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HOW TO SELECT SUITABLE PLC?

2019-03-27

In modern industrial production, there are a large number of digital and analog control devices, such as motors, solenoid valves opening and closing, product counting, temperature, pressure, flow setting and control, etc. These automatic control can be operated efficiently by one of the most effective tools, programmable logic controllers (PLCs).

 

There are many PLC brands on the markets, such as OMRON, MITSUBISHI, FUJJ, anasonic, SIEMENS, LG. In recent years, the price of PLC products has dropped significantly, which could be an important reason why many technicians select PLCs.

 

How to select PLC products?

 

1. System scale. First determine whether the system uses PLC single machine control, or use PLC to form a network, so that can calculate PLC input and output points. When purchase the PLC, it is necessary to leave a certain margin (10%) based on the actual number of points required.

 

2. Determine the load type. You need know weather the PLC output is DC or AC, whether it is a large current or a small current, and the frequency of the PLC output point, so as to determine whether the output uses the relay output or the transistor output. Different loads use different output modes, which is very important for the stable operation of the system.

 

3. Storage capacity and speed. Although the PLC products are generally the same, but there are certain differences. Products that are fully compatible between companies have not yet been discovered. The development software of each company is different, and the storage capacity of the user program and the execution speed of the instructions are two important indicators. Generally the higher the storage capacity and the faster the PLC, the higher the price, but the PLC product should be selected according to the size of the system.

 

4. Programming. PLC programming can be used in three ways:

 

(1) It is programmed with a general handheld programmer, which can only be programmed with statements in the merchant's specified statement table. This method is inefficient, but it is suitable for systems with small capacity and small dosage, and also small in size, easy to debug on site, and low in cost.

 

(2) It is programmed with a graphic programmer. The programmer uses ladder diagram for programming, which is convenient and intuitive. Generally the electrical personnel can apply freely in a short period of time, but the programmer is expensive.

 

(3) It is programmed with IBM personal computer plus PLC software package, which is the most efficient way, but most of the companies PLC development software package is expensive, and this method is not easy to debug on site.

 

Therefore, PLC products should be purchased reasonably according to the size and difficulty of the system, the length of the development cycle, and the funds situation.

 

5. It is suggested to use the products from large companies that the quality is guaranteed, and the technical support is good, the general after-sales service is also good, it is also conducive to your product expansion and software upgrade. 

 

Coolmay brand is estimated more than 13 years in China, specialized in developing and manufacturing HMI, PLC, HMI/PLC all-in-one and provides consulting and after-sale service with engineers and technicans team.



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