Base plate and rack module, which provide base plate for the installation of PLC modules and provide bus for the connection between modules. Some backplane connections use interface modules, and some use bus interfaces. Different manufacturers or the same manufacturer but different types of PLC are not the same.
The main box of box type small PLC integrates the above modules into a box, and is divided into different specifications according to the number of i/o points that may be provided.
The box type PLC also has an i/o expansion box, which does not contain CPU, but only has the function of power supply and i/o unit. The expansion box also has different specifications according to the number of i/o points.
In addition to the above modules, PLC has special or intelligent or functional modules. Such as a/d module, d/a module, high-speed counting module, position control module, temperature module, etc. These modules have their own CPU, which can preprocess or post process the signal, so as to simplify the PLC CPU's control of complex programmed control quantities. The types and characteristics of intelligent modules are also very different. PLC with good performance has many kinds of modules and good performance.
Communication module, which can communicate between PLC and computer, or between PLC and PLC after being connected to PLC. Some can also communicate with other control components, such as frequency converter and temperature controller, or form a local network. The communication module represents the networking ability of PLC and the important aspect of PLC performance today.
To master the performance of PLC, we must understand its module, and understand the performance of PLC by understanding the performance of the module.
In addition to modules, PLC has external devices.