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PLC Ladder Programming [Mechatronics]
1. PLC ladder Programming
Dr. S.N.Teli
Professor, Mechanical Engineering,
Bharati Vidyapeeth College of Engineering, NaviMumbai
Cell: 9987476524
Email: shivanandteli75@gmail.com
1Dr. S.N.Teli
2. PLC Ladder Programming
Que : What are main parts of Programmable Logic Controller
Fig: Programmable Logic Controller
2Dr. S.N.Teli
Solution:
3. PLC Ladder Programming
Que : Explain advantages of Programmable Logic Controller
3Dr. S.N.Teli
A Programmable Logic Controller, or PLC for short, is simply a special
computer device used for industrial control systems. They are used in
many industries such as oil refineries, manufacturing lines, conveyor
systems and so on. Where ever there is a need to control devices the
PLC provides a flexible way to "softwire" the components together.
The advantages of PLC as mentioned below;
• They are cost-effective
• They are flexible, reliable and compact
• They have significant advantages over traditional control systems
based on relay or pneumatics
Solution:
PLC originated in the late 1960s in the automotive industry in the USA
and were designed to replace relay logic systems. Manufacturer of PLC
are mentioned below;
ABB, General Electric, Mitsubishi, Motorola Omron, Panasonic,Rockwell
Automation, Schneider Electric, Siemens, Rockwell Automation etc.
4. PLC Ladder Programming
Que : Draw PLC Ladder for AND & OR Logic.
4Dr. S.N.Teli
Solution:
Fig: PLC Ladder for OR Logic
Fig: PLC Ladder for AND Logic
5. PLC Ladder Programming
Que: Draw PLC Ladder for Latching.
5Dr. S.N.Teli
Solution:
A simple example of such a
situation is a bulb, which is
started by pressing a button
switch. Although the switch
contacts do not remain closed, it
is required that the bulb continue
to run until a stop button switch
is pressed. The latching used to
stay the bulb run until the push
button is pressed again.
S1- Normally Open (NO) Push
button to start motor; S2-
Normally Closed (NC) Push
button to off the motor; B is
output (Say Bulb)
• S1 is on --- Bulb B is on
• Then, S1 is off---- still B is on
• S2 is off--- B is off
Fig: PLC Ladder for Latching
6. PLC Ladder Programming
Que: Draw PLC Ladder for A+A- for Pneumatic circuit.
6Dr. S.N.Teli
Solution: S1 and S2 are sensors; A+ and A- are solenoids
.
S1 S2
4 2
5
1
3
A+ A-
Fig: Pneumatic Circuit Fig: PLC Ladder Program
7. PLC Ladder Programming
Que: Draw PLC Ladder for A+A- for pneumatic circuit using latching.
7Dr. S.N.Teli
Solution: S1 and S2 are sensors; A+ and A- are solenoids
.
S1 S2
4 2
5
1
3
A+ A-
Fig: Pneumatic Circuit Fig: PLC Ladder
S1
A+
A+
S2
S2
A-
A-
S1
8. PLC Ladder Programming
Que: Explain On-delay Timer in PLC.
8Dr. S.N.Teli
.
Solution:Basically two types of timers. One is On-Delay Timer and second
is Off-Delay Timer
On-Delay Timer:
Ex: When the S1 switch is on the lubricant pump (LP) will start
immediately, but grinding machine (GM) will start after preset time(say 8
Sec) of timer. Here T is On-delay Timer.
When S1 switch is off both lubricant pump and grinding machine will off
immediately.
Fig: PLC Ladder Program
9. PLC Ladder Programming
Que: Explain On- off delay Timer in PLC.
9Dr. S.N.Teli
.
Solution:Basically two types of timers. One is On-Delay Timer and second
is Off-Delay Timer
Off –Delay Timer:
Ex: In a car when key (Switch) is on both Engine(E) and fan are on at
time. When key is off , the engine will off immediately but fan(F) will off
after preset time of timer (Say 15 Sec) .
Fig: PLC Ladder
10. PLC Ladder Programming
Que: Explain On-delay Retentive Timer.
10Dr. S.N.Teli
.
Solution: Retentive ON delay timer is to delaying the ON time, if input
goes off in between, it will resumes the accumulator value and input turns
ON, it will start running for the resumed value.
Example: when switch S1 is on the bulb should on after T (Say 10 ) Sec.
T- Retentive on delay timer
S1 is On the Timer will on after
preset time (say 10 Sec), even
though the S1 is off . The Bulb is on
after 10 Sec.
To off the timer press S2. It means
reset the timer. Once again to start
the timer press S1. As long as S2 is
on the timer is dead. It means in the
next cycle when S1 is on, the S2 is
off.
Fig: PLC Ladder Program
16. PLC Ladder Programming
16Dr. S.N.Teli
.
Solution: T is on-delay Timer.
Fig: Pneumatic Circuit
Fig: PLC Ladder
Que: Draw PLC Ladder for A+ (delay) for multiple cycle.
4 2
5
1
3
A+
S1 S2
17. PLC Ladder Programming
17Dr. S.N.Teli
.
Solution: T is on-delay Timer and C is Counter
Fig: Pneumatic Circuit Fig: PLC Ladder
Que: Draw Circuit for 4(A+ A-) delay and cycle should continue
S1 S2
4 2
5
1
3
A+ A-
18. PLC Ladder Programming
18Dr. S.N.Teli
.
Fig: PLC Ladder
Que: Draw a PLC ladder programming for the following water level
maintain in the tank automatically.
Solution: SO- On/off Switch; V- Solenoid Valve; S1& S2 Normally Open.
19. PLC Ladder Programming
19Dr. S.N.Teli
.
Fig: PLC Ladder
SO- Start push button
ST-Stop push button
V- Solenoid Valve
S1& S2 Normally Open
R-Intermediate Output
Que: Draw PLC ladder for the following water tank.The minimum
level should be S1 and maximum level S2. Start & stop are push
button. V and P may on simultaneously.
20. PLC Ladder Programming
20Dr. S.N.Teli
.
Fig: PLC Ladder
• SO- Start push button
• ST-Stop push button
• V- Solenoid Valve
• S1& S2 Normally Open
• R-Intermediate Output
Que: Draw PLC ladder for the following liquid tank. The minimum
level should be S1 and maximum level S2. Start & stop are push
button. When P is on V is off or P is off and V is on.
21. PLC Ladder Programming
21Dr. S.N.Teli
.
Fig: PLC Ladder
• SO: Start/Stop button
• S1& S2: Normally Open
• T: On- delay Timer
Que: Draw PLC ladder for the following liquid mixing process.
• Pumps have to start and stop when sensor S2 is on.
• When sensor S2 is on Fan should start for 10 Sec &stops
• As soon as fan stops, the discharge valve has to on & stops when
S1 is off.
22. PLC Ladder Programming
22Dr. S.N.Teli
.
Fig: PLC Ladder
Que: Write PLC ladder programming for count 100 bottles and stops
the conveyor belt for 10 sec and starts the cycle automatically.
Solution: T: On-delay timer;
SO: Start Push button; ST:
Stop push button; M-Motor;
S1: Sensor to sense the
object
23. PLC Ladder Programming
23Dr. S.N.Teli
.
Fig: PLC Ladder
Que: Write PLC ladder for count 100 bottles and stops the conveyor
belt for 10 sec and starts the cycle automatically.
Solution:
S1- Sensor (Start the motor)
S2- Stop the Motor
S3-Count the filled bottle
M- Motor; T –On-delay timer SO-
Start/STOP button (Toggle
Switch/Detent Switch)
24. PLC Ladder Programming
24Dr. S.N.Teli
.
Que : Design PLC Ladder diagram for the following process details;
When a part is placed on the conveyor at position 1, and when a start
button is pressed it moves to position 2. Upon reaching position 2, it
stops for the sampling operation to take place. After stamping it
automatically moves to position 3. It stops at position 3, where the
part is removed manually from the conveyor. Assume only one part
is on the conveyor at a time. Add limit switches, interlocks, push
buttons, etc. as required.
