Figure 1: Programmable logic controller (PLC).
(Go to Okmarts and pick the PLC you need)
Because PLC mostly adopts single-chip microcomputer, it has high integration. And it has corresponding protection circuit and self diagnosis function, which improves the reliability of the system.
Figure 2: Programming.
The programming of PLC mostly adopts relay control ladder diagram and command statement, and the number of instruction is much less than that of microcomputer. General small PLC has only about 16 instructions. And,because the ladder diagram is vivid and simple, it is easy to master and use. It can also be programmed without computer professional knowledge.
Because PLC adopts building block structure, users can flexibly change the function and scale of the control system only by simple combination. Therefore, it can be applied to any control system.
Figure 3: Configuration of PLC.
One of the greatest advantages of PLC is that for different field signals (such as DC or AC, switching value, digital or analog value, voltage or current, etc.) there are corresponding templates which can be directly connected with industrial field devices (such as buttons, switches, sensing current transmitters, motor starters or control valves, etc.) and connected with CPU motherboard through bus.
Figure 4: Installation of PLC.
Compared with the computer system, the installation of PLC does not require either a special computer room or strict shielding measures. It works as long as the detection device is correctly connected with the I / O interface terminal of the actuator and PLC.
Because the control of PLC is executed by program control, its reliability and running speed are unmatched by relays.
Figure 5: A microprocessor.
In recent years, microprocessors are used more and more, especially single chip microcomputer which greatly enhances the ability of PLC. And it also makes the difference between PLC and microcomputer control system become smaller and smaller, especially high-grade PLC.