Tag Archives: PLC Ladder Logic

how to program Power Delay on and Power loss delay off PLC ladder diagram

When the X0 is turned on, the timer T1 starts to delay, after 2S Timer T1 normally open contact closure (set point signal), hold instruction make the Y0 power and hold; When the X0 is off, the timer switch on T2 (normally open contacts at Y0) start delay, 4S timer T2 normally open contacts (reset signal), Y0 power loss


How to make the system start PLC ladder diagram Program

when your learn plc programming , you must need plc system start up. PLC system start up  include    Start self-locking, without self-locking.
but how you choose the ladder diagram?
If the hardware buttons circuit with a reset function you need to use with self-locking startup programs;

If the hardware buttons circuit without  a reset function you need to use without self-locking startup programs;


with self-locking startup program ladder diagram

without self-locking startup program  ladder diagram


How to use PLC control Motor starting voltage Ladder Diagram

Press the start button SB2, contactor KM1 coil get electricity and self lock, KM3 coil power, which normally open the main contact closure, motor access power supply, and Y connection to start running. At the same time, the time relay KT coil power, after the delay, the normally closed contact is disconnected, cut off the power supply of the KM3 coil, making the KM3 power loss, normally open contact off, normally closed contact closure. KT of the normally open contact is closed and a contactor km2 coil power, km2 main contact closure makes motor by Y connection switching method for delta connection operation.

Relay control circuit

Y-△ Buck start control Schematic diagram

PLC control program design

PLC control I/O

Ladder Logic


how to get a signal PLC ladder program

PLC programming often need to use different commands to obtain different information on the switch
this is plc programming examples

1. Get information on the rising edge

To obtain information on the rising edge of the input signal by the transition instruction, contacts and trigger rising edge pulse

2. Get information falling edge

To obtain information on falling edge the input signal drops by contact and falling edge pulse trigger

3. Get level information

     If the button corresponding to the input port is normally open, the program can be obtained through a high level of information normally open contact, normally closed contact information to obtain Low level

plc pulse signal dividing program

this is plc ladder diagram,about plc pulse signal dividing program
the rising edge of the X20 is used to trigger the output of the M0 coil, and the output of the M0 normally open contact is used to lock the output.

PLC Ladder Diagram same button multiple functions progrmming

this is PLC Ladder Diagram about  the same button needs to achieve a variety of functions, that is, the button 1 times to achieve the first function, according to the second to achieve second functions, according to the third to achieve third functions

The function procedure is triggered by the rising edge of the input signal, so the rising edge of the input signal needs to be acquired. At the same time, it is necessary to count the number of the input signals, and the different values will perform different functions. When the counter reaches a certain value, it is necessary to reset the counter.

PLC ladder diagram of the input signal to eliminate jitter processing programming

the PLC ladder diagram is used for Contact input key mechanical properties may cause some jitter.

PLC programming in Ladder Self-maintaining bit (self-locking) instruction

When any one of IR00004 and IR00005 is “ON”, HR0000 will be set to “OFF”.


PLC ladder programming Instruction control bits

        ① set and reset. When the condition becomes ON”, the set will be put in operation ON”, but not as output (OUT), when the condition becomes OFF”, the reset will not reset on the operation of OFF”. When the condition becomes ON”, the reduction in operation position reset OFF”, but does not output non-directive (OUT NOT), when the condition becomes OFF”, the reset will not reset on the operation ON”. In the following example, no matter how IR00100, IR00100 reset ON” IR20000 will reset when ON”, and can remain ON” until the IR00101 reset ON”. When IR00101 set ON”, the reset IR20000 reset OFF”. Set and

No function code set and reset. From the handheld programmer to enter them as FUN and SET key or FUN and RSET button, followed by the address.

       ② rise differential differential and the falling edge. Rise differential and the falling edge of the so-called differential refers to the input signal front porch and back operations. Rise differential differential command is used to enable and falling in a cycle time of the built-in ON”. In implementing the conditions OFF” to ON”, the rising differential instruction makes a cycle of operation ON”, in the implementation of conditions ON” to OFF”, the falling differential instruction makes a cycle of operation ON”. Both of these instructions requires only one line mnemonics.

Here, in IR00000 to ON”, IR20001 in a cycle will reset ON”. Then perform DIFU (13) 20001, no matter how IR00000, IR20001 will be OFF”. Falling edge differential instruction IR00001 to OFF” after (IR20002 OFF” until this time), the IR20002 will be built in a cycle ON”, and will be implemented in the next DIFD (14) 20002 post OFF”.
Rise differential and the falling edge of differential

       ③ maintain. Use directives to keep based on two perform conditional operations. Doing so will keep the instructions attached to two on the command line. When the first command line execution at the end of the condition for ON”, keep instructions operating position ON”. When the end of the second command line execution as ON”, keep instructions operating position OFF”. Even if it is located in the internal interlocking parts of the program, keeping the operation of the directive will save it to the ON” or OFF” State.
In the example shown in Figure 1-33, when IR00002 is ON” and IR00003 to OFF”, the HR0000 will be set ON”. HR0000 remain ON” until another IR00004 or IR00005 reset ON”. Keep instructions as the others, need more than one command line, the command line in the instruction encoding before they control.

Siemens S7-200 PLC’s Belt conveyor Control Programming Example

Three conveyor belts, respectively, by the motor M1, M2, M3 driven.

Requirements: After pressing the start button SB1, a startup sequence for M1, M2, M3, interval of 3s.
After the stop button SB2, Sequential stopping for M3, M2, M1, interval of 3s.
Three motors M1, M2, M3, respectively, through the contactor KM1, KM2, KM3 three-phase AC power supply is turned on, PLC control coil contactor