Hello Experts

                     I need a system based on S7 300 system, kindly help us in making a low cost effective system.

My system requirements are CPU S7 300, D/I:48, D/O :24, Power supply, and should have a monitoring HMI.

thanks in advance.

Thanks sir, the link is useful.Since, I am new with the system design. I need to clear few things:

As we have 40 D/I signals and 24 D/O only and the system is not big. My few question are:

1: If I use CPU 314 regarless of I/O cards, which other module should I used. Which will help with future extension of I/O modules and also module for HMI connections, as CPU 314 has no profinet connection for HMI screen?

2: If I go with compact models with DP options, which module should I use to extend my I/O's?

Hello.

With budget as the first concern, I would choose the S7-1200. The CPU1214 can handle 8 IO cards and 3 communication cards. Even if buying TIA Portal Basic (includes Step7 Basic and WinCC Basic), the pricing would be more affordable and future proof. 

CPU1214 (+ cards) with KTP700PN Basic would be a good choice.
Would this be viable for you?

The CPU313C-2DP would be a good starting point if an S7-300 is a must. Still TIA Portal Basic may be needed to get the KTP600DP or KTP700DP connected to the system. Those panels are more expensive.