ModBus RTU RS-485 communication using two differents connectors

Marcosbelgo · Jul 28, 2017

Hi friends, this is my first post in this forum.
I am Implementing an application that works like this:

I want use the RS-485 interface of MICROLOGIX 1400 communicating ModBus RTU with RS-485 interface of a Gateway (Modbus RTU/wirelles).

My question is:

If the RS-485 interface of Micrologix is a serial port DB-9 with many pins and the RS-485 interface of the gatway is just two connectors, is possible make the connetion?
Can I unplug the cables and just get the two cables from the communication and connect on the bournes of gatway? This work?

I attached the connetion schematic of AirGate-Modbus (from NOVUS manufacturer):
http://www.novus.com.br/downloads/Arquivos/v11x_c_manual_airgate-modbus_português_a4.pdf

Thanks

Epy · Jul 28, 2017

You need a 1763-NC01 cable for RS485, this will give you the A/B (D0/D1), and common RS485 connections you seek.

rQx · Jul 28, 2017

And it is not DB-9 port that is Channel 2 you should use, but the channel 0 Comm port 0 - 8-pin mini DIN RS-232C/RS-485 connector. Use the 1763-nc01 as Epy said , it will be marked on the terminals what is what

Marcosbelgo · Jul 28, 2017

Thanks,

I have another question:

Can I connect many PLC's in parallel and the last PLC connected to the gateway according the figure bellow?? If not, how do I do this Implementation?

nswu1 · Jul 28, 2017

rs-485 allows for this, the only issue maybe in the master radio, as to if it allows for point to multi-point, and multiple nodes.

Marcosbelgo · Jul 28, 2017

This cable 1763-NC01 is very expensive 1763-NC01 OMG, I have 20 PLC's to communicate ..... The Micrologix 1400 do not communicate Modbus throug the serial port (DB-9) ????

rQx · Jul 30, 2017

Im not suire but isn't the 1763-nc01 just a pinout? You could build your own?
Anyways it's not that expensive?

Kidblue · Jul 30, 2017

The Micrologix 1400 do not communicate Modbus throug the serial port (DB-9)

Yes - but only via RS232 not RS485 as you are looking for. Then you're into adding RS232 - RS485 converters...relatively expensive with the numbers you're looking at.

List price for a 1763-NC01 is about £36 over here - not sure what you consider expensive?

Regards,

Rob

AustralIan · Jul 30, 2017

Ahhh, the old "Here is a £1 PLC and a £360 cable for it."

Marcosbelgo · Jul 30, 2017

rQx said:
Im not suire but isn't the 1763-nc01 just a pinout? You could build your own?
Anyways it's not that expensive?

This is my question. If it is just pinout, why do not build my own? I searched for technical information aboult this cable and did not find anything. I would like to manufacture this cable...

rQx · Jul 30, 2017

Marcosbelgo said:
This is my question. If it is just pinout, why do not build my own? I searched for technical information aboult this cable and did not find anything. I would like to manufacture this cable...

It is always easier to use what the manufacturer make for us. In term of reliability and proffesionalism. It is really not that expensive, compare it to what all the PLC and cabinets cost it is really a small cost?

Marcosbelgo · Jul 30, 2017

Kidblue said:
Yes - but only via RS232 not RS485 as you are looking for. Then you're into adding RS232 - RS485 converters...relatively expensive with the numbers you're looking at.

List price for a 1763-NC01 is about £36 over here - not sure what you consider expensive?

Regards,

Rob

Thanks Rob,

It is the same case of the cable, isn't the RS232 - RS485 converters just a pinout? I found very cheap converters for sale, which is the chance of I have problens with cheap converters??

Thanks

Marcosbelgo · Jul 30, 2017

rQx said:
It is always easier to use what the manufacturer make for us. In term of reliability and proffesionalism. It is really not that expensive, compare it to what all the PLC and cabinets cost it is really a small cost?

I want start data acquisition from one of our plants and I am studying the possibilities. at first, how much can I make it cheaper is better. But, is sure that I have to make a professional work, not quick fix......

Marcosbelgo · Jul 30, 2017

Kidblue said:
Yes - but only via RS232 not RS485 as you are looking for. Then you're into adding RS232 - RS485 converters...relatively expensive with the numbers you're looking at.

List price for a 1763-NC01 is about £36 over here - not sure what you consider expensive?

Regards,

Rob

Here in Brazil, it is more expensive.... more or less $80 ....

brendan.buchan · Jul 31, 2017

The 1763-NC01 is basically just a breakout cable from 8-pin mini din to terminals.

You could just buy a cheap knock-off MicroLogix programming cable off ebay, and connect the relevant cores to terminals.

http://www.ebay.com.au/itm/Programm...996013?hash=item2813547d2d:g:B-UAAOSw5cNYYMyV

ModBus RTU RS-485 communication using two differents connectors

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