Application:-In electrical panel there are two switches given for panel ON
lamp. Both the switches are optional, the lamp can be ON either by switch 1 or
switch 2.Draw truth table, electrical wiring diagram and write PLC program for
this application.
Diagram:-Electrical wiring diagram and truth table of OR
operation
Components:-Programmable
logic controller, Electrical panel, wires, 24vDC switches with NO contacts,
24VDC indication lamp, 24 VDC relay.
Explanation:-
As
per our application, we can use above application for OR gate explanation. In
application we are using two switches and one lamp for indication. If switch 1
or switch 2 pressed, indication lamp should be ON. So in above electrical
wiring diagram we have used S1 and S2 in parallel connection so electrical
supply can flow either from S1 or S2.
In truth table we can
easily understand the conditions of OR gate,
As per truth table,
If S1=ON OR S2=ON, then R=1
If S1=ON OR S2=OFF, then R=1
If S1=OFF OR S2=ON, then R=1
If S1=OFF OR S2=OFF, then R=0
So the output will be OFF only in the last condition.
PLC
program:-
Write the ladder program for OR 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
S2=I0.1
Digital Output:-
Lamp=Q0.0
Memory coil:-
Memory bit-M0.0
PLC
program Explanation:-
In network 1 we have considered two digital inputs
for two switches S1 and S2. So we have taken NO contact of S1 (I0.0) in
parallel with S2 (I0.1) for OR operation. So when S1 or S2 ON,
memory bit (M0.0) will be ON.
In network 2 we have taken NO contact of memory bit
(M0.0) to operate panel ON lamp (Q0.0).