PLC examples

prob.1:
Write a plc program to start & stop a motor using one input.
sol.:
One input means one button





X=1 button is pressed.
X=0 button is not pressed.




Truth Table

X
Y
0
0
1
1

prob.2:
A motor operated with a push button.
sol.:
 (Bush Button)

 stop

X1=1 start button is pressed
X1=0 start button is not pressed

X2=1 stop button is pressed
X2=0 stop button is not pressed




 (AND)
 (OR)

 (output)



Truth Table:
X1
Y(old)
X2
Y(new)
0
0
0
0
0
0
1
0
0

1
0
1
0
1
1
0
1
0
0
1
1
0
1
0
1
1
0
1
1
1
1
0
X2
(AND)











Prpb.3:
We have machine will turn on if we bush two buttons.
Construct the ladder diagram and write truth table.

X1=1 button 1 is pressed.
X1=0 button 1 is not pressed.
X2=1 button 2 is pressed.
X2=1 button 2 is not pressed.



Truth table
X1(Button 1)
X2(Button2)
Machine
0
0
0
0
1
0
1
0
0
1

1
1





Prob.4:(final 2008 3-c):
A car door, seatbelt system. When the car door is open, or the seatbelt is
not done up, the ignition power must not be applied. if all is safe then the
key will start the engine.


X1=1 car door is closed
X1=0 car door is open
X2=1 seatbelt is closed
X2=0 seatbelt is open




X1
X2
Machine
0
0
0
0
1
0

1
0
0
1
1
1




prop.5:(final 2008 3-a):
Will cause output D to be on when push button A is on, or either B or C
are on.


A or B or C.

A=1 button A is pressed.
A=0 button A is not pressed.
B=1 button B is pressed.
B=0 button B is not pressed.
C=1 button C is pressed.
C=0 button C is not pressed.



A
B
C
Y

0
0
0
0
0
0
1
1
0
1
0
1
0
1
1
1
1
0
0
1
1
0
1
1
1
1
0
1
1
1

1
1


238


2
1



Prob.6:(final 2008 3-b):
-So that three switches in a room could turn the light on or of.



 

Sol.:


(Truth Table)


A=1 button A is pressed.
A=0 button A is not pressed.
B=1 button B is pressed.
B=0 button B is not pressed.
C=1 button C is pressed.

C=0 button C is not pressed.

Truth Table
A
B
C
Y
0
0
0
0
0
0
1
1
0
1
0
1
0
1
1
0
1
0
0
1
1
0
1

0
1
1
0
0
1
1
1
1







(ladder diagram)



Y= ABC + ABC + ABC + ABC
A: mean that A=0.

Ladder Diagram:
















(OR)










Prob.7:(final 2007 5):
An emergency system is to be designed for a certain production machine.
A single "start" button is used to turn on the power to the machine at the
beginning of the day, In addition, there are three "stop" buttons located at
different locations around the machine, any one is of which can be passed
to immediately turn off the machine.
 Write the truth table for this system.
 Construct the ladder logic diagram for the system.

Sol.:

Start=1 button start is pressed.
Start=0 button start is not pressed.
Stop1=1 button stop1 is pressed.
Stop1=0 button stop1 is not pressed.
Stop2=1 button stop2 is pressed.
Stop2=0 button stop2 is not pressed.
Stop3=1 button stop3 is pressed.
Stop3=0 button stop3 is not pressed.

Truth Table:




Start
Stop1
Stop2
Stop3
Machine
0
0
0
0
0
0
0
0

1
0
0
0
1
0
0
0
0
1
1
0
0
1
0
0
0
0
1
0
1
0
0
1
1
0
0
0
1
1

1
0
1
0
0
0
1
1
0
0
1
0
1
0
1
0
0
1
0
1
1
0
1
1
0
0
0
1
1
0

1
0
1
1
1
0
0
1
1
1
1
0
Ladder Diagram







Prob.8:


(ladder diagram)


C1 (relay)

S1 (solenoid)



Fs (Float Switch)

Fs

C2 (relay)

C2

T1 (timer)



T1


S2 (solenoid)

T1

T2


T1.