Tag Archives: PLC control system

How Siemens S7-200 series PLC’s power requirements and calculation?

S7-200 CPU module provides 5VDC and 24VDC power supply:
When an expansion module CPU through I / O bus to provide 5V power supply, all the expansion module 5V power consumption of the CPU and can not exceed the rated power provided. If not enough external 5V power supply. Each CPU has a 24VDC sensor power supply, it is native input and expansion module input and expansion modules provide relay coil 24VDC.
If the power requirement exceeds the power budget of the CPU module, you can add an external 24VDC power supply to provide to the expansion module.
The so-called power calculation is to use the CPU can provide power capacity, minus the modules required to power consumption.
Note: EM277 module itself does not require 24VDC power supply, the power supply is designed for communication port used. 24VDC power supply requirements depend on the size of the load on the communication ports.
Communication port on the CPU, you can connect PC / PPI cable and TD 200 and give them power, the power consumption has no longer included in the calculation.

Three types of Siemens industrial control software introduction

Siemens industrial software is divided into three different categories:
(1) programming and engineering tool for programming and engineering tool includes all PLC-based or PC for programming, configuration, simulation and control tools needed maintenance. STEP 7 standard package SIMATIC S7 for S7-300 / 400, C7 PLC and SIMATIC WinAC PC-based control product configuration programming and maintenance of project management tools, STEP 7-Micro / WIN is running on a Windows platform S7 -200 series PLC programming, on-line simulation software.
STEP7
(2) PC-based control software WinAC PC-based control systems allow the use of a personal computer as a programmable logic controller (PLC) run user programs run in Windows NT4.0 operating system installed on the SIMATIC IPC or any other commercial machine. WinAC offers two PLC, one is software PLC, on the user’s computer to run as a Windows task. Another is the slot PLC (install a PC card in the user’s computer), it has all the features of the hardware PLC. WinAC and SIMATIC S7 series processor is fully compatible with its unified programming SIMATIC programming tools (eg STEP 7), programmed to run on either WinAC, also runs on S7 series processors.
(3) human-machine interface software HMI automation software for users to project human-machine interface (HMI) or SCADA system that supports a wide range of platforms. HMI software, there are two, one is applied to the machine-level ProTool, the other is applied to monitor the level of WinCC.
ProTool for most HMI hardware configuration from the operator panel to a standard PC can be used to integrate effectively complete the configuration of ProTool in STEP 7. Configuring ProTool / lite for text display, such as: OP3, OP7, OP17, TD17 like. ProTool / Pro is used to configure all the standard PC and Siemens HMI products, ProTool / Pro not only configuration software, which runs Windows version is also used to monitor system platform.
WinCC is a truly open-oriented monitoring and data acquisition SCADA (Supervisory Control and Data Acquisition) software can be run on any standard PC. WinCC simple operation, high reliability, integration with STEP 7 function, direct access to the PLC system hardware failure, save project development time. It is designed for a wide range of applications, can be connected to the existing automation environment, a large number of communication interfaces and comprehensive process information and data processing capabilities, its latest WinCC5.0 support via IE browser dynamic monitoring of production at the office process

To simplify and write PLC ladder command statement table ladder program

201608281201608283After simplifying the ladder

2016-8283
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

SIEMENS S7-300 PLC CPU module component

S7-300 there are many different types of CPU, suitable for different levels of control. CPU module is integrated with the digital I/O, and integrated digital I/O and analog I/O.


CPU component is packaged in a sturdy and compact plastic enclosure, Panel on the status and error indicator LED, mode selection switch and communication interfaces. Micro memory card slot you can insert up to several megabytes of FEPROM micro memory card (MMC), after loss of program and data preservation. Some CPU, only one MPI interface.


1. Status and fault indication LED


CPU module Panel for LED (light emitting diode) the meaning of


CPU in RUN mode RUN LED lit; 2Hz frequency during boot shining; HOLD State with 0.5Hz frequency lights. When CPU is STOP, HOLD or restart STOP LED Permanent; request a memory reset to 0. 5Hz frequency blinking are the memory reset to 2Hz frequency lights.


2. CPU operation mode


1) STOP (stop) mode: the mode selector switch is in the STOP position, automatically enters STOP mode after power on the CPU module, which does not execute user program can receive global data and checking the system.


2) RUN (run) mode: execute user programs, refresh the input and output, handling interrupts and faults information services.


3) HOLD mode: start and RUN mode when debugging with breakpoints, the user program execution is suspended (paused), the timer is frozen.


4) STARTUP (boot) model: you can use the mode selector switch or STEP 7 start the CPU. If the mode select switch is in the RUN position, power on automatically when entering the start mode.


5) old CPU key to switch to select the operation mode, it also has a RUN-P mode, allows to read and modify the program at runtime. Simulation software simulation of the PLCSIM CPU RUN-P mode, certain monitoring functions can only be carried out in RUN-P mode.


3. Mode selector switch


CPU mode selector switch to the position of significance are as follows:


1) RUN (run): CPU execute user programs.


2) STOP (stop): CPU not execute user programs.


3) MRES (memory reset): MRES position cannot be maintained in this position when you let go the switch will automatically return to the STOP position. From the STOP position to pull the mode selection switch into the MRES position, can reset the memory, the CPU back to the initial state. Working memory and S7-400 of RAM loaded in memory user program and address area is cleared, all memory, timers, counters and data block is reset to zero, including the data hold function. CPU hardware, initializing the hardware and system parameters, system parameters, CPU and is restored to the default settings of the parameters of the module, MPI (multi point interface) parameter is reserved. CPU inside the MMC after the reset of the user programs and system parameters are copied to the storage area.


Reset memory operations in the following order: PLC power from the STOP position to pull the mode selection switch into the MRES position, STOP LED extinguished 1s, 1s, went out again after 1s remain on. Release the switch and make it return to the STOP position. 3S to pull to the MRES position, STOP the frequency flashing at least 3s LED 2Hz, said it is a reset, finally STOP LED on, reset the end, you can release the mode selector switch.


4. Communication interface


All CPU modules have a MPI (multi point interface) communication interfaces, some CPU module with PROFIBUS-DP interface or a point to point interface, model PN CPU modules in an industrial Ethernet PROFINET interfaces.


MPI interface is used with other Siemens PLC, PG/PC (programmer or a PC), OP (operator panel) through the MPI network communications.


PROFIBUS-DP can be used with other Siemens PLC, PG/PC, OP and other DP master and slave communications.


5. Power terminal blocks


The power supply module L+ and m terminals DC 24V output voltage anode and cathode, respectively. Use dedicated power connector or wires connected to the power supply module and the L+ CPU module, and m terminals.

The difference between Simens PLC programming FB and FC

FB–function blocks, blocks with background data
FC–function, or function
They Zhijian of main difference is: FC using of is shared data block, FB using of is background data block lift a example, if you to on 3 a parameter same of motor for control, so only need using FB programming plus 3 a background data block on can has, but, if you using FC, so you need constantly of modified shared data block, or will led to data lost. FB 3 motor parameters are ensuring noninterference.


FB,FC of the essence is the same, are equivalent to the subroutine can be called by another program (you can also call other subroutines). The biggest difference between them is that FB for use with DB, DB holds FB data, even if FB after the withdrawal will remain. FC does not have a data block to store the data permanently, will be assigned a temporary data at run time. In actual programming, are using FB or FC, depends on the actual needs. FB benefits upstairs to very well.


No much difference between FB and FC, FB with a background chunk, FC did not. FB data with different blocks, you can take different parameter values. So you can use the same FB and various background chunks, called by more than one object.


FC and FB like c functions, though FB can generate static variables, data will be saved in the next function call, and FC variable is only valid during the call period, the next call to replace.


S7-300plc FB and FC respectively? FB has its own background, DB and DB FC does not have its own background, FC and FB have a difference, they can achieve the control function, what to use FB or FC should be used, when using FB when FC?
No much difference between FB and FC, FB with a background chunk, FC did not. FB data with different blocks, you can take different parameter values. So you can use the same FB and various background chunks, called by more than one object.


FC and FB like c functions, though FB can generate static variables, data will be saved in the next function call, and FC variable is only valid during the call period, the next call to replace. Each call to the FC I/O areas must be of yourself each time you manually enter, and FB is not, save a lot of trouble, if the PC can control directly to the DB control address.

FX3U PLC external sensor connection

PLC FX3U some columns may be NPN type or PNP type sensor and wiring simple.


FX3U S/S on terminals, S/S by Terminal block of 24V and 0V terminals or terminal connected to leak, source input switch.


Missing input: connect the 24V and S/S terminals


Source input: connect the 0V terminals and S/S Terminal


By choosing you can set the basic unit of input enter input or source for the leak, but not mixed.


Basic unit and input/output expansion unit you can select leakage input or source input.

Mitsubishi PLC password settings

Passwords can limit set PLC programming tool, display module, interface to read and write procedures, monitoring, change the current values, and so on, to protect programs or restrict the operator‘s procedures for monitoring purposes.


Mitsubishi FX series PLC password set way: will PLC power, and through programming cable and computer connection, in programming software GX-DEVELOPER in the followed by select “online”–“login key word”–“new login”, in pop-up of dialogue box in the of “key word” Hou of box in the writes to set of password, set of password for 8 bit, can for 0~9 of digital or A~F of letters. Write and click execute, and follow the prompts to enter the same password again. Password settings are different for different protection levels of PLC, beginning of the keyword text for A,D~F,0~9 will be closed to all operations, start writing for b program will be prevented from reading and writing, rather than limit the control and change the current value, writes the letter c at the beginning of procedure of limitation, and other operations are not limited.

Design of PLC control system the main steps to be followed and the content

(1) technical analysis
In-depth understanding of process control object, features, requirements, and dividing control of all phases, summarized the various stages of, and between the various stages of transition conditions, draw the flowchart control flow chart or function.
 
(2) select the appropriate PLC type
 
When you select the PLC model, mainly consider the following points:
 1 choice of functions. For small PLC main I/O expansion module, a/d and d/a modules and features of the directive (such as interrupt, PID, etc).
 2 I/O number to determine. Statistical control system switches, analog I/O point numbers, and consider future expansion (General plus 10%~20% spare capacity), to choose the PLC I/O points and output specifications.
 
 3 memory estimate. User program memory required is mainly with the system‘s I/O points and control requirements, length of program structure and other factors. General estimation according to the following formula: storage capacity = switch input points x8+ points X10+ switch output analog channel number x100+ number x300+ number X2+ communications interface standby timer/counter.
 
(3) allocation of I/O points. Distribution PLC input/output points, write input/output allocation table or input/output terminals the wiring diagram, and PLC programming, both control cabinet or console design and field construction.
 
(4) program. For more complex control systems, according to the production requirements, draw the flowchart control flow chart or function, and then design a ladder diagram, again according to the prepared statement form the ladder program, staging and modifications to the program, up until the requirement is met.
 
(5) the controller or console design and field construction. Designing control cabinets and work station layout and installation of electric wiring diagram; design components of the control system of the electrical interlock diagram according to drawings for field wiring and check.
 
(6) using the integrated debugging. If the control system consists of several components, you should first make a local debugging, and make the whole debugging; more if you control the sequence, the segment can be debugged, and then dispatching and connected.
 
(7) prepare technical documents. Technical papers should include: programmable controllers wiring diagram electrical engineering, electrical layout, electrical component breakdown, sequential function chart, ladder diagram with notes and descriptions.

Design of PLC control system and debug steps

(A) analysis of controlled objects control requirements and


Detailed analysis of control processes and characteristics about control of interaction between mechanical, electrical, fluid, made the control requires control of PLC control system, identification of programmes, development proposal.


(B) determine the input/output devices


According to the system requirements, and determine all of the required input devices (such as push button, position switches, switches and sensors, and so on) and output devices (such as contactors, solenoid valves, signal lights, and other devices, and so on) to determine the associated with the PLC input/output devices, to determine the PLC I/O points.


(C) select PLC


PLC selection including the PLC model, capacity, I/O modules, power supplies and other options, as described in section II of this chapter.


(D) allocation of design PLC I/O and peripheral hardware lines


1. allocation of I/O points


Draw the PLC I/O points corresponding to the connection diagram input/output devices, or relational tables, which can be carried out in the 2nd step.


2. PLC peripheral hardware circuit design


Draw the electrical wiring diagram for other parts of the system, including the main circuit and do not enter the PLC control circuit and so on.


By the PLC I/O connection diagrams and PLC peripheral electrical wiring diagram the electrical schematics of the system. End system hardware circuit has been identified.


(E) programming


1. program design


According to the system requirements, using appropriate design methods to design the PLC program. Procedures to control to meet the system requirements as the main line, write the control functions or tasks one by one program, gradually improved the system to the specified function. In addition, programs should also include the following:


1) initialization program. PLC poweron, are generally required to do some initialization operations, to start the necessary preparations to avoid malfunction of the system. Initializes the main elements of the program are: to clear certain data, counters and other, to restore some data requirements data, to set or reset certain relays, to display certain initial state, and so on.


2) detection and trouble diagnosis and display program. These programs are relatively independent, generally when the program is completed, adding.


3) protection and linkage programs. Protection and chain are indispensable parts of the program, must be seriously considered. It can avoid the control logic confused due to illegal actions.


2. program debugging


Program the basic idea of staging is to facilitate simulations in the form of actual state, to run programs to create the necessary conditions. According to the signal in different ways, staging a hardware simulation and software simulations in two forms.


1) hardware simulation method is to use a hardware device (such as a PLC or other input device, and so on) simulate signals, and these signals to hard wire connected to the input of the PLC system, its effectiveness is stronger.


2) software in PLC, the modeling method is writing a simulation program, analog provide local signals, its simple, but time is not easy to ensure. In the staging process, methods that can be used to debug and program monitoring function.


(F) the hardware implementation


Hardware implementation is mainly to control cabinet (set), such as hardware design and field construction. Main content:


1) designing control cabinets and floor plan and console and other parts of the electrical installation wiring diagram.


2) design the electrical interconnection between the different parts of the system.


3) according to the construction drawings for field wiring, and to conduct an examination.


Due to programming and hardware implementation may simultaneously carry on, so can shorten the design cycle of PLC control system.


(G) debugging


Debugging is to further online tracking through the staging process. Debugging process should be gradual, from the PLC connected input device, and then connect the output device, and then connect to the actual load step by step debugging. If you do not meet the requirements, then adjust hardware and programs. Often only part of the program.


After the full commissioning, delivery operation. After a period of time, if working properly, the program does not need to be modified, procedures should be cured in the EPROM, in case the program is missing.


(H) the collation and preparation of technical documents


Technical documentation including design specifications, hardware schematics, wiring diagrams, electrical components, PLC program, and use the schedule description

Design of PLC control system of the four cardinal principles

1 meet control requirements of the controlled object.
2 in the premise of meeting the requirements to make simple, affordable, easy to use and maintenance of control system.
3 ensure that the control system is safe and reliable.
4 taking into account the development of the production and improvement of technology in select PLC capacity should be appropriate enough.

PLC control system design of the basic principles and main contents

1. design principles
 
In order to achieve controlled technology to improve production efficiency and product quality.
 
1. selection of PLC should not only meet the requirements of specification, you should also focus on technical support and after-sales service of the company‘s products. (Choose product)
 
2. to meet the control requirements of the controlled object.
 
3. meet the requirements of the premise, sought to make the control system is simple, economical, convenient operation and maintenance.
 
4. ensure the control system is safe and reliable.
 
5. taking into account the development of the production and process improvement, select PLC capacity should be adequate enough.
 
2. the design of the main content
 
1. preparation of technical conditions for design of the control system. General technical conditions to determine as a design task, it is the Foundation of the entire design;
 
2. Select electric drives and motors, solenoid valves, actuators;
 
3. the model of the selected PLC;
 
4. development of PLC input/output assign table drawing input/output terminals or wiring diagram;
 
5. prepared software specifications according to the system design, and then use the corresponding programming languages (ladder diagram) programming;
 
6. understand and follow the user‘s cognitive psychology, emphasis on human-machine interface design and enhance friendly relationship between man and machine;
 
7. design work, electrical cabinets and non-standard electrical components;
 
8. the preparation of design specifications and instructions;

Structure design of PLC control system

Linear programming Division of programming and structured programming (industrial mixing system).
Objects that are mixing requirements are as follows:


1. When component a (b) pump when required: 1) components of a (b) inlet valve has been opened, discharging valve is open; 2) mixing bucket is not full, the mixing valve closed; 3) the pump drive motor failure, do not have an emergency stop.
2. Mixing motor working conditions: 1) the mixing tank is not empty, mixing tank discharge valve closed 2) stirring motor failure, emergency stop without action.
3. Open discharge valve condition: mixing motor stop, emergency stop without action.
System of liquid level switch allows the operator understand the level of mixing drum, and provide linkage between pump and motor.


A linear programming
Linear programming is placed in a row within a block of instructions by the user program, that is, a simple block that contains all instructions of the system. Linear programming with no branches, usually OB1 sequentially each instruction, software management capabilities are relatively simple.


Second, partial program
Distributed programming tasks into a control several separate blocks, each block is used to control a device, or a set of logical instructions, these instructions within the block run by organizing block OB called.


Third, structured programming
Structure of program procedure requires the classification of similar or related functions, and tried to provide a universal solution can be used for several tasks. Provide relevant information to the instruction block (as a parameter), structured programs can reuse these common modules.


Control software consists of five functional blocks:
FC10 function block is used to control the ingredients a feed pump;
FC20 function blocks for controlling composition b material supply pump;
FC30 function block is used to control the mixing motor;
FC40 function block is used to control discharge solenoid valve;
FC50 function blocks for the LEDs on the control station.

PLC control system design methods

Application system design
 
1. PLC control system type
F composed of PLC control system.
Fcentralized control system made of PLC.
F composed of PLC distributed control system.
F with PLC remote I/0 control system.
 
2. System operation mode
F manual operation mode.
F semi-automatic operation.
F automatic operating mode.
 
B system hardware design under
 
1. Technological requirements
2. Equipment status
3. Control function
4. I/0 number and type
5. Advanced System
 
Three programmable controllers of type selection
1. the CPU features
2. I/0 points
3. response speed
4. instruction system
5. type select other considerations
 
The choice of four input/output template
1. Digital input module options
2. Digital output module options
3. Analog module selection
4. Application of intelligent I/o module selection
 
Five system hardware design files
1. System hardware configuration diagram
2. Module statistics
3. I/0 interface and I/0 address table
 
Six power supply design
1. Power supply protection
2. Selection of power supply module
4. I/0 module power supply design
5. the system grounding design
6. power supply system design of programmable controller
7. cable design and installation

What sources of electromagnetic interference in PLC control system

One, from space radiation interference
Space radiation electromagnetic (EMI) consists mainly of electrical equipment for power network, transients, lightning, radio, television, radar, high-frequency induction heating equipment, often referred to as radiation interference, its distribution is extremely complex. PLC systems in the RF field, it ***** to radiation interference, its influence through two paths; one is directly to the PLC‘s internal radiation, induced by circuit disturbance; but the radiation of PLC communication within the network, introduced by communication lines induced interference. Radiated interference and plant layout and the size of the electromagnetic fields generated by the device, in particular frequencies, generally through shielded cables and PLC local shielding and protecting high voltage discharge components.
Second, interference from the system leads to
Introduced mainly through the power and signal line, often referred to as conducted interference. This industrial field more serious interference in our country.
Third, interference from power supply
Practice has proved that the introduction of disturbance of PLC control system for a power supply failure of many, I encountered in the debugging of a project, after replacing the PLC isolated higher performance power supply, problem solved.
PLC system, the normal power supply by the power supply. Due to network coverage, will be subject to all the electromagnetic interference induced voltage on the wire and circuit. Especially within the grid changes into a switching surges, large-scale power equipment starts and stops, AC and DC rotating equipment caused by harmonics, power short-circuit transient shocks, through transmission lines to the power supply side. PLC power supply usually isolated power supply, but the institutions and the manufacturing process so that their isolation is not ideal. In fact, given the existence of distribution parameters, especially the distributed capacitance, absolute isolation is impossible.
Four, from the signal lines of interference
Connection with PLC control system signal transmission cable, other than the effective signal transmission, there will be external interference signal intrusion. This interference there are two main ways: through transmitters or shared the interference signal power supply for instruments in series, this was often ignored; the second is interference of signal lines by space radiation sensors, namely external inductive interference on the signal line, which is very serious. Introduced by signal interference can lead to I/O signals working and accuracy is greatly reduced, serious damage caused when components. For isolation system with poor performance, will also lead to mutual interference between signals, causing total system bus back, resulting in logical data changes, malfunction and crash. PLC control system I/O module is due to signal interference is introduced quite badly damaged, and the resulting system failures are many.
When he was five, from the grounding system disorder interference
Grounding is to improve the electronic equipment electromagnetic compatibility (EMC) is one of the most effective methods. Proper grounding, which can inhibit the effects of electromagnetic interference and suppression equipment issued to outside interference and error of grounding, but will introduce serious interference, the PLC system will not work properly. PLC control system of wire including system, shielding, communication and protection, and so on. Grounding system disorder interference of the PLC system is that the uneven distribution of grounding potential, ground potential difference exists between the different locations, cause a ground loop currents, impact system working properly. For example, the cable shield must be grounded if the cable shield at both ends of a and b are grounded, there is the potential difference, there is current flowing through the shield, exceptions occur when lightning strikes, ground current will be greater.
In addition, shielding, grounding wire and the Earth is likely to form a closed loop, in the presence of variable magnetic field, the shield appears in induced currents through the coupling between the shield and the core line, interference signal circuit. If systems and other ground handling messy, the circulation of potential distribution range may produce on the ground, effects of PLC logic circuit and analog circuit to work properly. PLC logic voltage interfere tolerance low, logic ground potential interference affects distribution of PLC logic operations and data storage, resulting in data corruption, that program runs or panics. Simulation of electric potential distribution will lead to decreased accuracy, caused serious distortion to the signal control and malfunction.
Six from the interference of PLC system
Primarily by system internal components and circuit interaction between electromagnetic radiation, such as logic circuits mutual radiation and its effects on analog circuits, analog and logic of interaction and components do not match each other and so on. It belongs to the PLC manufacturers electromagnetic compatibility design of the system, more complicated, as the sector cannot be changed, without much thought, but you want to select more performance or the tried and tested system.