Learning anything takes time; it's not something that can be achieved overnight. It involves accumulating knowledge, understanding and innovating, and finally creating your own work. Based on my work experience, I've divided this process into five stages, which I've outlined below, along with a summary of the characteristics and key points of each stage.
First, the simple logic control stage.
The logic stage means that logic control design can be implemented in a relay system. The main components of a relay system are: 1. Coil; 2. Normally open; 3. Normally closed. These correspond to the most basic elements in a PLC , only the way they are represented differs. Similarly, a relay system mainly consists of three components: A. Normally open; B. Normally closed; C. Coil. This corresponds to the basic elements in a PLC, only the reading method is different. It is crucial not to simply copy the relay system at this stage! This is incorrect! The two systems operate fundamentally differently. A PLC operates in a scanning cycle, while a relay system operates simultaneously in a "competitive" manner.
Key points: 1. Design several simple systems. 2. Learn the basics of electric drive.
II. Sequential Control Phase
This control method is very common in real life; basically, the machine tools we see every day are designed in a sequential manner.
There are two ways to implement sequence control in everyday design:
1. Certain PLCs have sequential control instructions, such as Mitsubishi's;
2. Start-stop control method. Regardless of the control method used in our program design, its system structure has three essential aspects: 1. "Step" / 2. "Active Step" / 3. "Transition Condition".
Key points: 1. Deep understanding of the "start-stop" control method; 2. Conversion between flowcharts and ladder diagrams.
III. Programming Language Stage
This stage, sometimes called the assembly stage, is fundamentally different from relay control. It's a stage that relay control cannot achieve and is the core difference between PLCs and relays. It's called the programming language stage because this stage requires instructions to implement the corresponding functions.
Key points: 1. PLC working principle; 2. Computer principle; 3. Programming basics (C language or assembly language); 4. Programming thinking.
IV. Special Control Phase
The specific features at this stage depend on the actual functions of the system, such as motion control of a lathe or PID temperature control of a factory water tank. There are significant differences between different brands of PLCs; for example, some PLCs integrate PID control while others do not.
Key points: 1. Automation-related knowledge; 2. Frequency converters, etc.; 3. Extended knowledge of PLC systems.
V. Network Configuration Phase
With the development of automation technology, some working conditions require multiple PLCs to work collaboratively, or to operate as a whole with upper and lower level mechanisms. At this stage, it's necessary to learn some network knowledge, such as communication protocols and bus protocols.
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