Mitsubishi PLC English name is also known as: Mitsubishi Programmable Logic Controller, is the main product of Mitsubishi Electric in Dalian. It uses a class of programmable memory for its internal memory program, performing user-oriented instructions such as logic operations, sequence control, timing, counting, and arithmetic operations, and controlling various types of machinery through digital or analog input/output. Or the production process. Mitsubishi PLC has the following models commonly found in the Chinese market: FR-FX1N FR-FX1S FR-FX2N FR-FX3U FR-FX2NC FR-A FR-Q).

principle

The composition of the PLC system and the functions of each part:

 PLC related components

1. System composition.

The role of each part.

CPU computing and control center

It plays the role of "heart".

Vertical: When the program input from the programmer is stored in the user program memory, the CPU translates the user program into a user compiler approved by the PLC according to the function assigned by the system (the interpretation program of the system program memory).

Horizontal: Input status and input information are input from the input interface, and the CPU stores it in the working data memory or into the input image register. The data and the program are then organically combined by the CPU. The result is stored in the output image register or working data memory, and then output to the output interface to control the external drive.

Composition: The CPU consists of a controller, an operator, and registers. These circuits are integrated on one chip. The CPU is connected to the I/O interface circuit through an address bus and a data bus.

2. Memory

A semiconductor circuit with a memory function.

Divided into system program memory and user memory.

The system program memory is used to store system programs, including the management program, the monitoring program, and the interpretation compiler for compiling the user program. It consists of a read-only memory. The content used by the manufacturer cannot be changed, and the power failure does not disappear.

User memory: divided into user program storage area and working data storage area. It consists of random access memory (RAM). Used by the user. The power outage disappeared. A commonly used high-efficiency lithium battery is used as a backup power source, and the service life is generally 3 to 5 years.

3. Input / output interface

(1) Input interface:

The photocoupler consists of two light-emitting diode tubes and a phototransistor.

Light-emitting diode: A variable electrical signal is applied to the input end of the photocoupler, and the light-emitting diode generates an optical signal having the same regularity as the input signal.

Photoelectric three-stage tube: Conducted under the illumination of the optical signal, the degree of conduction is related to the strength of the optical signal. In the linear working area of the optocoupler, the output signal is linear with the input signal.

Input interface circuit working process: When the switch is closed, the diode emits light, and then the transistor is turned on under the illumination of light, and the signal is input to the internal circuit. When the switch is turned off, the diode does not emit light and the transistor does not conduct. Input signals to internal circuits. That is, the external switching signal is converted into a digital signal acceptable to the PLC through the input interface circuit.

(2) Output interface

PLC relay output interface circuit

Working process: When the internal circuit outputs digital signal 1, there is current flowing, the relay coil has current, and then the normally open contact closes, providing current and voltage for the load to conduct. When the internal circuit outputs a digital signal of 0, no current flows, the relay coil has no current, and then the normally open contact opens, disconnecting the load current or voltage. That is, the internal digital circuit is converted into a signal through the output interface circuit to make the load act or not.

Three types:

Relay output: contact, short life, low frequency, AC and DC load

Transistor output: no contact, long life, DC load

Thyristor output: no contact, long life, AC load

4. Programmer

There are two types of programmers, one is a handheld programmer, which is convenient. Our lab uses a handheld programmer. The second is through the RS232 port of the PLC. Connected to a computer. Then tap the keyboard. The program is input to the PLC through the NSTP-GR software (or software under WINDOWS).

The second section of the basic working principle of PLC

1. PLC adopts the "sequential scanning, continuous circulation" working mode

1. Each scanning process. Focus on sampling the input signal. Focus on refreshing the output signal.

2. Enter the refresh process. When the input port is closed, when the program is in the execution phase, the input has a new state and the new state cannot be read. The new state is only read when the program performs the next scan.

3. One scan cycle is divided into input sampling, program execution, and output refresh.

4. The contents of the component map register vary as the execution of the program changes.

5. The length of the scan cycle is determined by three bars. (1) The speed at which the CPU executes the command (2) The time the command itself occupies (3) The number of instructions

6. Due to the use of centralized sampling. The way to concentrate output. There is a phenomenon of input/output hysteresis, that is, input/output response delay.

2. PLC and relay control system, microcomputer difference

1. The difference between PLC and relay control system

The former works in "serial" and the latter works in "parallel".

The former uses "software" and the latter uses "hardware".

2. PLC and microcomputer difference

The former works in a "cyclic scan". The latter way of working is "standby or interrupted"

PLC programming method

The most prominent advantage of PLC is the use of "soft relays" instead of "hard relays". Replace "hardware routing logic" with "software programming logic".

PLC programming languages are ladder diagrams, Boolean mnemonic languages, and more. Especially the first two are commonly used.

Ladder language features:

1. Each ladder diagram consists of multiple steps.

2. The vertical lines on the left and right sides of the ladder diagram represent the imaginary logic power supply. When the logical operation result of a certain step is "1", an imaginary current passes.

3. The relay coil can only appear once, and its normally open and normally closed contacts can appear countless times.

4. The result of each step is immediately used by the subsequent steps.

5. The input relay is controlled by an external signal. Only contacts appear and no coils appear.

Section 4 Main technical performance

User program storage capacity: A measure of how much user applications can be stored. Usually in words or K words. The 16-bit binary number is one word, and each 1024 words is 1K words. The PLC stores instructions and data in word units. The general logical operation instructions each occupy 1 word. Timing/counting, shift instructions occupy 2 words. The data operation instruction occupies 2~4 words.

Section 5 Classification of PLC

Classified by structure:

1. Integral: It is to install the PLC components together or a few printed circuit boards, and together with the power supply, it is installed in the casing to form a single whole, called the main unit or the basic unit, small and ultra-small. The PLC uses this structure.

2. Modular: It is to make the basic components of PLC into independent modules. Medium and large PLCs are used in this way for easy maintenance.

Product Series

FX1S series:

 Several commonly used Mitsubishi plc

Mitsubishi PLC is an integrated small unit PLC. It has full scalability such as performance and communication capabilities. If you consider the installation space and cost is an ideal choice.

FX1N series:

It is a powerful popular PLC launched by Mitsubishi Electric. With extended input and output, analog control and communication, link function and other scalability. It is a widely used Mitsubishi PLC for sequential control.

FX2N series:

At the time, Mitsubishi PLC was the most advanced series in the FX family. Features high-speed processing and the ability to expand a wide range of special function modules to meet individual needs, providing maximum flexibility and control for factory automation applications.

FX3U series:

It is a new third-generation Mitsubishi PLC newly launched by Mitsubishi Electric Corporation, which may be called a small supreme product. The basic performance is greatly improved. The basic unit of the transistor output type has built-in 3-axis independent maximum 100kHz positioning function, and adds new positioning commands, which makes the positioning control function more powerful and more convenient to use. The FX3U series products are FX2N replacement products, and the FX2N series products are no longer available in December 2012. Everyone will choose FX3U series products in the future. Mitsubishi PLC-FX3U series product introduction:

● FX3U series PLC third-generation micro programmable controller with built-in RAM memory of up to 64K.

● Built-in high-speed processing of the industry's highest level of 0.065μS / basic instructions.

● Control scale: 16~384 (including CC-LINK I/O) points.

● Built-in independent 3-axis 100kHz positioning function (transistor output type).

● A powerful and easy-to-use adapter can be connected to the left side of the base unit.

● The built-in programming port can achieve high-speed communication of 115.2kbps, and can use up to three communication ports at the same time.

● Up to 84 points (including remote I/O) can be controlled by extension of the CC-Link network.

● The device can be monitored, tested, and clocked.

● The FX3U series can also be mounted on the panel of the control cabinet.

● FX3U series PLC programming software: GX Developer 8.23Z or higher is required.

FX3G series:

It is a new third-generation Mitsubishi PLC newly launched by Mitsubishi Electric Corporation. The basic unit comes with two high-speed communication interfaces (RS422 & USB, built-in up to 32K large-capacity memory, basic command processing speed of 0.21μs in standard mode, control scale: 14~ 256 points (including CC-LINK network I/O), easy to set positioning function (up to three axes), up to 4 FX3U special adapters can be connected to the left side of the basic unit, which can realize floating point calculation, and can set two levels of passwords, each level 16 characters, enhanced password protection

FX1NC FX2NC FX3UC Mitsubishi PLC:

On the basis of maintaining the original powerful functions, the extremely large scale reduction I/O type wiring interface reduces the wiring cost and saves time.

Q series Mitsubishi PLC:

The large PLCs introduced by Mitsubishi Electric Corporation include CPUs of basic type, high-performance CPUs, process control CPUs, motion control CPUs, and redundant CPUs. Can meet a variety of complex control needs. Mitsubishi Electric's rapid development in China, in order to better meet the domestic users' requirements for high-performance and low-cost products of Mitsubishi PLC and Q series products, Mitsubishi Electric Automation has launched the economical QUATESET-type Mitsubishi PLC, which is equipped with 64 points. 5-slot Q00JCOUSET for high-density mixing unit; another 8-slot Q00JCPU-S8SET with two 16-point switching inputs and two 16-point switching outputs. Its performance is fully compatible with Q00J and fully supports GX-Developer. And so on, so it has an excellent price/performance ratio.

A series Mitsubishi PLC: Mitsubishi PLC\A series uses Mitsubishi dedicated sequence chip (MSP), speed / command comparable to large Mitsubishi PLC; A2ASCPU supports 32 PID loops. The number of loops of the QnASCPU is unlimited, and can vary with the size of the memory; the program capacity is from 8K steps to 124K steps. If the memory card is used, the QnASCPU can be expanded to 2M bytes; there are a variety of special modules to choose from. Including network, positioning control, high-speed counting, temperature control and other modules.

Network structure

The Mitsubishi PLC network inherits the traditional MELSEC network and makes it superior in performance, function and ease of use. Q series PLC provides a clear three-layer network, providing the most suitable network products for various purposes.

(1) Information layer/Ethernet (Ethernet) The information layer is the highest layer in the network system. It mainly transmits data such as production management information, quality management information, and equipment operation status between PLC, device controller, and production management PC. The information layer uses the most common Ethernet. It can not only connect PCs on Windows systems, workstations on UNIX systems, but also connect various FA devices. The Ethernet module of the Q series PLC series has an increasingly popular Internet e-mail transceiving function, enabling users to easily send and receive production information e-mails anywhere in the world to build a remote monitoring and management system. At the same time, the FTP server function of the Internet and the MELSEC-specific protocol can easily implement program upload/download and information transmission.

(2) Control layer/MELSECNET/10(H) is the middle layer of the entire network system, and it is a control network that facilitates and transmits data to each other conveniently and at high speed between control devices such as PLC and CNC. MELSECNET/10, as the MELSEC control network, has achieved high market evaluation with its good real-time performance, simple network setting, non-program network data sharing concept, and redundant loop. The number of devices used is Japan has reached its highest level and is one of the few in the world. MELSECNET/H not only inherits the excellent features of MELSECNET/10, but also makes the network more real-time and has more data capacity to further adapt to the needs of the market.

(3) Device layer/field bus CC-Link device layer is a field network that connects PLC and other control devices with sensors and drive devices, and is the lowest layer network of the entire network system. With CC-Link fieldbus connection, the number of wires is greatly reduced, improving system maintainability. Moreover, not only ON/OFF and other switching data, but also intelligent systems such as ID systems, barcode readers, inverters, and human-machine interfaces can be connected, from the completion of various data communication to the management of terminal production information. The realization, coupled with the centralized management of the machine's operating state, has greatly improved the efficiency of maintenance. Used in Q series PLCs, CC-Link has better functions and is easier to use.

When communicating in Mitsubishi's PLC network, you will not feel the difference and discontinuity of the network type, and can perform data communication and remote monitoring, modification, debugging, etc. between the networks without considering the network hierarchy and type. . MELSECNET/H and CC-Link use cyclic communication to automatically and periodically send and receive information. No special data communication program is required, and simple parameter setting is required. MELSECNET/H and CC-Link use the broadcast method for cyclic communication transmission and reception, so that data sharing on the network can be achieved. For Ethernet, MELSECNET/H, and CC-Link networks used in Q series PLCs, network parameters and various functions can be set on the GX Developer software screen, which is simple and convenient.

In addition, in addition to the network mentioned above, Q series PLC can also support networks of other manufacturers such as Profibus, Modbus, Devicenet, ASi, etc., and can also perform RS-232/RS-422.