Tag Archives: Learn PLC programming

what basic knowledge to learn plc?

Need to have an electrician, assemble secondary lines, and understand the basics of various relays.

Learning the PLC can be done as follows:

1. Buy this book about PLC, learn about electrician knowledge, understand the electrical appliances, and go to control and understand various actuators.

2, is to understand the working mode of PLC, find a PLC, according to the example on the book, consider a small project, to achieve a function.

3, practice the true knowledge, understand the corresponding process, do a PLC project independently, the project is completed, the PLC will also master the Siemens 200 series of small PLC is very suitable for novice learning, easier to get started.

What is the foundation for learning plc programming?

The conditions for self-learning PLCs should be as follows:
1, you have to learn programming software PLC (such as Siemens, Delta, Omron, etc.), each brand of PLC its programming software is slightly different, so what software to prepare what PLC.
2, it is best to reserve an HMI (Human Machine Interface), because PLC often needs to do some configuration control, it is really not good to achieve this, of course, now a lot of two in one, you can prepare a two-in-one device it is good.
3, a set of PLC programming software and HMI programming software
4. Relevant circuit design knowledge.

how to connect plc to hmi

How to connect plc to hmi

I want to modify the timer’s time with the touch screen.
1. Read out the program in FX2N PLC with software, find the constant value K of the timer used to set the time, modify the constant K to D directly when programming, D should choose power off to keep the data register, the range is between D200-D511, and other fixed, and then write it into PLC.
2. Choose the type of touch screen, it is recommended to choose the Vinylon MT6056iv touch screen, programming with software, a numeric setting button, the button corresponding to the PLC data register D, when the finger touches the button, there will be numeric input keyboard, at this time, you can modify the timer time.
In the market, any touch screen and PLC usually do not communicate well. There are four problems to be confirmed.
1, is the PLC parameter consistent with that in the project?
2, whether the communication line is connected to the pin according to the wiring diagram.
3, the project set up the COM port on the screen when the correct 4. Parameters and line confirmation OK, in the case of PLC program or PLC address problem.

Methods: (first judge parameters:)

1. Use the programming software of PLC to connect with the PLC test to see what the parameters of PLC are and whether the parameters set in the project are consistent with the test results.
2. On-line simulation: with our configuration software, using the plc’s own communication cable and computer connection, on-line simulation to see if the project is communicating. You can use a numeric input unit or switch to operate on it, to see if the simulator is turned off and then on-line simulation before the operation is still, whether direct prompt NC. (NC and previous operations have not been written down.
(test line): use the multimeter to define the test wiring according to the pin of the wiring diagram.
A: parameters of touch screen. Check the parameter settings of the touch screen.
There are several parameters that need special attention.
1: Communication Port Settings – – – – – – – – – – Make sure that the PLC connects to the touch screen COM1 port or COM2 port
2: Type of equipment – – – – – – – – – – – – – – – – – – – – – – This is the most important, if the agreement is not chosen correctly, the others do not have to say
3: Connection mode – ————– PLC and touch screen connection, confirm good news RS485, or RS232C
4: Interface parameters and PLC station number – ———– must be consistent with the PLC settings.
B: if the parameter confirmation is set up, then check the wiring problem. Confirm the correctness of RS485 and RS232C, and touch screen is different from all kinds of PLC wiring. This can refer to dimensional control (PLC and touch screen communication line help files).
This is the basic method of normal troubleshooting communication problems.
Next we will teach you how to bypass the problem of touch screen — online simulation.
When communication fails, some customers guess that it may be a touch screen problem or an interface problem.
Online simulation is to bypass the touch screen and connect directly to the computer with PLC.

Specific measures:

1:PLC is connected to the computer through RS232. Some PLC have RS232 interface, some do not, and none can connect to the computer through the adapter.
2: build a simple project. Put two components, a numeric value, a numeric input. Address to set the address in PLC.
3: the setting of engineering parameters must be the same as that in PLC.
4: click on the online simulation function, so you can clearly check whether PLC can communicate with PC. If you can communicate, you can exclude the problems of PLC, and the problem of parameter setting.

MITSUBISHI PLC programming software GX Developer operation method

1. Download and install Gx Developer
2. Connect PLC. First, connect the PLC with the serial line, PLC to power, and switch to the STOP mode.
3. Software settings. Enter Gx Developer, create a new project, menu “online” – “transmission settings” – select the right COM port – click “communication test” – if successful, OK.

4. Programming
5. Compiler, F4
6. Write to PLC. Menu “online” – “PLC write”, select “parameter + program”, point “execute””
7.PLC switch to RUN state, programming completed!

PLC encryption, when writing, click “login keywords”, to 8 bits

MPS, MPP, MRD in PLC

1, MPS (into the stack instruction): The result of the operation into the first segment of the stack memory, while the previously sent data to move to the next section of the stack.

2, MRD (read stack instruction): the first paragraph of the stack memory data (last into the stack of data) read and the data continues to be stored in the first paragraph of the stack, the data in the stack does not move.

3, MPP (out of the stack instruction): The stack memory of the first piece of data (the last stack of data) read and the data from the stack disappeared, while the other data in the stack in turn up.

What‘s’ mean of Mitsubishi PLC directive MOVP HOFF k2y0

The MOVP represents the pulse transmission instruction,The h in Hoff represents the 16 binary, which represents the hexadecimal FF,K2y0 represents Y7y6y5y4y3y2y1y0, which is the two sets of 4 digits starting with Y0, and if K1y0 represents Y3y2y1y0,This directive indicates that the 16-in-system FF is delivered to the results of the y7y6y5y4y3y2y1y0 execution y7=1, y6=1, Y5=1, Y4=1, Y3=1, Y2=1, Y1=1, Y0=1.

What is the meaning of MOVP in PLC?

The MOV in PLC is the transmission instruction, for example [mov K15 D100] means to transfer the decimal constant K15 to register D100.

MOV is continuous execution, that is, each scan cycle is transmitted once.

Example:

LD X0

MOV K100 D10

When X0 is ON, K100 is transmitted to D10 and automatically converted to binary number.

MOVP is a pulse execution, that is, the instruction is activated once, and a transfer is performed.

Example:
MOVP K2M200 D40

The value of m200–m207 in decimal form is assigned to D40
MOVP K11 D0:

A transfer process is performed when conditions are available.

(pass constant 11 to D0 data register). It is usually performed only when there is a rising edge.

MOVP H1A2 U0/G0

It is to transmit H1A1 to module 0, buffer 0.

Application of PLC in capsule curing machine

In the tire curing process, the capsule as the necessary parts of the tire processing, there is a high performance requirements. It needs to undergo repeated expansion and contraction, stretching and other deformation, but also experienced a sharp rise and cooling. Capsule curing is one of the key processes to obtain high quality performance, and it is also one of the most important processes in capsule production. The process is to first make the rubber material through the appropriate processing of semi-finished products, and then through the chemical effect, the semi-finished products made capsule shape, to meet the performance of the use of tire processing.

Capsule curing process includes mold, mold, mold, mold, and so on. Capsule vulcanizing machine controlled by the movements of the core rod, the core rod and the main oil cylinder, combined into the core mold cavity the formation of capsule vulcanizing pressure required, at the same time through the access control to control the steam curing temperature required. Most capsule curing machine adopts hydraulic system. The hydraulic pressure station controls the upper die, the lower die and the main oil cylinder by the oil pipeline.

With HOLLiAS LM series PLC analog acquisition of high precision, good ductility, network characteristics, and put forward a set of small PLC based on Hollysys capsule vulcanizing machine control system solutions. This scheme overcomes the traditional relay of capsule in curing pressure, temperature and time of the three elements of the control is not precise, high failure rate shortcomings, has a certain reference value for the application of PLC in industry capsule vulcanizing machine.

According to the input and output point requirements, select the 40 point CPU module LM3109 and 4 channel analog input module LM3310. The switching input of the control system mainly includes the operation mode switching button, the setting button and the action button. The analog input of the system includes a temperature transmitter signal input and a pressure transmitter signal input. The output of the system includes a motor, an electromagnetic valve, an indicator light, etc.. Touch screen for input parameters, while monitoring the current state of operation and time. Computer as a remote monitoring equipment, can be connected with the PLC, used to save and monitor the running state of the capsule curing machine. The control system of the capsule curing machine mainly realizes the accurate control of pressure, temperature and time in each stage of curing, the fault detection and alarm, the parameter record and communication.

The HOLLiAS LM series PLC designed a capsule vulcanizing machine temperature and pressure control system has high control precision, network interface and features rich, achieve a capsule vulcanizing machine, automation control and network management, greatly improving the capsule production efficiency and product quality, to meet the high quality, high efficiency, low failure rate etc..

The MITSUBISHI A series PLC as the bridge between the TS3000 system and the CENTUM system

1 Introduction
Due to the impact of GMP certification for pharmaceutical machinery industry, nearly one or two years of shrinking purchases of domestic users of the equipment, the survival problem that placed in front of the pharmaceutical equipment manufacturers is quite brutal, waiting for the market to rise again or find another way out, obviously langtaosha behind, some go to get involved in other businesses in order to life in some industries, to open up foreign markets, but all will be faced with a problem: how to attract your customers. A little experience in this paper in our machine industry, on the delta automation products in electronic tablet machine on the application.
Mechanism and working principle of 2 number plate machine

2.1 what is the number of tablets

The number of medical and health care products are machine tablets (tablets, capsules, pills) after packaging and bottling equipment for grain number. Tablet machine is the highest and most commercial value of packaging machinery in the pharmaceutical and health care products. The number of speed, several pieces of machine precision, several pieces of sheet type specifications, waste elimination, or even several pieces of hardness and so on technical indicators and FDA (U.S. Food and Drug Administration) certification system to ensure the machine design and so on to determine the number of commercial value. A United States, Germany, the United Kingdom or Italy, the world famous brand high-speed intelligent electronic number of machines can be a business offer to millions of dollars.

Electronic chip can be used in a number of advanced PLC programmable control technology, digital technology, modern sensor technology, computer control technology, network technology in one, to achieve human-computer interaction interface, easy to operate and reliable. Automatically complete the bottle, counting, filling, bottle and other processes, widely used in medicine, chemical industry, food industry, tablets, pills, tablets, capsules and tablets of the filling.

This project is divided into single channel, dual channel, multi-channel. Each channel is generally composed of 8 sets of optoelectronic components, each bottle of medicine is completed by a channel. In order to improve the yield, the machine can be developed into a single or multiple head models, but the principle is the same, are composed of several parts shown in Figure 1: electromagnetic vibration feeding device, pneumatic closing device, automatic counting system, centralized monitoring and sorting system.

2.2 feeding device

After the system works automatically, the position of the pre installed bottle is correctly judged by photoelectric. When all the signals are correct, the vibration feeding system will start after receiving the signal. The vibration system is divided into three stages: the first stage is to discharge the vibration, slow feeding, three for feeding channel packaging. After three stages of adjustment, in order to achieve the material uniformity, the number of grains accurate, strong adaptability.

2.3 automatic number plate and closed system

When the tablets during the process of falling through several pieces of photoelectric switch, automatic counting system will send a signal to the sorting system (PLC), then PLC will quickly control the movement of the cylinder according to the number of cans set by the user, to achieve real-time closed, to achieve accurate canned to improve system stability and accuracy.

2.4 centralized monitoring and sorting system

All counting machine parameters and operation conditions, will be through the monitoring system — delta human-machine interface to the working condition of inspection. Including the cylinder action time, automatic number of pieces of the system is normal or not will be clear at a glance.

3 Delta Electromechanical Product Solutions

The system requirements for PLC is very high, the requirements of the PCL has 100 1ms of the timer, the program in a timely manner, the scanning period is short, the control stability and other characteristics, and the product has a high price advantage. According to these characteristics, the project adopts delta high performance EH series programmable controller (DVP64EH00T). The controller has dual communication port, convenient programming and monitoring; at the same time there are 100 1ms timer (similar products unique), can be more accurate, the number of fast measurement of several pieces, and the scan cycle of PLC is very short, in the same function of products, leading the industry. The monitoring interface using the intelligent man-machine touch screen multi delta communication port (DOPA57GSTD), the product with its powerful communication function, more deeply to win customers free communication, strong macro function, solves the problem of the industry. Through the function of both the size of the pills or thin, as long as a light correction through man-machine interface, the system will automatically record, and the optimal parameters automatically stored in the screen. The core control system uses a set of delta products, tablet counting machine in the overall price, better than that of European and American products, rather than on the same brand.

Talk about how to learn for beginners PLC

I am now a lot of online publicity to spend hundreds of pieces of information to buy some of the information can get a monthly salary of tens of thousands of monthly salary, the first: the light to see the data video you are not learning PLC, unless you have an IQ of 250. Second: General engage in PLC can not get so high wages, of course, some of the high level of the exception. But you do not have to be discouraged, if you want to engage in industrial control, PLC is necessary to master, as well as wages to see your standard, and efforts will be rewarded.

For the beginner a PLC entry is not the biggest difficulty how to learn programming, not how to make a motor to rotate (these things everywhere, but how to find the answer). The sensor switch motor access system, and how to connect the PLC, how to set the program, including how to understand the various components such as sensor switch. The motor and so on, these are the details of things, but this is for beginners very confusing thing, no one will be confident for beginners a fatal blow, but these books basically can not find or do not sum up. All of it to learn the most important is the practice of PLC. I summed up the following several ways to learn PLC, a total of your reference, mainly depends on their own situation.

1: you have to get ready for a few things.

A) you must first select machine models of MITSUBISHI, Delta have started good which you from their first

B) with the goal you have to prepare the corresponding software programming software and a simulation software

C) there is a second-hand PLC or high imitation board, taking into account the future of the servo motor and so on, so it is best to choose the output of the transistor
D) a download line and find some other people made the program case

2: find some PLC tutorials, and the corresponding video tutorial

3: Learning in practice

Through the PLC software simulation, or in the learning software simulation, is able to learn some of the basic procedures

But a little more complicated procedures, it is difficult to find the feeling in the software, even if there is a PLC in front of, also can not understand because should give full consideration to the site, mechanical action, as well as a variety of unexpected factors mature PLC program, there are 1/3 or more parts in order to deal with a variety of non normal. For example, alarm, fault, pause, or prevent mistakes so if possible,
To try some small electrical items, the PLC on the handle to pick up the false load directly to observe their input and output

Or to do along the way or even engineers do not earn

Money is required. The role of PLC is to control the machine, if out of the machine that is not empty talk, first of all, to understand the PLC connection, and peripheral equipment, how the signal is over, the line is how to X, then

And what devices are transmitted, and how Y wiring

Self time may be Y output on the line, but in the device if the Y has been output, the cylinder may have been straight back, it should be the actual test for how long it is good.
After some understanding, you can try to pick some simple

PLC programming, may encounter a lot of problems, remember to and do machinery to maintain communication, understanding of the mechanical process. Their own 
programming ideas clear point, if one way does not work, another way to try, not to engage in a little clever or stupid way.
To the scene of the debugging, the most flexible and most critical, because we are staring at it, do not go to a dead way. Which is the quickest way to solve the problem, what kind of.

On the back of the scene to meet the problems and then review, if you can not solve the problem, go home to study or consult others.

Some devices will be used on the inverter, servo, stepper, touch screen and other equipment, this will be used to simulate the amount of temperature, pulse, 
communication and other functions.

At the same time, but also to learn more content, but relatively speaking, the difficulty of those things is less than PLC, learning is also very fast.

The book is likely to be a self.

In practice, will use a lot of strange instructions or do not understand the function, while learning progress quickly. Continue to practice, and constantly overcome difficulties, and gradually learn more deeply.

PLC how to learn, how to learn for beginners PLC?

Develop a good interest

Since all of the PLC programming is not interested, then how can learn it. So it can be programmed as an interesting intellectual game, this will cause you to have enough patience and perseverance to complete the program.

PLC learning to focus on practice, there is no practice is absolutely not good. This is also the most critical learning PLC.


So when programming need as practice object PLC and related hardware equipment, it can also program intuitive response with the actual equipment action in the detection procedure, so that the error action of equipment can easily find the point of failure, or no control object, fault point to analysis, to program it is difficult to judge the correctness of.

Develop the good habit of programming

In the preparation of a slightly complex project, we need to analyze the process of the project —- that is, drawing the flow chart

In the preparation of procedures, the use of the intermediate relay to have the order and rules, otherwise the program will be very disordered, and in the future of the program changes and their troubles.

At the same time, in the preparation process, the every step, the role of each signal and the intention to mark, so you know your own programming every step of the intention, and in the process of looking back at a glance.

Often communicate with peers

PLC application and its wide range, its control function is also changing, and peer exchanges can promote the development of knowledge, and in the exchange process can reflect their own shortcomings.

At the same time when you encounter problems, the exchange is particularly important, they do not understand the technology, there may be a little hint, it will become very simple to solve.

Finally, on the network at present there are a lot of PLC learning materials and related technology, can understand the relevant technology through the network, so you can have to understand the various techniques for later use when targeted learning.

Art lantern shape PLC Ladder programming and wiring experiment

This article describes an artistic lantern shape PLC ladder programming and wiring experiment described, as follows:

1. Project the necessary equipment, tools, materials

PLC: FX2N-32MR

2, the training content:
1, project description
The shape of an art lantern demonstration board as shown in Figure 6, A, B, C, D, E, F, G, H for the eight lights, a ring distribution. The control requirements are as follows:
Will start switch K1 close, eight lighting light at the same time, namely abcdefgh light at the same time a second, then eight lighting according to counter clockwise rotate the light seconds, a bright 1s > b 1s > C bright bright 1s > d 1s > e bright bright 1s > f light 1 second g > bright 1s > h light 1 second; next eight lighting and light at the same time 1: abcdefgh and light 1 second; and eight lighting according to clockwise rotate the light 1 second, namely h bright 1 g > light 1 second > f light 1 second, e light in the 1s > d 1s > C bright bright 1s > B bright second, a bright light for 1 second. Then repeat the execution in this order. Press the stop switch K1, all the lights off.

2.2 PLC wiring diagram
According to figure 7 to meet the good line. Note that the COM1 and COM2 are connected, as the same as the rated voltage of the indicator light. Input and then start switch and stop switch.
2.3 program design
Figure 8, PLC operation, the program 9 to 19 step, M11 conduction, due to the step program of 50 to 120, M11 dynamic contact closure, respectively control the Y0 Y7 conduction and lantern abcdefgh lit up at the same time, the due t0 delay 1 seconds, so the abcdefgh lit up at the same time 1 seconds. To 1 seconds, the program step 40 t0 dynamic contact closure, shift instruction execution, implementation turns light, namely abcdefgh turns light, because a second clock t0 closed once, so abcdefgh turns light interval for a second. Step 20 to 29, when the M20 pass, the M101 set, the M101 moving contact with MI2 ~ M19 moving contact with the contact, respectively, turns lit H ~ A, that is, G, F, H, E, D, C, B, A turns lit every second. Step 30 to 39, when the M20 pass, the M101 reset, M101 dynamic break contacts with MI2 ~ M19 dynamic contact contact, respectively, in series lit A ~ H, that is, A, B, C, D, E, F, H, G turns lit every second. At any time will stop the switch K2 closed, in the 114th step, the interval reset command so that M19 ~ M12 all reset, all the lights are not bright.
2.4 run and debug program
(1) the ladder diagram program is entered into the computer, check the power supply is correct.
(2) to debug the program.
A. connected to the PLC power supply, the PLC will be RUN state, the K1 closed, observation of A, B, C, D, E, F, G, H, the light show.
K2 will be closed, A, B, B., C, D, E, F,, G, H, the light show.
(3) debug running record.

Application and characteristics of PLC in control system

What is the meaning of the programmable controller:

Acronym PLC programmable controller or PC, is evolved from the early relay logic control system, which constantly absorbing function of the microcomputer technology to growing gradually for complex control tasks.

Since 1836 relay came, people began to use it skillfully wire connected with the switching device, constitute use different logic control or sequential control. So far, the PLC Ladder programming language can also see the shadow of these wires. Until the late 1960s and early 1970s, the advent of programmable controllers, with the rapid development of microelectronics technology, computer technology and data communications technology, as well as the emergence of the microprocessor, PLC products towards small and ultra-small aspects of a leap , and finally to the early PLC from the initial logic control, sequential control, it has developed into a modern PLC logic, timing, counting, memory and arithmetic operations, data processing, communications and networking functions such as PID loop controller.

PLC viable reason is that it is more suitable for industrial field and the requirements of the market: high reliability and easy ability against various disturbances, programming installation, low price and long life. Than the microcontroller, its input and output closer to the field devices, without adding too many intermediate member or need more interfaces, which saves users time and money. PLC lower end (input) for the relay, transistor and thyristor control means and the upper end is generally user-oriented microcomputer. When people use it, you can not carry out specialized training in computers, programmable controllers can be operated and programmed. Used to perform a variety of different complexity industrial control tasks.
First, the main function of the programmable controller

PLC application is very broad, very rapid development of industrial automation equipment, factory automation (FA) and computer integrated manufacturing system (CIMS) in the important role. Today’s PLC function, far not only replace the traditional relay logic.
PLC system is generally constituted by the following basic functions: a variety of control functions. Data collection, storage and processing capabilities. Communications networking. Input / output interface conditioning. HMI function.

Programming, debugging features:
1, the control function logic control: PLC has the AND, OR, NOT, XOR logical operations and other functions, and triggers can replace relay switch control.
Time control: It provides users with a number of electronic timer, users can set their own: on-delay, off delay and timing pulses and other means.
Count Control: pulse control can add, subtract counting mode, you can connect encoder for position detection.
Sequence control: the first after the procedure is completed, it is transferred to the next process, so that a PLC can use as a multi-step controller.
Data collection, storage and processing math functions:
Basic arithmetic: add, subtract, multiply and divide.
Extended arithmetic: square roots, trigonometric functions and floating point arithmetic.
Compare: greater than, less than and equal to.
Data processing: Select, organize, normalize, move, and first in first out.
Analog data processing: PID, integral and filtering.
2, the input / output interface conditioning functions having A / D, D / A conversion, complete analogue control and regulation through the I / O modules. Median and accuracy can be selected according to user requirements.
3. Has the temperature measurement interface, direct connection to a variety of resistance or galvanic.
4, communications, networking have adopted most modern PLC communication, network technology, RS232 or RS485 interface for remote I / O control, more than one PLC to one another networking, communications, external devices and one or more between the programmable controller signal processing unit, program memory and data exchange, such as the transfer of the program, data file transfer, monitoring and diagnostics.

The communication interface or communication processor hardware interface standard or proprietary communication protocols and data transfer process is completed. Such as the Siemens S7-200 Profibus fieldbus port, the communication speed may reach 12Mbps.
When the system is constituted by a computer with multiple PLC constitute centralized management, decentralized control of distributed control network to complete large-scale complex control. Commonly referred to as SCADA systems, on-site and remote terminal PLC terminal can also be used for live machine. 5, man-machine interface function provides the operator to monitor machine / process work necessary information. Allows the operator and PC systems interacting with their applications, in order to make decisions and adjustments.

Means to achieve human-machine interface functions: from the grassroots operator screen text display, the stand-alone CRT display and keyboard operation and decentralized communication processor, a dedicated processor, a personal computer, industrial computers, and centralized operation and monitoring system. Use 6 different complexity, programming, debugging and other hand-held, portable and desktop programmer, and operator workstation screen, programming, debugging, monitoring, testing and records, and printing out the program files.

Second, the main features of the programmable controller
1, high reliability PLC’s MTBF is generally 40000 ~ 50000h above, Siemens, ABB, Panasonic and other micro PLC of up to 100,000 h or more, and have a sound self-diagnostic function to determine the fault quickly and easy to maintain. 2, the modular combination of flexible programmable controller series products, the module structure commonly used to accomplish different tasks combinations. I / O from 8 to 8192 points, there are a variety of models, a variety of function modules can be flexibly combined, structure is also diverse. 3, powerful PLC application of microelectronics and micro-computer, simply type have logic, timing, counting sequence control. The basic types plus analog I / O, the basic arithmetic operations, communications and so on. In addition to the basic types of complex types of functions, but also has a scalable computing power, multi-level terminal mechanism, intelligent I / O, PID regulation, process monitoring, network communications, remote I / O, multiple processors and high-speed data processing capability . 4, convenient programming PLC control suitable for industrial ladder, function block diagram, instruction list and sequential function chart (SFC) programming, without much knowledge of computer programming. The new programming workstation with a comprehensive software toolkit, and on any PC-compatible programming. 5, to adapt to the technical conditions of the industrial environment PLC can work under the general high temperature, vibration, shock and dust and other harsh environment, can work reliably under strong electromagnetic interference environment. This is the market value of existence PLC products. 6, installation and maintenance is simple compared with the computer system, PLC installation does not require special rooms and rigorous screening. When you use as long as connectivity to various devices is correct, the system can work with operating and fault indication means on each module, easy to find fault, most of the modules can be hot plug, the module can be replaced, so that users can in the shortest isolated time fault, and exclude, to maximize compression downtime, rapid recovery of production. Then repair fault module, which is particularly suitable for large-scale production situations.
Some PLC housing is made of an alloy that can operate under poor working conditions, with the simple structure, with a heat sink above, at high temperatures, unlike the housing plastic deformation, as also anti-radio frequency (RF high frequency) electromagnetic interference, fire and so on. 7, fast with microprocessor applications, so that the speed of the PLC faster, make it more in line with the processing speed of complex control tasks, the difference between it and the microcomputer is not very obvious. 8, the low weight of the total price of the PLC, volume, power, and hardware prices have been reduced, although the proportion of total software price has increased, but the manufacturers to compete also a corresponding reduction in prices. In addition, the use of PLC can also greatly shorten the design, programming and commissioning period, bringing the total price is further reduced.
PLC systems and industrial computer bus and DCS system of mutual penetration, mutual learn, compete and development. Promoting the progress of industry.
PLC fieldbus products face development, innovation will once again meet the higher needs of the industrial and civilian control. Third, communications and networking PLC communication between the PLC, including PLC, the communication between PLC and host computer and PLC and other intelligent devices. PLC system can be a general purpose computer or via the communication processing unit, a communication adapter connected directly to form a network to achieve the exchange of information and may constitute centralized management, decentralized control of distributed control system to meet factory automation (FA) systems development needs of each PLC or remote I / O module according to the functions of each place at the production site decentralized control, then using a distributed network system connected to form a network of centralized management.
Siemens company SIMATICNET example, in the Totally Integrated Automation (TIA) system concept proposed in its core content which includes integration and integrated communication configuration and programming of integrated data management. Communication networks are important, the key components of this system to provide inter-network components and improve the industrial communication.

SIMATICNET contains three main levels:
International standard AS-I network sensors and actuators communication scan time 5ms, the transmission medium is twisted pair, unshielded line length of 300m, a maximum of 31 slaves.
PROFIBUS industrial field bus, the international standard for the workshop and field level, the maximum transmission rate of 12m / s, the transmission medium is shielded two-wire cable (up to 9.6km) or cable (up to 90km), can connect up to 127 from station.
International standard industrial Ethernet networking for regional and unit, the network size of up to 1024 stations 1.5km (electrical network) or 200km (optical network).

In this network system, it is particularly worth mentioning is the PROFIBUS fieldbus, PROFIBUS field bus is one of the most successful, have been widely used. It is not dependent on the manufacturer, open field bus, a wide range of automation devices can exchange information through the same interface. A large number of manufacturers to provide high-quality products PROFIBUS, the user can freely choose the most suitable product. PROFIBUS has become the national standard DIN19245 German and European standards prEN50170, and in the world has the largest number of users. Four, PLC and industrial control computer (IPC) to compare and distributed control systems (DCS) 1, the origin of their computer technology to meet the rapid development of large amounts of data processing equipment required. Hardware structure, high degree of standardization of the bus, compatibility, rich software resources, especially the support of real-time operating system, so the requirements of fast, real-time control and computation model complex workload industrial objects advantage.

Distributed system development from the industrial automation instrumentation control systems to industrial control computer as the center of the distribution system, so its processing in the analog loop adjustment has certain advantages, mainly used in the initial stage continuous process control, focusing loop control functions.
PLC is evolved by the relay logic system, mainly used in discrete manufacturing, process control, instead of the initial main relay control system, switch the order of emphasis on control.

With the development of microelectronics technology, large scale integrated circuit technology, computer technology and communication technology, etc., PLC happened leap in technology and functionality. On the basis of the initial logic operation, an increase of numerical computation, loop adjustment and other functions, and adds analog PID control function modules; computing speed, CPU capacity to catch up with industrial control computer; enhance communications capabilities developed more species and local bus network (LAN), and thus can also be configured as a distributed system. Especially personal computer can also be absorbed into the PLC system.

PLC ladder programming rules

Although the ladder and relay circuit is similar in structure, elements, symbols and logic control functions and other aspects of phase, but they have many differences, the ladder program has its own rules.

1) Each logical line is always to the left from the bus, and then the contact is connected, the final termination of the coil or the right bus (right bus can not draw). Note: The bus between the left and the coil must be contacts between the coil and the right bus but you can not have any contact.

2) The ladder can contact any series or in parallel, but only in parallel to the relay coil and not in series.

3) the use of contacts unlimited number of times.

4) In general, the same coil can appear only once in the ladder. If in the program, the same coil is used twice or more times, known as “dual-coil output.” For the “dual-coil output”, some PLC treats it as a syntax error, and definitely not; some will be in front of the PLC output as invalid, only the last valid output; and some PLC, containing a jump or step ladder instruction allowed dual coil output.

5) For non-programmable ladder must be equivalent transformation into programmable ladder.
6) when there are several series circuit in parallel, the circuit with many serial contacts should be on the top, as shown in Figure 5-2a. There are several in parallel circuit in series, the circuit should be parallel contacts on the left, as shown in Figure 5-2b. Such a program compiled concise, less statements.


In addition, the input of the relay contacts in the design of the ladder according to the best state of all the input device is normally open to design more appropriate, less error-prone. Is recommended as an input device open with a constant contact with the PLC input terminal, the signal can only be used if some normally closed input, press input device is normally open to design, and then the ladder corresponding input relay contacts point negated (normally open into a normally closed, normally open normally closed change).

PLC ladder programming principles and programming methods

(1) Input / output relay, internal auxiliary relays, timers, counters and other devices of the contact can be used repeatedly, without complex program structure to reduce the use of contacts. (2) Each line ladder left the bus started, the coil terminates at the right bus. Contacts are not on the right side of the coil, as shown below

(3) In addition to stepping procedure, any coils, timers, counters, and other advanced instruction can not be directly connected to the left bus bar.
(4) In the process, does not allow the same number twice coil output (dual coil output). The following ladder is not allowed.

(5) does not allow the bridge circuit.

(6)Shall be prepared by the sequential program from top to bottom, from left to right to prepare the way. To reduce the number of steps in the implementation of the program, the program should be to the left and right big small big small.

(7) as an input device with a normally open contact

(8) PLC programming experience commonly Design
In the traditional relay – contactor control diagram and typical PLC based control circuit, based on the experience accumulated translation, revised and improved to give final control procedures.

how to Learn Mitsubishi PLC ladder programming

Beginner PLC ladder programming should be to follow certain rules, and develop good habits. In this paper, Mitsubishi FX series PLC, for example, briefly explain the Mitsubishi PLC ladder programming rules to be followed, allowing users to better understand how to learn to see the Mitsubishi PLC ladder programming, we want to help. One thing to note is that although this article Mitsubishi PLC, for example, but these rules when other PLC program must also be observed.

1, PLC ladder ladder are starting left bus, and finally the right bus (usually can be omitted without painting, painting only left bus). The left side of each line is a combination of contacts, it represents the logical drive coil conditions, and represents the result of logic coil can only be connected on the right bus. Contact can not appear in the right side of the coil. The following figure (a) should read (b):


2, the contact should be plotted on the horizontal line, vertical line should be drawn on the relationship as shown in (a) contacts and other contacts between the X005 does not recognize. For such a bridge circuit should be from left to right, top to bottom, the principle of one-way, single draw all the way. FIG. (B) below:


3, parallel block series should contact many of the path on the ladder to the left (left and right light-weight principle); parallel blocks in series, parallel path should be more contacts on the top of the ladder (top heavy the rules). To do so, the program is simple, thus reducing scan time directive, which is particularly important for some large programs. As shown below:


4, not to use double-coil output. If the same ladder, more than two coils of the same component or twice, then known as the reuse or dual-coil output coil. Usually one of the dual-coil output ladder for beginners easy to commit wrong. In the double-coil output, only the last coil to be effective, and front coil is invalid. This is caused by the PLC scan feature of the decision.
PLC uses the CPU work cycle scan. Generally consists of five phases (as shown): internal diagnostics and treatment, and communication peripherals, input sample, the user program execution and output refresh. When the mode switch is in STOP, before performing only two phases: internal diagnostics and treatment, and communications peripherals.

1, the input sampling stage
PLC sequential reads the state of each input, and the input image is stored in the register we call the internal unit. When entering the program execution stage, such as the input changes state corresponding cell information input image area does not change with it, only the next input sampling phase of the scan cycle, the input image area corresponding to the cell information will change. Therefore, PLC will be overlooked pulse variation is less than the amount of the scan cycle switch input.
2, program execution stage
PLC from the program step 0, beginning with the first following the first left and right sequence scans the user program and logical operations. PLC input image by content area for logical operations, and the result is written to the output image area, rather than directly to the output terminals.
3, the output refresh period
PLC output terminal changes depending on the content of the output image area. This is the actual output of the PLC.
Above brief description of the working principle of PLC, the following examples explain why we then to write ladder program should not be repeated using a coil. As shown below, when the reset input is sampled input image area X001 = ON, X002 = OFF, Y003-ON, Y004 = ON is actually written to the output image area. But to continue down, because X002 = OFF, so Y003 = OFF, this is after the result has been written to the output image area, change the original state of Y003. Therefore, the output refresh period, the actual external output Y003 = OFF, Y004 = ON. Many newcomers to come across such a problem, why X001 has been closed, and no output Y003 it? Logic is wrong. In fact, because the use of double coil caused.

Note: we are talking about is not (should not) use dual-coil, double coils are not absolutely prohibited, in some special occasions can also use double-coil, then you will need a more extensive programming the experience and skills. Let’s talk about this. But still do not risk it for beginners. In fact, it can be seen from the above examples, the reason will result in Reuse coil output Y003 confusion is due to the reason the program is executed sequentially from top to bottom caused. But if we can change the order of program execution, at any time to ensure that the two coils is only one logical drive occurs, you can use double-coil. The most common method is to use a jump instruction

Program Analysis: M0 closed, the program jumps to at P0 (no X001 statement), M0 normally closed off, CJ P1 does not occur, the next statement. In this case, Y003 to X002 state drive. State M0 disconnected, according to the order of execution of T003 X001 is driven M0 NC closed skip P1 state by X003 to drive on Y004, which skips the X002 drive Y003 statements. Visible at the same time, Y003 drive only one can occur. In this case, the use of double-coil is possible.
But in ladder programming, we still have to try to avoid the use of dual-coil, and the introduction of auxiliary relay is a commonly used method. As shown below:

Figure (b),, X001 and X002 contact control auxiliary relay M000, X003 ~ X005 contact control auxiliary relay M001, and then by two relays M000, M001 parallel combination of contacts to control the coil Y000. Such logic has not changed, yet the double coil into a single coil.

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The difference between Siemens PLC and Mitsubishi PLC

PLC dealing with for so many years, often met with some beginners asked about the difference between PLC Siemens PLC and Mitsubishi PLC, there are many novice distress to choose which brand to learn, share this article the difference between Siemens PLC and Mitsubishi PLC to everyone.
First, the concept of different programming

    Mitsubishi plc is a Japanese brand, intuitive programming, it would be relatively easy to learn, but more instruction. Siemens plc is a German brand, more abstract instruction, learning more difficult, but less instruction, so learning and learning Mitsubishi Siemens cycle is the same.
Personally I think Mitsubishi (high-end Japanese brand) PLC Siemens software behind at least more than five years, and medium-sized Leaving aside, took advantage of the comparative Mitsubishi FX series minicomputers and Siemens S7-200 series, compared with the following Siemens Advantage:
    
1, Mitsubishi programming software from the early FXGPWIN to recent GX8.0 (I know the latest), and all the Japanese brands, the software programming ideas a single vertical structure from top to bottom, and Siemens MicroWIN it is both vertical and horizontal structures, and subroutines support local variables, the same functions can be programmed once the program can greatly reduce development effort and time.
    
2, S7-200 has been the strong support floating-point operations, programming software directly supports decimal input and output, and until recent years, Mitsubishi FX3U series introduced only this function, the previous FX2N series of floating-point capabilities are false.
    
3, S7-200 analog input and output process is very simple, AD, DA values ​​can be programmed without direct access, and former Mitsubishi FX2N series requires very cumbersome FROM TO instruction. FX3U down now support this feature, but a full five years or more late.

    4, of course, Mitsubishi FX2N series has its own advantages, one high-speed counter instruction convenient than S7-200, the second is more than 422 Siemens PPI port rugged (200 series because of non-PPI port optically isolated, non-standard operation and generic programming cable may cause damage to the serial port).
    
The above comparison merely minicomputer, as the Siemens 300 and 400 series and the larger TDC series, needless to say up here.
    
Learn PLC, Mitsubishi is very easy to use, because the simple idea to go straight, but from the perspective of learning, Siemens is definitely better.
Second, different chips
This is mainly reflected in the capacity and speed of operation. Siemens CPU226 program capacity 20K, the data capacity of 14K; Mitsubishi FX2N a total of only 8K, later 3U actually improved.
Siemens CPU226 and CPU224XP standard configuration that is 2 485 PPI port, the maximum communication speed of 187.5K; and Mitsubishi all series FX3U is a 422 before, but the speed is 9.6K. If you need even a smart meter what you must purchase another FX2N0-485BD other special modules. And two communication ports can be a link to download the data cable connected to a touch screen debugger, or you will disconnect the touch screen cable to connect a touch screen and then the data line, back and forth adjustment process is very cumbersome.
Third, the control of the different strengths
Siemens strengths are process control and communication control, Siemens analog modules are inexpensive, simple procedures, and Mitsubishi analog modules are expensive, complicated procedures, Siemens Communications is also easy to do, simple procedures, Mitsubishi in this function is weak. (Today’s signal is forwarded: ITVID Warranty: half replacement, 5-year warranty and lifetime maintenance)

    Mitsubishi has the advantage of discrete control and motion control, Mitsubishi’s instruction rich, special positioning instructions, control servo and stepper easy to implement some complex motion control is the strengths of Mitsubishi, Siemens will in this weak no special instructions, do not servo or stepper positioning control can not be achieved, but the complexity of the procedure, the control accuracy is not high.

    For example, a device just some motion control, such as a robot, you can choose Mitsubishi PLC, a device for a servo or stepper positioning control, also selected Mitsubishi PLC. Like central air conditioning, sewage treatment, temperature control and other such election will have a lot of Siemens PLC analog to deal with more appropriate to use a data communications equipment on the site have a lot of instruments for the collection, choose a good control of Siemens.
So for different devices in different control methods, we want a reasonable selection of PLC, with their strengths and avoid their weaknesses.