All,

I am using a S7-1200 PLC with a 15 Inch Comfort Panel.

I have six scales which utilize RS232C protocol -- and I want to read the weight of the scale to my PLC/HMI.

Could someone please explain to me how I can do this?  Do I need some sort of expansion module?  Can I use a hub to connect all six units and then use one to the HMI?  I'm looking for the best advice/recommendation.

 Hi SagarDPatel,

First of all the communication between PLC and HMI will be by profinet cable since it is a S7-1200 CPU and there won't be any problem about displaying the result on the screen. Although i actually could not understand the type of scale but, i haven't ever seen a rs232 hub which have 6 ports that is connected to a S7-1200. So i think that might not be possible. And even as a communication protocol RS232 was used with S7-200. So if you are decisive, determined to use those scales you would need an interface unit that converts the signal to an analog signal. 

My advice to you is to use a Swarex module which is a function module for weighting precisely. You can find more detailed info about it on this site. Or you may change your scales to the ones which you can obtain analog signals from them. And also for this condition you would need an extra analog input expansion module. Good luck with your project.

   Have a nice day :)

SagarDPatel

All,

I am using a S7-1200 PLC with a 15 Inch Comfort Panel.

I have six scales which utilize RS232C protocol -- and I want to read the weight of the scale to my PLC/HMI.

Could someone please explain to me how I can do this?  Do I need some sort of expansion module?  Can I use a hub to connect all six units and then use one to the HMI?  I'm looking for the best advice/recommendation.

 RS232 (version C) is a hardware description
and does not tell you which protocol is used.
RS232 is however used for 1-to-1 / point-to-point connection.

There are converters for converting RS232 to RS485.
RS485 can be networked... but it means x6 RS232 converters.

The next problem is the protocol. Possibly it is ASCII based. Another problem.. no address identification. So even if you can network the RS232 devices via RS485, there are no way to identify who-is-who.

There are always ways to "cheat" it (example - multiplex switching) - but best to question the original design to get a standardized method.

Your thoughts?
w

Hello,

sry but can you confirm that 6 independed devices use RS-232 medium? If yes, simply my first quick idea is use independent 6 Ethernet to RS-232 Gates. You can exactly set to each (as Server of course) unique IP address and Port. Then you can connect as Client (your S7-1200) to every Server as you need, you can connect repeatedly to each one and request for data, simply your communication resources are not big enough. Simply via this system you will have right data from every Server, you can connect all with Hub, Gates convert your Ethernet communication to serial RS-232 without problems. I use Moxa NPort Gates and are perfect, also price is good. Helpful?

Hello

I know CM1241 Module to communicate with RS232 Hardware.

In This FAQ is a PDF where you gen an overview to all the cummunication modules for serial communication.

EDIT: ImSorry here is the FAQ ;-)

https://support.industry.siemens.com/cs/de/en/view/109477693

Bye Murof

Duris_I

Hello,

sry but can you confirm that 6 independed devices use RS-232 medium? If yes, simply my first quick idea is use independent 6 Ethernet to RS-232 Gates. You can exactly set to each (as Server of course) unique IP address and Port. Then you can connect as Client (your S7-1200) to every Server as you need, you can connect repeatedly to each one and request for data, simply your communication resources are not big enough. Simply via this system you will have right data from every Server, you can connect all with Hub, Gates convert your Ethernet communication to serial RS-232 without problems. I use Moxa NPort Gates and are perfect, also price is good. Helpful?

Thanks for the advice and help.

The following scale I am using is:  http://www.scalesgalore.com/and_eki_digital_scales.htm

It shows RS-232C standard.  Would you recommend using a standard DB-9 to Ethernet (CAT5/CAT6/RJ-45 port) cable?

If so, how would I connect to the PLC?  Would I go to an Ethernet switch, and if so, then how do I assign the IP address in terms of my S7-1200 LAD logic?

Hello,

I'm working with this type:

http://www.moxa.com/product/NPort_6150.htm

Each Moxa can be (as mentioned) set as Server with unique IP and Port. Look to my previous attachment achema, with this system you can work via Ethernet port on your PLC with each of Scale and request/receive data from it. All can be done with Open Communication via T instructions.

How much is each MOXA unit?  Also, could you provide an example in ladder logic on how I would read a value of my RS232?

Duris_I

Hello,

I'm working with this type:

http://www.moxa.com/product/NPort_6150.htm

Each Moxa can be (as mentioned) set as Server with unique IP and Port. Look to my previous attachment achema, with this system you can work via Ethernet port on your PLC with each of Scale and request/receive data from it. All can be done with Open Communication via T instructions.