Modbus for dummies

[SquarePLC]

I am very green on MODBUS , I am trying to set up a simple force coil command to turn on MB6 in a secondary PLC. (I am using 2 x Vision 1210) . There seems to be communication between the 2 PLC's but I think I have the Slave:Operand Address wrong on the master force coil FB ( I have it as hexi decimal 6) .  Any advice would be appreciated.

[Joe Tauser]

We need to see if you have the rest of your Modbus configuration set up correctly.  Please post both programs.

Joe T.

[Isakovic]

It looks correct (you even have a response for every command you sent to slave), but value to force is 0. Force coil command is reading status of MB6 (0 or 1) and writing it to slave when command is called. If this command is always writing 1 use SB1 (always on) for "Value to Force".

You can write just 6 in destination address.

[SquarePLC]

Thanks for your answers. On my slave end I also had a button controlling MB6 this was stopping the MODBUS force coil from working, got rid of the button now good to go!

[SquarePLC]

OK now I want to transmit the RS232 via blue tooth or wireless between the 2 PLC's. I bought the following adapters and some RJ11 to female serial cables but am getting no signal through.  The 2 devices are connecting up but there is no data transfer. I tried changing some of the jumpers in the instructions but the language is a bit beyond me. Any suggestions on this or other easy to set up blue tooth/wire less RS232 devices?

https://gridconnect.com/bluetooth-to-serial.html

Thanks

 

 

[Joe Tauser]

Have you tried asking them?

These are modems.  You need to be using modem cables, which don't have transmit and receive crossed.  Do you have the pinout on the cables you bought?

Look at the Unitronics Help on RS232 to see what signals go to which pins on the RJ11 connector.

You don't want to use flow control on the modems.

Joe T.