Application:-Consider there is one machine in which one water Valve used for
cleaning the job. Valve should be operate on following condition,
-machine door should be
closed
-Vale should be on after 10
second if door is closed and start switch is pressed.
Components:-Programmable
logic controller, Electrical panel, wires, 24V DC switch with NO contacts,
24VDC solenoid valve, and 24 VDC timer, door close Limit switch.
Diagram:-Electrical
wiring diagram for the above application.
Explanation:-
Here we need to use
door close switch feedback for valve. As per the condition door close feedback
is required for timer. So we need to put NO contact of limit switch in series
with Start switch. So when switch and limit switch feed backs are ok, timer will
be ON and after 10 seconds valve will 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 start pushbutton 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
Door close =I0.1
Digital Output:-
Valve=Q0.0
PLC
program Explanation:-
In network 1
we have taken ON delay timer. Timer can be ON by using NO contact of start
switch S1 (I0.0) and door close feedback (I0.1). On delay can be set at PT
(10s) so after 10 seconds valve (Q0.0) will be ON.
Here PT is preset time
at which we can set time and ET is elapsed time at which we can monitor time.