Modbus commucication

midhundas093

Can somebody help me to program this configuration? I didn't handle such a big project before. there is a lot of Modbus communication and SCADA is there. If anyone has an idea please help me. I am going to use s7 400 Plc. 

Please be very specific to what type of help you are looking for. Perhaps you are looking for someone with experience to work as paid sub-contractor. Or you might be asking what type of hardware suits your PLC? The picture is not helping to clarify what your needs are.

Clarify also what type of Modbus: Modbus TCP or Modbus RTU.

PS: Refrain from publishing more than one topic on the same subject matter. If you in a hurry, you should contact the Siemens office closest to you to supply an Engineer to your project.

hi midhundas093,

What kind of help do you have in mind? Programming the controller for this config?

I think this kind of task shouldn´t be done in a forum.

If I were in your position, I would tell my boss that I need help for this task from someone who has done this before. The earlier, the better.

hope this helps,

regards,

No sir, For Redundancy operations which plc that I can use s7 400 or s7 300. 

I think the forum is to help each other. I know you guys have a lot of years of experience in this field so I thought somebody can give me some inputs regarding this. 

Hello Midhunda;

You are right, the participants on this forum have a helping attitude, and will generlly answer well-presented questions in the forum's threads.

This, I am afraid, is not the case in your situation.

Your first post refers to Modbus communictions, but the diagram you show is very confusing. There seem to be no Modbus slaves attached to either PLC-PI-01 or PLC-P1-02, the Modbus cable symbols are all brought back to Collector/DCM/BMS controller higher up in the design. We ca help you if we know what family of Siemen PLCs you have developped the Modbus master on, and if we know the Modbis mapping for each slave on the network. You give us no information on neither of these.

Then suddenly you intorduce a question on S7-400 or s7-300 redundancy. Totally differrent subject, I think you will agree, with no relation with the first one. In such cases, to make things less confusing, it is suggested you open a new thread only for the new theme.

So: tell us what the Modbus master is in your project design, maybe we can help you there, maybe not, since we work with Siemens PLCs. If the master is a Siemens PLCs (precise part number, please), tell us what make and model the slaves are, and if possible give, links to the Modbus manuals for these drives and instruments. Then we might be able to help.

For the second question: hot-redundancy can be achieved with S7-400H PLCs, wjhich mean easy to implement, with very short changeover times (in the order of ms) and automatic transfer of the program status and contents from the primary to the standby controller at every cycle.

- SIMATIC Fault-tolerant systems S7-400H (V6.0)

https://support.industry.siemens.com/cs/ww/en/view/82478488

You can achieve warm-redundancy with  standard S7-300 CPUs (or standard S7-400 CPUs) if you use the Software Redundancy package (SWR, optional).Warm redundancy means a musch longer changeover time between promary and standby CPu, in the order of 1 sec. And you have to introduce and program blocks dedicated to the redundancy setup yourself, implement network connections between the CPUs and with the remote I/O, and in general make sure that your program does not violate any SWR rule.

- SIMATIC S7-300/S7-400 Software redundancy for SIMATIC S7

https://support.industry.siemens.com/cs/ww/en/view/1137637

A brief comparison between the 2 tyes of redundant connections: S7-400H are more expensive at purchase, but require much less development and programming on your part; changeover time is also extremely fast and reliable. SWR is cheaper (but you need to purchase CPs for the intra-CPU connections), but requires many hours of programming and allows for longer interruptions of communications between the CPUs if there is a fault on the primary CPU.

Study the manuals cited above and make your decision based on project requirements.

Hope this helps,

Daniel Chartier

To me the picture looks like the "MODBUS" is a Modbus RTU connection.
7 separate channels are used and it is not connected to the PLCs.

The left-hand and right-hand are copies of one another. It is not clear if these are backups of each other (redundancy). It is also not clear how the evaluation is done which instrument and PLC has the correct reading / action.

The illustration looks like something that is pulled up for the purpose of making a quotation. I guess the client is 'sharing' the document to get a competing quote. There is a real danger of making a quote that is below the market value which will harm the suppliers.