Explain basic pulse timer of PLC using example

Application:-Explain pulse timer using example. Operate solenoid after 10 second in the control panel when start button pressed. Solenoid should be ON after 10 seconds. Draw electrical circuit and write PLC program using ladder diagram language.

Components:-Programmable logic controller, Electrical panel, wires, 24vDC switches with NO contacts, 24VDC solenoid valve, and 24 VDC timer.

Diagram:-Electrical wiring diagram of solenoid operation with pulse timer.

Explanation:-

Generate pulse timer can be used for many application. It can be used to set output for some duration.

The instruction is started when the result at IN changes from 0 to 1.Positive edge of the input can be used in this timer. Once positive edge of the signal is detected timer will start and it will remain ON till its time completed.

Here in above application we will use pulse timer. We want to ON solenoid after 10 seconds and we have one push button. So when operator press start button, after 10 second solenoid should be ON. In above application when start button is pressed timer will start and after 10 second timer’s NO contact will start the solenoid.

PLC program:-

Write the ladder program for above application using ladder diagram language. Here for ladder logic we can use any supported PLC system like S7-1200, S7-300, S7-1500 or any other PLC which can support this instruction. For PLC logic we need digital inputs and outputs.

For our application start pushbutton is digital input and valve is the digital output. So define digital input address and output address as per below explanation,

Digital inputs:-

Start PB=I0.0

Digital Output:-

Valve=Q0.0

PLC program Explanation:-

In network 1 we have taken NO contact of Start push button (I0.0) so when push button pressed, timer will get positive edge of start pushbutton and start to count time. Once 10s is completed, valve (Q0.0) will be ON.

Here user can set required time at PT and can watch time at ET (Elapsed time).

Combinational logic operation using AND gate and OR gate

Application:-Draw electrical diagram and write PLC program for combinational logic for 3 switches. Use AND gate and OR gate for three switches combinational logic. Operate lamp in the following condition,

If S1 or S2 is ON and S3 is ON, the lamp will be ON.

Components:-Programmable logic controller, Electrical panel, wires, 24VDC switches with NO contacts, 24VDC indication lamp, 24 VDC relay.


Diagram:-Electrical wiring diagram for combinational logic.

Explanation:-

Here we have 3 switches S1, S2, and S3. So the condition is either S1 or S2 should be ON or S3 should be ON. So S1 and S2 should be put in OR gate and this combination should be put in series with S3.

Hence the lamp will be ON if S1 or S 2 is ON and S3 is ON.

PLC program:-

Write the ladder program for combinational logic using ladder diagram language. Here for ladder logic, we can use any PLC system. For PLC logic we need digital inputs and outputs.

For our application, all switches are digital inputs, and the lamp is a digital output. To define digital input address and output address as per below explanation,

Digital inputs:-

S1=I0.0

S2=I0.1

S3=I0.2

Digital Output:-

Lamp=Q0.0

Memory coil:-

Memory bit-M0.0

PLC program Explanation:-

In-network 1 we have considered three digital inputs for three switches S1, S2, and S3. So we have taken NO contact of S1 (I0.0) and S2 (I0.1) in OR gate and. So when S1 or S2 OFF, memory bit (M0.0) will be ON.

Two switches series operation

Application:-Operate lamp if two-panel switches are from different two panels. Draw electrical drawing and write PLC programs using ladder diagram language.

Diagram:-Electrical wiring diagram of two switches series operation.

Explanation:-

For series operation of two switches we can use AND gate logic. Here there are two switches, panel 1 switch, and panel 2 switches. As per AND gate we need to put panel 1 switch NO contact in series with panel 2 switch NO contact as shown in the above electrical diagram.

PLC program:-

Write the ladder program for series operation using ladder diagram language. Here for ladder logic, we can use any PLC system. For PLC logic we need digital inputs and outputs.

For our application, all switches are digital inputs and the lamp is a digital output. To define digital input address and output address as per below explanation,

Digital inputs:-

Panel 1 switch=I0.0

Panel 2 switch=I0.1

Digital Output:-

Lamp=Q0.0

Memory coil:-

M=Memory bit

PLC program Explanation:-

In-network 1 we have considered two digital inputs for two switches panel 1 switch and panel 2 switch. So we have taken NO contact of panel 1 switch (I0.0) in series with panel 2 switch (I0.1) for series operation. So when both are ON, memory bit (M0.0) will be ON.

In-network 2 we have taken NO contact of memory bit (M0.0) to operate a lamp (Q0.0).