Introduction
Siemens makes several PLC product lines in the SIMATIC S7 family. They are: S7-200, S7-300, and S7-400. Siemens Step 7 is a powerful integrated software solution for automation.
Types of Siemens PLC
Compact:- I/O number fixed.
Modular :- I/O can be as per selection.
Types of PLC
S5-STEP5 – DOS base system.
S7-STEP7 – WINDOWS base system.
STEP-7 Groups
(STEP – Siemens Technical Education Program)
1) S7 200 :-
Compact Type PLC.
Use for small scale industry.
CPU Available – CPU 212 to CPU 226.
Digital I/O Capacity – 256.
Analog I/O Capacity- 38.
Programming software – micro win.
Communication Driver – PPI (Point to Point interface).
2) S7 300 :-
Compact and Modular type PLC
Use for Small and Medium Scale industry.
CPU Available – CPU 312 to CPU 318.
Digital I/O Capacity – 1024.
Analog I/O Capacity- 256
Programming software – Simatic Manager.
3) S7 400 :-
Modular Type PLC.
Use for Large Scale industry.
DP Port Available.
CPU Available – CPU 412 to CPU 418.
Digital I/O Capacity – 16384.
Analog I/O Capacity- 4000.
Programming software – Simatic Manager
Siemens PLC Hardware
PS : – Power Supply.
CPU:- Central Processing Unit.
IM:- Interface Module.
SM:- Signal Module(I/O modules).
Bus Connector Rack (rail): – Eleven slot rail.
CP:- Communication Processors.
FM:- Function Module.
IM – Interface Module:-
Interface Module use to connect or interface one rack to another rack.
SM – Signal Module (I/O modules):-
Simple Input/output can be Interfaced with through Signal Module.
CP – Communication Processors:-
Communication Processor used in Networking Communication Between many processors or plc.
FM – Function Module:-
Special Purpose controlled like PID, CNC, position controller, Cam controller can be interfaced to PLC through FM cards.
CPU memory Organization
CPU memory divided in blocks:-
OB -Organization Block(OB1-main block)
FC -Functions(Subroutine -user defined)
FB -Functional Block(defining function)
DB -Data Block(creating memory data)
Types of CPU Memory:-
Load memory:- User program stored, capacity can be changed by MMC up to 256k.
Work memory:-Instructions required program execution.
System memory:-Timer, Counter, memory bits, Process Image Memory, buffer diagnostics.
Communication Protocols :-
1) RS232 :- Bound rate 19,200 bits/sec. maximum length 10m. connector nine pin delta.
2)DH485:- Data Highway,32node components, bus rate 19,200 bit/sec. Maximum length 4000 feet (1.2 km) connector RJ 45 (radio jack).
3)MPI :- multi Point interface bound rate 1.5 mbps default,187.5 kbps, no of maximum nodes 32, network length 4000 ft, MPI use for PLC programming, inter CPU Communication, Scada/HMI communication.
4) Profibus:- Process field bus, Bound Rate 12 mbps, no of maximum nodes 126, network length 4000 ft, Profibus also used for remote I/Os and drives Communication.
