Application:-Explain greater than 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 than (>) instruction
in the Programmable Logic Controller (PLC). Here we have considered 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 than set temp,
temperature indication will be ON.
If set temperature is 100 degree and temperature
read by temperature controller is more than 100 degree or consider 102 degree,
lamp should be ON because 102 degree is greater than 100 degree.
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. Set temp
is the input word.
Digital Output:-
Temp Lamp=Q0.0
M
Memory:-
Set temp.:-MW10
Actual temp:-MW20
PLC
program Explanation:-
In network 1
actual temperature (MW10) will be compared with set temperature (MW20). So if
the measured temperature (MW10) is greater than set temperature (MW20),
temperature indication lamp (Q0.0) will be ON
In greater or equal (>) instruction, two operands
are compared, we can set data type in comparator instruction.
