Thanks, JesperMP, mk42.
There are ome unclear questions to me.
What do you think of maximum current-carrying capacity(10A) for one PM module?
It says "Thie must not exceed 10 A in total".
So, if rate current of I/O module is 0.5A (4DI 24VDC or 4DO 24VDC), is maximum module 5 EA ?
2 A (0.5 x 4 ) x 5 = 10 A ? <<---------- Is it wrong ??
Input modules usually take a very small amount of current, (often only 100ma, or .1 A for the whole module), so check the technical specs for each module to see how much it needs.
For outputs, your math above is correct. If you do it that way, you will never run short.
However, one thing to consider is that even though the module is rated for .5A, teh actual device connected to it might only use .2A. Also, often you might have two outputs that could never be on at the same time, for example if you have one output for Forward and another output for Reverse. This means that you might be able to get away with 6 output modules instead of 5, or maybe more, depending on what you are trying to do.
Siemens has a tool that can help you build IO racks, to ensure you are following all the rules, like rack length, max number of modules, etc.
www.siemens.com/tia-selection-tool
As for Input and Ourput module 24VDC supply,
do both modules supply 24VDC power to attached device ( relay or sensor etc.. ) ?
Are they different with just connection ? (it means 24VDC circuit route)
Input module : PLC(+) -> device -> PLC address point(-)
Output module : PLC address point(+) -> device -> PLC(-)
Do I understand correctly ?
Most ET200S input modules don't supply their own power, so it would be: 24V (+) -> device -> PLC input point
Most ET200S output modules don't need to return to the PLC, so it would be: PLC output point -> device -> 0V (-)
I think this is the same thing you had in your example, but I wasn't sure what you meant by PLC +/-.
However, some modules, like Safety IO, do require the same IO card to be both the source and the sink. Then it would be PLC Output -> device -> PLC Input, with the input and output actually being the same module, and in specific pairs.