[industrial control old horse] detailed explanation of the design scheme of the running lamp control system based on Siemens S7-200PLC

Based on Siemens S7-200PLC The design scheme of the control system of the running lamp based on

1、 Design background
application S7-200 PLC The hardware circuit of the lantern design , And make use of OB1 Ladder diagram control program design . By controlling S7－200 PLC The function of the timing relay is to realize that each color lamp lights up and goes out according to a certain law .

Turn on the delay timer SD Characteristics （ If RLO There is a positive jump edge , Then turn on the delay timer start command , Start the timer of the command with the set time value ）. This control circuit has a simple structure , High reliability , Strong applicability ; The software program has a wide range of applications , The control of lighting and extinguishing the colored lights according to certain rules , Just change the time of the corresponding timer .

2、 Basic requirements of the system
2.1. The operation of the system is controlled by a switch :
Start switch “ON” The system works ; Start switch “OFF” The system stops working ;

2.2. S7-200 The command system of ：
Turn on the delay timer SD, If RLO There is a positive jump edge , The on delay timer starts , Start the specified timer with the set time value . After reaching the set time , The dynamic contact of the timer is closed and maintained , until RLO Turn into 0 when , The timer is reset . If the timer runs for （RLO by 1 when ） Less than the timer time setting , Then when RLO from 1 Change to 0 when , The timer is also reset .

2.3. The law of control ：
L1_{L7 common 7 A light-emitting diode , Ask to press the start button to run the lantern L1}L7 Every... In positive order 1 Seconds turn on , When L7 After light , stop 2 second , then , Reverse reverse sequence 1 Seconds turn on , When L1 After re lighting , stop 5 second , Repeat the process . Press the stop button , The running lamp stops working .

2.4. Design principle
（1） Shift instructions
Shift instructions include unsigned number shift and signed number shift . The unsigned shift contains the word shift left instruction 、 Word shift right instruction 、 Doubleword left shift instruction and doubleword right shift instruction ; Signed number shift includes integer shift right instruction and double integer shift right instruction .＊ Unsigned number shift instruction .

1. Word shift left instruction
   When it is allowed to enter EN Bit is high “1” when , The word shift left instruction will be executed , take IN The content specified by the end is sent to the accumulator 1 In low words , And left N The number of bits specified at the end , And then write OUT.

2. Word shift right instruction
   When it is allowed to enter EN The status of is “1.

（2） Sequential control design method
The so-called sequence control , That is, according to the predetermined sequence of production process , Under the action of each input signal, according to the internal state and time sequence , In the production process, each actuator operates automatically and orderly . Generally, sequential control design method is used , The sequence function diagram shall be drawn , The structure of the sequential function diagram has a single sequence 、 Select sequence and parallel sequence . A single sequence has no branches or merges , Branches of the selection sequence cannot be activated at the same time , Branches of parallel sequences can be activated at the same time .

2.5. Hardware selection
S7－200 Programming software based on STEP 7－MicroWIN32 Equipped with a large number of programming wizards , Such as PID、 Network reading and writing 、 Programming wizard for high-speed counters and high-speed output instructions , Position control module 、 Text display TD200、 Modem module 、 Ethernet Module 、 Internet module 、AS－i Programming wizard of communication module, etc . When using these programming wizards , Just enter the required data or determine the options , Programming software can automatically generate user programs .

With programming software and simulation function , yes , we have PLC The manufacturer provides the software to run on the computer , Can be used instead of PLC Hardware debugging user program simulation software , For example, Siemens and STEP 7 The programming software is used together S7－PLCSIM Simulation software 、 Mitsubishi Corporation and SW3D5C－GPPW－C Programming software SW3D5C－LLT－C Simulation software , Omron and CX－Programmer Simulation software for programming software CX－Simulator etc. , Siemens “LOGO！ ” The programming software of the programmable logic module also has the simulation function .

PLC The simulation software is also a good learning tool for beginners to learn programming and program debugging methods .

2.6. The project design
The trend of the running lantern is as follows ： When the start button is pressed ,L1、L2、L3、L4、L5、L6、L7 In order of 1 The second interval is lit ; When L7 After light , Pause 2 second , Reverse reverse sequence 1 Seconds turn on , When L1 After re lighting , stop 5 second , Repeat the process . For emergency stop, press the stop button , The running lamp stops working .

2.7. Element list

surface 2-1 List of components for multi period intersection traffic lights

3、 PLC control system design
From the definition of programmable controller ,PLC It is also a kind of computer , It has a structure similar to that of a general-purpose computer , The programmable controller is also controlled by the central processing unit （CPU）、 Memory 、 Input / Output （I/O） Interface and power supply . However, it has stronger interface ability to connect industrial processes and more direct programming language to meet control requirements than general-purpose computers .

3.1. I/O Assignment and numbering of points
surface 3-1 System I/O Address assignment table

3.2. PLC External terminal wiring diagram
PLC The working time reference is provided by the circuit of the running lamp . stay PLC The end of the output of , Connecting a resistor and a light-emitting diode or connecting two light-emitting diodes in parallel with a resistor constitutes PLC The circuit of the running lantern , Pictured 3-1 Shown .

The device selection in the circuit can be determined by calculation and experiment , You can also refer to some typical circuit parameters . In circuit , Resistance has partial voltage function , The resistance value is about 13KΩ , The voltage borne by one and two parallel LED is 3V about , PLC The operating voltage of the is +24V, This can make the running lamp work normally .

The switch is PLC Signal input port . The switch at the input end is used to control the operation of the output end and the operation of turning off the traffic lights , Start switch sd1, I0. 0 Power on （“1” state ）, The traffic lights operate according to the designed procedure , sd2 closed , I0. 1 power failure （“0” state ） The system stops working .

chart 3-1 The design diagram of the hardware circuit of the running lantern