Up counter instruction using example.

Application:-Understand the concept of UP counter instruction in the PLC. Explain UP counter concept using PLC program.

Components:-Programmable logic controller.

 

Explanation:-

Generally counter is used to count events in the application. Counter is used in so many application like object count, students counts, cars count etc. Counter instruction used in programmable logic controller for deferent types of logic. Here our aim is to understand UP counter, UP counter counts the objects. 

 

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 ON/OFF button is digital input and lamp is the digital output. So define digital input address and output address as per below explanation,

Digital inputs:-

ON/OFF button=I0.0

Counter Reset=I0.1

Digital Output:-

Lamp=Q0.0

 

PLC program Explanation:-

In above network 1, we have used UP counter (CTU). We can use INT data type for the counter. When ON/FF button (I0.0) is pressed five times, valve (Q0.0) should be ON.

Here UP counter will continue to count till reset button pressed. If we will not press reset button, counter will continue to count after five. UP counter should be reset after its PV value over.

In in PV, we can set preset count value and actual count value can be monitored in CV (current count value).

Sequential operation of two lamps.

Sequential operation of two lamps.

Application:-Operate two lamps in sequence. There are two lamps in the system and we need to operate it in sequence, hence first L1 will be on and after 10s second L2 will be ON.

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

Explanation:-

As per above application, there are two lamps in the system and we need to operate them in sequence. So when lamp on/off button is pressed L1 will be on and second lamp L2 will on after 10 second delay. In this case we need to use on delay timer because we are giving delay between two lamps.

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 on/off switch is digital input and lamps are the digital output. So define digital input address and output address as per below explanation,

Digital inputs:-

Digital Output:-

L1=Q0.0

L2=Q0.1

Memory Coil:-

On/off switch:-M0.0

PLC program Explanation:-

In network 1, we have used NO contact of lamp ON/OFF (M0.0), so when switch is pressed L1 (Q0.0) will be on immediately.

In network 2, we have used NO contact of L1 (Q0.0) to operate L2 (Q0.1). Here we used on delay timer to provide delay between two lamps.

Explain OFF delay timer using example

Application:-Explain OFF delay timer using example. Also draw electrical diagram and PLC program for example

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

Diagram:-

Explanation:-

Consider one example for OFF delay timer explanation. For example there is a valve in our application and we need to close it after 20sec when switch S1 is pressed. So as shown in above circuit supply will pass from No contact of the switch and will go to timer supply. When switch is pressed timer will start first and operate valve and meanwhile off delay will start so after time valve will be close automatically.

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 switch S1 is digital input and valve is the digital output. So define digital input address and output address as per below explanation,

Digital inputs:-

Start switch S1=I0.0

Digital Output:-

Valve=Q0.0

PLC program Explanation:-

In network 1 we have taken NO contact of Start switch S1 (I0.0) so when switch is pressed, timer and valve (Q0.0) will start. The set time is 20sec so timer will generate OFF command to stop valve (Q0.0).

Here PT is preset time at which we can set time and ET is elapsed time at which we can monitor time. Do not mix up the pulse timer and OFF delay timer. In pulse timer, timer needs pulse of the digital input for operation and in OFF delay timer, timer needs digital input for operation.