Application:-Explain the NOT gate operation using
electrical diagram and ladder diagram language. Draw electrical diagram for
electrical panel in which lamp should be on when switch is off and lamp should
be off when switch is off. Also write PLC program for this application using
ladder diagram language.
Components:-Programmable
logic controller, Electrical panel, wires, 24V DC switches with NO contacts,
24V DC indication lamp, 24 VDC relay,24V DC source.
Diagram:-Electrical
wiring diagram and truth table of NOT gate operation
Explanation:-
In this application we need to use NOT gate logic.
As shown in figure we can draw electrical diagram for NOT gate operation so that we have taken NO contact of switch S1 to
operate lamps as per the NOT gate logic. Hence when switch is ON, relay is
operated and lamp will be OFF due to NC contact of relay and when switch is OFF,
lamp will be ON.
We can easily understand the NOT gate function with
truth table,
If S1=ON, then R=0
If S1=OFF, then R=1
So NOT gate inverse the logic.
PLC
program:-
Write the ladder program for NOT gate 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 lamp is digital output. So define digital input address and output address
as per below explanation,
Digital
inputs:-
S1=I0.0
Digital Output:-
Lamp=Q0.0
Memory
coil:-
Memory bit-M0.0
PLC
program Explanation:-
In network 1 we have used NO contact of switch S1 (I0.0) to operate
memory bit (M0.0).So when S1 (I0.0) is ON memory coil (M0.0) is ON and switch
S1 (I0.0) is OFF, memory coil (M0.0) will be OFF.
In network 2 we have
used NOT gate function so when switch S1 (I0.0) is ON, it will inverse logic
and makes lamp (Q0.0) OFF. And when S1 (I0.0) is OFF, lamp (Q0.0) is ON