Answer: Hardware components, software components.
Answer analysis:
The composition of programmable ladder logic (PLC ladder diagram) mainly involves two levels: hardware and software, as well as specific graphic symbols and logic elements. The following is a detailed summary of these components:
1. Hardware components
Although the ladder diagram itself is an expression at the software level, the hardware of the PLC (programmable logic controller) is the basis for realizing these logics. The hardware of the PLC usually includes the following main parts:
Central processing unit (CPU): The control center of the PLC, responsible for executing user programs, performing logical and mathematical operations, and controlling the entire system to make it coordinated.
Memory: Used to store system programs, user programs, logical variables and some other information. The system program is a program that controls the PLC to implement various functions. It is written by the PLC manufacturer and solidified into the read-only memory (ROM); the user program is a control program written by the user according to actual needs.
Input unit: The input interface connected to the PLC and the controlled device receives signals from the master command element and the detection element. Input types include DC input, AC input, etc.
Output unit: The connecting part between PLC and controlled equipment, which transmits the output signal of PLC to the controlled equipment and drives its actuator. Output types include relay output, transistor output, etc.
2. Software components
As a graphical representation of PLC control program, ladder diagram is mainly composed of the following software components:
Graphic symbols: including normally open contacts, normally closed contacts, coils, timers, counters, etc. These graphic symbols are combined according to specific rules and syntax to form logical paths and control processes.
Logical operations: The ladder diagram contains logical operations such as OR, AND, NOT, XOR, etc., which are used to perform logical judgment and control on input signals, output signals, etc.
Program segments: The program logic in the ladder diagram consists of different program segments, each of which has specific functions and control logic. Program segments can be called and transferred to each other to achieve complex logical control and data processing.
Programming and debugging tools: The programming and debugging of PLC ladder diagrams are mainly completed by software tools. These tools provide a graphical interface to facilitate users to write, modify and debug ladder programs. Users can modify program logic, optimization algorithms and parameter settings at any time as needed.
3. Specific components of ladder diagrams
In ladder diagrams, specific components include:
Input part: indicates the location of input signals, which can be external devices such as sensors and buttons. In ladder diagrams, these input signals are usually used as input conditions for logical operations.
Output part: indicates the location of output signals, which can be output devices such as motors and lights. In ladder diagrams, these output signals are the results of logical operations and are used to control the actions of external devices.
Ladder part: consists of multiple logic elements, such as switches, timers, counters, etc. These logic elements are used to implement logical operations and convert input signals into output signals.
In summary, the components of programmable ladder logic include CPU, memory, input unit and output unit at the hardware level, and graphic symbols, logical operations, program segments and programming debugging tools at the software level. These components together form the basis of PLC ladder diagrams and realize precise control of industrial equipment.