Tag Archives: PLC ladder

What time relay is used for Mitsubishi PLC power-off delay

Mitsubishi does not have a power-off delay to close the relay. Only the power-on delay closes the relay, but it can be implemented by a program.

as the picture shows,
When X0 is ON,
M0 reset,
M0 is disconnected in front,
T0 does not count,
When X0 becomes OFF,
M0 is set and T0 starts counting.
Time is up,
When the contact T0 is output, the function of closing the power-off delay is reached.

FX2N Series PLC data communication module

PLC communication module is used to complete with other PLC intelligent control, other communication between devices or computers. Following brief introduction to FX serial communication function expansion board, adapter and communication modules.

(1) communication expansion board FX2N-232-BD. FX2N-232-BD is to connect standard PLC and other RS-232C transport device interface board, such as personal computers, bar code reader, or printer. The panels can be installed inside the FX2N extension. The maximum transmission distance is 15m, the maximum baud rate for 19200bit/s. PLC using special software for the extension plate can be running monitoring, can also be transmitted from the PC to the PLC program.

(2) communication interface module FX2N-2321F. FX2N-2321F on connect FX2N series PLC can realize RS-232C with the other fullduplex serial communications interface devices, such as personal computers, printers, bar-code reading device and so on. FX2N series FX2N-2321F modules can connect up to 8 blocks. The module using FROM/TO command to send and receive data. Maximum transmission distance is 15m, the maximum baud rate for 19200bit/s. The modules take up to 8 I/O point. Data length and serial communication baud rate can be set by a special data register.

(3) communication expansion board FX2N-485-BD. FX2N-485-BD for RS-485 communication. It can be applied to no agreement on data transfer, FX2N-485-BD at the time of the original agreement, as a way, using RS instruction in personal computers, barcode reader, printer, data transfer between. Transmitting maximum transmission distance is 50m, the maximum baud rate for 19200bit/s. Each of the FX2N series PLC expansion boards can be fitted with a FX2N-485-BD communication. In addition to using this communication expansion boards and computer communications, it can also be used to achieve two parallel between FX2N series PLC.

(4) communication expansion board FX2N-422-BD. FX2N-422-BD to RS-422 communications, can be connected on the FX2N series PLC, and as a tool for programming or control a port. This interface is available outside of the PLC connected to PLC devices, data storage unit, and human-machine interface. FX2N-422-BD can be used to connect two data storage unit (DU) or DUseries unit and a programming tool, but one can only connect a programming tool. Every basic unit can be connected to a FX2N-422-BD and cannot be used with FX2N-485-BD or FX2N-232-BD.

(5) the interface module MSLSECNET/MINI

Use MSLSECNET/MINI interface module, series PLC of FX series PLC can be used as a local control station, constitute a distributed control system.

Above on the FXseries only gives a brief introduction to the communication module, specific application again in detail in later chapters.

Siemens PLC S7-300 controls the motor to start up Ladder Diagram programming examples

Today we’ll make a plc ladder diagram for siemens plc s7-300 control the motor start up. plc ladder diagram  is very important to learn plc programming.
(1) Control requirements.
There are three motors M1, M2, M3, press the start button to start M1, M2 starts after delay 5s, M3 starts again after 16s.
(2) Programming element symbol address

Programming element symbol address

(3) PLC Ladder Diagram

PLC Ladder Diagram

PLC ladder programming sequence control

Learning PLC programming, we often encounter the sequential control, but how to make plc ladder diagram
there is  example Shuttle program.

The initial state of the car parked in the middle (limit switch X0 is pressed, the normally open contact closure),Press the Start button (X3 closed), the car began to follow the direction shown to reciprocate when you need to stop, press the stop button (X4 closed), stop automatically when the car moves to the middle position. Here all the buttons and travel switches are normally open contacts are connected to the input terminals of the relay.

how to program long delay PLC ladder diagram

When plc programming often need several hours, or even longer delay, the best way is  series timer, or  PLC internal counter.Using the timer series Can be a long delay, in essence, it is to allow multiple timers turn ON, delay time is Accumulating multiple timer settings.

Serial time delay

Set time of the timer T1 is a counter C100 input pulse signal, so that the delay time is several times of  T1 setpoint.

Timers and counters associated with long time delay
The internal special relay R901E (1 min clock) as the counter C100 input signal, so that the time delay is a few minutes. If a counter does not meet the requirements, the counter can be used in series, that is, the contact of the front counter is used as the input pulse signal of the back of a counter to achieve a longer time delay.
Counter long time delay

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


PLC alarm circuit Ladder Logic

 That is the condition for the alarm input X0 X0 = ON alarm requirements.
Alarm lamp output Y0, Y1 alarm buzzer.
Y0 flashing alarm when its oscillation cycle 1s;
Y1 tweet.
X1 alarm response, alarm X1 after blinking and stays ON Y0, Y1 tweet closed.
X2 is alarm lamp test signal, i.e., Y0 X2 turns ON.

①Y0 need an oscillator signal.

alarm response after Y0 after flash lit, so the application of an intermediate relay R0 will hold X1 signal and with R0 normally open contact in parallel with the oscillating signal to reach steady Y0 purpose, while the normally closed contact with R0 disconnect the buzzer Y1.

PLC oscillation circuit Ladder Logic

Oscillation circuit analysis
X0 turns T1 coil excited,4s after T1 delay normally open contact closure,While T2, Y1 coil excited, Y1 output.After T2 coil excited 2s produce a series of actions in the following order (note the timing chart corresponding analysis).

①T2 normally closed contacts disconnect
make T1 energized coil,
③ T1 coil power loss and enable T1 normally open contact disconnect leading to
④T2, Y1 coil is energized at the same time,
⑤T2 coil power loss making T2 NC reset,
next scan cycle, T2 after reset normally closed contact and so excited coil T1, after 4s T2, Y1 coil excited again …….
Analysis shows Y1 generates a cycle of oscillation signal 6s

PLC ON delay circuit Ladder Logic

Input Ⅹ0, X1 is not connected with self-locking button controlled device connected to the output terminal Y0.

When the input signal is turned Ⅹ0 terminal, enter the relay coil Ⅹ0 turned on, its normally open contact Ⅹ0 closed, internal relay R0 is turned on, its normally open contact closure R0, ON timer T0, T0 is set K50 value decrements. Reduced to 0″ T0 normally open contacts closed, the output relay Y0 with respect to the delay 5s after X0 is turned on. When the input Ⅹ1 turned on, the internal relay is energized R0, R0 normally open contacts disconnect, reset the timer T0. T0 normally open contacts disconnect the output Y0 is 0FF.

Siemens S7 series PLC Data Block Instructions PLC Ladder Logic

Open the data block
<span title="指令格式:OPN           “>Instruction format: OPN

          Description: open a data block as a shared data block (DB) or as an instance data block (DI).

              You can open a shared data block and one instance data block at the same time.
Example 4.9.1: OPN DB 10 // open a data block as a shared data block DB 10

          L DB W35 // the DB data words W35 10 is loaded into the accumulator
Low Word 1.

          T M W22 // transfer low word of accumulator 1 to M W22.

          OPN DI 20 // open a data block as the instance data block DI 20

          L DI B12 // will DI B12 20 byte data is loaded into the accumulation
Low Word 1

          T DB B37 // the low word of accumulator 1 transmission word to DB 10
Section 37.

Exchange of shared data blocks and instance data blocks

        Instruction format: CDB

        Description: Exchange shared data block and instance data block.
shared data block into instance data block,
instance data block becomes shared data block.
The length of the loading shared data block into accumulator 1

        Instruction format: L DBLG

        Explanation: The length of shared data block is loaded into the accumulator 1.
The number of loaded shared data block into accumulator 1

        Instruction format: L DBNO

        Description: The number of shared data block is loaded into the accumulator 1.
Length loaded instance data block into accumulator 1

        Instruction format: L DILG

        Explanation: The length of instance data block is loaded into the accumulator 1.

The number of installed instance data block into accumulator 1

        Instruction format: L DINO
Description: The number of instance data block is loaded into the accumulator 1.