Several elements of PLC selection

PLC, also known as PLC, is a good tool for multi node industrial control, and also one of the key tools to build the future industrial Internet, with a broad development space. With its development prospect, it is a huge business opportunity. Therefore, this kind of industrial control equipment from abroad is now taking root in our country. According to incomplete statistics, at least dozens of relevant manufacturers are engaged in the research and production of PLC equipment. For the vast majority of consumers, this undoubtedly adds a lot of options. However, when choosing domestic PLC equipment, you should pay attention to the following factors. Now let's talk about it briefly:

1. Selection of PLC manufacturer

To determine the manufacturer of PLC, we should mainly consider the requirements of equipment users, the familiarity and design habits of designers with different manufacturers of PLC, the consistency of supporting products, technical services and other factors. For some special industries (such as metallurgy and tobacco), PLC system with mature and reliable operation performance in relevant industries should be selected.

 

2. Input / output (I / 0) point number estimation

The number of input / output points of PLC is one of the basic parameters of PLC. The determination of I / O points shall be based on the sum of all input / output points required by the control equipment. In general, the I / o point of PLC should have appropriate margin. Generally, according to the statistics of input and output points, an additional 10% - 20% of the expandable margin is used as the input and output point estimation data.

 

3. Capacity estimation of PLC memory

Memory capacity refers to the size of the hardware storage unit provided by the PLC itself. The memory capacity of various PLCs can be found in the basic parameter table of the PLC. The program capacity is the size of the storage unit used by the user program in the memory, so the memory capacity should be greater than the program capacity. In the design phase, because the user application program has not been compiled, the program capacity needs to be estimated.

 

4. PLC communication function selection

Now the communication function of PLC is more and more powerful. Many PLCs support a variety of communication protocols (some need to be equipped with corresponding communication modules). When selecting, the appropriate communication mode should be selected according to the actual needs.

 

The main forms of communication network of PLC system are as follows:

 

(1) the PC is the master station, and many PLCs of the same model are the slave stations, forming a simple PLC network; (2) one PLC is the master station, and other PLCs of the same model are the slave stations, forming a master-slave PLC network; (3) the PLC network is connected to the large DCS through a specific network interface as a sub network of the DCS; (4) the special PLC network (the special PLC communication network of each manufacturer). In order to reduce the communication task of CPU, the communication processor with different communication functions (such as point-to-point, fieldbus, industrial Ethernet, etc.) should be selected according to the actual needs of network composition.

 

5. According to the structure, PLC can be divided into integral type and modular type; integral type PLC has less I / 0 points and is relatively fixed, so there is less room for users to choose, which is usually used in small control system. The modular PLC provides a variety of I / O modules which can be plugged in the PLC base plate, so that users can reasonably select and configure the I / O points of the control system according to their needs. Therefore, the configuration of modular PLC is relatively flexible, which is generally used in large and medium-sized control systems, such as gcan-plc-400 of Shenyang Guangcheng technology, etc.

 

6. I / O module selection (1) selection of digital I / O module

 
From the above introduction, we can see that the choice of PLC is very learned. You must find out what kind of equipment you want before you use it. The gcan-plc-400 PLC of Shenyang Guangcheng technology basically meets all the above needs. If you want to know more about it, please click the link below for specific understanding. Or call the engineer directly, we will answer your questions at any time.