modbus rtu to TCP

hi folk,

I try to link up the kaeser compressor with Modbus RTU and using RED Lion convert it into Modbus TCP and after that link it to intouch wonderware.


do u know the kaeser Modbus communicator unit is using 4 wire or 2 wire?


I have attached the kaeser Modbus rtu pin assignment here..

Looks like it can do both. Depends on if you connect pins 2 &3 together or not.

i would like to link in RS485... with red lion... below is connection of red lion

No, it is not both, it is 2 wire 485.

When Rx+ and Tx + are combined on a single terminal, then it is "2 wire".

It appears that there are connections to +5v and/or ground for what I would call "biasing", but which they call "termination".

A Termination resistor is across the (+) and (-) data lines (at the ends of a multidrop network) and are used to dissipate the energy from a "reflection".

Most 485 devices have pre-installed bias resistors, this the first circuit I've seen with connection points

Why do you want to use RS-485, and not RS-232?

by this way.. is it the termination resistor MUST be connected in this RS485 loop?

danw, I use rs485 due to the distance...

my connection now

redlion-----------kaeser Compressor

1, 7 -----------------5---------------( TxB )

2,8------------------9----------------( TxA )

6--------------------1----------------Gnd


no termination Resistor 120ohm at terminal 1 , 2 ( Kaesor compressor )

I hv no put the resistor cause the Bandrate is set to 19200 only

would the circuit are ok?

I have try many days on this but no respond

Your termination seems to be ok.
Though terminal 1 and 7 seems to be connected internally. The same with 2 and 8.

Have you set parity, stop bits and baud rate in both the master (Red Lion) and the compressor, and have you given the slave (the compressor) a slave ID?

And you must switch A and B connections at least 17 times before it works .

Datasheet

Does anyone have a datasheet for this Kaeser MOdbus module, I can't seem to find the info listing registers and pin out anywhere.

Thanks