PLC specifying


Thread Starter


I am look for someone to help us to learn how to choose the Siemens PLC S7-300 to install it in concrete batching plant. It has 19 digital I/O
and 3 weigher scale has RS-485 com port. Finally, which PC-based SCADA tools are suitable on that application to do recipe, database, control, Alarm, printing?

Thank you,

Marc Sinclair


This sounds as though an S7-200 would do the job, and you could use a CP243-IT for web based access and control. The CPU224/6 has two RS485 ports, but depending on the protocol you may be able to add more ports. (The S7plus, out in Q3, promises much more.) You might consider SIWAREX modules for weighing. The major benefit would be in cost savings in hardware costs, plus the programming software is low cost and non-dongled. Using a web based SCADA is FREE (no run-time fees) and multiplatform.

Marc Sinclair

Michael Griffin

If you are only using 19 digital I/O you might also want to look at the Siemens S7-200 series. The S7-200 is a lot easier to understand and program than the S7-300 but is still a very capable PLC. The S7-226 has 2 serial ports, so you could use one of those for the weigh scales while leaving the other one free for programming and possibly for the SCADA connection (there are also interface modules that provide additional types of network connections).

I don't want to recommend a particular SCADA for your application, but you could talk to Siemens about their WinCC product.
A bit of the exact configuration depends upon your present and possible future needs. There are several SCADA packages available.

Questions to think about:
1. Upgradability
2. Interoperability
3. Support
4. Market share and knowledge base of users.

Wonderware, Intellution and Citect are some very good SCADA packages.

If you need some further questions answered, email me at nkinze @ att. net

Contact an authorized Siemens Automation Distributor in your area. They should have someone on staff that can help you with your application.
Siemens' WinCC flexible might be a good candidate for you SCADA needs.

David Adams