Ideal S7-300 + OPC + HMI communication setup

Hello,

I'm in the phase of dimensioning the PLC hardware setup for a machine.

So far I've chosen to work with the 314C-2 DP CPU since it fulfills all my needs when it comes to counter inputs etc.
Also, I'll need to fetch and store data values onto a server that functions as a storage device, and by what I'm reading in the forums, that would require an OPC client. For that I'm using Kepware products since they are compatible with Profibus DP, which is the interface included on the CPU. The server / OPC client shall only fetch and log data - not change any PLC variables.
Last, I'll need an HMI for the operator to analyze and intervene with the machine by changing PLC variables and so on.

My question is, what would be the most ideal communication setup for above?

1. Should the HMI be a client to the OPC server.. or
2. Should the HMI and OPC server be a client to the PLC?

Since the OPC only should fetch data and not edit any variables I like the idea of the OPC to be isolated from the HMI, so both functions as client to the PLC. If that's the case I suppose I'll need some sort of Interface module since the CPU only has one Profibus DP - what module/interface would be recommendable?

Your contribution are very welcome, since I do not know what setup would be the easiest and most ideal? You're also welcome to change any of the products that I've chosen if you dont feel it's appropriate for the setup you would suggest.

Additional question: Do any of you guys know if the 4x counter inputs in the 314C-2 DP CPU are effective from 0 kHz? I know the max freq. is 60 kHz, but I'm not sure about the minimum freq.?

Kindly Regards.

I've also considered a simple datalogger like the ACCON-S7-EasyLog, would it be possible to have the datalogger running simultaneously with the HMI with the 314C-2 DP CPU or would an Interface module be necessary?

It would also be greatly appreciated if you could suggest a datalogger you have good experience with.

What brand of HMI do you intend to use?

There are HMIs with built in data storage for trending purposes and can directly communicate with SIEMENS PLC. In that case, you will no longer need an OPC server.
Your data storage server can be separate depending on your requirements.


You will only need an OPC server if your data storage server or HMI cannot directly communicate with the PLC. It will depend on the communication capabilites of of your data storage server and HMI.

Hej Clemenzo.

I seriously warn you against chosing a PLC without ethernet.
If you must chose a "C" CPU, then chose 314C-2PN/DP. It is more expensive than the 314C-2DP, but you save the money by not having to buy a Profibus card for the PC.
Ethernet will be a much better solution than Profibus for your application.

1. Should the HMI be a client to the OPC server.. or
2. Should the HMI and OPC server be a client to the PLC?

Click to expand...

The HMI will be an OPC client. You therefore need an OPC server. I suggest this one: Simatic Net IE LEAN (for ethernet, not Profibus). It is the least expensive and will work fine enough for your application.

ACCON S7 Easylog can work in parallel with the OPC Server, despite that it uses its own driver instead of OPC. It has its own driver for Ethernet.

Thank you both for your very helpful answers.

Purrdie said:

What brand of HMI do you intend to use?

There are HMIs with built in data storage for trending purposes and can directly communicate with SIEMENS PLC. In that case, you will no longer need an OPC server.
Your data storage server can be separate depending on your requirements.

You will only need an OPC server if your data storage server or HMI cannot directly communicate with the PLC. It will depend on the communication capabilites of of your data storage server and HMI.

Click to expand...

I'm intending on using the TP700 Comfort, it doesn't seem like it supports storage compatibilities besides the two SD card slots, no HD or similiar. What's your take on this, what HMI should I go for instead to obtain the storage option.

JesperMP said:

I seriously warn you against chosing a PLC without ethernet.
If you must chose a "C" CPU, then chose 314C-2PN/DP. It is more expensive than the 314C-2DP, but you save the money by not having to buy a Profibus card for the PC.
Ethernet will be a much better solution than Profibus for your application.

Click to expand...

Thanks for the warning, much appreciated, and I see the logic in your recommendation. I'll go for the 2PN/DP edition instead to have the Ethernet option.

I do have an additional question though:

Since I'm pretty new to Siemens, I'm wondering which memory area (M or DB) would be the most ideal to use, when moving converted REAL values from analogue inputs, to be used on the OPC server / HMI?

What's the obvious differences between these two types of memory areas, pros and cons? In which situations do you use one over the other?

Since you have do not a lot of legacy code to maintain, you can choose your HMI freely. Definitely go for one of the new comfort panels like the TP700 you suggested yourself. They are both better and less expensive than the other Siemens panels.

Get accustomed to use DBs for everything.
Merkers and S5-Timers are mostly there for backwards compatibility.

Thank you JesperMP, I'll keep that as a rule of thumb.

Do you have any experience when it comes to protection of the user program. The 128-bit encryption 'Block Privacy' method seems to be the strongest and most reliable, can you confirm this? Or are there any better protection solutions?

Block Privacy is best.