Why use PLC instead of microcontroller in industry?
The primary factor of industrial production is stability! Therefore, the first factor we consider when designing an industrial control hmi system is reliability! The plc is specially designed for industrial production, its essence is a single chip microcomputer system, but it is more reliable than the single chip microcomputer, more stable, less susceptible to interference. Now, due to vicious competition, in order to reduce costs, they are replacing PLC with single-chip computers, seemingly reducing costs, but actually hiding the bell. Imagine, a system you use a single chip computer instead of PLC to save some money, but due to instability caused by production, your loss is far greater than the cost you save.
The biggest advantage of single chip microcomputer compared with PLC is cheap, plc is flexible than single chip microcomputer, reliable is too expensive, from the writing language, plc is closer to the electrical diagram, easy to get started, but the writing language of each brand is not the same, different brands exchange trouble. The MCU generally uses C or assembly, and the language is interchangeable between the same different brands, but it is relatively difficult to get started.
But in the industry, many targeted changes for different customers or in the normal use of process innovation requirements to increase hardware, at this point PLC is much stronger than the MCU, the MCU layout out after the basic shape, but plc at any time free to increase or decrease. For example, at first, the requirement was only 7 axis servo, and only 134 io points were made 2 sets, but the subsequent increase was increased to 13 axis servo, 176 IO, and there were increases and decreases for different customers. Single-chip microcomputer can also be done but the cycle will be dragged out for a long time, single-chip microcomputer is more suitable for single-machine large-batch equipment.
The main reasons are as follows:
1: the use of pLC is more flexible than the single-sided machine. Rich function configuration. PLC version of many functions are to do the first layer need to use what function can be directly called, more versatile. The single chip microcomputer is somewhat similar to custom development.
2 :plc can flexibly add functions according to needs. In the case of adding functions, if the number of points is not enough, you can flexibly add the expansion l0 module, or other expansion modules such as analog quantity or temperature. This is the single chip does not have.
3: From the perspective of stability, due to the strong versatility of plc, large customer base, PLC hardware and underlying algorithms are verified and constantly improved by many users, relatively speaking, more stable.
4: From the perspective of after-sales. At present, plc is produced by several mainstream manufacturers. Each pLC is relatively easy to buy. If there is a hardware problem, it can be replaced quickly. Of course, the main advantage of single-chip microcomputer is that once mass production, the cost is relatively low. For many contralequipment shipments are relatively large, and the pursuit of cost customers. Willing to use a single chip computer.
