Connection details for RJ45 connector
Pin Function
1 120Ω Termination resistor
2 RX TX
3 Isolated 0V
4 +24V (100mA)
5 Isolated 0V
6 TX enable
7 RX\ TX\
8 RX\ TX\ (if termination resistors are required, link to pin 1)
Shell Isolated 0V

6.16.2 Multi-drop network
The drive can be used on a 2 wire EIA485 multi-drop network using the drive's serial communications port when the following guidelines are adhered to.
Connections
The network should be a daisy chain arrangement and not a star, although short stubs to the drive are allowed.
The minimum connections are pins 2 (RX TX), 3 (isolated 0V), 7 (RX\TX\) and the shield.
Pin 4 (+24V) on each drive can be connected together but there is no power sharing mechanism between drives and therefore the maximum power available is the same as a single drive. (If pin 4 is not linked to the other drives on the network and has an individual load then the maximum power can be taken from pin 4 of each drive.)
Termination resistors
If a drive is on the end of the network chain then pins 1 and 8 should be linked together. This will connect an internal 120Ω termination resistor between RXTX and RX\TX\. (If the end unit is not a drive or the user wishes to use their own termination resistor, a 120Ω termination resistor should be connected between RXTX and RX\TX\ at the end unit.)
If the host is connected to a single drive then termination resistors should not be used unless the baud rate is high.
CT Comms Cable
The CT Comms Cable can be used on a multi-drop network but should only be used occasionally for diagnostic and set up purposes. The network must also be made up entirely of Unidrive SPs. If the CT Comms Cable is to be used, then pin 6 (TX enable) should be connected on all drives and pin 4 (+24V) should be linked to at least 1 drive to supply power to the converter in the cable. Only one CT Comms Cable can be used on a network.

 

[sjohnson]

It does look like
HMI5070TH Can be a SLAVE-SERVER it has many com capabilities. I used one MODBUS TCP and a GE SRTP works really well.

I'm not familiar with C-More HMI nor what your trying to accomplich or much about your system. Your CNC Machine Runs on PC and software and PLC? I looked over the manual for some C-more didn't see anything on just master -client specific but I didn't really look that hard.. if your Software is Client-Master and the CNC itself (?(PLC)or? )Slave-Server you should be able to use a HMI Modbus and Drive