What Siemens PLC

I hope someone can help.

I have a new project to do that requires profibus dp to four accopus drives. I am looking at using a siemens s7-300 313C-2DP cpu. Am I correct in thinking that I can configure this as the DP master and the accopus drives as the slaves?

Yes. You can do like that. For the Accopus drives there must be a socalled GSD file. This GSD file must be imported into the HW configuration in STEP7. This allows you to setup the accupus drives as DP slaves to the 313C-2DP master.

Apart from that I dont like the 313C-2DP CPU so much. Actually I dislike any "brick" type of PLC.
You get a slightly less expensive solution as compared to if you use a separate CPU and i/o modules. But any saving comes at the cost of not being able to exchange the CPU for another type if the need rises. This because the onboard i/o locks you into using that particular CPU.

I was looking at a Siemens CPU, what would you recommend then?

Let me ask back:

How many i/o ?
Any specialty i/o ?
How complex is the program ?
Any high-speed i/o ?
Any distributed i/o besides the drives ?
Any communication requirements ?
What kind of HMI do you foresee, if any ?
Any other out-of-the-ordinary stuff that could be relevant for the choice of PLC ?

There are others on this forum that seem to "love" bricks. Strange fellers.

The programme will be pretty basic.


The application is a modular conveyor system that is already controlled by micro plcs. There is five modules on the conveyor that all require 4 outputs and 2 inputs from the main plc. I then have the four accopus drives which use Profibus and another three micro plcs that control some index units.There is also an interface with a couple of ultrasonic welders and then some positional sensors.

I hope this makes sensce, it has been a number of years since I had to build a system.

So it is "approximately"
5 x interface signals to Micro PLCs for conveyors, 4 outputs + 2 inputs each.
3 x interface signals to some Micro PLCs for "index units"
1 x interface to "welders" (how many analog or digital ?)
"some" x positional sensors (how many analog or digital ?)
4 VFD drives on Profibus.

It is not at all clear to me how many i/o we are talking about.

If this is supposed to be one integrated system, I would try to eliminate all the small micro PLCs sitting around.
And since you are going Profibus already, you should consider to place distributed i/o blocks locally where they are needed.

A 315-2DP sounds as the obvious minimal CPU choice.
You probably also must think about what HMI, and if you decide upon a locally placed panel, then you can connect it via the MPI port, leaving the DP port to handle only the DP slaves.
If on the other hand you need a HMI in a remote location, say in an office away from the control room, or you need many HMI's, then you should consider a 315-2PN/DP because of the ethernet port.

The Index units will have 6 outputs and 5 inputs.
Welders will have 3 output and 2 inputs.

The positional sensors will just be two sensors to show that parts are there to be welded.

As I have profibus, I was thinking of using a siemens ET200eco and a ET200L for distributed i/o's

The whole thing is to be integrated into one, the micro plcs are pre-programmed to run the conveyor system, so can't be taken out.

The HMI will be local.

saleshark said:

As I have profibus, I was thinking of using a siemens ET200eco and a ET200L for distributed i/o's

Click to expand...

Dont use ET200L, it is obsolete. The natural successor to ET200L is ET200S.

saleshark said:

The whole thing is to be integrated into one, the micro plcs are pre-programmed to run the conveyor system, so can't be taken out.

Click to expand...

Integrated into one system, but still separate.
Is there a law against the micro PLCs being ripped out ?
I know what I would do.