Tag Archives: PLC programming

To simplify and write PLC ladder command statement table ladder program

After simplifying the ladder

Instruction Statement List
a) LD        01600
AND       00002
LD-NOT    00001
OR-LD
AND       00000
OUT       10000
b)LD-NOT    00004
AND       00005
LD         10000
AND       00006
OR-LD
AND       00003
LD         00002
AND       00004
OR-LD
AND       00001
OUT       10000
c)LD         10000
AND       00003
AND       00004
OR         00001
AND       00000
LD         10000
AND       00001
LD         00003
AND       00004
OR-LD
AND       00002
OR-LD
OUT       10000

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.

Turning hydraulic control system

Turning hydraulic control system

How to read the S7-1500 CPU running time

Read S7-1500 CPU running time There are many ways, are described below in several ways.

1 reads out the running time by the startup parameters OB1 OB1 start in non-optimized run-time information with the OB1

The startup information passed to the global variable parameters can be read out of the CPU the last scan, minimum, maximum scan time, programming is very convenient.

2 Call RD_SINFO function reads the running time
If you are using an optimized OB1, simplified startup information without running the information shown in Figure 2, you must call the function reads

For example in OB1 RD_SINFO function reads the run time, the program shown in Figure 3. TOP_SI parameters for the current OB1 start information,
Data type SI_classic, need to manually type, ZI1 for the last scan time, ZI2_3 contains the minimum, maximum scan time, low-word minimum scan time,
The high word is the maximum scan time, the examples are transferred to MW10 and MW12. START_UP_SI start to warm start information of the OB,
Example, no reference.

3 Call RT_INFO function reads the running time
By function RT_INFO to be read out of the CPU running time

1,2,3 pattern can be read out by the CPU last scan, minimum, maximum scan time, in these three modes, the data type of the parameter INFO LTIME, can be read directly. You can also read out the percentage of uptime through other modes.

4 Call RUNTIME instruction read operation time
RUNTIME can be read out by CPU instructions directly from the parameter RET_Val running time, in seconds, MEM to save the program to run intermediate memory, two parameters are the type LREAL, in addition you can also read out a program run time

Siemens PLC S7 300/400 master relays orders

Main control relay (Master Control Relay), abbreviated as MCR. MCR Master relay command is used to control whether normal execution of the instruction in the region, equivalent to a connect and disconnect the flow of the main switch. MCR instruction is not much used, S7-200 is no MCR instruction.

MCRA to activate the master relay instructions, MCRD to deactivate the master relays orders.

Open the master relays orders MCR< in the MCR before you save the results of logical operations on the stack RLO (MCR), close the master relays orders MCR> MCR saved out of the stack in the RLO. MCR< and MCR> used to indicate controlled temporary power cord formation and termination.

MCR instructions can be nested, MCR the MCR can be another zone. MCR stack is a LIFO stack, allowing the maximum nesting depth of 8 levels.

MCRI0.2 control, I0.2 and MCR MCR in the stack level of the same State. MCR bit is 1 when will perform Q4.0 coil MCR control area and MOVE instructions. MCR bit is 0 when Q4.0 is 0.

Siemens plc S7 300/400 ladder logic blocks in calling instructions

CALL in the ladder diagram coil can call functions (FC) or system functions (SFC), the call cannot be passed parameters. Calls can be unconditional, CALL directly connected to the vertical line on the left side of the coil, equivalent to UC in the statement table orders; can also be conditional, condition provided by the control CALL contact circuits of coils, equivalent to CC in the statement table instructions.


Logical block is called if you need to pass parameters, you can use the command to invoke the function block in the box. FB 3-70 box in Figure 10 is the function that is being invoked, DB3 is called FB 10 o’clock block of background data.


Conditions for return instructions (Return,RET) appears as a coil, left logic for conditional block conditions provided by the contact circuit to control it, RET coil cannot be connected directly on the left of the vertical power cord. If you call it is the unconditional return, at the end of the block does not require the use of RET instruction.
 
 

FX2N series PLC analog I/O modules

(1) analog input module FX2N-2AD. The module is a 2channel voltage input (DC 0~10V,DC 0~5V) or current input (DC 4~20mA), 12-bit high accuracy resolution conversion speed for the 2.5ms/channel. This module occupies 8 I/O point applies FX1N and FX2N, FX2NC series.


(2) analog input module FX2N-4AD. The module has 4 input channel, 12-bit resolution. Select a current or voltage input, choose user wiring is to be achieved. Optional analog value from DC ± 10V (resolution of 5mV) or 4~20mA, and -20~20mA (resolution of 20 μA). Convert at a speed of up to 6ms/channel. FX2N-4AD using 8 I/O point.


(3) analog output module FX2NP2DA. This module is used to convert the 12-bit digital 2 analog outputs. Output can be in the form of voltage or current. Their choice depends on the wiring. Voltage output, two analog output channels of the output signal is a DC 0~10V,DC 0~5V current output for the DC 4~20mA, resolution of 2.5mV (DC 0~10V) and 4 μA (4~20mA). Digital to analog conversion characteristics can be adjusted, conversion speed for the 4ms/channel. This module requires 8 I/O points for FX1N and FX2N, FX2N series.


(4) analog output module FX2N-4DA~ which has 4 output channels, providing precision 12-bit high resolution digital inputs. Conversion speed is 2. 1ms/channel, the channel number will not change conversion speed. Other properties of the module is similar to FX2N-2DA.


(5) analog input module FX2N-4AD-PT. This module matches the PT100 temperature sensor, will come from the 4 foil temperature sensors (PT100,3 line, 100 ω) input signal amplification, and convert it into 12readable data that is stored in the main unit. Celsius and Fahrenheit data can be read. Internal temperature transducers and analog input circuit, can rectify the sensor‘s nonlinear. Read a resolution of 0.2~0.3 degrees Celsius. Conversion speed: 15 Ms/channel. All the data and parameter settings can be done through the FX2N-4AD-PT software configuration, realized by FX2N TO/FROM application instructions. FX2N-4AD-PT using 8 I/O points can be used for FX1N and FX2N, FX2NC subsystem.


(6) analog input module FX2N-4AD-TC. The module match the thermocouple type temperature sensor, from 4 thermocouple sensor input signal is amplified and converted to 12-bit data can be read, stored in the main unit. Celsius and Fahrenheit data can be read. Reading of the resolution type k is 0.2 deg c; type j for 0.3 c, can be used with k(100~1200℃) and j (100~600℃) supporting the use of thermocouples, 4 channel using k/j type, conversion speed for the 240ms/channel. All the data and parameter settings can be done through the FX2N-4AD-TC software configuration. This module takes up 8 I/O point.