Power module
Provide internal power for PLC, and some power modules can also provide power for input signals.
It is the input/output module module, I stands for input, and o stands for output. I/O modules can be divided into discrete modules, simulation modules and special modules. These modules can be installed on a rail or rack with multiple slots, and each module is inserted into one of the slots according to the number of points.
Memory module
Mainly store user programs, and some memory modules can also provide auxiliary working memory for the system. Structurally, all memory modules are connected to the CPU module.
Backplane, rack module
As the name implies, in the installation process of various PLC modules, the backplane and rack modules act as the backplane, providing a bus for communication between the modules. Some connections between multiple backplanes use interface modules, and some use bus interfaces. Different manufacturers are different, but PLC varies by type.
The specifications of the main box of the box-type small PLC vary depending on the number of I/O points that can be provided by combining the above-mentioned modules in one box. The box-type PLC does not contain a CPU, and there is also an I/O expansion box that is only used as a power supply and I/O unit. The specifications of the expansion box vary depending on the number of I/O points.
In addition to the above-mentioned modules, PLC also has special intelligent or functional modules. For example, A/D (model) module, D/A (model) module, high-speed counting module, position control module, temperature module, etc. These modules have their own CPU. By pre-processing or post-processing the signal, the control of the PLCCPU can be simplified, and the control of the complex program can be simplified.
The types and characteristics of smart modules are also quite different. PLC with excellent performance has various types and excellent performance.
After the communication module is connected to the PLC, it can communicate between the PLC and the computer, between the PLC and the PLC, can communicate with other control units such as frequency converters, thermostats, and can also form a local area network. The communication module represents the network function of the PLC and represents an important aspect of the current PLC performance.
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