Hello vivekkansara;
You can download Step 7 Lite from the following site:
http://support.automation.siemens.com/WW/llisapi.dll?query=step+7+lite&func=cslib.cssearch&content=skm%2Fmain.asp&lang=en&siteid=cseus&objaction=cssearch&searchinprim=0&nodeid0=10805055&x=15&y=9
They will request that you register, free of charge, then you can dowload the software.It is quite a large download, I suggest you make sure you have an ADSL line and lots of time.
Step 7 Lite will allow you to practice all your Siemens PLC skills, except for communications (no Ethernet, Profibus, As-i, Modbus...); it is designed for stand-alone projects. Basic manuals will be installed on your PC, along with the software (look at the new SIMATIC folder in the START button). More manuals can be found on Siemens' support website, for example here:
http://www2.automation.siemens.com/simatic/portal/html_76/techdoku.htm
You can download a 60-day/100 openings demo for Step 7 Microwin (S7-200 programming) from this Siemens site:
http://www.automation.siemens.com/_en/s7-200/support/tools_downloads/microwin.html
The basic manual for this processor is S7-200_e.pdf, available from Siemens support webpage. There are also some very ionteresting Tips and Tricks files for the S7-200, including example programs; look for them here:
http://www2.automation.siemens.com/microset/html_76/support/tipps/tt-steuerungstechnik.htm
Others with their own special affinities with other manufacturers will probably give you links to their PLC software; when you face problems in your initial programs, come back and ask questions, we'll be glad to help. Just make sure you show that you are not pirates, that you really want to learn, and that you have something to show for trying (a bit od code, a flowchart, something)before you come to us.
Hope this helps,
Daniel Chartier
