Networking S7-200

I want to gather data from several S7-200 (+15).

Ths is the first time I will be doing networking for PLC, I have little experiece with Computers



the attached picture (JPEG) shows three options.

I have a couple of questions, to help me decide which one would be good choice, as I dont want to mess-up this project!


HARDWWARE used is

15units of S7-200 PLCs, acting as slave.
1unit Master to gather 4 Byte of data from each slave.
15units of tp-070 each attached to the slave.

A) The siemens book says that the TP-070 does not work with another master on the network!!! can someone pls. shed light on this? or how I can by-pass this restriction.

B) considering the above environment, should I use the 1st option in the picture?

because I recall there is a restriction in the number of network nodes in case of PPI network

or would I have to go for PROFIBUS or a ETHERNET based network?

Any other restrictions / advantages you think, may help me select the right product.

Well???


isnt there anyone here who can help me?

The Siemens tech. ppl say:

that for a profibus network of this type, it is not possible to use S7-200 as a master to acquire the data.

They suggest I install a S7-300 as a master.

any comments? the reason I'm trying to avoid S7-300 is b'coz I've only used the S7-300 during the training session at siemens long time back, though I have the software.

But since this Network thing is new to me, I dont want TWO new things with me on a big project at the same time. trying to keep it simpler.

Thanks and I really appreciate the help. (I'm getting tired of talking to myself)

profibus

Hi mjamil
I have done something similar by only using S7-200 CPUs with four CPUs on the network but you can do it with more (32). In your case if you have 15 PLC and 15 TP070 you have 30 devices so I dont see any problem.I believe you don't need the profibus card either.You can use profibus adaptors with auxiliary port for the TP070.Each device will have it's own identity from 1 to 30 .
Use NETWORK READ/WRITE commands to read from/write to the PLCs.Use this command to gather all data to one PLC.

Thanks Geofra,

sometimes asking too many questions create more confusions.

The reason I did not contact Siemens earlier was because they are more interested in selling a solution, instead of selling hardware. (atleast thats my experience!)

The cable I would need for this setup, I assume is the same you mentioned in your earlier post to me, I think it was a straight connection 3 to 3 and 8 to 8, right?


Another thing i was considering, what if the PLC I use to gather information (MASTER) fails to operate for some reason, this would mean no data at all, right?

How about I install a separate PLC for this purpose? (because all the individual PLCs are used in the running of machines and to SEND 4BYTES of data to the MASTER, this would mean if a machine has a breakdown (elec. or mech.) the PLC has to be turned off)


Another thing, any sugestions, to bring this DATA to a COMPUTER, instead of installing a separate PLC? (have u had any chance to use MICROWIN as I was considering this software from SIEMENS)

Thanks a lot again.

profibus

Hi mjamil
No you cannot do your own cable here as you need to have an extra port to connect the TP070 for each PLC.You have to buy the ready made from SIEMENS which is not expensive.
Yes it would be better to use an extra PLC to gather the data.
No you cannot use microwin for gathering data.Microwin is used only for programming the PLC.
You need special software to gather data on a PC. Visit this www.windmill.co.uk .I have never used it but it may be good for you.

Dear Geofra,

1) I will be using S7-226, it has two ports, I hope this solves the requirement issue for two ports, unless there are any other conflicts.

2) Regarding the Cable, I'm not sure how far apart the Machines are going to be placed, so how do I handle the Cable length issue?

3) Sorry, I didnt mean microwin, I meant Siemens MICRO-COMPUTING, I once saw its capabilities in a Siemens seminar, but you know these guy really boast about thier products, and dont mention the dis-abilities.
I downloaded the PC Access too, but it was far too much complicated, than what I was thinking of.

You will have to use a 277 DP module or an ethernet module to collect data. You are limited by the number of connections on the PPI network, even though you have multiple ports. I would use the 277 DP modules on each S7-200 PLC and set up a master, a 300 or 400 with alot of memory for the master.

mjamil,

You are on the right track. Since you are using S7-226, hook your TP070s to Port 1. Network each CPU with RS-485 (Profibus) cable/connectors on Port 0. In the CPU that will be the data concentrator, use the NETR instruction to pull peer-to-peer data from the other slave CPUs. Then use a MicroWIN status chart to display the data from the data concentrator. You can also copy and paste the status chart data into a spreadsheet, Word, or other application.

You can pull up to 16 bytes of data from the slave CPU with one NETR request. If you want more data, issue a series of NETR requests with different offset addresses.

lawsce, that won't work. You are limited to 8 connections, even thouh they are on different ports on each PLC. 8 connections on a PPI network is the limit.

Its my understanding (and I think I provided the info on another post) that Micro/Win is always a Master in a Profibus system....from the manual Chapter 7: http://cache.automation.siemens.com/dnl/DY1NjExNQAA_1109582_HB/S7-200_e.pdf

Using Master and Slave Devices on a PROFIBUS Network
The S7-200 supports a master-slave network and can function as either a master or a slave in a PROFIBUS network, while STEP 7--Micro/WIN is always a master.
Masters
A device that is a master on a network can initiate a request to another device on the network. A master can also respond to requests from other masters on the network. Typical master devices
include STEP 7--Micro/WIN, human-machine interface devices such as a TD 200, and S7-300 or S7-400 PLCs. The S7-200 functions as a master when it is requesting information from another S7-200 (peer-to-peer communications).

Click to expand...

If you are going to use Micro/Win on a PC then that can be the master. Technically you can do a multiple Master system, just depends.

RRobbins,

The 8 connection limit does not apply in this case. The NETR is a request/response protocol, so it only uses one connection. The connection is dynamic, not static. Once the response is returned, the connection is terminated and you can go on to the next CPU.

I just tried this on a mixed master/slave network with 12 CPUs and three TD200s. I added another CPU with the data concentrator program that pulled data from each of the 12 CPUs, one at a time. Took about 1.8 seconds to go around and collect again at 187.5K baud.

This would not work if you needed realtime data to trigger alarms.

Also, you probably will not be able to set this up using the MicroWIN NETR/NETW wizard. You will need to manually write the NETR STL code.

The problem is not the net reads and writes. The problem is the TP's. You will only be able to use 4.

thanks guys,

Robbins, is the problem restricted to TP's and not TDs? if so I can switch over to TDs?

Coz. somewhere in the Siemens Manual I was reading that the TP-070 does not work while another master is working on the same network.

I could just use a TP-070 on the Master S7-226, and use TD with the rest of 15plcs if it is because of the TP.


second Phase, the Data aquisition, I was thinking of installing a ETHERNET or another device, to a master S7-200, to send all the gathered data to the standalone PC, running a software, which I will decide once I DECIDE IF THE NETWORK BEING DISCUSSED WILL WORK!!!

geofra, could you shed light on what u'ave been doing for S7-200 netowrking, in a bit detail?

cable

The other issue remains, the Profibus cable of my required lenght(s) ?????

suggestions anyone?