Siemens 1214C software interfacing

zoomable

Member
Z
Join Date
Oct 2021
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Ontario
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Hello all;

I need to create a software program that is a stand-in for a PLC I/O card.

My program will be controlling a coordinate measuring machine (CMM).

Am I on the wrong track to be considering OPC-UA for communication to/from the PLC? Is there another way of interfacing to a PLC?

Thanks.
z
 
zoomable said:
Hello all;

I need to create a software program that is a stand-in for a PLC I/O card.

My program will be controlling a coordinate measuring machine (CMM).

Am I on the wrong track to be considering OPC-UA for communication to/from the PLC? Is there another way of interfacing to a PLC?

Thanks.
z
Click to expand...

Firs off, you should be ashamed of yourself for not being able to find the answer on your own. Back when I was this and that, I was able to do the stuff that needed doing without any help certainly not from strangers.

Now seriously, welcome to the jungle.
I am not entirely sure what a stand-in program means.
What brand and model is your I/O, if they're Siemens and profinet capable then that is the the best way to communicate and if they're not and OPC-UA capable then that could be a good choice for the newer firmware in the 1200s.

Perhaps you can explain more what you have and what you want to do.
 
Ah, thanks for the jolt, stranger :)

Apologies for not being more clear. Basically, I am tasked with writing a software piece that will replace the need to purchase an expensive card for the PLC to be able to control the CMM.

So, this software will subscribe to the PLC to watch for events of interest, then direct commands to the CMM, then report/push back to PLC variables to update its state...

I don't know enough about OPC-UA to understand whether it can be used for (critical) control, or whether it is just for monitoring, reporting, etc.

We do have data acquisition on the radar, but the first task is just to control the CMM via software.

The PLC is: Siemens Simatic S7-1200 CPU 1214C
 
Last edited:
zoomable said:
Ah, thanks for the jolt, stranger :)

Apologies for not being more clear. Basically, I am tasked with writing a software piece that will replace the need to purchase an expensive card for the PLC to be able to control the CMM.

So, this software will subscribe to the PLC to watch for events of interest, then direct commands to the CMM, then report/push back to PLC variables to update its state...

I don't know enough about OPC-UA to understand whether it can be used for (critical) control, or whether it is just for monitoring, reporting, etc.

We do have data acquisition on the radar, but the first task is just to control the CMM via software.

The PLC is: Siemens Simatic S7-1200 CPU 1214C
Click to expand...


S7-1200 firmware version 4.4 and higher can be setup as a server only no client. You your OPC-US capable CMM will see the tags in the PLC and be able to write to them. The PLC will not be able to write to your CMM. In any way you PLC had to be firmware 4.0 or higher to be upgraded to 4.4, if it's not already
 
Ok, so a custom OPC-UA client could write to the CMM (or issue commands to it).

Is it fairly standard to 'control' a component using OPC-UA? i.e. by writing tags?

I've only ever seen OPC used for logging, monitoring, reporting. . .i.e. reading tags....thks
 
Siemens 1200 series is pretty reasonable price wise.
When say "expensive PLC card", how expensive?
Buy OPC software and writing custom code may be more expensive? OPC software often cost more than a 1200 plc system.
The OPC software will be running on a PC in most cases, I do not like using a standard PC for controls.
 
zoomable said:
I don't know enough about OPC-UA to understand whether it can be used for (critical) control, or whether it is just for monitoring, reporting, etc.
Click to expand...


How fast is your critical control? How critical is it?



OPC UA data won't be able to be polled faster than 100ms, and I haven't tried with a 1200 to know how much longer it would be. Might be 500ms or 1s depending on how much data you need.



I'm not familiar with the specifics of programming an OPC UA client, but I'm sure you could create a watchdog to let you know if you aren't getting data in a timely manner, and take action on the CMM side accordingly if needed. For the PLC to notice the communication break, though, you'd need to create a heartbeat of some kind.



Ken Moore said:
Siemens 1200 series is pretty reasonable price wise.
When say "expensive PLC card", how expensive?
Buy OPC software and writing custom code may be more expensive? OPC software often cost more than a 1200 plc system.
The OPC software will be running on a PC in most cases, I do not like using a standard PC for controls.
Click to expand...


To me, this is the key point. 1200's and their cards are usually fairly inexpensive, unless your concern is cards on the CMM end?



Even if you write it from scratch, you'd need to be building a LOT of these systems for any potential savings to show up. Your time as a programmer costs money, plus all the bugs you need to fix. And that's on top of any potential increased costs if you license a library or need to add PC hardware: even an RPi would cost about the same as most 1200 cards, making it a wash.
 
mk42 said:
How fast is your critical control? How critical is it?



OPC UA data won't be able to be polled faster than 100ms, and I haven't tried with a 1200 to know how much longer it would be. Might be 500ms or 1s depending on how much data you need.



I'm not familiar with the specifics of programming an OPC UA client, but I'm sure you could create a watchdog to let you know if you aren't getting data in a timely manner, and take action on the CMM side accordingly if needed. For the PLC to notice the communication break, though, you'd need to create a heartbeat of some kind.






To me, this is the key point. 1200's and their cards are usually fairly inexpensive, unless your concern is cards on the CMM end?



Even if you write it from scratch, you'd need to be building a LOT of these systems for any potential savings to show up. Your time as a programmer costs money, plus all the bugs you need to fix. And that's on top of any potential increased costs if you license a library or need to add PC hardware: even an RPi would cost about the same as most 1200 cards, making it a wash.
Click to expand...

I hear ya. I am told it is a $50K cost for the 2 cards (hardware only, 1 per CMM).

The control isn't super critical. Cycle time is on the order of minutes.

We are looking to do data acq. down the road as well.
 
zoomable said:
I hear ya. I am told it is a $50K cost for the 2 cards (hardware only, 1 per CMM).

The control isn't super critical. Cycle time is on the order of minutes.
Click to expand...
Surely this is a joke ?
If not, I suspect someone sense that you are an easy victim and is trying to take advantage of you.

You dont need special hardware cards on the PC side. Standard ethernet is enough.

The 2 easiest solutions for the software side, in vase you are writing an application yourself:

1. OPC UA client. You would need an OPC UA Client framework.
2. Dedicated driver for S7-1200/1500. I recommend Deltalogic Accon AG Link since it can access optimized DBs. You can integrate it with MS .net programming, java, ...
 
No joke. For clarity, the quote was for this setup:
one_judksw.png

Each card above quoted at 20K.

The alternative I am seeking is to do this:
two_rnjetb.png


It sounds like I need to question the original quote?

Thanks,
z
 
What are the communications options for the CMM? Is the thing you're calling a "PLC I/O card" a custom communications module specifically for interfacing with that particular model Siemens PLC? Does the CMM speak Modbus TCP or is it limited to its own proprietary communications protocol?
 

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