SIMATIC S7-300 PLC is a modular design, widely various between separate modules that can be combined and extended. The main components of the system include:
1) central processing unit (CPU): SIMATICS7-300 provides a wide range of different performance of CPU in order to meet the requirements of different users, including CPL3121FM, CPU313, CPU314, CPU315, CPU315 2 and so on. CPU module in addition to the main task of the completed user, but also provides the S7-300 backplane with 5 v DC power supply, and communicate with other central processing unit or programming device by MPI.
2) signal module (SM): signal module SM so that different process matches the signal level and S7-300 of the internal information, mainly the SM321 digital input module, SM322 digital output module, SM331 analog input module, SM332 analog output module. Each signal before the modules are equipped with self coded screw-type connectors, external signals can be easily connected to the signal on the module front connector. Particular its analog inputs can be connected thermocouple, RTD, current 4~20mA, voltage 0~10V 18 different signal input range is very wide.
3) communications processors (CP): for the network and point to point connections, for example, CP340 with RS-232C interface, CP342-5DP with the fieldbus network.
4) function module (FM): for high speed counting, positioning (open–loop or closed–loop control), and closed–loop control. FM351 servo motor position control module, FM352 electronic cam control module, FM353 stepper motor positioning module.
5) load power supply module (PS): use to connect a SIMATIC S7-300 120/230V AC power or DC power supply 24/48/60/110V.
6) interface module (IM): when used in a rack configuration connected hosts (CR) and expansion racks (ER). S7-300 by distributed hosts (CR) and 3 expansion bays (ER), can operate up to 32 module.
S7-300 electromagnetic compatibility and strong with high resistance to vibration and impact, to industries with high environmental adaptability.
S7-300 structure is simple, flexible, and easy to maintain, use DIN standard DIN rail mounting, easy to install. On the backplane bus integration module, modules are connected by bus connector, makes the replacement module is simple, all of which have a reliable connection terminals. Signal modules and communication can be inserted without restriction to any one on the slots, free configuration of the system. When the user control tasks require more than 8 signal module or when a communication module, you can use the S7-300 extension rack, extended easily.