Explain Not equal (< >) instruction using example

Application:-Explain not Equal instruction in the PLC. Write PLC program for explanation using ladder diagram language in the Programmable Logic Controller (PLC).

Components:-Programmable logic controller, HMI panel, wires, 24 VDC lamp, 24 VDC power source.

Diagram:-

Explanation:-

Consider a simple example for explanation of not equal instruction in the PLC. Here we have taken simple HMI (Human Machine Interface) for display and programmable Logic Controller (PLC) for programming. Take two values, set value 1 and set value 2 for example. Here if both the value in the set value 1 and set value 2 equal then lamp will be OFF. So we need to use not equal (< >) instruction for above example.

Enter 20 value in the value 1 box and enter 20 value in the value 2 box so lamp should be OFF and if someone enter 21 value in the set value 1 box, lamp should be ON.

 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 lamp is digital output. Two set values from the HMI are input words.

Digital Output:-

Lamp=Q0.0

M Memory:-

Value 1:-MW10

Value 2:-MW12

PLC program Explanation:-

In network 1 two values are compared in the comparison instruction. Value 1 (MW10) is compared with Value 2 (MW12).Hence if both values are not equal, lamp (Q0.0) will be ON.

In not equal (< >) instruction, two operands are compared, we can set data type in comparator instruction.

Normally open (NO) contact concept.

Normally open (NO) contact concept.

This is PLC Program for NO contact.

Normally open contact is known as NO contact. When the quantity has signal state 1, the open contact closes and therefore the signal state of the output is changed.

When the quantity has signal state zero, the open contact closes is not activated and therefore output state is zero.

If two NO contacts are connected in series, the power flows once all contacts are closed

If two NO contacts are connected in parallel connection, the power flows once one contact amongst all contacts are closed.

Example of the NO contacts.

In above example two NO contact s are connected in series (tag 1 and tag 3). When both signal state is 1 then tag 2 state is 1.

Explain greater or equal (>=) instruction using example

Application:-Explain greater or equal instruction in the PLC. Write PLC program for explanation using ladder diagram language in the Programmable Logic Controller (PLC).

Components:-Programmable logic controller, HMI panel, wires, 24 VDC lamp, 24 VDC power source, 24VDC temperature controller.

 

Diagram:-

Explanation:-

Consider a simple temperature controller example for explanation of greater equal instruction in the PLC. Here we have taken simple HMI (Human Machine Interface) for display and programmable Logic Controller (PLC) for programming. Consider one temperature control which is displaying the temperature given by temperature sensor, here we haven’t considered analog signal calculation and scaling so we directly consider actual value in the PLC. Here if the actual temp value in the actual temp box is greater or equal than set temp, temperature indication will be ON.

If set temperature is 50 degree and temperature read by temperature controller is 50 0r 52 degree, lamp should be ON because 52 degree is greater than 50 degree.

Normally open (NC) contact concept.

Normally open (NC) contact concept.

This is PLC Program for NC contact.

Normally closed contact is known as NC contact. When the quantity has signal state 0, the NC contact allow signal flow and output result is 1.

When the quantity has signal state 1, the closed contact is not activated and therefore output state is zero.

If two NC contacts are connected in series, the power flows once all contacts have zero signal state.

If two NC contacts are connected in parallel connection, the power flows when one NC contact amongst all have zero signal state.

Example of the NC contacts.

In above example two NC contact are connected in series (tag 1 and tag 3). When both signal state are zero, output result is 1.