SIEMENS

I. Product Model Series
This is the Siemens SIMATIC S7-300 modular PLC programmable controller. The entire chassis is composed of various modules:
The first module on the left, number 1: PS 307 power module
Example model: 6ES7307-1EA01-0AA0, providing DC24V working power for all modules of the entire chassis.
The core module number 2: S7-300 CPU host
Common models: CPU312, CPU313, CPU314, CPU315, CPU317, etc. (in the figure, it is the standard CPU300 series appearance), is the core computing and control core of the entire equipment.
3, 4, 5, 6 blue modules: SM300 I/O signal module
SM321: Digital input module, collecting button, sensor, proximity switch signals;
SM322: Digital output module, controlling contactors, solenoid valves, indicator lights;
SM331: Analog input module, collecting temperature, pressure, level, voltage and current transmitters;
SM332: Analog output module, outputting 0-10V/4-20mA to control frequency converters, regulating valves;
Installation: U-shaped backplane chassis, all modules are inserted on the backplane and communicate through the backplane bus. Product positioning
S7-300 is a classic medium-sized modular PLC from Siemens, belonging to an older but mature product line. It has now been gradually replaced by S7-1500, but there is a huge amount of stock in the industrial field.
II. Main Functions of the Entire System

1. Automated logic control (core function)
   The CPU executes the control programs written by users in a loop, completing the fully automatic process of the equipment:
   Collecting sensor and instrument signals from the site;
   Automatically outputting signals according to the process logic, controlling solenoid valves, motors, indicator lights, servo / frequency converters;
   Realizing sequential start-stop of the assembly line, interlock of workstations, fault alarms, and automatic cycling.
2. Analog closed-loop process control
   Combined with SM331/SM332 analog modules, with built-in PID calculation functions, it automatically stabilizes control:
   Temperature heating / cooling, pressure stabilization, constant water level of liquid level, flow regulation;
   Widely used in chemical, water treatment, boilers, HVAC industries.
3. Motion control
   Can be combined with FM351, FM353, FM354 positioning modules to achieve point control of stepper / servo motors, multi-axis synchronization, used in machine tools, packaging, mechanical hand equipment.
4. Industrial communication networking
   The CPU is equipped with MPI interface, and the DP communication module (CP342-5) can be expanded to realize the PROFIBUS-DP bus, connecting:
   Touchscreen (HMI): Human-machine interface for displaying parameters and manual operation of the equipment;
   Frequency converters, remote ET200M distributed IO, upper-level monitoring computer;
   Networking data exchange between multiple S7-300s.
5. Fault diagnosis and data recording
   The module has built-in hardware self-diagnosis, which can detect short circuits, breaks, and module faults in real time; the program can record production data and fault records, facilitating the tracing of equipment abnormalities.
   III. Typical Application Scenarios
   Traditional assembly lines: packaging machinery, conveying and sorting lines, automotive welding / painting production lines;
   Process industries: sewage treatment plants, chemical reaction vessels, boilers, HVAC;
   Mechanical equipment: small and medium-sized CNC machines, injection molding machines, printing equipment;
   Buildings / energy: pump stations, air compressor stations, small power station auxiliary control systems.
   IV. Companion Programming Software
   Use STEP7 V5.x software for programming, and it can be compatible with TIA Portal for configuring S7-300.
   V. Product Feature Comparison
   Modular free expansion: I/O points can be increased or decreased as needed, with a maximum expansion of 32 modules;
   Strong stability, anti-interference, suitable for harsh dust and vibration environments in factories;
   Disadvantages: outdated hardware, slow computing speed, no native Profinet Ethernet, currently new projects mostly choose S7-1500 as a replacement, and a large number of existing equipment are still maintained and used.

For more models, please contact via email: plcvarious@foxmail.com